星形成ゼミ #373 15-30
2024/03/08 片岡

Stability of Dusty Rings in Protoplanetary Discs
Kevin Chan1★ and Sijme-Jan Paardekooper2,1
1Astronomy Unit, School of Physical and Chemical Sciences, Queen Mary University of London, Bethnal Green, London E1 4NS 2Faculty of Aerospace
Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands
ABSTRACTDust rings in protoplanetary discs are often observed in thermal dust emission
and could be favourable environments for planet formation. While dust rings
readily form in gas pressure maxima, their long-term stability is key to boththeir observability and potential to assist in planet formation. We investigate thestability of the dust ring generated by interactions of a protoplanetary disc witha Neptune sized planet and consider its possible long term evolution using the
FARGO3D Multifluid code. We look at the onset of the Rossby Wave
Instability (RWI) and compare how the addition of dust in a disc can alter thestability of the gas phase. We find that with the addition of dust, the rings
generated by planet disc interactions are more prone to RWI and can cause thegas phase to become unstable. The instability is shown to occur more easily forhigher Stokes number dust, as it accumulates into a more narrow ring which
triggers the RWI, while the initial dust fraction plays a more minor role in thestability properties. We show that the dusty RWI generates vortices that collectdust in their cores, which could be sites for further planetesimal formation. We
conclude that the addition of dust can cause a ring in a protoplanetary disc tobecome more prone to instability leading to a different long term evolution
compared to gas only simulations of the RWI.
Key words: protoplanetary discs - hydrodynamics - method: numerical planet-disc interactions• ロスビーウェーブ不安定（RWI）の駆動条件について、ダストを足すとどうなるかを調べたシミュレーション論文• 結果は• Stの値が大きいとよりRWIが発生しやすい• Dust / Gas 質量比はそんなに影響しない• まとめ• ガスのみシミュレーションに比べ、ダストをいれるとより不安定になりやすくなるので、観測されている円盤を説明するという観点からも、長時間の安定性は調べたほうが良さそう。

ring may be to
man & Rafikov
protoplanetarye edge of planet

2.1 Computational Setup
We perform gas and dust simulations of a global disc using
FARGO3D Multifluid (Benítez-Llambay et al. 2019). The locally
isothermal terminal velocity approximation where the two fluids are
combined as a single fluid presented caveats (Chan & Paardekooper2022) when a larger planet was embedded in the disc, therefore wewill use the two fluid system where the gas and dust are evolved
separately for our simulations. We assume a geometrically thin discin 2D cylindrical coordinates (A, q) with vertically integrated quantities. The equations we solve are the continuity equations for the gas
and dust respectively,

基礎方程式

ns et al. (2019)
net and pebble
rough the RWI.
seous disc, theyratios, which aal. (2020), theyscale instability
lity was caused
outside the ring,g to rotate near
hey investigate
in an inviscid
icty discs withe dusty vortices
e planet’s initial
generated canways. The dustof the possible
sc morphology

gas, dustの2流体、backreactionあり、自己重力無し、isothermal

ressure bumps,
ons and theory.

m⌃g+ r · (⌃g ug ) = 0,
mC

(1)

m⌃d
+ r · (⌃d ud ) = 0,mC(2)

where ⌃ denotes the surface density and u the 2D velocity, with
subscripts g and d referring to the gas and dust. The momentum
equations are solved,m (⌃g ug )+ r · (⌃g ug ug ) =mCm (⌃d ud )+ r · (⌃d ud ud ) =
mC

(ud
(ud

ug )

r? g + ⌃g r + r · Tg , (3)ug ) + ⌃d r + r · Td ,(4)

aardekooper

ガスのみの場合(過去によくやられている)

粘性を変えて、RWIが発生するかを確認する
4

K . Chan and S-J . Paardekooper• kinematic viscosity νを1e-5, 1e-6,
1e-7 と変えた。

• 100周回した。
• セットアップは、粘性なしならRWIが

us disc with a Neptune sized planet embedded at 1Ap after C = 100 orbits. The kinematic viscosity is varied, a 2
RWI has developed in the rightmost plot with the lowest kinematic viscosity at the inner and outer rings and has caused
FigureDensity
as rings and gap edges(A =1.0.9,
1.1Aplotsp ). for a gaseous disc with a Neptune sized planet embedded at 1Ap after C = 100 orbits. The kinematic viscosity is varied, a 2[10 5 , 10 6 , 10 7 ] from left to right. RWI has developed in the rightmost plot with the lowest kinematic viscosity at the inner and outer rings and has caused
vortices to emerge, destabilising the gas rings and gap edges (A = 0.9, 1.1Ap ).

t fraction and Stokes number can
St = 0.01. We study how the dust fraction and Stokes number cansection 3.3.
eﬀect the evolution of the ring in section 3.3.
bility of the ring is In
notordercausedbythat the instability of the ring is not caused by
to show
ude in section 3.4 results
whereto weeﬀects related
gas drag we include in section 3.4 results where wecoupling
as and dust at the force
pointperfect
where
the between gas and dust at the point where thering would
go unstable, and since the instability proceeds as normal,
the instability proceeds
as normal,
we conclude that drag does not play a significant role in making
play a significant therole
makingdustinring
unstable. Finally in subsection 3.5 we investigate thesubsection 3.5 wevortices
investigate
thegeneratedby dusty RWI and briefly present the possible longtermpossible
evolution longand show the possible implications.
nd briefly present theble implications.

Figure 2. Radial profile of the azimuthally averaged key functions for a 2[10 5 , 10 6 , 10 7 ]. The lower viscosity setups have a larger peak at the
3.1 Stability of Gas Rings
locationof the gap(A = 0.9A
1.1A
Figure 2. Radial profile of the azimuthally
averaged
keyedgesfunctions
forp , a2p ) which lead to development of
6 , 10 7 ]. of
RWI. have a larger peak at the
For our test cases we ran benchmark
gaslower
only discs
The
viscositythesetups[10 5 , 10simulations

with an embedded Neptunelocation
sized planet,whilevaryingtheuniform
of
the
gap
edges
(A
= 0.9Ap , 1.1Ap ) which lead to development ofkinematic viscosity, a 2 [10 5 , 10 6 , 10 7 ]. We use a resolution of
the RWI.
ark simulations of(768,1536)
gas onlycells
discs
the lowest kinematic viscosity we see that the gap edge created hasin the radial and azimuthal direction respectively
planet, while varying
thesimulation
uniformtime for each case is 100 orbits. We ran thesetriggered the RWI within 100 orbits and vortices have been generated
and the出るとされているものde Val-Borroet al. (2006)• 粘性が低いとより深いギャップが開く。

• 1e-6では、200周まで行くと不安定だったがすぐ粘性でsupressされる。

• 1e-7では見て分かる通りギャップの内と外にgas overdensities として渦が見えている。

Dusty Ring Stability

addition to presenting a necessary condition for instability, itwith as the drag coeﬃcient between the two phases and ? g theprovides a useful view on the emergence of vortices, since in ou
gas pressure. We use a locally isothermal equation of state, ? g =cally isothermal simulations the key function is closely related t
22B (A)⌃g where 2 B (A) is the fixed radial profile of the gas sound speed
inverse of the vortensity. When the instability triggers, vortice
throughout the disc. Apart from the drag forces, the forces appearing
planet embedded at 1Ap after C = 100 orbits. The kinematic viscosity is varied, a 2
generated and the extremum in the radial profile of the key func
on
the
right
hand
side
includethegravitational
force,
expressed
tmost plot with the lowest kinematic viscosity at the inner and outer rings and has caused
Dustykey
Ringfunction
Stability is 5given as, in a gas disc,is dampened. This
through the gravitational potential , and the viscous forces through, 1.1Ap ).
the stress tensor, T8 which includes a as the kinematic viscosity (seeEq. 3 of Benítez-Llambay et al. 2019) given in units of A p2 ⌦ : (A p ).
2/W
⌃
(
g
er canOur computational setup does not include dust diﬀusion and the
L (A) =,2(r ⇥ u) Îequationsaresolvedthroughthemethodofoperator
splitting(Stonesed by•W& Norman 1992).
ere wewhere ( is the entropy given by ( = ? g /⌃g with W as the adia
ere theDimensionless units are adopted whereby the unit of mass is the • Sがエントロピー。rot
index. In this study weuはvortensityなので、だ
investigate how eﬀective the key func
ormal,
mass of the primary "P . Our standard planet mass corresponds tois in predicting when the instability occurs. However, equation
いたいエントロピー割るvortensityみたいな量。
making4
a Neptune-like planet with mass " ? = 10 "P . This corresponds
has typically been used to present the onset of RWI in gas
ate theto a ratio of planet to thermal mass of "p /"C ⌘ = 0.8 (Goodman • この関数が極大を持つところでRWIが発生すると
simulations of protoplanetary discs and not in dusty discs. In
e long& Rafikov 2001). The radial domain is from 0.4 to 2.5A p (de Val言われているof the thermodynamic interpretation of Lin & Youdin (2017),
Borro et al. 2006) where A p is the orbital radius of the planet. We
useful to treat the gas and dust as a single fluid. In order to incorpo
Figure 2. Radial profile of the azimuthally averaged key functions for a 2
note that the planet is on a fixed orbit at 1A p to generate the outer • radial
the keyprofileの図を見ると、確かにν=1e-5でfunction into our 2D disc setup of firstly, a locally isothe[10 5 , 10 6 , 10 7 ]. The lower viscosity setups have a larger peak at thebump
location of the gap edges (A = 0.9Ap , 1.1Ap ) which leadpressure
to developmentof which we will be analysing in the results. The disc has
はRWIが発生しないことなどがおおよそあっていequation of state (W = 1) and secondly, with the addition of
the RWI.
y discs
a constant aspect ratio ⌘0 = /A = 0.05 with as the scale height
we simply take the barycentric velocities of the dust and gas ph
そう。
niformand there is no flaring of the disc. The sound speed profile is given
given by,ion ofas 2 (A) = ⌘0 ⌦K A and the planet potential is smoothed over 0.6 . • ν=1e-7のときの2Dプロットを、t=60と80で
the lowest kinematic viscosity we see that the gap edgeB created has
ctivelyThelowestresolution used in the simulations are (768,1536) cells in
見る。80で明らかに4つの渦がある。これが弱い
triggered the RWI within 100 orbits and vortices havebeen
generatedthese⌃g ug + ⌃d udtheberadial
andasazimuthal direction respectively corresponding to 12
interior and exterior to the planet. These vortices canidentified
bit theub =profile of the azimuthally averaged, key functionfunctionのradial
腕を作っていて、これはkey
Figure 4. Radial(top) for⌃+⌃gas overdensities, and alter the region of the pressure
bump
and
ring
would
g
d
cells per scale height at the planets location. The gas and dust surfacestable (solid
blue line) and unstable (dotted orange) gaseous discs. 2D key
profileを弱くして入るものの、極大値を見る分
function plot (bottom) for a gaseous disc with Neptune sized planet embedded
generated by the planet through their own interactionsof aremergingof thedensity
set to,at 1Ap afterwith
C = 100 subscripts
orbits. The kinematic
viscosity
is settothe
a = 5gas⇥ 10 7and
.
g
and
d
as
dust respectively and theには問題ないtogether in the azimuthal direction. One important question introed theIn this case the kinematic viscosity is large enough to suppress the onset of
the RWI during
its evolution
with a smoothgapdensity,⌃asT shown= ⌃ingthe+bottom⌃d ,plotwhen
representing
the "mixed" key func
duced then, which will be explored briefly in the last subsection ofedge interior and exterior to the planet, however it is not as indicative in the! 0.5
the results, is "What is the long term evolution of the vortices exterior
ematicgiven
基本的にはν=1e-7と1e-6（及びその中間のradialprofileof the keyby,
function compared to the lower viscosity case which•
Figure 3. Key function plot for a gaseous disc with Neptune sized planetA
goes unstable.
to a gap carving planet?". As isolated vortices are subject to viscous
us caseembedded at 1Ap after C = 60, 80 orbits. The kinematic viscosity is, a = 10 7
⌃g =⌃0(1 5dand), the gap edges interior (A = 0.9Ap ) and exterior (A = 1.1Ap ) to the (5)値）を使ってこれから議論する。
damping (Fu et al. 2014a) while a planet carving a deep enoughin theA p gap
planet has triggered the RWI generating a number of vortices which are more2in the disc can trigger the RWI into generating vortices, this would
gap inpronounced exterior to the planet.
⌃
(
T
! 0.5
⇤ edges interior and exterior have triggered the RWI,
see that the gapL(A) =be key to the evolution and possible further planetesimal andAplannchedgenerating at least four vortices
outer gap edge. This in2(rexterior⇥ ubto)theÎ

RWIを発生させるかどうかを表す関数

key function (Lovelace et al. 1999)

d
g
d
h
e
).
e
e

cally isothermal simulations the key function is closely related to theinverse of the vortensity. When the instability triggers, vortices are
keyfunctionのガスダスト系への拡張
generated
and the extremum in the radial profile of the key function
is dampened. This key function is given as, in a gas disc,he stress tensor, T8 which includes a as the kinematic viscosity (seecq.has3 of Benítez-Llambay
et al.of
2019)
given(Win unitsof A p2and⌦ : (A p secondly,).
equation
state
= 1)
with
⌃g ( 2/W the addition of dust,
Our computational setup does not include dustDusty
diﬀusionand the
L (A) = 3
,
(7)
Ring
Stability
eight
2(r
⇥the
u) Î dust and gas phase,
we
simplytakethebarycentric
velocities
ofquations are solved through the method of operator splitting (Stone
W&iven
Norman 1992).given by,
where( is the entropy given by ( = ? g /⌃g with W as the adiabatic
addition to presenting a necessary condition for instability,
it alsotheDimensionless
units
are
adoptedwhereby
the
unit
of
mass
is
the
index.
In
this
study
we
investigate
how
eﬀectivethekeyfunction.
providesa
usefulview
onthe
emergenceofvortices,
since
in
our
lo?.6
=
g
mass of the primary "P . Our standard planet mass corresponds tois in topredicting
when the instability occurs. However, equation (7)callyisothermal
simulations
thekeyfunctionisclosely
related
the
peed
ls
in
Neptune-likeplanet with mass " ? = 10 4 "P . This corresponds
hastypically
been
used
to
present
the
onset
of
RWI
in
gas
only
the
When
the instability
triggers, vortices are⌃vortensity.
+⌃ug umassdoring
a ratioガスのみのkey
ofinverse
planet of
tofunction
thermal
of
"
/"
=
0.8
(Goodmang
p d C⌘
simulations of protoplanetary discs and not in dusty discs. In viewo12
generatedandtheextremumintheradialprofileofthekeyfunction
uThe
=
,
(8)
&ssed
Rafikov 2001).
radialdomain
is
from
0.4
to
2.5A
(de
Valb
p
of
the
thermodynamic
interpretationofLin&
Youdin(2017),
itis
シミュレーションはisothermalなので⌃+⌃
isdampened.
This
keyfunction
is
given
as,
in
a
gas
disc,
ough
g
d2/W
Borro
radius of the planet. We
faceet al. 2006) where Ap is the orbital
useful to treat the gas and dust as a single fluid. In order to incorporate(seethat the planet is on a fixed orbit
ote
g at 1Ap to generate the outer Gamma=1とした。
the key function into our 2D disc setup of firstly, a locally isothermal
ressurewe
willbeanalysingintheresults.
The
disc
has
(A
2/W
p ). bump whichwithsubscripts
g
and
d
as
the
gas
and
dustofrespectively
thewithtotal
equationstate (W = 1) and andsecondly,
the addition of dust,⌃g (constant
aspectthe
L (A) ratio= ⌘0 = /A, = 0.05 with Îas the scale height(7) take the barycentric velocities of the dust and gas phase,
we simply2(r⇥u)disc.
density,
⌃
=
⌃
+
⌃
,
when
representing
the"mixed"keyfunction
Î
g
T
d
nd
there
is
no
flaring
of
the
The
sound
speed
profile
is
given
tone
速度は、ガスダストの重心速度を使う。
given by,W
s 2 B (A) = ⌘0 ⌦Kgiven
A and theby,
planet potential is smoothed over
0.6 .
where ( is the entropy
given by ( = ? g /⌃g with W as the adiabatic
ただしエントロピー
Wused in the simulations are (768,1536) cells in
shethelowest resolution⌃g ug + ⌃dgud
index. In this study we investigate how eﬀective the key function
g
(5)
he to
radial and azimuthal direction respectively corresponding to 12
ub = (7)
,
(8)
ds
is
in
predictingwhentheinstability
occurs.
However,equation⌃g + ⌃d
ガスダストに拡張したkeyfunction
ells
per
scale
heightattheplanets
location.
The
gas
and
dust
surfaceonds
hasto,typically been used to present
the onset of RWI in gas only2
ensity are set⌃ (with subscripts g and d as the gas and dust respectively and the total⌃ (L (A) =,2(r ⇥ u)•(7)•
where ( is the entropy given by ( = ? /⌃ with W as the adiabaticeindex. In this study we investigate how eﬀective the key function
T discs and not in dusty discs. In view
⇤ of protoplanetaryoman simulations
L
(A)
=
is
in
predictingwhentheinstability
occurs.
However,equation(7)
density,
⌃
=
⌃
+
⌃
,
when
representing
the"mixed"keyfunction
g
T
d
Valof
the
thermodynamic
interpretationofLin&
Youdin(2017),
it
is
! 0.5
2(r
⇥
u
)
f̲d
=
Σ̲d
/
Σ̲T
Î
b
•
given
by,
dsWe
(6)
A useful
to treatthe gas and dust
as a single
fluid. In order
to incorporate the onset of RWI(9)hastypically
been
used
to
present
in
gas
only
=⌃
(1
5
),
(5)
g
0
d
4
2
outer
the
key
function
into
our
2D
disc
setup
of
firstly,alocally
isothermal
Ap
2
(1
5
)
⌃
T
d
B
2
n
c has
⌃
(
T
discs
not in dusty discs. In view
= (W = 1)ofandprotoplanetary
equationof statesecondly, ,with the addition! simulations•
0.5
L ⇤of(A)dust,= andeight A we simply take the barycentric
2(r
⇥
u
)
2(r
⇥
u
)
velocities
of
the
dust
and
gas
phase,
Î
b
Î
b
net’s
=⌃
5
,
(6)
l-iven
(9)
0
d
d
of
the
thermodynamic
interpretationofLin&
Youdin(2017),
it
is
4 (1
2⌃
A p given
by,
2
5
)
T
d
4
B
=
,
10
.6 .
where 5 is the dust fraction, 5 = ⌃ /⌃ 2(rsinceWe⇥ u )our vertically inte-RWI不安定のガス(ν=1e-7)にダストを足す
d:g= 1:100(質量)、St=0.01（ガスによくカップルしたダストの場合）
6 K . Chan and S-J . Paardekooper
6

K . Chan and S-J . Paardekooper

t=80

t=90

• 基本的にはガスのみの場合と違いはない。

• 例えば、t=90では、4つの渦がある
Figure 5. Radial profile of the azimuthally averaged "mixed" key function(top) for dust and gas (solid orange) and radial profile of gas only key function(dotted blue). 2D key function plot (bottom) for the dust and gas disc with
Neptune sized planet embedded at 1Ap after C = 80 orbits. The dust fraction is
set to 5d = 0.01, Stokes number, St = 0.01 and kinematic viscosity, a = 10 7 .
With the addition of dust the gap edges interior and exterior still trigger the
RWI which generates vortices but has little diﬀerences compared to the gas
only case.

• ただし、ダストがouter edgeに溜まっているので、この先はどうかは定かではない

key function for this simulation is shown in Fig. 4, both azimuthally
averaged (top panel) and the full 2D structure (bottom panel). Fromthe bottom panel, it is clear that after 100 orbits no vortices haveformed, and while the RWI may be triggered at later times, after 100
orbits the gas disc looks quiet and stable. The peaks in the 1D key
function are comparable to those in the (unstable) a = 10 7 case, butnote that the latter will have been aﬀected by the emerged vortices.
3.2 Dust in an RWI Unstable Gas
We first set the kinematic viscosity to a = 10 7 , a case where the gasonly RWI develops within 100 orbits, and investigate whether adding
Figure 5. Radial profile of the azimuthally"mixed"key offunction
dust makes a averaged
noticeable change
in the evolution
the disc compared
to
the
gas
only
case.
We
test
how
the
evolutionofthedisc may change(top) for dust and gas (solid orange) and radial profile of gas only key function
with a typical dust to total ratio of 1:100. The Stokes number we use(dotted blue). 2D key function plot for(bottom)dust
andgascorresponds
disc withthe first testfor
is Stthe= 0.01which
typically
to smaller
grain sizes or strong drag of the gas onto the dust, making it tightly
Neptune sized planet embedded at 1Acoupled.
C=
80 orbits. The dust fraction isp afterWe
present the plots of the azimuthally averaged and 2D7.
set to 5d = 0.01, Stokes number, St =key0.01
andofkinematic= 10function
this simulationviscosity,
after 80 orbitsa
in Fig.
5.
From the plots we see that after 80 orbits the evolution of the discWith the addition of dust the gap edges
interior and exterior still trigger thewith dust added are very similar to the gas only case when plotting the"mixed"keydiﬀerences
function. The radial
profile of theto
azimuthally
RWI which generates vortices but has
littlecompared
the gasaveraged
key function has the same features as in Fig. 2 with a larger peak

only case.

Figure 6. 2D density plots for the dust (top), gas (middle), and total (bottom)
of a Neptune planet embedded disc at C = 90 orbits. The dust fraction is set to5d = 0.01, Stokes number, St = 0.01 and kinematic viscosity, a = 10 7 . We
see that the dust from the outer ring is accumulated quickly into the vortices
generated by the gap edge triggering the RWI.

RWI不安定のガス(ν=1e-7)にダストを足す
d:g = 1:100(質量)、St=0.1（ガスからdecoupleしたダストの場合）
Dusty Ring Stability

7

at the inner gap edge and smaller peak at the outer gap edge. The
exact values at the peaks and troughs for the gas only and "mixed"
key function can not be directly compared, however the features
themselves in the "mixed" key function plots show good indicationof places prone to the RWI. In terms of the 2D plot we see the similarfeatures of the gap edges triggering the RWI and generating vortices
outside the gap edges with minor diﬀerences. The vortices generated
by the unstable gas quickly destabilise the dusty ring building up
exterior to the planet, accumulating the material into the vortices.
In Fig. 6 we show the density plots of the dust, gas and total, ten
orbits later at C = 90. We see that the outer ring is broken up by thefour vortices while the dusty ring interior to the planet remains stable
but undergoes the same evolution by 100 orbits when the inner gap
edge triggers the RWI. In this case we see that the gas RWI is largely
unaﬀected by the presence of dust, when comparing the key function
plots, as it is swept into the vortices. We note however that the longterm evolution of the disc is expected to be diﬀerent as the vortices
are loaded with more dust.
When we increase the Stokes number to 0.1, a similar evolution
is observed however in this case, the dusty ring formed exterior to
the planet is much thinner in the radial direction before the vortices
destabilise the ring and accumulate the material into the vortex centres. We present the density plots in Fig. 7 where we see that thematerial built up in the vortex cores after 90 orbits start to launchspiral density waves throughout the disc as dust builds up. Whenobserving the gas phase for this setup, we can see that by 90 orbits
the vortices are not as defined as in the previous case of St = 0.01 as
more dust is loaded into the vortex cores. A reason for this would be
drag instabilities occuring in the vortices between the dust and thegas. Therefore in this case, we do see a larger diﬀerence between theevolution of the vortices generated by the triggering of the RWI at
the gap edge for a gas only and dust+gas disc. However we do not
observe if the dust makes the disc less prone to the RWI within 100
orbits as the RWI is triggered by the gas at an early stage in bothscenarios of adding dust to a disc. In these cases, the gas RWI dominates the early evolution of the disc and the dust does not contributesignificantly to the triggering of the instability.
As 10 7 for the kinematic viscosity is typically a very low viscosity
value compared to observations and current upper constraints insome discs (Rosotti 2023), it is important to note that regions of low
viscosity can occur in discs such as the dead zones (Gammie 1996;
Armitage 2011).
3.3 Dust in an RWI Stable Gas

Figure 7. 2D density plots for the dust (top), gas (middle), and total (bottom)
of a Neptune planet embedded disc at C = 90 orbits. The dust fraction is set to5d = 0.01, Stokes number, St = 0.1 and kinematic viscosity, a = 10 7 . The
thin dusty ring built exterior is destabilised by vortices at the gap edge andmaterial is accumulated into vortex centres which causes weak spiral density
waves to be launched from the vortices.

Following on, we investigate if there is a point where the dust canmake a noticeable diﬀerence in the evolution of the disc for a stable
gas and whether it makes the gap edges more prone to the RWI or if
the dust buildup could source a new location for the RWI to occur.
From our test case of 5d = 0.01, St = 0.01 and a = 10 7 we varied
the three parameters to find if there was a defining factor to triggering
the onset of the RWI. As seen before, the kinematic viscosity plays
an important part in suppressing the instability therefore for the next
results we use a kinematic viscosity of a = 5 ⇥ 10 7 to comparewith our gas only results in Fig. 4 where the evolution of the region
exterior to the planet’s outer gap edge remained stable.
3.3.1 Varying the Dust Fraction
With a focus on St = 0.01, we found that our standard dust fraction
5 = 0.01 made no diﬀerence to the stability of the disc within• outer edgeに集まるダスト
層がより薄い• だが、ガスにさっき見えていた渦がない。これはダストガ
ス相互作用のせいかも。

• (まとめ：gas only及びSt=0.01ではこの場合渦ができていたが、St=0.1では渦ができなかった)RWI安定のガス(ν=5e-7)にダストを足す
8

St=0.01のまま
f̲d=0.1,0.2にしてみた。
K . Chan and S-J . Paardekooper
8

K . Chan and S-J . Paardekooper• f̲d=0.1,0.2にしてみた。
• mixed key functionはさっき

Figure 8. Radial profile of the azimuthally averaged "mixed" key functions
for a dust and gas disc with dust fractions of 5d = 0.1, 0.2 and Stokes number,
St = 0.01. The kinematic viscosity is set to a = 5 ⇥ 10 7 and the evolutionof the disc has reached C = 100 orbits. We see that large peaks have formed at
the location of the gap edges showing the growth of the "mixed" key function
compared to initial.

より極大値が際立つ。

Figure 8. Radial profile of the azimuthally averaged "mixed" key functions
for a dust and gas disc with dust fractions of 5d = 0.1, 0.2 and Stokes number,
100 orbits. We now investigate7 whether larger dust fractions, where
St = 0.01. The kinematic viscosity
is set to a = 5 ⇥ 10 and the evolution
the feedback is more important, changes this situation. In Fig. 8 weof the disc has reached C = 100 orbits.
see that large
peaks
have key
formedat for discs withpresentWethe azimuthally
averaged"mixed"functiondust fractions,
5d = 0.1,
0.2."mixed" key function
the location of the gap edges showing
the growthof theWe see that after 100 orbits, the peaks formed at the gap edges arecompared to initial.

much larger than previous radial profiles of the "mixed" key function
especially comparing to Fig. 5 which had a smaller dust fraction of
0.01 and lower kinematic viscosity. Normally with extremum in the
100 orbits. We now investigate
whetherdust fractions,whereradialprofile, welarger
would expect
the RWI to trigger
but the gap edges
still remained
is shown in
9 wherethe feedback is more important,changesstable.
thisThissituation.
InFig.
Fig.
8 wewe present the
2D plot of the "mixed" key function. In both cases, the gap edges
present the azimuthally averaged"mixed"functiondiscs
withremainstable andkey
smoothgenerally.for
In thesecondcase of 5d = 0.2
dust fractions, 5d = 0.1, 0.2. we see that there is a hint of an instability occurring soon or being
suppressed at the gap edges near the azimuthal coordinate q ⇡ 2.5,
We see that after 100 orbits,
the peaks formed at the gap edges are
however it is not clear enough to discern during the evolution of themuch larger than previous radial
the"mixed"keyfunctiondisc. profiles
In terms ofofthe
density,
the dust
build-upin the ring interior
exterior had
to theaplanet
reacheda ratioof aroundespecially comparing to Fig. and5 whichsmallerdust
fractionof 1 : 2 of dust
to gas and the total density in the exterior ring was larger than in
0.01 and lower kinematic viscosity.
Normally with extremum in thethe gas only case, causing a steeper gradient between the gap edge
radial profile, we would expect
triggerbuta higher
the gap
edges to the RWI
and thering RWI
which toshouldindicatesusceptibility
TheFig.
initial9 dust
fractionplay a partstill remained stable. This is triggering.
shown in
where
wemay
present
the in how prone
the gap edges are to the RWI, as dust may build-up in the rings that2D plot of the "mixed" key would
function.
Ina steepbothenoughcases,
the andgapmoreedges
generate
gradient
should be exploredin further studies
we canseeof
in thissetup,
remain stable and smooth generally.
In thehowever
secondcase
5d =0.2that increasing
dust fraction of the disc up to 5d = 0.2, that the gap edges
we see that there is a hint oftheaninitial
instability
occurring soon or being
are not more prone to the RWI after 100 orbits.
suppressed at the gap edges nearcoordinate⇡ 2.5,We thenote azimuthalthat the azimuthally
averagedq"mixed"
key function so
indicate during
possible thelocationsof the RWI
triggering but the
however it is not clear enoughfartomay
discern
evolutionof the• だが、gap edgeは安定なママである。f̲d=0.2, Φ=2.5の付
近でなんかあるが。

• というわけで、f̲dを上げるこFigure 9. "Mixed" key function plot for dust and gas disc with dust fractions,
5d = 0.1 (top) and 0.2 (bottom) with Stokes number, St = 0.01 for both cases.
The evolution of the disc has reached C = 100 orbits. The gap edges interior
and exterior to the planet remain generally stable during its evolution withthe dusty rings being largely undisrupted.

kept the original dust fraction of 0.01. For this, we first highlight theとは、あまりRWI不安定にはさせないという結論。

RWI安定のガス(ν=5e-7)にダストを足す
d:g=1:100 のまま、Stを上げる作戦。St=0.2
Dusty Ring Stability

t=60

9

10

10

K . Chan and S-J . Paardekooper
K . Chan and S-J . Paardekooper

t=70

t=100

• t=60とt=100を比べる• t=100でRWIができている原因は、gap edgeのFigure12.12.
Radialaveragedsurface
surfacedensities
FigureRadialprofile
profileofofthe
the azimuthally
azimuthally averaged
densities
for forthe thedustdust(orange)and= 70
70orbits.
orbits.The
Thedustdust
evolutionshows(orange)andgasgas(blue)(blue)after
after CC =evolutionshows
a sharppeakbuilding
bumpbefore
beforethethe
instability
a sharppeakbuildingatatthe
the outerouter pressurepressure bumpinstability
is istriggeredat aroundC C==78.
78.
triggeredat aroundgradientではなく、sharp peak in the outer ring.
これはダスト起因。
Figure14. 2D
key function
plot at Cplot= 100
for orbits
a dust foranda dust andFigure14."mixed"
2D "mixed"
key function
at Corbits= 100
gas disc
withNeptunesizedplanetembedded
disc.
The
dust
fractionisset
to is set togas disc with Neptune sized planet embedded disc. The dust fraction
5d = 0.01, Stokes number, (C = 0.2 and kinematic viscosity a = 5 ⇥ 10 7 .
7• t=78でRWIがトリガーされていたので、t=70を調べ

5d = 0.01, Stokes number, (C = 0.2 and kinematic viscosity a = 5 ⇥ 10.

るbeen generated at the location of the outer ring. The thin ring of dust
generated
at thelocationof theouter ring.
thin ring of dust
thatbeen
had built
up in thepressure
bump
is distortedby Thethe vortices
that
had
built
up
in
the
pressurebump
isdistortedby the vortices
and the dust itself is being accumulated in the centres of the vortices
and thedustshaped
itself is
being
accumulated
the centres
ofsee
the vortices
creatinga wavering.
Looking
at the gasin
densityplot, wethatcreating
the gas phaseitselfhas become
unstable atexterior
the planet.
a waveshapedring. Looking
the gastodensity
plot, we see
Comparing
this
with
our
control
case
of
a
gas
only
disc
we
show
that
that the gas phase itself has become unstable exterior to the planet.
the additionof dustcanhaveoura significant
eﬀect
howonlypronediscthe disc
Comparing
thiswithcontrol case
ofon
a gas
we show that
can the
be to
the
RWI.
Surprisingly,
the
cause
of
the
RWI
in
this
case
is the discaddition of dust can have a significant eﬀect on how prone
not duenear
the gap edgesthebutcause
due toof
thethesharp
peak
can tobethe
togradient
the RWI.
Surprisingly,
RWI
in in
this case is
the outer ring. This is to say that the dust phase has triggered the RWI
not due to the gradient near the gap edges but due to the sharp peak in
due to the contribution of the sharp dust density peak accumulating
the outer ring. This is to say that the dust phase has triggered the RWI
in the middle of the gas ring that forms in the outer pressure bumpto thethe region
contributionof thesharpgenerating
dust density
peakwhichaccumulating
and duecausesto becomeunstable,vorticesthe middle
ringin thethe
outer
bump
are invisiblein both ofthethedustgasandthethatgas forms
even thoughdiscpressure
onlyandcausestheregiontobecomeunstable,
generating
vorticeswhich
comprises of 1% dust.
are visible
in we
both
dust
gas even
thoughFrom
our data,
findthethattheandRWIthetriggers
at around
C =the78disc only
orbits.
Therefore
comprises
ofwe
1%analyse
dust. and present the next figures from thedata atFrom
C = 70which
we C = 78
our data, iswebefore
find thethatinstability
the RWI triggers.
triggers Firsly
at aroundpresent
the Therefore
azimuthallywe
averageddensitiesthe
fornext
the dust
and from theorbits.
analysesurface
and present
figuresgas data
in Fig.at12.
We
note
that
the
sharp
dust
peak
in
the
density
profileC = 70 which is before the instability triggers. Firsly weof the disc at C = 70 reaches a value that is below 1:3 for the dust topresent the azimuthally averaged surface densities for the dust andgas ratio at the outer pressure bump compared to the wide dust bumpgas in Fig. 12. We note that the sharp dust peak in the density profile
build-up for the higher dust fraction case, 5d = 0.2, which reachedof tothegasdisc
at of
C =around
70 reaches
a value thatweispoint
below
a dustratio
1:2. Additionallyout1:3
thatforthethe dust to
gas ratio
at the outerpressurebump
compared
tothe
thepeak
wideofdust bumpmaximum
azimuthally
averagedtotal
densityvalue fortheincreased
higher dust
= 0.2,
which
the build-up
outer ringfor
in thedustfraction
fraction case,
case is5dlarger
than
this reachedto gasStokes
ratio number.
of around
Additionally
we point out
caseaofdust
a higher
This1:2.
indicatesthat the amplitudeof that thethe extremum
the total density
profile is
lessdensity
indicativeof thefor
RWI
maximuminazimuthally
averaged
total
value
the peak oftriggering
comparedtheincreased
width of theextremumshown than thisthe outerring intothe
dust
fractionwhichcase is larger
as acase
sharpofpeak
inthehigher
Stokesnumbercase.
a higher Stokes number. This indicates that the amplitude of
Inthe
Fig.
13
we present
thetotal"mixed"key profile
functionisplots
the higher
extremumin thedensityless forindicativeof the RWI
Stokesnumber
case
at
C
=
70.
Firstly
we
point
out
that
are is shown
triggering compared to the width of the extremumthere
which
sharp lines at the planets location and the inner minimum at aroundas a sharp peak in the higher Stokes number case.
A = 0.87A p that are temporary (lasting one or two timesteps) and we
In Fig. 13 we present the "mixed" key function plots for the higher
believe are due to the dust and gas phase interacting more erratically• dustはピークを持っているが、RWIをトリガーしているわけではない。

• key function plotでr=1.17rpに注目。これは、ダストがエントロピーを下げているから。

• まとめ：St=0.2くらい大きいときにのみ、dustの顕Figure 10. Density plots for dust (top left), gas (top right) and total (bottom) of
the Neptune planet embedded disc with dust fraction, 5d = 0.01 and Stokes
number, St = 0.2. The evolution of the disc is at C = 60 orbits. We see asmooth thin dust ring has accumulated exterior to the planet and the features
are currently stable.

Figure 11. Density plots for dust (top left), gas (top right) and total (bottom)of the Neptune planet embedded disc with dust fraction, 5d = 0.01 and Stokes
number, St = 0.2. The evolution of the disc is at C = 100 orbits. The dust ringhas triggered the RWI at the rings location and generated vortices which also
aﬀect the gas phase and not at the gap edge as previous cases.

Figure 13. Radial profile of the azimuthally averaged "mixed" key functionof a dust and gas disc (blue line) compared to gas key function for a gas only
disc (dashed orange line) (top plot) and 2D key function plot (bottom) for adust 13.
and Radial
gas discprofile
with Neptune
sized planet embedded
at 1Ap after= 70
Figureof the azimuthally
averaged "mixed"
keyC function
orbits. The dust fraction is set to 5d = 0.01, Stokes number, St = 0.2 andof a dust and gas disc (blue line) 7compared to gas key function for a gas only
kinematic viscosity, a = 5 ⇥ 10 . The radial profile shows a sharp minimum
discat(dashedorange line) (top plot) and 2D key function plot (bottom) for a
the dust ring’s location and indicates that the width of the extremum is anafter C = 70
dustimportantand gas factor
disc withplanetembeddedat the1ApRWI.
whichNeptune
indicatessized
locationof regions
prone toorbits. The dust fraction is set to 5d = 0.01, Stokes number, St = 0.2 andkinematic viscosity, a = 5 ⇥ 10 7 . The radial profile shows a sharp minimumat the dust ring’s location and indicates that the width of the extremum is an

著な影響が出る。このときは外側のdust ringをぶっ壊しそう。

y remove thevaluating thet (top of Fig.
ave been seen
ction locatedction, the gap
only case andnd at the gap
hich is instead
mum does not
gas only disc.
he build up offunction. We
ma at the gap
width of theore indicative
he ampltiude
gger. The 2D
he location of
the gas only
Additionally,
at C = 100 in
erated by thethe material
nalysis of the
discussed in

不安定の成長(skip)−7
𝑓𝑑 = 0.01, St = 0.2,
𝜈
=
5
×
10
. で、azimuthal
Fouriercomponentsを見る。
12
K . Chan and
S-J . Paardekooper
Dusty Ring Stability 11
dust

gas

• r=1.2rpで発展。
• dust: t=80のときは、m=2,3,5が
m=1,4より早く発展。

• gas: 弱いが、ｔ＝80でm=2,3が成長。

gaseous discbut only for
I is triggereds that disrupt
ations for thehology as wering location,
possible plancation further

isc can causeof the perturmodes in gas

uthal Fourier

Figure 15. Time evolution of the Fourier amplitudes of modes, < = 0 to
5, for the dust in a Neptune planet embedded dusty disc with dust fraction
5 3 = 0.01, Stokes number, (C = 0.2 and a = 5 ⇥ 10 7 . The growth of theFourier amplitudes at A/A ? = 1.2 dominates where the location of the thin
dusty ring is formed and triggers the RWI.

2 and 3 we can see limited growth in the region between the outer

Figure 16. Time evolution of the Fourier amplitudes of modes, < = 0 to 5, forthe gas in a Neptune planet embedded dusty disc with dust fraction 5 3 = 0.01,
St = 0.2 and a = 5 ⇥ 10 7 . The evolution of the Fourier amplitudes for allmodes show little variance in the region of the dusty ring location until C = 80
when the RWI is triggered, growing in amplitude from the outer gap edge anddusty ring location.

Figure 17. Time evolution of the Fourier amplitudes of modes, < = 0 to 5
for the gas in a Neptune planet embedded gaseous disc with a = 1 ⇥ 10 6 .
In this disc, the gas is stable up to C = 100, showing no features of instability
growth in the outer pressure bump.

we wanted to test a case where both the dust fraction of the disc andStokes number are increased to 0.1, which is lower in Stokes number

dust fractionが高い場合
skip

Dusty Ring Stability

13• dustの内側になみなみ構造

Figure 19. Density plots for dust (top left), gas (top right) and total (bottom)of the Neptune planet embedded disc with dust fraction, 5d = 0.1 and Stokes
number, St = 0.1. The evolution of the disc is at C = 50 orbits. The dust ring
formed exterior to the planet is smooth with vortices starting to be generated
in the gap that the Neptune planet has carved for the dust phase which aﬀects
the gas phase and total density with weak spiral arms being launched throughthe disc.

Dusty Ring Stability

長時間進化
𝑓d =0.01,St=0.2and𝜈=5×10−7.

17• gas onlyに比べ、密度プロットに渦が強く出る、かつdusty
Dusty Ring Stability
17
な渦は壊れてまた再生産を繰り返す。（ガスの場合は一つの大きな渦に収束する）• できた渦がr=1.16rpから

Figure 27. Total density plots for region exterior to a Neptune planet that isembedded in a dust and gas disc with dust fraction, 5d = 0.01, Stokes number,
St = 0.2 and kinematic viscosity, a = 5 ⇥ 10 7. The plots shown are the time
evolution of the disc, C 2 [50, 100, 200, 300, 400, 500].

from the dusty ring triggering the RWI would smooth out the density
extremum. In this subsection we evolve the disc to 500 orbits in thefirst figure and consider the evolution of the vortices generated, thedusty ring and future implications for the disc as a whole with thesecond figure with evolution of the disc up to 1500 orbits.
In Fig. 27 we present the evolution of the total density of theouter region of the planet up to 500 orbits with the previous setupof 5d = 0.01, St = 0.2 and a = 5 ⇥ 10 7 . As previously seen up to
100 orbits, the dusty ring that is accumulated in the pressure bumptriggers the RWI and the smooth ring is distorted around the disc. The
vortices at the dusty ring’s location start to accumulate material fromthe ring and the surroundings towards the centre of the vortex which
is highlighted further in the middle left plot of C = 200 where vortices
can be seen to have a considerable amount of material accumulated
and the dusty ring is now fainter. From the next evolution plot of
C = 300, two of the vortices have merged into one, where we cansee now five vortices in the outer region of the planet. Compared
to a gas-only RWI, the vortices appear much stronger in density
because of dust accumulation. Another diﬀerence is that the dusty
vortices are continuously destroyed and regenerated. This is diﬀerent
to typical unstable gas-only disc cases (e.g. rightmost panel in Fig.
1) where the vortices tend to merge into a larger vortex within an
earlier timescale. From these initial plots we see that the vortices
generated by the dusty RWI exterior to a planet could in principle belocations of planetesimalformation as they are able to accumulatedmaterial which radially averaged density values exceeds unity of thedust to gas ratio. In the radial profiles which are not presented we seethat the vortices accumulate dust close to 3-4 times the gas density
at that radial location after the 500 orbits. Observationally, the dust
ring itself will at this point be much harder to see as the vortices
accumulate all the material.
An important feature shown in the evolution of the disc is thatthe dusty ring which started at around A = 1.16A p is distorted by thegenerated vortices and moved outwards from C = 50 to C = 100. Further evolution shows that the vortices which have accumulated thematerial start to migrate outwards as after 500 orbits, the radial location of the vortices generated and the material accumulated reachFigure 27. Total density plots for region exterior to a Neptune planet that isembedded in a dust and gas disc with dust fraction, 5 = 0.01, Stokes number,
St = 0.2 and kinematic viscosity, a = 5 ⇥ 10 7. The plots shown are the time
evolution of the disc, C 2 [50, 100, 200, 300, 400, 500].

from the dusty ring triggering the RWI would smooth out the density
extremum. In this subsection we evolve the disc to 500 orbits in the

1.24rpまで外側に動くことにも注目(Paardekooper et al.
2010)• t=1000,1500までいくと、ダストリングがあるが、gas
profileはもはやflatになっている。
Figure 28. Total density plots for the disc at C = 1000 (top) and C = 1500
(bottom) with dust fraction, 5d = 0.01, Stokes number, St = 0.2 and kinematic
viscosity, a = 5 ⇥ 10 7. A secondary wider dusty ring is shown to be forming
exterior to the locations of the vortices which have merged into three distinct
points.

. The observation of small scale structures in a protoplanetary disc have been
limited and the origin of the small scale structures observed is unclear. For
example in Tsukagoshi et al. (2019), they report an AU-scale dust clump which
they hypothesise to be material accumulating in a vortex or a massive
circumplanetary disc around a Neptune sized planet embedded in a disc. In the
future we hope advances would lead to better resolved small scale substructures tostudy their origins.

sity waves launched the vortices can cause a net exchange of angularmomentum which leads to the migration of the vortices. In the studyof the gas only case, vortices move to regions of higher gas pressure
and in our results we see that the dusty vortices migrate towards thepressure maxima in the outer pressure bump which is shifted outwards during the evolution of the disc, which occurs in our gas only
disc as well with the planet carving a gap. Therefore, vortices as wellas the remnants of the dust ring end up at the pressure maximum, thelatter through usual radial drift.
Evolution of the disc up to 1500 orbits is presented in Fig. 28
where we present the density plots at C = 1000, 1500. Comparing
the evolution between C = 500 from the previous figure and 1000 we
see that a dusty ring is accumulating exterior to the radial locationof the vortices. We note that this is a diﬀerent ring to the original
dusty ring that has gathered into the vortices. This is more clearly

JWST/NIRCam Imaging of Young Stellar Objects. II. Deep Constraints on Giant Planets and aPlanet Candidate Outside of the Spiral Disk Around SAO 206462
Gabriele Cugno et al.
We present JWST/NIRCam F187N, F200W, F405N and F410M direct imaging
data of the disk surrounding SAO 206462. Previous images show a very
structured disk, with a pair of spiral arms thought to be launched by one or more
external perturbers. The spiral features are visible in three of the four filters, with
the non-detection in F410M due to the large detector saturation radius. We detectwith a signal-to-noise ratio of 4.4 a companion candidate (CC1) that, if on a
coplanar circular orbit, would orbit SAO 206462 at a separation of ∼ 300 au,
2.25σ away from the predicted separation for the driver of the eastern spiral.
According to the BEX models, CC1 has a mass of MCC1 = 0.8 ± 0.3 MJ. No
other companion candidates were detected. At the location predicted bysimulations of both spirals generated by a single massive companion, the NIRCamdata exclude objects more massive than ∼ 2.2 MJ assuming the BEX evolutionarymodels. In terms of temperatures, the data are sensitive to objects with Teff ∼650−850 K, when assuming planets emit like blackbodies (Rp between 1 and
3RJ). From these results, we conclude that if the spirals are driven by gas giants,
these must be either cold or embedded in circumplanetary material. In addition,
the NIRCam data provide tight constraints on ongoing accretion processes. In the
low extinction scenario we are sensitive to mass accretion rates of the order Ṁ ∼10−9MJ yr−1. Thanks to the longer wavelengths used to search for emission lines,
we reach unprecedented sensitivities to processes with Ṁ ∼ 10−7MJ yr−1 eventowards highly extincted environments (AV ≈ 50 mag).

• SAO 206462 (Muto-spiral円盤)のJWST/NIRCamの観測• もしspiralが惑星起因なら、あんまり温度が高くないことがわかった6

ows cast on the transition disk of HD 135344B

015). Fore forward
ain radiusmultipler. A hardquired to

N
E

Ma

jor

S1

axi

S3

s

Blob
Kink

S2

0.2"≃ 28 au

no
ra
xis

Bright wedgeMied surface
ent aroundd from thecavity, theuter radius

Far side

striped pattern

Near side

Fig. 4. Color composite RGB image of ZIMPOL R-band (blue),
ZIMPOL I-band (red), and the average of R and I-band (green). The
field of view is 1.00 4 ⇥ 1.00 4 and the main features that have been identified
are labeled.

Stolker et al. 2016, SPHEREa position angle (east of north) of ⇠80 and spiral arm S2 at

Figure 1. SAO 206462 residuals in the four filters observed with our program. The central masks have radii of 0.00 3 in F187N,
F200W and F405N, and 0.00 8 in F410M. In all images North points to the top, East to the left and the field of view is the same.
The colorscale has been adapted based on the strength of the disk signal.

to 1.00 0 in order to focus only on the central region of the
PSF. The P330-E spectrum has been taken from Rieke
et al., submitted to AJ.

This is due to the strong saturation in the image corethat made the inspection ofThis
the innerregionsJWST
not feasiwork,
ble. Due to the two-rolls PSF removal strategy, a considerable fraction of the disk intensity is lost in the PSF

0.1

0.3

0.5
0.7
radius[asec]

0.9

1.1

Figure 3. Top: azimuthal SB profile at r = 0.!! 5 (left) and r = 0.!! 7 (right) with PA measured from north to east. Bottom: radial profile alongerrors indicate the FWHM of the PSF. SB errors are estimated using frame-by-frame deviations.

予期された惑星の場所

Xie et al. 2021, Muto et al. 2012
The Astrophysical Journal Letters, 906:L9 (7pp), 2021 January 10

Xie et al.

Figure 1. r2-scaled  f images of the SAO 206462 system on (a) 2015 May 3 and (b) 2016 May 4. The central dashed circles are the physical size of the coronagraphs,
the cross is the location of the star, the longer side of the cross matches the major axis of the disk. Note: the color bars share the same units; θ and r are measured in thedisk plane; the dotted lines are the boundaries for motion measurement in Figure 2.
(The data used to create this ﬁgure are available.)The
AstrophysicalJournal906:L9in(7pp),
20213,January
10 thein Section
2, analyze
the Letters,
observations
Sectiondiscussﬁndings in Section 4, and summarize this Letter in Section 5.
2. Observations and Data Reduction

Xiewe
et al.
arm location measurement. In the interpolation procedure,
adopt the physically motivated cubic splines, which minimize
the elastic energy for a system (Horn 1983), implemented in
the scipy.interpolate.interp2d function in scipy(Virtanen et al. 2020).

We obtain the SPHERE/IRDIS J-band dual-polarization
imaging observations of SAO 206462 in polarized light presented
3. Analysis
in Stolker et al. (2016a, 2017). There is one observation in 2015
May, and four observations between 2016 May and 2016 June,
We use the two observations on 2015 May 3 and 2016 May 4
establishing a 14 month temporal baseline for motion measurethat provide a temporal separation of 1.00 yr with the highest data
ment. The 2015 observation uses apodizer APO1 (optimized for
quality for analysis. The exposure times of the rest of the
4λ/D focal masks), and Lyot mask ALC1 (diameter: 145 mas;observations are 17 or 34 minutes (Stolker et al. 2017), which arecoronagraph combination name: N_ALC_YJ_S); the 2016 obsera factor of more than twice shorter and thus provide compromised
vations use apodizer APO1 and Lyot mask ALC2 (diameter:
data quality. In addition, the three shorter observations constitute a
185 mas; N_ALC_YJH_S). In all observations, the pixel scale istemporal separation of less than 50 days, which provide a shorter
12.25 mas (Maire et al. 2016); the detector integration time is 32 s
timeline for spiral motion. We discuss the contribution of theseper frame. The total integration time spans from 17 to 102 minutes,
three short observations in Section 4.2.
with the 2015 May 3 and 2016 May 4 observations being the twolongest integrations (76.8 minutes and 102.4 minutes, respectively;
3.1. Spiral Locationsee Stolker et al. 2017 for the observation log).
We measure the spiral locations after transforming the
We reduce the ﬁve observations using IRDAP (van Holstein
deprojected r2-scaled  f images into polar coordinates, where
et al. 2020) with identical default parameters to minimize
the horizontal axis is the counterclockwise angular deviation θsystematic offset, and analyze the output star-polarizationfrom the northwest semiminor axis of the disk, and the verticalsubtracted  f ﬁles that trace the surface distribution of dust
Figure 3. The best-ﬁt ±1σ orbits for assumed planetary drivers with circular orbits overlaid on ALMA contours (1.9 mm; Cazzoletti et al. 2018) and r2-scaled
particles(Monnieretal.
2019).
To
minimizestellarillumination
SPHERE  f image (1.2 μm). (a) Double-driver scenario. (b) Single-driver scenario. axis is the stellocentric distance r. For each θ, we ﬁt a Gaussian
proﬁle to its radial proﬁle with scipy.optimize.curve_
effects, we follow the Ren et al. (2020) procedure to scale the  fﬁt to obtain the peak location r with an error6 of δr.
images: we ﬁrst compute the stellocentric distance, r, for eachindividual
pairs,
randomly discard
20%
andat When
0.1 au.weNonetheless,cannotproperly
2 , where
inspect the weradialproﬁles
for thedecompose
θ values, thesewe f value(r ther0 )pairs
pixel and data
multiplyitswe
correspondingbyof
4
effects
until
time
seriesmonitoringofthesystemisavailable.
2 analysis procedure 10 times. We ﬁnd that
repeatthemotionnotice multiple peaks or ﬂat plateau in some regions in the S2
r0 = 0 5 (i.e., “r -scaled”), assuming an inclination of 11° fromfor
S1, thebest-ﬁtrotation
rate
forforthethedriverisaxis1°. of
32 the± 0°. 07
spiral, which is indicative of resolved and unresolved subface-on,
andaposition
angle
of
62°
major
disk
−1
−1
, 0°et. 38al.±2005;
0°. 06 Pérez
yr−1 etforal.S2,
andWe
0°. 57± 0°. 04foryr(Dent
Motion their potential
spirals; we ignore 4.3.
theseIndependent
points to minimize2014).
present
the yrr2-scaled
comotion;
withinfrom
our initial
measurements.
impact for location and subsequent speed measurement. See
2015 Mayall
3 and20161σMay
4 imagesin Figure1 and annotate the
For the S1 arm, its motion is consistent with being driven by
We have
only Maire
used etthe
two observations
thatsethavethe
Figure 2 for the (θ, r ± δr) measurements used for subsequentfeaturesfollowingal. (2017).
For a completeof all the

Figure 4. Left: red and green points indicate the locations of the maxima of radial profiles for S1 (top) and S2 (bottom). The green ones a
Equation (1) (Section 4). Dashed lines indicate circles with r = 0.!! 39 (top) and r = 0.!! 3 (bottom). Right: the spiral shape given by Equaparameters of S1 (top) and S2 (bottom). Crosses show the locations of (rc , θ0 ).

7
To include the requirement that the contaminantshouldbe unresolved, we can take the e↵ective radius re of eachsource and convolve it with the FWHM of the F410M
PSF (seeq Table 2. In practical terms, we verify that theterm re2 + FWHM2F410M is smaller than a thresholdthat we set to 1.5FWHMF410M . This reduces the probability of the contaminant scenario to ⇠ 4.2% (galacticand extragalactic). Follow-up observations in future cycles will help determining the true nature of CC1.
5.2. Sensitivity limits

To estimate the contrast limits we used applefy(Bonse et al. 2023), a python package that estimates
contrast
curvesby injecting
artificial
sources in the data
Figure 2. F410M residuals highlighting the companion candidate to SAO 206462.
Left:
Residualsof the F410M
data, similar
Figure 4. NIRCam 5 flux sensitivity limits for SAO 206462
to Fig. 1. In this instance we applied a larger central mask to force the PCAintosteps
focus onregion of thearound
⇠ 1.00 9. at each sepaof the
1 FWHM(seeimage
Table2), where
The data reveals a point source in the NW region of the image. North points to the top, East to the left. Center: Zoomed-in
as a function of separation. The dashed vertical line repration
we
inspected
6
di↵erent
azimuthalpositions.
We
portion of the image, highlighting the candidate. The negative-positive-negative pattern, indicative of a point source with the
resents the size of the scattered light disk observed in oursetthedetection
threshold
to
a
False
Positive
Fraction
JWST two-rolls observing strategy is clearly visible. Right: Same portion of the residuals as in the central panel, but the CC1
data, while the gray shaded area highlights the area around7
pattern was removed injecting one single negative PSF in the data, demonstrating
thecorrelation
betweenthenegative
andthe(FPF) of 2.87 ⇥ 10 , corresponding to 5 in the case
120 ± 30 au where Xie et al. (2021) predicted a planet could
positive components of the signal.
of Gaussian noise. The noise was estimated as individbe located. The green square represents the measured flux
11 consider
the central
signal, and by
being
able toachieved with Reference Di↵erential Imaging via synual positive
pixels separated
1 FWHM(Bonse et al. 2023).
for CC1 in the F410M filter detected with a confidence ofthe correlated
symmetric
patternthe
wouldcertainly
thetic PSFs (see Greenbaum et al. 2023).
⇠ 3.8 . On the left (right) side of the plot, we marked the
To takeinto accountspecklesfieldproin the residuals,
vide a higher confidence. Note that even though other
The inspection of the residuals at larger separations
flux expected in the SW (LW) filters for a 1,2 and 5 MJ obat each separation the noise configuration was measured
regions in the image have similar brightness (in particreveal a companion candidate in F410M that we will disject at ⇠ 12 Myr according to the BEX evolutionary model.
360
di↵erent
times,eachwithslightlydi↵erent
angularular above the North-East edge of the central mask),
cuss in Sect. 5.1. No other point-like signal is detected inusing theobtainedfor the con- CC1というクランプを検出。0.8
they areorientation,
part of an extended
diagonal
noisemedianfeature value
rethe images at any separation, in particular closer to the
0.3 MJ.
•
trastPSF
andspiders
the standard
deviationas an uncertainty on
sulting fromresiduals andare not physicalspirals, and in Sect. 5.2 and 5.3 we present the detection
at larger separation the data are background limited.
sources the(see contrast
Fig 7, where
we masked out the extended
limits achieved by our observations.
measurement.
Conversely, F200W images are contrast limited at ev予期された位置に惑星は見られず。
feature). In
App.
B we
providesaturation
examples ofininjected
•
Due
to
the
centralourimages,weused
5.1. A companion candidate at large separations
ery separation, and the sensitivity limit of the filter issources atthe sameas CC1
and3)
with
PSFs
fromseparation
P330-E (seeSect.
to similar
inject fake companAt large separations the residuals in the F410M imintensity, but at di↵erent position angles. In most cases
expected to be almost two orders of magnitude lower
ions.
This
choiceprevents
usfromobtaining
contrast
00
For
the
BEX models, our limits•
ages revealed a companion candidate at ⇠ 2. 2 from thethe injected sources indeed look very similar to CC1 inthan what we achieve at large separations. In the LW
estimates
comparedtothecentralstar,
butguarantees
star that we designate CC1. The candidate is best visiFig. 2.
00 than 2.2+0.5 M
excludeaplanetmore
massivechannel,
F405N
is
more
sensitive<
0.
9, while at larger
anaccurate
photometriccalibrationof
ourlimits.
Inble when using a larger mask to cover the central region
To characterize the companion candidate, we adapted
separation F410M could detect fainter sources. Indeed,of the images, allowing the principal components to fodeed,used
the incontrast
estimatedwithrespectthe methods
Stolker etal. (2020b)
to the
NIR- to the P330-E ­0.9 J
Figure 5. Mass and temperature limits of SAO 206462 as a function of separation obtained from the 5 flux limits. The
at short separations the e↵ect of saturation and its concus on dashedremoving
the PSF pattern at large separations.
Cam
data
structure
determine
three
sepPSF
betodirectly
combinedwith theflux of the stan- could
vertical line represents the size of spirals in scattered light andthe shaded
areacanhighlights
the predicted
planetparameters:
location
be locatedat ~ 120 au.
Inand
terms
of
temperasequenceslikethebrighter-fattere↵ectchargemiIn Fig.from
2 wethe residuals
using
a central
Xiereport
et al. (2021).
Left: Mass whenupper limit
whenusing the BEX cooling
curve
for
the
age
of
the
system.
The
uncertainties,
aration,positionangle
andcontrast.
Briefly,
we
used
dard
star
(20.17,21.23,
5.81
and 5.84 mJy for F187N,
00
represented
bytheshadedarea,
includetheageuncertainties
ofthesystem
(6
16
Myr).
The
estimated
mass
of
CC1
is
showedmask of 1. 9 arcsec (left panel) and a zoom-in on the
an MCMC algorithm to explore the parameter spacegrationan importantrole inwarmer
limiting ourthansensitivity
tures,
we playexcludeobjects
660­810 K
F200W,
andF410M,
inorder
toas a black square. At ⇠ 120 au, the NIRCam data exclude planets with masses& 2.2 MJF405N. Right: E↵ective
temperaturerespectively)
5
area of upperinterest(central panel). Despite several speckles
with1, 200
in F410M. Both LW filters are far away from being backlimits when assuming protoplanets emit as blackbodies with radii
2, andwalkers
3 RJ . performing a chain of 400 steps each.
haveacalibrated
flux
limit.
(1­
3
RJ).
having similar strengths as CC1, the negative-positiveAt each step, artificial negative copies of the PSF (obground limited, even at large separations.
constraints
on the possible
planetlonger wavelength
observations
might
be able weto trace
Following
thisprocedure
estimated
the5
contrast
negative
pattern expected
for a temperaturepoint sourceofinthe
observatained from the P330-E data) were inserted in the dataaround SAO 206462. Cold-start models predict smaller
colder temperatures and reveal the light reprocessed by
We used the same evolutionary models from Sect. 5.1

two flare events in TESS sector 43 data for this BD and estimated the flared energies as 4.59 ⇥ 10
erg, which sit in the superflare range.

erg and 2.64 ⇥ 10

TIPSY: Trajectory of Infalling Particles in Streamers around Young stars. Dynamical
analysis of the streamers around S CrA and HL Tau

Aashish Gupta, Anna Miotello, Jonathan P. Williams, Til Birnstiel, Michael Kuﬀmeier, Hsi-Wei Yen F Context.

Elongated trails of infalling gas, often referred to as "streamers," have recently been observed around young stellar
objects (YSOs) at diﬀerent evolutionary stages. This asymmetric infall of material can significantly alter star andplanet formation processes, especially in the more evolved YSOs. Aims. In order to ascertain the infalling nature ofobserved streamer-like structures and then systematically characterize their dynamics, we developed the code TIPSY(Trajectory of Infalling Particles in Streamers around Young stars). Methods. Using TIPSY, the streamer molecularline emission is first isolated from the disk emission. Then the streamer emission, which is eﬀectively a point cloudin three-dimensional (3D) position-position-velocity space, is simplified to a curve-like representation. The observed
streamer curve is then compared to the theoretical trajectories of infalling material. The best-fit trajectories are used
to constrain streamer features, such as the specific energy, the specific angular momenta, the infall timescale, andthe 3D morphology. Results. We used TIPSY to fit molecular-line ALMA observations of streamers around a Class
II binary system, S CrA, and a Class I/II protostar, HL Tau. Our results indicate that both of the streamers are
consistent with infalling motion. TIPSY results and mass estimates suggest that S CrA and HL Tau are accreting
material at a rate of & 27 Mjupiter Myr 1 and & 5 Mjupiter Myr 1 , respectively, which can significantly increase
the mass budget available to form planets. Conclusions. TIPSY can be used to assess whether the morphology andkinematics of observed streamers are consistent with infalling motion and to characterize their dynamics, which is
crucial for quantifying their impact on the protostellar systems.

11Aashish Gupta et al.: TIPSY: Trajectory of Infalling Particles in Streamers around Young stars• Streamer天体のPPVから 軌跡をも

a)

とめる。
b)

c)

• これを理論線とフィットする。基本
Intensity-weighted means

的には初期速度を与え、自由落下した？っぽい。

Aashish Gupta et al.: TIPSY: Trajectory of Infalling Pa

Table
streamLine of sightDecl.

• S CrA 13CO2-1
e)

𝜙

d)
Best Fit

Best Fit

•

𝜽
R.A.

See

Fig. 2: Flow of S CrA 13 CO (2–1) data in the TIPSY pipeline. Panel a: Intensity-weighted velocity (moment 1) map in colors,
overlaid with contours representing the integrated intensity (moment 0; see Fig. E.1). The red segments in the bottom-left corners
depict a length scale of 1,000 au. The pink ellipses in the bottom-right corners depicts the beam size of the data. Panel b: Isometricprojection of the 3D PPV diagram of pixels with intensity > 5 in the whole field of view. Panel c: Isometric projection of the
PPV diagram of an isolated and cleaned streamer. The red square and its error bars represent intensity-weighted means and standard
deviations, respectively. Panel d: Same as Panel c, but with the best-fit trajectory, as represented by the black line. Black circles
denote the interpolated values of the theoretical trajectory, which are directly compared to the intensity-weighted means. Panel e:
Same as Panel b, but with the best-fit trajectory, as represented by the black line. Note: 3D interactive versions of panels d and e areavailable online.
Article number, page 5 of 14

Fig. 1: Schematic diagram of coordinate axes used to computethe theoretical trajectories of infalling gas (green cloud) arounda protostellar system (orange star), as discussed in Sect. 2.1. !
r0!
and v0 denote the initial position and velocity vector of infallinggas, respectively. !
r represents the position vector of gas at a future point in its trajectory (circumference of blue ellipse), with ✓and denoting the polar and azimuthal angles, respectively. The
dashed red arrows show the unit vectors x̂, ŷ, and ẑ, defined using the directions of !
r0 and !
v0 . Together they set the coordinate
frame in which TIPSY solves the Mendoza et al. (2009) equations. The gray plane represents the POS, with the overlaid darkgray arrows denoting the coordinate frame of our observations.

sourcepholowhichlines ually excube tand R
low a
selectlectedthe finlimitsemiss
more

A&A proofs: manuscript no. 48007corra)• HL Taub)c)Intensity-weighted means• どちらの天体も基本的にはinfall• TIPSY results and mass estimatese)d)Best Fit

Best Fit

Fig. 3: Same procedure as described in Figure 2, but for HL Tau instead of S CrA. Note: 3D interactive versions of panels d and e
are available online.
tems can be approximated as a point source and the gas density

should mostly be valid for low-density streamers; for stream-suggest that S CrA and HL Tau areaccreting material at a rate of 27
Mjupiter Myr­1 and 5 MjupiterMyr­1, respectively, which cansignificantly increase the mass budget
available to form planets.
https://github.com/AashishGpta/TIPSYstructure and provided an empirical basis for future studies that address the angular momentum problem with astatistically broad sample.

JWST/NIRCam Imaging of Young Stellar Objects. II. Deep Constraints on Giant
Planets and a Planet Candidate Outside of the Spiral Disk Around SAO 206462

Gabriele Cugno, Jarron Leisenring, Kevin R. Wagner, Camryn Mullin, Roubing Dong, Thomas Greene, Doug
Johnstone, Michael R. Meyer, Schuyler G. Wolﬀ, Charles Beichman, Martha Boyer, Scott Horner, Klaus
Hodapp, Doug Kelly, Don McCarthy, Thomas Roellig, George Rieke, Marcia Rieke, John Stansberry, Erick
Young F We present JWST/NIRCam F187N, F200W, F405N and F410M direct imaging data of the disk surrounding

SAO 206462. Previous images show a very structured disk, with a pair of spiral arms thought to be launched by one ormore external perturbers. The spiral features are visible in three of the four filters, with the non-detection in F410M
due to the large detector saturation radius. We detect with a signal-to-noise ratio of 4.4 a companion candidate (CC1)that, if on a coplanar circular orbit, would orbit SAO 206462 at a separation of ⇠ 300 au, 2.25 away from the predicted
separation for the driver of the eastern spiral. According to the BEX models, CC1 has a mass of MCC1 = 0.8 ± 0.3 MJ .
No other companion candidates were detected. At the location predicted by simulations of both spirals generated
by a single massive companion, the NIRCam data exclude objects more massive than ⇠ 2.2 MJ assuming the BEX
evolutionary models. In terms of temperatures, the data are sensitive to objects with Teﬀ ⇠ 650 850 K, whenassuming planets emit like blackbodies (Rp between 1 and 3RJ ). From these results, we conclude that if the spirals
are driven by gas giants, these must be either cold or embedded in circumplanetary material. In addition, the NIRCamdata provide tight constraints on ongoing accretion processes. In the low extinction scenario we are sensitive to massaccretion rates of the order Ṁ ⇠ 10 9 MJ yr 1 . Thanks to the longer wavelengths used to search for emission lines,
we reach unprecedented sensitivities to processes with Ṁ ⇠ 10 7 MJ yr 1 even towards highly extincted environments(AV ⇡ 50 mag).

Stability of Dusty Rings in Protoplanetary Discs

Kevin Chan, Sijme-Jan Paardekooper F Dust rings in protoplanetary discs are often observed in thermal dust

emission and could be favourable environments for planet formation. While dust rings readily form in gas pressure
maxima, their long-term stability is key to both their observability and potential to assist in planet formation. We
investigate the stability of the dust ring generated by interactions of a protoplanetary disc with a Neptune sized planetand consider its possible long term evolution using the FARGO3D Multifluid code. We look at the onset of the Rossby
Wave Instability (RWI) and compare how the addition of dust in a disc can alter the stability of the gas phase. We findthat with the addition of dust, the rings generated by planet disc interactions are more prone to RWI and can cause
the gas phase to become unstable. The instability is shown to occur more easily for higher Stokes number dust, as itaccretion rates of the order Ṁ ⇠ 10 MJ yr . Thanks to the longer wavelengths used to search for emission lines,
we reach unprecedented sensitivities to processes with Ṁ ⇠ 10 7 MJ yr 1 even towards highly extincted environments(AV ⇡ 50 mag).

Stability of Dusty Rings in Protoplanetary Discs

Kevin Chan, Sijme-Jan Paardekooper F Dust rings in protoplanetary discs are often observed in thermal dust

emission and could be favourable environments for planet formation. While dust rings readily form in gas pressure
maxima, their long-term stability is key to both their observability and potential to assist in planet formation. We
investigate the stability of the dust ring generated by interactions of a protoplanetary disc with a Neptune sized planetand consider its possible long term evolution using the FARGO3D Multifluid code. We look at the onset of the Rossby
Wave Instability (RWI) and compare how the addition of dust in a disc can alter the stability of the gas phase. We findthat with the addition of dust, the rings generated by planet disc interactions are more prone to RWI and can cause
the gas phase to become unstable. The instability is shown to occur more easily for higher Stokes number dust, as it
accumulates into a more narrow ring which triggers the RWI, while the initial dust fraction plays a more minor role inthe stability properties. We show that the dusty RWI generates vortices that collect dust in their cores, which could
be sites for further planetesimal formation. We conclude that the addition of dust can cause a ring in a protoplanetary
disc to become more prone to instability leading to a diﬀerent long term evolution compared to gas only simulationsof the RWI.

7

The GRAVITY young stellar object survey XIII. Tracing the time-variable asymmetricdisk structure in the inner AU of the Herbig star HD98922

V. Ganci, GRAVITY Collaboration F Temporal variability in the photometric and spectroscopic properties ofprotoplanetary disks is common in YSO. However, evidence pointing toward changes in their morphology over shorttimescales has only been found for a few sources, mainly due to a lack of high cadence observations at mas resolution.
We combine GRAVITY multi-epoch observations of HD98922 at mas resolution with PIONIER archival data coveringa total time span of 11 years. We interpret the interferometric visibilities and spectral energy distribution withgeometrical models and through radiative transfer techniques. We investigated high-spectral-resolution quantities toobtain information on the properties of the HI BrG-line-emitting region. The observations are best fitted by a modelof a crescent-like asymmetric dust feature located at 1 au and accounting for 70% of the NIR emission. The feature hasan almost constant magnitude and orbits the central star with a possible sub-Keplerian period of 12 months, althougha 9 month period is another, albeit less probable, solution. The radiative transfer models show that the emission
originates from a small amount of carbon-rich (25%) silicates, or quantum-heated particles located in a low-density
region. Among diﬀerent possible scenarios, we favor hydrodynamical instabilities in the inner disk that can create alarge vortex. The high spectral resolution diﬀerential phases in the BrG-line show that the hot-gas component is oﬀset
from the star and in some cases is located between the star and the crescent feature. The scale of the emission does
not favor magnetospheric accretion as a driving mechanism. The scenario of an asymmetric disk wind or a massive
accreting substellar or planetary companion is discussed. With this unique observational data set for HD98922, wereveal morphological variability in the innermost 2 au of its disk region.

Deciphering the Hidden Structures of HH 216 and Pillar IV in M16: Results fromJWST and HST

L. K. Dewangan, O. R. Jadhav, A. K. Maity, N. K. Bhadari, Saurabh Sharma, M. Padovani, T. Baug, Y. D.
Mayya, Rakesh Pandey F To probe the star formation process, we present an observational investigation of the Pillar

IV and an ionized knot HH 216 in the Eagle Nebula (M16). Pillar IV is known to host a Class I protostar that drives

reveal morphological variability in the innermost 2 au of its disk region.

Deciphering the Hidden Structures of HH 216 and Pillar IV in M16: Results fromJWST and HST

L. K. Dewangan, O. R. Jadhav, A. K. Maity, N. K. Bhadari, Saurabh Sharma, M. Padovani, T. Baug, Y. D.
Mayya, Rakesh Pandey F To probe the star formation process, we present an observational investigation of the Pillar

IV and an ionized knot HH 216 in the Eagle Nebula (M16). Pillar IV is known to host a Class I protostar that drives
a bipolar outflow. The outflow has produced the bow shock, HH 216, which is associated with the red-shifted outflow
lobe. The James Webb Space Telescope’s near- and mid-infrared images (resolution ⇠0.07 arcsec - 0.7 arcsec) reveal
the protostar as a single, isolated object (below 1000 AU). The outer boundary of Pillar IV is depicted with the 3.3 µm
Polycyclic aromatic hydrocarbon (PAH) emission. HH 216 is traced with the 4.05 µm Br↵ and the radio continuum
emission, however it is undetected with 4.693 µm H2 emission. HH 216 seems to be associated with both thermal andnon-thermal radio emissions. High-resolution images reveal entangled ionized structures (below 3000 AU) of HH 216,
which appear to be located toward termination shocks. New knots in 4.693 µm H2 emission are detected, and aremainly found on Pillar IV’s northern side. This particular result supports the previously proposed episodic accretionin the powering source of HH 216. One part of the ionized jet (extent ⇠0.16 pc) is discovered on the southern side ofthe driving source. Using the 12 CO(J = 1-0), 12 CO(J = 3-2), and 13 CO(J = 1-0) emission, observational signposts ofCloud-Cloud Collision (or interacting clouds) toward Pillar IV are investigated. Overall, our results suggest that theinteraction of molecular cloud components around 23 and 26 km s 1 might have influenced star formation activity in
Pillar IV.

Disentangling CO Chemistry in a Protoplanetary Disk Using Explanatory Machine
Learning Techniques
Amina Diop, Ilse Cleeves, Dana Anderson, Jamila Pegues, Adele Plunkett F Molecular abundances in protoplan-etary disks are highly sensitive to the local physical conditions, including gas temperature, gas density, radiation field,
and dust properties. Often multiple factors are intertwined, impacting the abundances of both simple and complex
species. We present a new approach to understanding these chemical and physical interdependencies using machinelearning. Specifically we explore the case of CO modeled under the conditions of a generic disk and build an explanatory regression model to study the dependence of CO spatial density on the gas density, gas temperature, cosmic ray
ionization rate, X-ray ionization rate, and UV flux. Our findings indicate that combinations of parameters play aPillar IV.

Disentangling CO Chemistry in a Protoplanetary Disk Using Explanatory Machine
Learning Techniques
Amina Diop, Ilse Cleeves, Dana Anderson, Jamila Pegues, Adele Plunkett F Molecular abundances in protoplan-etary disks are highly sensitive to the local physical conditions, including gas temperature, gas density, radiation field,
and dust properties. Often multiple factors are intertwined, impacting the abundances of both simple and complex
species. We present a new approach to understanding these chemical and physical interdependencies using machinelearning. Specifically we explore the case of CO modeled under the conditions of a generic disk and build an explanatory regression model to study the dependence of CO spatial density on the gas density, gas temperature, cosmic ray
ionization rate, X-ray ionization rate, and UV flux. Our findings indicate that combinations of parameters play asurprisingly powerful role in regulating CO compared to any singular physical parameter. Moreover, in general, we
find the conditions in the disk are destructive toward CO. CO depletion is further enhanced in an increased cosmic
ray environment and in disks with higher initial C/O ratios. These dependencies uncovered by our new approach
are consistent with previous studies, which are more modeling intensive and computationally expensive. Our work
thus shows that machine learning can be a powerful tool not only for creating eﬃcient predictive models, but also forenabling a deeper understanding of complex chemical processes.
8

PDRs4All. V. Modelling the dust evolution across the illuminated edge of the OrionBar

M. Elyajouri, N. Ysard, A. Abergel, E. Habart, L. Verstraete, A. Jones, M. Juvela, T. Schirmer, R. Meshaka, E.
Dartois, J. Lebourlot, G. Rouille, T. Onaka, E. Peeters, O. Berne, F. Alarcon, J. Bernard-Salas, M. Buragohain,
J. Cami, A. Canin, R. Chown, K. Demyk, K. Gordon, O. Kannavou, M. Kirsanova, S. Madden, R. Paladini, Y.
Pendleton, F. Salama, I. Schroetter, A. Sidhu, M. Rollig, B. Trahin, D. Van De Putte F We study the emissionof dust grains within the Orion Bar - a well-known, highly far-UV (FUV)-irradiated PDR. The Orion Bar because of
its edge-on geometry provides an exceptional benchmark for characterizing dust evolution and the associated driving
processes under varying physical conditions. Our goal is to constrain the local properties of dust by comparing its
emission to models. Taking advantage of the recent JWST PDRs4All data, we follow the dust emission as traced by
JWST NIRCam (at 3.35 and 4.8 micron) and MIRI (at 7.7, 11.3, 15.0, and 25.5 micron), along with NIRSpec and MRS
spectroscopic observations. First, we constrain the minimum size and hydrogen content of carbon nano-grains from aenabling a deeper understanding of complex chemical processes.

PDRs4All. V. Modelling the dust evolution across the illuminated edge of the OrionBar

M. Elyajouri, N. Ysard, A. Abergel, E. Habart, L. Verstraete, A. Jones, M. Juvela, T. Schirmer, R. Meshaka, E.
Dartois, J. Lebourlot, G. Rouille, T. Onaka, E. Peeters, O. Berne, F. Alarcon, J. Bernard-Salas, M. Buragohain,
J. Cami, A. Canin, R. Chown, K. Demyk, K. Gordon, O. Kannavou, M. Kirsanova, S. Madden, R. Paladini, Y.
Pendleton, F. Salama, I. Schroetter, A. Sidhu, M. Rollig, B. Trahin, D. Van De Putte F We study the emissionof dust grains within the Orion Bar - a well-known, highly far-UV (FUV)-irradiated PDR. The Orion Bar because of
its edge-on geometry provides an exceptional benchmark for characterizing dust evolution and the associated driving
processes under varying physical conditions. Our goal is to constrain the local properties of dust by comparing its
emission to models. Taking advantage of the recent JWST PDRs4All data, we follow the dust emission as traced by
JWST NIRCam (at 3.35 and 4.8 micron) and MIRI (at 7.7, 11.3, 15.0, and 25.5 micron), along with NIRSpec and MRS
spectroscopic observations. First, we constrain the minimum size and hydrogen content of carbon nano-grains from acomparison between the observed dust emission spectra and the predictions of the THEMIS dust model coupled to thenumerical code DustEM. Using this dust model, we then perform 3D radiative transfer simulations of dust emission
with the SOC code and compare to data obtained along well chosen profiles across the Orion Bar. The JWST data
allows us, for the first time, to spatially resolve the steep variation of dust emission at the illuminated edge of theOrion Bar PDR. By considering a dust model with carbonaceous nano-grains and submicronic coated silicate grains,
we derive unprecedented constraints on the properties of across the Orion Bar. To explain the observed emission
profiles with our simulations, we find that the nano-grains must be strongly depleted with an abundance (relative tothe gas) 15 times less than in the diﬀuse ISM. The NIRSpec and MRS spectroscopic observations reveal variationsin the hydrogenation of the carbon nano-grains. The lowest hydrogenation levels are found in the vicinity of theilluminating stars suggesting photo-processing while more hydrogenated nano-grains are found in the cold and dense
molecular region, potentially indicative of larger grains.

Vertical shear instability in two-moment radiation-hydrodynamical simulations of irradiated protoplanetary disks I. Angular momentum transport and turbulent heating
Julio David Melon Fuksman, Mario Flock, Hubert Klahr F We studied the linear and nonlinear evolution of

the Vertical Shear Instability (VSI) in axisymmetric models of protoplanetary disks, focusing on the transport ofangular momentum, the produced temperature perturbations, and the applicability of local stability conditions. We

Vertical shear instability in two-moment radiation-hydrodynamical simulations of irradiated protoplanetary disks I. Angular momentum transport and turbulent heating
Julio David Melon Fuksman, Mario Flock, Hubert Klahr F We studied the linear and nonlinear evolution of

the Vertical Shear Instability (VSI) in axisymmetric models of protoplanetary disks, focusing on the transport ofangular momentum, the produced temperature perturbations, and the applicability of local stability conditions. We
modeled the gas-dust mixture via high-resolution two-moment (M1) radiation-hydrodynamical simulations including
stellar irradiation with frequency-dependent opacities. We found that, given suﬃcient depletion of small grains (witha dust-to-gas mass ratio of 10% of our nominal value of 10 3 for < 0.25 µm grains), the VSI can operate in surface disk
layers while being inactive close to the midplane, resulting in a suppression of the VSI body modes. The VSI reduces
the initial vertical shear in bands of approximately uniform specific angular momentum, whose formation is likely
favored by the enforced axisymmetry. Similarities with Reynolds stresses and angular momentum distributions in 3D
simulations suggest that the VSI-induced angular momentum mixing in the radial direction may be predominantly
axisymmetric. The stability regions in our models are well explained by local stability criteria, while the employmentof global criteria is still justifiable up to a few scale heights above the midplane, at least as long as VSI modes areradially optically thin. Turbulent heating produces only marginal temperature increases of at most 0.1% and 0.01%
in the nominal and dust-depleted models, respectively, peaking at a few (approximately three) scale heights above themidplane. We conclude that it is unlikely that the VSI can, in general, lead to any significant temperature increasesince that would either require it to eﬃciently operate in largely optically thick disk regions or to produce larger levelsof turbulence than predicted by models of passive irradiated disks.

The Kinematic and Dynamic Properties of HBC 494’s Wide-Angle Outflows

Austen Fourkas, Dary Ruiz-Rodriguez, Lee G. Mundy, Jonathan P. Williams F We present Atacama Large

Millimeter/sub-millimeter Array (ALMA) Cycle-5 observations of HBC 494, as well as calculations of the kinematicand dynamic variables which represent the object’s wide-angle bipolar outflows. HBC 494 is a binary FU Orionis typeobject located in the Orion A molecular cloud. We take advantage of combining the ALMA main array, Atacama
Compact Array (ACA), and Total Power (TP) array in order to map HBC 494’s outflows and thus, estimate their9midplane. We conclude that it is unlikely that the VSI can, in general, lead to any significant temperature increasesince that would either require it to eﬃciently operate in largely optically thick disk regions or to produce larger levelsof turbulence than predicted by models of passive irradiated disks.

The Kinematic and Dynamic Properties of HBC 494’s Wide-Angle Outflows

Austen Fourkas, Dary Ruiz-Rodriguez, Lee G. Mundy, Jonathan P. Williams F We present Atacama Large

Millimeter/sub-millimeter Array (ALMA) Cycle-5 observations of HBC 494, as well as calculations of the kinematicand dynamic variables which represent the object’s wide-angle bipolar outflows. HBC 494 is a binary FU Orionis typeobject located in the Orion A molecular cloud. We take advantage of combining the ALMA main array, Atacama
Compact Array (ACA), and Total Power (TP) array in order to map HBC 494’s outflows and thus, estimate theirkinematic parameters with higher accuracy in comparison to prior publications. We use 12 CO, 13 CO, C18 O and SO
observations to describe the object’s outflows, envelope, and disc, as well as estimate the mass, momentum, and kinetic
9 near systemic velocities, we estimate a mass of 3.0 ⇥ 10 2energy of the outflows. After correcting for optical opacity
M for the southern outflow and 2.8 ⇥ 10 2 M for the northern outflow. We report the first detection of a secondary
outflow cavity located approximately 15" north of the central binary system, which could be a remnant of a previous
large-scale accretion outburst. Furthermore, we find CO spatial features in HBC 494’s outflows corresponding toposition angles of ⇠ 35 and ⇠ 145 . This suggests that HBC 494’s outflows are most likely a composite of overlapping
outflows from two diﬀerent sources, i.e., HBC 494a and HBC 494b, the two objects in the binary system.

JOYS: MIRI/MRS spectroscopy of gas-phase molecules from the high-mass star-forming
region IRAS 23385+6053
L. Francis, M. L. van Gelder, E. F. van Dishoeck, C. Gieser, H. Beuther, L. Tychoniec, G. Perotti, A. Caratti oGaratti, P. J. Kavanagh, T. Ray, P. Klaassen, K. Justtanont, H. Linnartz, W. R. M. Rocha, K. Slavicinska, M.
Güdel, T. Henning, P. O. Lagage, G. Östlin F Space-based mid-IR spectroscopy provides tracers of warm gas instar-forming regions that are inaccessible from the ground. Past mid-IR spectra of bright high-mass protostars in the
hot-core phase typically showed strong absorption features from molecules such as CO2 , C2 H2 , and HCN. However,
little is known about their fainter counterparts at earlier stages. We thus aim to characterize the gas-phase molecularfeatures in JWST MIRI/MRS observations of the young high-mass star-forming region IRAS 23385+6053. Spectra
were extracted from two mid-IR sources and three H2 bright outflow knots in the MIRI/MRS field of view. Rich
molecular spectra with emission from CO, H2 , HD, H2 O, C2 H2 , HCN, CO2 , and OH are detected towards the two
mid-IR sources. However, only CO and OH are seen towards the brightest H2 knots, suggesting that the majority ofthe observed species are associated with disks or hot core regions rather than outflows. Simple Local thermodynamic

outflows from two diﬀerent sources, i.e., HBC 494a and HBC 494b, the two objects in the binary system.

JOYS: MIRI/MRS spectroscopy of gas-phase molecules from the high-mass star-forming
region IRAS 23385+6053
L. Francis, M. L. van Gelder, E. F. van Dishoeck, C. Gieser, H. Beuther, L. Tychoniec, G. Perotti, A. Caratti oGaratti, P. J. Kavanagh, T. Ray, P. Klaassen, K. Justtanont, H. Linnartz, W. R. M. Rocha, K. Slavicinska, M.
Güdel, T. Henning, P. O. Lagage, G. Östlin F Space-based mid-IR spectroscopy provides tracers of warm gas instar-forming regions that are inaccessible from the ground. Past mid-IR spectra of bright high-mass protostars in the
hot-core phase typically showed strong absorption features from molecules such as CO2 , C2 H2 , and HCN. However,
little is known about their fainter counterparts at earlier stages. We thus aim to characterize the gas-phase molecularfeatures in JWST MIRI/MRS observations of the young high-mass star-forming region IRAS 23385+6053. Spectra
were extracted from two mid-IR sources and three H2 bright outflow knots in the MIRI/MRS field of view. Rich
molecular spectra with emission from CO, H2 , HD, H2 O, C2 H2 , HCN, CO2 , and OH are detected towards the two
mid-IR sources. However, only CO and OH are seen towards the brightest H2 knots, suggesting that the majority ofthe observed species are associated with disks or hot core regions rather than outflows. Simple Local thermodynamic
equilibrium (LTE) slab models were used to fit the observed molecular features. The LTE model fits to 12 CO2 , C2 H2 ,and HCN emission suggest warm 120 200 K emission arising from a disk surface around one or both protostars. Weak
⇠ 500 K H2 O emission at ⇠ 6-7 µm is detected towards one mid-IR source, whereas 250 1050 K H2 O absorption
is found in the other. The H2 O absorption may occur in the disk atmosphere due to strong accretion-heating of the
midplane, or in a disk wind viewed at an ideal angle for absorption. CO emission may originate in the hot inner diskor outflow shocks. OH emission is likely excited in a non-LTE manner through water photodissociation or chemical
formation. The observations are consistent with disks having already formed in the young IRAS 23385+6053 system,
but further observations are needed to disentangle the eﬀects of geometry and evolution.

On the evolution of the observed Mass-to-Length relationship for star-forming filaments
Jiancheng Feng, Rowan J. Smith, Alvaro Hacar, Susan E. Clark, Daniel Seifried F The interstellar medium isthreaded by a hierarchy of filaments from large scales ( 100 pc) to small scales ( 0.1pc). The masses and lengths of thesenested structures may reveal important constraints for cloud formation and evolution, but it is diﬃcult to investigate
from an evolutionary perspective using single observations. In this work, we extract simulated molecular clouds fromthe Cloud Factory galactic-scale ISM suite in combination with 3D Monte Carlo radiative transfer code POLARIS toinvestigate how filamentary structure evolves over time. We produce synthetic dust continuum observations in three
regions with a series of snapshots and use the Filfinder algorithm to identify filaments in the dust derived column
density maps. When the synthetic filaments mass and length are plotted on an M-L plot, we see a scaling relation

formation. The observations are consistent with disks having already formed in the young IRAS 23385+6053 system,
but further observations are needed to disentangle the eﬀects of geometry and evolution.

On the evolution of the observed Mass-to-Length relationship for star-forming filaments
Jiancheng Feng, Rowan J. Smith, Alvaro Hacar, Susan E. Clark, Daniel Seifried F The interstellar medium isthreaded by a hierarchy of filaments from large scales ( 100 pc) to small scales ( 0.1pc). The masses and lengths of thesenested structures may reveal important constraints for cloud formation and evolution, but it is diﬃcult to investigate
from an evolutionary perspective using single observations. In this work, we extract simulated molecular clouds fromthe Cloud Factory galactic-scale ISM suite in combination with 3D Monte Carlo radiative transfer code POLARIS toinvestigate how filamentary structure evolves over time. We produce synthetic dust continuum observations in three
regions with a series of snapshots and use the Filfinder algorithm to identify filaments in the dust derived column
density maps. When the synthetic filaments mass and length are plotted on an M-L plot, we see a scaling relationof L / M 0.45 similar to that seen in observations, and find that the filaments are thermally supercritical. Projectioneﬀects systematically aﬀect the masses and lengths measured for the filaments, and are particularly severe in crowded
regions. In the filament Mass-Length (M-L) diagram we identify three main evolutionary mechanisms: accretion,
segmentation, and dispersal. In particular we find that the filaments typically evolve from smaller to larger masses
in the observational M-L plane, indicating the dominant role of accretion in filament evolution. Moreover, we find apotential correlation between line mass and filament growth rate. Once filaments are actively star forming they thensegment into smaller sections, or are dispersed by internal or external forces.

10

The magnetic field in colliding filaments G202.3+2.5

Qi-Lao Gu, Tie Liu, Pak Shing Li, Zhi-Qiang Shen, Xunchuan Liu, Junhao Liu, Xing Lu, Julien Montillaud,
Sihan Jiao, Mika Juvela, Mark G. Rawlings, Qizhou Zhang, Patrick Koch, Isabelle Ristorcelli, Jean-Sébastien
Carriere, David Eden, Zhiyuan Ren, Ken’ichi Tatematsu, Naomi Hirano, Qiu-yi Luo, Xiaofeng Mai, Namitha
Issac F We observe the magnetic field morphology towards a nearby star-forming filamentary cloud, G202.3+2.5,

by the JCMT/POL-2 850 µm thermal dust polarization observation with an angular resolution of 14.4" ( 0.053 pc).
The average magnetic field orientation is found to be perpendicular to the filaments while showing diﬀerent behaviors
in the four subregions, suggesting various eﬀects from filaments’ collision in these subregions. With the kinematics
obtained by N2H+ observation by IRAM, we estimate the plane-of-sky (POS) magnetic field strength by two methods,
the classical Davis-Chandrasekhar-Fermi (DCF) method and the angular dispersion function (ADF) method, Bpos,dcf
and Bpos,adf are 90 µG and 53 µG. We study the relative importance between the gravity (G), magnetic field (B)and turbulence (T) in the four subregions, find G > T > B, G >= T > B, G T > B and T > G > B in the northtail, west trunk, south root and east wing, respectively. In addition, we investigate the projection eﬀect on the DCF
and ADF methods based on a similar simulation case and find the 3D magnetic field strength may be underestimatedby a factor of 3 if applying the widely-used statistical Bpos -to-B3D factor when using DCF or ADF method, which
may further underestimate/overestimate related parameters.

Photometric Variability of Low Mass Stars and Brown Dwarfs in IC 348 and Taurus
Star-Forming Regions

Samrat Ghosh, Soumen Mondal, Santosh Joshi, Sneh Lata, Rajib Kumbhakar F Low-mass stars belonging to the

M spectral type are the most numerous stars in our Galaxy, amounting to about two-thirds in number, and are foundat the bottom of the main sequence in the H-R diagram. star-forming regions help to understand the census of PMS
stars, their formation process, and the interaction of expanding H II regions harboring massive stars with their natal
molecular clouds. Photometric studies of low-mass stars, including brown dwarfs (BDs), provide several important
evolutions of their atmosphere, magnetic flares and chromospheric activity. This paper highlights a few interesting
results from our optical I-band observations of 2MASS J03435638+3209591 in the young star-forming IC 348 region
and three BDs in Taurus star-forming regions using ground-based telescopes as well as a space-based telescope. We
estimated the fast periodicities in the range of 1.5 to 3 hours in Taurus BDs. Furthermore, using the long-term
photometry from the Transiting Exoplanet Survey Satellite (TESS), we have conducted a time-resolved variability

by a factor of 3 if applying the widely-used statistical Bpos -to-B3D factor when using DCF or ADF method, which
may further underestimate/overestimate related parameters.

Photometric Variability of Low Mass Stars and Brown Dwarfs in IC 348 and Taurus
Star-Forming Regions

Samrat Ghosh, Soumen Mondal, Santosh Joshi, Sneh Lata, Rajib Kumbhakar F Low-mass stars belonging to the

M spectral type are the most numerous stars in our Galaxy, amounting to about two-thirds in number, and are foundat the bottom of the main sequence in the H-R diagram. star-forming regions help to understand the census of PMS
stars, their formation process, and the interaction of expanding H II regions harboring massive stars with their natal
molecular clouds. Photometric studies of low-mass stars, including brown dwarfs (BDs), provide several important
evolutions of their atmosphere, magnetic flares and chromospheric activity. This paper highlights a few interesting
results from our optical I-band observations of 2MASS J03435638+3209591 in the young star-forming IC 348 region
and three BDs in Taurus star-forming regions using ground-based telescopes as well as a space-based telescope. We
estimated the fast periodicities in the range of 1.5 to 3 hours in Taurus BDs. Furthermore, using the long-term
photometry from the Transiting Exoplanet Survey Satellite (TESS), we have conducted a time-resolved variability
analysis of CFHT-BD-Tau 4. The periodogram analysis of TESS data reveals an orbital period of ⇠ 3 days. We found
two flare events in TESS sector 43 data for this BD and estimated the flared energies as 4.59 ⇥ 1035 erg and 2.64 ⇥ 1036
erg, which sit in the superflare range.

TIPSY: Trajectory of Infalling Particles in Streamers around Young stars. Dynamical
analysis of the streamers around S CrA and HL Tau

Aashish Gupta, Anna Miotello, Jonathan P. Williams, Til Birnstiel, Michael Kuﬀmeier, Hsi-Wei Yen F Context.

Elongated trails of infalling gas, often referred to as "streamers," have recently been observed around young stellar
objects (YSOs) at diﬀerent evolutionary stages. This asymmetric infall of material can significantly alter star andplanet formation processes, especially in the more evolved YSOs. Aims. In order to ascertain the infalling nature ofobserved streamer-like structures and then systematically characterize their dynamics, we developed the code TIPSY(Trajectory of Infalling Particles in Streamers around Young stars). Methods. Using TIPSY, the streamer molecularline emission is first isolated from the disk emission. Then the streamer emission, which is eﬀectively a point cloudin three-dimensional (3D) position-position-velocity space, is simplified to a curve-like representation. The observed
streamer curve is then compared to the theoretical trajectories of infalling material. The best-fit trajectories are used
to constrain streamer features, such as the specific energy, the specific angular momenta, the infall timescale, andthe 3D morphology. Results. We used TIPSY to fit molecular-line ALMA observations of streamers around a Class
II binary system, S CrA, and a Class I/II protostar, HL Tau. Our results indicate that both of the streamers areMapping dust in the giant molecular cloud Orion A

Amery Gration, John Magorrian F The Sun is located close to the Galactic mid-plane, meaning that we observe

the Galaxy through significant quantities of dust. Moreover, the vast majority of the Galaxy’s stars also lie in thedisc, meaning that dust has an enormous impact on the massive astrometric, photometric and spectroscopic surveysof the Galaxy that are currently underway. To exploit the data from these surveys we require good three-dimensional
maps of the Galaxy’s dust. We present a new method for making such maps in which we form the best linear unbiased
predictor of the extinction at an arbitrary point based on the extinctions for a set of observed stars. This method
allows us to avoid the artificial inhomogeneities (so-called ’fingers of God’) and resolution limits that are characteristicof many published dust maps. Moreover, it requires minimal assumptions about the statistical properties of theinterstellar medium. In fact, we require only a model of the first and second moments of the dust density field. The
method is suitable for use with directly measured extinctions, such as those provided by the Rayleigh-Jeans colour
excess method, and inferred extinctions, such as those provided by hierarchical Bayesian models like StarHorse. We
test our method by mapping dust in the region of the giant molecular cloud Orion A. Our results indicate a foregrounddust cloud at a distance of 350 pc, which has been identified in work by another author.

Spectroscopic confirmation of high-amplitude eruptive YSOs and dipping giants fromthe VVV survey
Zhen Guo, P. W. Lucas, R. Kurtev, J. Borissova, C. Contreras Peña, S. N. Yurchenko, L. C. Smith, D. Minniti,
R. K. Saito, A. Bayo, M. Catelan, J. Alonso-García, A. Caratti o Garatti, C. Morris, D. Froebrich, J. Tennyson,
K. Maucó, A. Aguayo, N. Miller, H. D. S. Muthu F During the pre-main-sequence (pre-MS) evolution stage of astar, significant amounts of stellar mass are accreted during episodic accretion events, such as multi-decade FUor-type
outbursts. Here, we present a near-infrared spectroscopic follow-up study of 33 high-amplitude (most with Ks >4 mag) variable sources discovered by the Vista Variables in the Via Lactea (VVV) survey. Based on the spectralfeatures, 25 sources are classified as eruptive young stellar objects (YSOs), including 15 newly identified FUors, sixwith long-lasting but EXor-like bursts of magnetospheric accretion and four displaying outflow-dominated spectra. By
examining the photometric behaviours of eruptive YSOs, we found most FUor-type outbursts have higher amplitudes( Ks and W 2), faster eruptive timescales and bluer infrared colours than the other outburst types. In addition,

excess method, and inferred extinctions, such as those provided by hierarchical Bayesian models like StarHorse. We
test our method by mapping dust in the region of the giant molecular cloud Orion A. Our results indicate a foregrounddust cloud at a distance of 350 pc, which has been identified in work by another author.

Spectroscopic confirmation of high-amplitude eruptive YSOs and dipping giants fromthe VVV survey
Zhen Guo, P. W. Lucas, R. Kurtev, J. Borissova, C. Contreras Peña, S. N. Yurchenko, L. C. Smith, D. Minniti,
R. K. Saito, A. Bayo, M. Catelan, J. Alonso-García, A. Caratti o Garatti, C. Morris, D. Froebrich, J. Tennyson,
K. Maucó, A. Aguayo, N. Miller, H. D. S. Muthu F During the pre-main-sequence (pre-MS) evolution stage of astar, significant amounts of stellar mass are accreted during episodic accretion events, such as multi-decade FUor-type
outbursts. Here, we present a near-infrared spectroscopic follow-up study of 33 high-amplitude (most with Ks >4 mag) variable sources discovered by the Vista Variables in the Via Lactea (VVV) survey. Based on the spectralfeatures, 25 sources are classified as eruptive young stellar objects (YSOs), including 15 newly identified FUors, sixwith long-lasting but EXor-like bursts of magnetospheric accretion and four displaying outflow-dominated spectra. By
examining the photometric behaviours of eruptive YSOs, we found most FUor-type outbursts have higher amplitudes( Ks and W 2), faster eruptive timescales and bluer infrared colours than the other outburst types. In addition,
we identified seven post-main sequence variables apparently associated with deep dipping events and an eruptive starwith deep AlO absorption bands resembling those seen in the V838 Mon stellar merger.

Multi-wavelength detection of an ongoing FUOr-type outburst on a low-mass YSO

Zhen Guo, P. W. Lucas, R. G. Kurtev, J. Borissova, V. Elbakyan, C. Morris, A. Bayo, L. Smith, A. Carattio Garatti, C. Contreras Peña, D. Minniti, J. Jose, M. Ashraf, J. Alonso-García, N. Miller, H. D. S. Muthu

F During the pre-main-sequence evolution, Young Stellar Objects (YSOs) assemble most of their mass during theepisodic accretion process. The rarely seen FUOr-type events (FUOrs) are valuable laboratories to investigate theoutbursting nature of YSOs. Here, we present multi-wavelength detection of a high-amplitude eruptive source inthe young open cluster VdBH 221 with an ongoing outburst, including optical to mid-infrared time series and nearinfrared spectra. The initial outburst has an exceptional amplitude of >6.3 mag in Gaia and 4.6 mag in Ks , witha peak luminosity up to 16 L and a peak mass accretion rate of 1.4 ⇥ 10 5 M yr 1 . The optical to infrared
spectral energy distribution (SED) of this object is consistent with a low-mass star (0.2M ) with a modest extinction