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N T L IK - ( )/,THE PHYSICS OF PROTOPLANETESIMAL DUST AGGLOMERATES. X. HIGH-VELOCITY COLLISIONSBETWEEN SMALL AND LARGE DUST AGGLOMERATES AS GROWTH BARRIER
Rainer Schräpler1 , Jürgen Blum1 , Sebastiaan Krijt2,3 and Jan-Hendrik Raabe1
Accepted by ApJ

ABSTRACTIn a protoplanetary disk, dust aggregates in the µm to mm size range possess mean collision velocities of 10 to 60 m s 1 with respect to dm- to m-size bodies. We performed laboratory collisionexperiments to explore this parameter regime and found a size- and velocity-dependent threshold
between erosion and growth. By using a local Monte Carolo coagulation calculation and complementary a simple semi-analytical timescale approach, we show that erosion considerably limits particle
growth in protoplanetary disks and leads to a steady-state dust-size distribution from µm to dm sizedparticles.
Subject headings: methods: laboratory - methods: numerical - protoplanetary disks
1. INTRODUCTION

0
In the planetesimal-formingparm, process, dust and ice1m
ticles grow from µm-sized grains to larger agglomerates.
Weidenschilling (1977) showed that the typical collisionvelocity of dust particles is directly connected to theirsizes. Due to their di↵erent coupling times to the gas in
the disk, dust agglomerates of di↵erent sizes gain relative velocities by drift motions and coupling to the gas
turbulence. In the past decades, large e↵orts have beenspent in the laboratory to investigate the outcomes of

/

-

/

2. EXPERIMENTAL APPROACH

0

/

d1
2.1. Particle Samples
6
For the dust-aggregate projectiles and targets, weused 1.5 µm-sized spherical particles consisting of whitecolored (targets) and black-colored (projectiles) amorphous SiO2 . The material parameters of the whitemonodisperse particles have been described by Blumet al. (2006). Unfortunately, no material properties forblack-coated particles are available. However, as we willshow below, the projectiles always completely stayed in-Disk Masses for Embedded Class I Protostars in the Taurus Molecular Cloud
Patrick D. Sheehan

and Josh A. Eisner

Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721, USA
Received 2017 July 9; revised 2017 October 31; accepted 2017 November 7; published 2017 December 11

Ø

k

dna

3IA

88fk

Abstract

f

k

h

à>A

3IA

8

v

thought
early stage in theØ 32 :2 )* Class
6 I protostars‒ are=MGP
D to represent
8=5 8an2=
ilifetime=> of protoplanetary disks, when they are stillembedded in their natal envelope. Here we measure the disk masses of 10 Class I protostars in the TaurusØ~ Molecularry0+ the initial
W mass: budget IforG formingt planets in disks. iP
K radiative
APDC CGtransfer
H
0 CG H
Cloud to >constrain
We use* , ﬁtA the models
produceobservations
to December
a multi-wavelength
data set using au modelingzrlto 1(
A synthetic
fEprotostar
KAstrophysicalA and0(2017
The
Journal,AT
851:45(14pp),10AR
DKR
Markov Chain Monte Carlo ﬁtting procedure. We ﬁt these models simultaneously to our new Combined Array for
Research in Millimeter-wave Astronomy 1.3 mm observations that are sensitive to the wide range of spatial scaleshcØ
24:3%*4
UMD G disks
K and envelopes so as to be ablethat are expectedxw
from protostellar
to distinguish each component, as well as)m:3:3kD broadband
DD
kSRGenergy
S=540( (fcompiled from the literature. We ﬁnd a median disk mass of 0.018 M: onspectral
distributions: 8 average, more massive). 3than the Taurus( kClass II disks, which have median disk mass of ~0.0025 M:. This decreasein disk mass can be explained if dust grains have grown by a factor of 75 in grain size, indicating that by the Class-.
II stage, at a few Myr, a signiﬁcant amount of dust grain processing has occurred. However, there is evidence thatsigniﬁcant dust processing has occurred even during the Class I stage, so it is likely that the initial mass budget isthan )-(
the value quoted here.
Øe higher+ (disks – stars: formation
i Key words:
t protoplanetaryl
Supporting phmaterial: ﬁgure setsoh
1. Introductions

Sheehan & Eisner

Figure 2. We show the 1.3 mm visibility proﬁle (left), 1.3 mm image (middle), and broadband SED (right) for IRAS 04016+2610 with the best-ﬁt disk+envelopemodel curves overplotted in green on the left and right and as contours in the middle panel. We also show the disk contribution to the visibilities as a gray dashed line.
The green curve shows our base model, which matches the visibilities but does not extinct the spectrum sufﬁciently at short wavelengths. If we include someforeground extinction in the ﬁt (the red line), however, the models ﬁt the data. Parameters for these models can be found in Table 2. All the proﬁles are available in theﬁgure set.

the envelope is thought to have been depleted onto the disk andprotostar, exposing the stellar photosphere to observers.
Stars form from clouds of gas and dust that collapse under
Finally,Class
are dominatedby theof suggestedthegood agreement with
Eisner et al.
(2005), III
who protostars
ﬁnd a disk radius
surveys (Doppmann
et al. light2005) havethat it might be
the strength of gravity. Conservation of angular momentumof 30 au, an envelope
radius
of
500
au,
and
an
inclination
of
24°.
more
massive.
Some
studieshaveclassiﬁed
IRAS
04158+2805
protostar with a small amountof infrared excess and are
disk is signiﬁcantly more massive than ouras a Class II disk, and indeed Glauser et al. (2008) suggested
causes the majority of the material to be deposited They
intoﬁnda that the central
to alsobe suggest
disks thatin thiswhich
the gasdepletedandonly
is likely
results (Mdisk ~ 0.5thought
thathasthe beennear-infrared
scatteredlight
image and SED for theM:), but they
circumstellar disk. Viscosity in the disk causes materialtoan overestimate. a small amount of rocky material system
could
be
ﬁt
withoutanenvelope
component. However,remains.
accrete onto the star. The viscous time in these disks
is & Goldreich (1999) suggested that the SED of thisChiangtheir model needs a much larger disk radius (Rdisk ~ 1150 au)
studies
to besuggest that the disk
source could be ﬁt Previousby an inclined
ﬂared haveaccretionshown
disk, thisthanclassiﬁcation
what we ﬁnd here.scheme
Our observations
comparable to theoretical expectations of planet formationsuggesting that the prone
disk mayto
be errors.
an edge-onFor
Classexample,
II disk ratherit is ispossible
much smaller
than
that,
althoughstill quite large compared toto mistake an edge(The complete ﬁgure set (10 images) is available.)Kenyon et al. 1993; Whitney et al. 1997; Furlan
et al. 2016). These surveys have tended to target the populationor just the scattered
light
image
(Lucas&Disk Masses for EmbeddedofClass
I protostar
Protostars
the Taurus
CloudClass IIdisksinbecause
they are Molecular
no longer embedded
ark et al. 2006) typically ﬁnd similar results.
in anenvelope, andandJoshso A.
estimatesof their disk masses are more b T
PatrickD.
SheehanEisner
The Astrophysical Journal, 851:45 (14pp), 2017 December 10
Sheehan & Eisnerstraightforward.
Wecancomparethe85721,
Class
Steward Observatory, Universityof Arizona, 933 N.
CherryAvenue,Tucson, AZ
USA I disk masses
Received 2017 July 9; revised 2017
October 31;
accepted
November
7; published
December11
measuredhere
with2017
thoseof theolder 2017Class
II disks.
4.10. IRAS 04365+2535
Ø 278
b sample cs
We show histograms of disk
masses.for ourof Classprac
Abstract
i of ClassSM+2535 is one of the few in our sample with a
I disks compared with the sample
II disks in Taurus N
I protostars
thought
to represent an early stage in the lifetime ofprotoplanetarywhen
are still H9 cian rotating disk (e.g.,Class
Harsonoet al.are
2014;
Aso
Øin
((
( 4. disks,b show
M theyIHH=Taurus
fromAndrewsetal.
(2013)
FigureWethetheiranatal
envelope.
Here we measure the disk masses of 10 Class I protostars in the Taurus
r best-ﬁt model for it embedded
has a diskinwith
radiusofbin are
Smyu
tSeg=
Class
II budget
disk masses
becausetheysame
regionas = CN
Molecular Cloud to constrain the initial
mass
for forming
planets
disks.fromWe theuse radiativetransfer
and a mass of 0.03 modelingin a fairly
M: embeddedàadisksa otherdata
Mhave
9a C H9 N
ourobservations
Class I sample,
butmodelsClasstoIIfromregions
to produce synthetic protostar
and ﬁt themulti-wavelength
set usingappears
to procedure.
M:) envelope of material.
MarkovThe
Chaindisk
Monte
Carlo ﬁtting
ﬁt these models
simultaneously
new Combined
Array forsimilarWe
distributions(see
Ansdell et toal.our2017).
We calculate
theFigure 3. 0.8 μm scattered light images from HST for the four sources where such images were available. We show a 0.8 μm scattered light image produced from thei ~model55as grayed, best-ﬁt. The
proﬁleisﬁt ﬂatfrom50
ResearchinMillimeter-wave
Astronomy
1.3modelmmdoesobservations
that areIIsensitive
the wide rangeof spatial
contours.visibility
In all fourcases, although
we didnot
our model
to the scattered
light data, thebest-ﬁta reasonablejob of reproducing
disk
massesfor theClass
sampletoassuming
optically
thinscales
dust
the scattered light distribution. IRAS 04032+2247 shows a more edge-on morphology than we ﬁnd when ﬁtting the combined millimeter visibilities and broadband
The Astrophysical Journal, 851:45 (14pp), 2017 December 10
thatareexpectedfromprotostellar
disks
and
envelopes
so
as
to
be
able
to
distinguisheachcomponent,
as
well
as
elySEDindicating
the a disk
presenceof misalignment
an unresolved
data set, possibly indicating
warp or disk/envelope(see Section 4.9).
sothat
broadband spectralenergytrace
distributions (compiled
the literature. We ﬁnd a median disk mass of 0.018 M: on
K ( fromtward
thisof33ourthe
rise
and
Ø
1
N
0(
)
4
% at0
The ofdisk9
mass
best-ﬁtvisibilities
model for IRAS 04166+2706
Becausethis object has few ﬂux
measurements
millimeterN)
average,more(2012),
massivethanthe Taurus
Class
IIadisks,
which
have
median disk mass of ~0.0025 M
1:.9This 33decrease
19 3
is
in
good
agreementwiththeresultsfrom
Eisnerbut
wavelengths,
there
have
been
lack
of
studiestodetermine
thetheØ
envelope.
There
is
no
clear
evidence
of
a
c1
9
3
5
M1
9
33
(
5
N
2
in disk
be explained
if dustgrainsgrown
factorindicating that by
the Classdisk radius we measure is muchsmallermass(180 aucan
comparedparameters
for thesystem,haveand
has bybeena done
onlyof 75 in grain☉☉ whatFn d size,
89I
Ithat
with 450 au). Furlan
et al. (2008)
ﬁnd
a
disk
radiusof300
au,considered
the
SED.
Our
results
areingood
agreement
withvisibilities
atshortbaselines,soitislikely
that
M
=
.
(7 )
II
stage,
at
a
few
Myr,
a
signiﬁcantamount
of
dust
grain
processing
hasoccurred.
However,
thereisevidence
disk
Ø
b
d1
9
3
5
M7
8b
d
N
although note that a disk of 200 au can also provide a good ﬁt.
what ☉
was found by Furlan et al. (2008), who ﬁnd a lowk
B(T)
signiﬁcant
has occurred
duringso it isthat the initial mass budget isn likelyned outLike
Kenyonet al. (1993) ﬁndstructurea smaller
disk of(70 theau)dustbutenvelope.
a processing
similarinclination
radius of
50 au andenvelopeIwithaØlarge-scale
nloS
fdisk with aeven
a thean Class
N stage,inclination (30°). Our millimeterdata set,thanhowever,much quoted
radius of
10,000 au. Kenyon et al. (1993) also ﬁnd that the disk
higherthe isvalue
here.
higher resolution than what was available for Eisner (2012),
is compact (Rdisk = 70 au) and low inclination (i = 30 ).
and Kenyon et al. (1993) and Furlanal. (2008)protoplanetarymodel only
Key etwords:
disks – stars: formation
the SED, so we are able to constrain the structure of the disk.
4.7. IRAS 04181+2654B

10
3 d/,
5
N1
9 33c
S
i
☉
Supporting material: ﬁgure
sets
IRAS 04181+2654B is detected in the near- to far-infrared
4.5.
‒IRAS 04169+2702c
SM1 9 but
3 hasdnot been S
f1This9detected T
at millimeter wavelengths.
true of our own observations, which detect no 1.3 mm
IRAS 04169+2702 has a compact (R ~ 40 au) disk
Nfour times more remains
hidden d
in a larger envelopecthat is about
emission. It seems to be embedded based on CO ice

Ø 19

disk

b
c
5576

Introduction
thewithenvelope
is thought to have been depleted onto the disk and~ 0.012,
massive than the disk. The disk has a mass of Mdisk 1.
absorption in its Spitzer IRS SED and its associationtheand it is being viewed at a moderate inclination of ~41 . The
embedded source IRAS 04181+2654A. We have included
theprotostar, exposing the stellar photosphere to observers.
millimeter visibility amplitudes
ﬂattenfrom
out at clouds
around 50 of
kλ,gas sourcein our thatmodeling,
but the undermodels are not constrainedStars formand dust
collapse
Finally,
likely where the disk begins to dominate over the envelope.
well. We show that the disk is likely small and low
mass, but Class III protostars are dominated by the light of thethe strength of gravity. Conservationof angular momentum
This source was modeled previously by Eisner (2012), who
we can say little else deﬁnitively. At 31″from IRAS
04181protostar with a small amount of infrared excess and are
Figure 4. Histograms of the disk masses of Class I (green) sources in ourcausesthe majorityof although
the material
to orbeinto a it falls central
found a much larger
disk, typically
250–450 au,+2654A,
4300deposited
au projected separation,
well within
II (blue)sourcesin Taurus (Andrews
et al. 2013). The redthought
the andgasClass
has
been
depletedand only
weighting up the SED produces a ﬁt with a 100 au disk, but
the envelope we measure for IRAS 04181+2654A.
As that to be disks in whichsamplelines show the range of lower limits for the MMSN (e.g., Weidenschilling
circumstellar
disk.
Viscosity
in
the
disk
causesmaterial
tocomparable disk masses and inclinations. Furlan et al. (2008) ﬁt
envelope is quite large and massive, it could be thatathis
sourceamount of rocky material
1977). We ﬁndthat our Class I disks, on average, are more massive than theremains.
star.
The
time
in thesedisksbehindis the IRASsmall
the SED with a diskaccrete
about twiceonto
the sizethe
we ﬁndhere, butwithviscousis simply
a low-mass
disk hidden
04181
Taurus Class II disks, likely due to dust grain processing hiding matter in larger
Previous studies have shownclassiﬁcation
schemebodies inthis
the olderClass II disks. However,there is still toa lackbeof massive, >0.1
a high inclination, comparable
while Robitaille ettoal. theoretical(2007) found from
+2654A envelope.
expectationsof planet formation
M: disks, which may be needed to form giant planets.
SED ﬁtting that Rdisk < 150 au and i > 30 , both in agreement
prone to errors. For example, it is possible to mistake an edge2

indicatpopulacompa
distribu
stellarIf w
are disassumpthen aare drinsteadand bewhichthat C
distribu
II sourc
follow
the disII samp
as the edrawn
sourcessampletest tothis prhypothdifferen990

A disrupted molecular torus aro
A disrupted molecular torus around Eta Carinae as seen in 12 CO with ALMA
12
CO with ALMA Nathan Smith,1‹ Adam Ginsburg2,3† and John Bally4 The CO torus of1‹Eta Car 4991
2,3
12

CO with ALMA

STELLAR WIND STRUCTURE OF ! CARINAE

433

Nathan Smith, Adam Ginsburg†ahas suffered1 a blowout, as if something has disrupted the torusinNational Radio Astronomy Observatory, Socorro, NM 87801, USA
mn
ip
Steward
Observatory, University of Arizona, 933 N. Cherry Ave., Tu
Interestingly,
2,3
4 2, D-85748 Garchingthis
European Southern
Observatory, Karl-Schwarzschild-Strae
beidirection.
München,Germany this is a special direction in the η Car
2 National
†
and
John
Bally
Ø r +3A Nathan
ae Smith,1‹ AdamgGinsburg
ʼRadio
Observatory,
Socorro, NM 87801, USA
system,as
discussed
later.
First,Astronomy
we discuss the
kinematic structure
M
Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309, 3USA
1 Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721, USAof the CO emission
detectedby ALMA.
EuropeanSouthern
Observatory, Karl-Schwarzschild-Strae 2, D-85
Ø aeg 2 Nationald Radio Astronomy
lLo
P
y
” h S
d 4 Center for Astrophysics and Space Astronomy, University of Colora
Observatory, Socorro, NM 87801, USA
H emission and kinematic structure
2, D-85748
Garchingbei
München,Ø -.
334 European Southern+ Observatory, Karl-Schwarzschild-Strae
Accepted 2017 November
17. Received
2017
November
14;Germany
in original form 20173.2
JulyNear-IR
14
1 Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson,
deep at higher(not85721,
lower)
Traditionally,a slowthelatitudes.
impression
that
this portion of the torus in the blueshifted side
AZ
USA
2
3
4

N. Smith, A. Ginsburg and J.Center
Bally for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309, USA

SLIT

N

equatorial wind is supposed to be denser than the associatedfast polar wind, and the mass-loss rate may increase withdecreasing geff (Friend & Abbott 1986); some examples are
B[e] stars (Zickgraf et al. 1986), wind-compressed disks orzones (Bjorkman & Cassinelli 1993; Ignace, Cassinelli, &Bjorkman 1996; Owocki, Cranmer, & Blondin 1994), andbistable winds (Lamers & Pauldrach 1991). Our observations of ! Car, however, suggest that its wind is densest near
the poles despite higher velocities there. Other interpretations are conceivable but require detailed models of linetransfer.
If ! Car’s wind densities are highest near the poles as one
2
might guess from the deeper hydrogen P Cyg absorption,then this tends to support recent comments by Owocki andothers concerning the importance of nonradial forces andgravity darkening in line-driven winds of massive stars(Cranmer & Owocki 1995; Owocki, Cranmer, & Gayley
1996; Owocki & Gayley 1997; Owocki, Gayley, & Cranmer
1998; Maeder & Meynet 2000; Meader & Desjacues 2001).
Specifically, these studies predict that if a luminous star isrotating fast enough for gravity darkening to be important(i.e., at e70% of the ‘‘ critical ’’ rotation speed), then stronger radiative flux at the hot poles will tend to drive a higher
mass flux. Glatzel (1998) and Maeder (1999) have discussed
modifications to the ‘‘ critical ’’ rotation rate near the
Eddington luminosity.
We describe new STIS observations in x 2, hydrogen line
profiles in x 3, and helium profiles in x 4. In x 5 we discussvarious likely implications of the observed wind geometry.
Then in x 6 we examine older STIS spectra and discuss temporal variability of the wind structure. Finally, in x 7 wemention consequences that a variable, bipolar wind may
have for interpretations of ! Car’s 5.5 yr spectroscopic
cycle.

NE 5

E

In the previous section, a comparison of the newshadow
CO emission to5"
the previously
known dusty
torus gave thethattheseNovember 14; in origi
Accepted
2017IRNovember
17.impression
Received
2017
two are closely related. The structure in images suggested that,
ABSTRACTFig. 1.—Orientationtraces
and size of the
STIS slit used infor the2000 March
like the IR torus, the COobservations.
emissionmaterialthethin walls
A second 1 square aperture located 5 northeast of the star
was used to extract the spectrum of one position in the equatorialIt
12ejecta.near
Accepted 2017 November 17. Received 2017 November 14; in original form 2017
July
14of the Homunculus,
which
is NE
brightest
inin xthe
pinchedwaist
the emissionis labeled
5 andis discussed
5.4. The
dashed lineofshows
the orientaWe present Atacama Large Millimeter
Array (ALMA)
observations
CO
2–1
tion of the 0>1 wide slit used in 1998 March and 1999 February (see x 6),
which was intentionally oﬀset from the star by 0>4. The dark spot labeledequator.
‘‘shadow’’isdiscussed
in
x
4.
The
HST/WFPC2
image
shown
here
was
A Bobservations
STRACT
from circumstellar material aroundThis
theinterpretation
massive star
Eta
Carinae(η Car). Thesein 1995 (see Morse et al. 1998), but its scale has been adjusted
is obtained
supportedby thekinematics. Fig. 2 (top)slightly
to allow for expansion
since then.
We
present
Atacamareveal new structural details about
thea cool
equatorial
toruswithlocated
∼4000
au
from
the star.
shows
position–velocity
diagramthe positional
coordinate
To study positional variation of line profiles in thethe major axisof theHomunculus,
andmissing
withextractions
the flux
Homunculus,
we made several
spectralat integrated
posiABSTRACT
The CO torus is not a completealong
azimuthalloop,
butrather,
is
its
near
side,
which
from circumstellar mations along the slit listed in Table 1. Positive oﬀsets arein the direction perpendicular
thestar,polaraxis.oﬀsets
This
that
northwest toof theand negative
are indicates
southeast.3
12 material
appears toArray
have beenclearedaway.
Themissing
matchesthedirectionof apastronThe spectrum
atemission
each
oﬀset position has
a net redshift
due reveal
We present Atacama Large Millimeter(ALMA)
observations
of
CO
2–1
new structural
the CO emission has a flattened
to reflection bydistribution,
expanding dust. Weelongatedcorrected for thisperpendiceﬀect
by aligning the blue side of the H" emission-line profile at
2. STIS SPECTRA OF THE HOMUNCULUS
in thetheeccentric
binarysystem,makinglikelythatη
Car’s
companion
playedanimportantular to(η
theit
polar
axis,
in 10
antimes
expandingequatorial
the continuum
flux (however, torus.
a diﬀerent
choice The
from circumstellar material aroundmassive
starThese
Eta
CarinaeCar).
These
observations
CO torus is notobservations are part of an intensive HST/STIS
would not alter the results substantially because the profiles
2soon(bottom)
theMolecularofCOseenin by
project to study ! Car and theFig.
Homunculus
during their cur- comparesmatch well). The
net kinematics
shift applied at eachgas
positionis givenroleindisrupting
portions
of
the
torus
after
ejection.
seen
ALMA
data
rent
5.5
yr
spectroscopic
cycle(Davidson
et
al.
1999,
2000,
as Dvfrom
Table 1. We
used thesevalues of Dv to correct the appears to have been
reveal new structural details about the cool equatorial
torus located∼4000
auapparent
the
star.
ALMA
the
kinematics
ofinmolecularhydrogen,seenlater.
in high2001; Gull et al. 1999; Gull
& Ishibashito
2001).
Early
observelocities of otheremission lines as
discussed
vations in dust
1998 Marchand 1999 February
used onlypreviously
a naraligns
well withthe butcool
aroundη Carobserved
mid-infrared(IR) maps,
Each resulting
line profile samplesinof the cenresolutionof nearthe
Homunculus
inpositions
thethe inspectrum
2.122µm H2 line
row 0>1 wide
STIS slit with
exposures,spectra
inadequatefor
The CO torus is not a complete
azimuthalloop,rather,isshortmissing
its
side,
which
tral star seenfrom diﬀerent
the reflection neb- intheeccentric binar
outer parts of the Homunculus (however, we did obtain aula, and each corresponds to a diﬀerent latitude as depicted(Smith surface
2004,2006).
theredshifted sideof theThe
CO COtorus also(and coincides
whereas hot dust resides
atexposurestheatinnerthemolecular
torus.
few deeper
wavelengths
nearH" thatwereofoﬀ- Onin Figure 3. This technique works because the polar lobes
set
from
the
star;
see
below).
Moreover,diﬃculties
inappears to have been cleared away. The missing material
matchesthe direction
are offsets
mostlyofhollow,
as indicatedby limbthebrightening
in role in disrupting port
towardinapastronFig.
1), Smith,where
COtheseemissionscheduling HST prevented
the slitnegativefrom being positionalalignedthermal-infrared
images (e.g., Together,
Gehrz, & Krautter
emission.
suggest thatwith the spatial and velocity
structureof near-IR
H2Smithclosely with the Homunculus bipolar axis during those ear1998;
et al. 2002).
isbrightest
and
where
the
CO
torus
traces
the
IR
torus
(see
above),
lier observations.
Therefore,
we planned a special played
set ofin the eccentric binary system, themakingit likely
ηobservations
Car’s
companion
The ancase of important! Car is unique, because the geometry of the aligns well with the candpinchedlonwitha wider
52 ! 0>2 aperture
CO torus
seenthat
bySTIS
ALMA
isactually
the
waist
of
the
Homunculus
polar lobes,
bright,nebulaoverlaps
is known suﬃciently
wellstructureofthehollow
COreflection
emission
perfectly
withger exposures, and withthea slitkinematicorientation closer
to thethat we can correlate position in the nebula with stellar latiHomunculus axisMolecularat position angle 138=9gas$ 318=9,as
whereasdust resirole in disrupting portions of thewhich
torusglows
soon brightly
after ejection.
seen
in
ALMA
data
tude
(assuming
that
the
polar
axis
of
the
star
and
nebulaareemission.
This confirms
theconclusionfrom comnear-IR
becauseit theisclose
toH2thestaraligned—inandwarmerthan
the poles.
The nearhot
side
shown
in Figure 1. Here
we discussobservations
sampledthis case, the assumption is justified by thewith STIS gratings G430M and G750M at standard tilts
results;(seesee x 3).
Davidson thatet al. (2001)
estimated
the shape
paring
the
CO
and
IR
maps
above)
theCOemission
seen
withWethediscussspatial and v
gave central
wavelengths of 4961,
and 7283 Å.
aligns well with the cool dust aroundη Car
previously
observed
in6768,mid-infrared
(IR)
maps,
orientationof the Homunculus
from the same data
setof the torus
appears
tothatbea blowout,
associatedwithandextended
fragmented
equatorial
ejecta.
Achieved on 2000 March 13, these are the same data used inhere, and we discuse theirstructure‘‘ compromise separate’’ shape (shownfrom
inby ALMA is not a moreusedthea paper on the Homunculus shape (Davidson et al. 2001). In
Fig. 3) to derive the latitude for each extraction position as the CO torus seen by
whereas hot dust resides at the implications
inner surface
molecular
The
CO
also
coincides
order
to reduce
light,torus.
we occulted
thestar withain fact
forof
thetheoriginofscatteredvariousfeaturesofthe star.
CO
Homunculus,butisnorth-west
just themolecular
gas inthe emission
thin walls from the0>65 bar across the slit, but other STIS observations gave a
direct view of the star aof
week
later
(see
below).
Figure
2
the
polar
that
pinchedequator.
Theco-⊙ orTable
1 lists information
H"thatprofiles,but the same
extractions
were whichglows(possibly
upspatial
to
5M
more,brightly
main torus
gasof massintheforlobes
range
ofare
0.2–1
Mat⊙forthe
emission.
Together,suggestwith the spatial and velocity structureof implies
near-IRa totalH
showslong-slit STIS
spectraa few brightthese2 examples
made for other emission lines
discussed later. Some oﬀsets listed in figuresreflected emission lines inincidence! Car’s stellar windconfor resolved
other emission lines
diﬀeremission
from those in Table
1, becauseadjacentof(reflected
the spatially
CO
with
both
the cool
tracings were combined to increase signal to noise.
tinuumhas
been
subtracted).
assumptions).
Deeper observations
are needed toofconstrain
the torusCO
appears to
the CO torus seen by ALMA isalthough
actuallywith
thequestionablepinched waistof
Homunculus
polar lobes,
dusttheand H
2 emission from the outer shell of the Homunculus walls
thestarcoolandpolar
lobes.
indicates
the poles.
CO is a goodof thecooler, dense, shielded
implications for the owhich glows brightly because itemission
is closefrom
to thewarmerthanthatthe
Thetracernear
sidezones in the Homunculus walls where most of the mass resides
main torus implies a tof the torus appears to be a blowout,
associatedwith fragmented
equatorial
ejecta.
We
discuss
Key words:
circumstellar
matter(Smith– stars:
evolution–stars:
outflows.
& Ferland2007).
The
CO
iswinds,
notlimitedto a thin skin on theof thesewalls of thefrom
Homunculus
hotterwith questio
implicationsFigurefor 2.theof various
featuresof innerthe surface
star. COemissionthe (where the although
12 CO 2–1 data
Top:origin
position–velocity
diagram of
the ALMA north-west
dust resides), and so it is likely that the CO 2–1 emission is tracing
emission from the coowith the position
runningalongmass
the major
Homunculus
at P.A. M
main torus implies
a totalgasinaxistheof therange
of 0.2–1⊙the(possibly⊙ or more,regions withup
mostto
of 5
theM
mass.
= −50◦ , integrated over a spatial width of 5 arcsec (across the width of the
Theareredshiftedpeaktoof thetorus has a COradial velocity of about
although withquestionable
Deeperobservations
neededconstrain‘torus’).
Middle: integrated assumptions).
spectrum of the CO emission.
The blackline
from words: circums+81 km s−1 , which corresponds to an expansion speed awayKey
ure 1. The top two panels show maps of the peak emission (a) and zeroth moment or integrated line flux (b) from the ALMA 12 CO 2–1 isdataemission
cube. RA from the full torus integrated over −5 to +5 arcsec along the◦ much of the star’s tremenThe
dust
shell
aroundthestarabsorbs
Dec. offsets are relative to the star, for which the registration uncertainty is about 0.5 arcsec. Contours in panel (a)emission
are at 10, 20, 30, from35, 40, 45, the50, 55,cool polar lobes.
the star (correcting for an inclination of i = 41 ; Smith 2006) of
positionin the1 Ifactor
N Tis ROU, using
Caxis
TaI O
N top panel, the blue line is the blueshifted NW side of
60 mJy. Contours in (b) are at 200, 400, 600, 800, 1000, 1200, 1400, 1600, and 1800 mJy km s−1 . The Jy to K conversion
18.1 JyD
K−1
dous 123
luminosity
andisreradiates
thatin the as
infraredabout
km s−1 . This
the same as
theenergy
H emission,noted (IR), mak-

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A disrupted molecular torus aro
A disrupted molecular torus around Eta Carinae as seen in 12 CO with ALMAF
N. Smith, A. Ginsburg and 12
J. Bally
CO with ALMA Nathan Smith,1‹ Adam Ginsburg2,3† and John Bally4
1‹
2,3
12

CO with ALMANathan Smith, Adam Ginsburg † a
1 Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tu2,3
4 2, D-85748 Garching bei München,ØKarl-Schwarzschild-Strae
SBallyS
1 Germany
525Radio Astronomy
5 2 Observatory, Socorro, NM 87801, USA
European Southern
Observatory,
2 National
Nathan Smith,1‹ Adam Ginsburg
†
and
John
Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309, 3USA
1 Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson,ØAZ 85721,( USA awScdi4 European Southern
V Observatory, Karl-Schwarzschild-Strae 2, D-85
2 National Radio Astronomy Observatory, Socorro, NM 87801, USA
Center for Astrophysics and Space Astronomy, University of Colora
1<0
V
gi]
n
3 European Southern Observatory, Karl-Schwarzschild-Strae 2, D-85748Ø
Garchingbei
München,
1<0
Accepted 2017 November 17. Received
2017
November
14;Germany
in original form 2017 July 14
4 Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309, USAØ )0 SU
Accepted 2017 November 17. Received 2017 November 14; in origi
Ø A B S T R A C[
ei S.
/
T
Accepted 2017 November 17. Received 2017 November 14; in original form à
2017
14
”S
p observations of 12 CO 2–1 emission
WeJulypresent
Atacama Large Millimeter Array (ALMA)A Bobservations
STRACT
from circumstellar material around the massive star Eta Carinae (η Car). These< We
present
Atacamareveal new structural details about the cool equatorial torus locatedThe
∼4000
from
the Car
star.
CO au
torus
of Eta4993
1 Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721, USA
2 National Radio Astronomy Observatory, Socorro, NM 87801, USA
3
4

1<0

ABSTRACTThe CO torus is not a complete azimuthal loop, but rather, is missing its near
side,
which
from
circumstellarma
12
appears toArray
have beenclearedaway. The missing
material
matches the directionofapastron
We present Atacama Large Millimeter(ALMA)
observationsof CO
2–1 emission
reveal new structuralin thetheeccentric
binarysystem,makinglikelyThese
that ηobservations
Car’s companion played
an CO
importantfrom circumstellar material aroundmassivestar Eta
Carinae(η itCar).
The
torus is notroleindisrupting
portions
of
the
torus
soon
after
ejection.
Molecular
gas
seen
in
ALMA
reveal new
structuraldetails about the cool equatorial torus located ∼4000 au from the star.
appears todata
have been
These are the same 12 CO contours from Figs 1(a) and (b) (peak emission and zeroth moment, respectively),
but superposedon the HST/WFPC2aligns
well
with
the
cool
dust
aroundηCarpreviously
observedin
mid-infrared
(IR)
maps,
ge from Morse et al. (1998).
The CO torus is not a complete azimuthal loop, but rather, is missing its near side, whichin the eccentric binar
whereas hot dust resides at the inner surface of the molecular torus. The CO also coincides
ØSl
appears to have been cleared away. The missing material matches the direction of apastronrole in disrupting port
verlaps with the near-IR H2 emission from the NW polar
emission a few arcseconds to the N and E of star corresponds to with the spatial and velocity structure of near-IR H2 emission. Together, these suggest thatalignswellwith the cin theejecta,
eccentric
binarysystem,in Fig. 2. There are, however, some fainter CO clumps
dark patches in the equatorial
which havebeen inferred
to making it likely that η Car’s companion played an important
the CO torus seen by ALMA is actually the pinched waist of the Homunculus
polar
lobes,
W/blueshifted side of the torus that are farther from thebe regions of higher visual-wavelength extinction in the equatorial
whereas hot dust resi
disrupting
portionsof the torus soon after ejection. Molecular gas seen in ALMA datar, and more ragged;
show up in
skirt based on multiwavelength
imaging(Smith, Gehrz which glows brightly because it is close to the star and warmer than the poles. The near side
Ø although these do nott
S role inoptical/IR
j
withWethediscussspatial and v
withthe cool dust aroundη Car
previously
observedassociatedin mid-infrared(IR) maps,
ated position–velocity diagram in Fig. 2, they can be& Krautter 1998, 1999;aligns
Smith et wellal. 2002a,
2003).
of the torus
appears
to be a blowout,
with fragmented
equatorial ejecta.
g. 1. CO structures appear to be less dense S
and more
The gap toI
the NW may holdvital clues and may haveimportantSr
the COfrom
torus
whereas hot dust resides at the implications
inner surface
molecular
torus.
The north-west
CO also coincides
forof
thetheoriginof various
featuresof the star. CO emission
theseen by
he NW direction, as compared to the rest of the torus.
implications for understanding the time sequence of mass ejecglows
up to which
5 M⊙ ormore,brightly
main torus
gas mass in
the rangetheseof 0.2–1
M⊙ (possibly
Together,suggestthat
the spatial
andof implies
near-IRa total
H2 emission.
, the IR and CO images give the impression that thetion that produced the with
Homunculus,
because the
NWvelocity
direction is structureof the torus has been disrupted or blown out, with thin
special. In the central binary system, the NW corresponds to the although with questionable assumptions). Deeper observations are needed toofconstrain
the torusCO
appears to
CO torus orbit
seen(Gull
byetALMA
is actually the pinched waist of the Homunculus polar lobes,
Sbroke direction
V of apastron oftheshed to larger distances from the star as something
the very eccentric nV
al. 2009;
thestarcoolandpolar
lobes. than the poles. The near side
implications for the o
which
glows
brightlyspends
becauseis closefrom
to thewarmere torus. This may be related to many of the interesting
Madura et al. 2012), whereη Car’s
hot companion
most itemission

F

ar aspects of the equatorial ejecta to the NW of the starbeen noted by many authors, as discussed in the next

Øblowout’ on the near side of the torus, and its relation
atorial ejecta

previous sections, we noted how the observed CO struc-Uof its time during the 5.5 yr cycle (see Fig. 4). The opening of theof the torus appears to be a blowout, associated with fragmented equatorial ejecta. We discuss
colliding-wind shock cone therefore points in this direction most of Key words: circumstellar matter – stars: evolution – stars: winds, outflows.
implications
the(seeoriginof various features north-west of the star. CO emission from thethe time. There are several
notable nebular forfeaturesFig. 4) thatare all associated with this direction in the equatorial plane of themain torus implies a total gas mass in the range of 0.2–1 M⊙ (possibly up to 5 M⊙ or more,
Homunculus.

omain torus implies a t
although with questio
emission from the coo

although with questionable assumptions). Deeper observations are needed to constrain CO
Key words: circums
The dust shell around the star absorbs much of the star’s tremenemission
from
the
cool
polar
lobes.
(i) The Weigelt knots and
This
1 INW
N TdustROcomplex.
DUCT
I OisNa series of

12 CO flux in an image, deprojected for an inclination angle
Figure 4. Sketch of the equatorial geometry. The red/orange
contours correspondto the ALMAthat
dous luminosity
and reradiates
energy in the infrared (IR), mak-

CHARACTERIZING TW HYDRA

04785v1 [astro-ph.SR] 13 Dec 201785v1 [astro-ph.SR] 13 Dec 2017

10

CHARACTERIZING TW HYDRAØpKimberly R. Sokal,1 Casey P. Deen,2 Gregory N. Mace,1 Jae-Joon Lee,3 Heeyoung Oh,3 Hwihyun Kim,4Characterizing TW Hydra
Benjamin 2T. Kidder,1 and Daniel
T. Jaffe1 31
1
34
Kimberly R. Sokal, Casey P. Deen, Gregory N. Mace,
Jae-Joon& Batalha2002). To thenLee,
enable a Heeyoung
direct comparison Oh, Hwihyun Kim,
to our IGRINS spectra, we convolve
Benjamin T. Kidder,1 andDaniel T. Jaffe1 the synthetic specB
tra with a gaussian kernel to simulate the R = 45000

m

resolvingof IGRINS; additionally, we sample thelnmk
A power
4UBn
tra
U
A 4UD B B NCIBRINMn
U by pixels of finite size. When we need a theoretical
2 Max Planck Institut für Extraterrestrische Physik, Giessenbachstrasse 1, spectrumwith TbeiorMünchen,log g values thatlie between the
Garching
Germany
1 Department of Astronomy, The University of Texas at Austin, Austin,valuesofthepublished
MARCS
models,we linearly inTX,
78712,
USA
Ø d d
h
)
U
i
@=
3 Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Korea
terpolate between synthetic spectra for parameter values
2 Max Planck Institut für Extraterrestrische Physik, Giessenbachstrasse 1, Garching bei München, Germany
in between grid points.
àc 4 Geminil‒h 603, es
Observatory, Casilla
La Serena, Chile
3 Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Korea
4. SPECTRAL ANALYSISØ 53 5 =L 4B KBM =LIRH EKE CNOE
.S RIM 7.=54 Gemini Observatory, Casilla 603, La Serena, Chile
4.1. Highlighting Sensitive Spectral Features(Accepted December 12, 2017)() V ) WL 4 7y,()
The sensitivity of the shapes and strengths of the spectral lines present in the observations of TW Hya in the
Submitted
to ApJØ NNG=RNJE
1 8 2
l
m
n
2.10-2.45µm2017)
spectral region to e↵ective temperature,(Accepted
December
12,
surface gravity, and magnetic field strength give us theability to measure all three parameters. We evaluate and
T IM I,) JL V
Submitted to ApJ

5k7

1 Department of Astronomy, The University of Texas at Austin, Austin, TX,
synthetic
spectra USA
to simulate the digitization of the spec78712,
e↵Sokal et al.

0show examples of the change in line profiles through difABSTRACT

ferentials of the MoogStokes models. The di↵erentials
represent the average change in flux from models with apositive and negative step of size for an individual parameter. We center our di↵erential illustration
on a baseEmodel of Te↵ = 3800K, log g = 4.2, and B= 3.0 kG, andvary one of the parameters from those starting values
while holding the other parameters constant. Figure 2,
which is composed of three subfigures of specific spectral regions, shows the di↵erentials pertaining to eachplotted in the top panel (colored lines) andTable 2. The Stellarparameter
Parameters
the fiducial flux of the baseline spectral model in the bote↵of TW Hya
tom panel. The illustration in Figure 2 uses step sizes
that correspond to the maximum step sizes defining themodel grid.
The
shown in Figure 2 serve ase↵a guide
ReferenceTe↵log
g di↵erentials
B
to the parameter values that may be important in shap[K] ing the absorption[kG] lines of TW Hya and to develope
intuition for the parameter(s) responsible for altering
YJV054125 line
4.8 profiles
2.7in this part of Te↵ , log g, B space. Using
this guide, we identify these spectral regions to later dea
stellarparameters (Section 4.2), which are
VS113400 termine
3.8 the0.0
the Na interval (2.202-2.212 µm), the (2-0) 12 CO interµm), and Ti lines near 2.221µm andThis Work 3800 val
4.2(2.2925-2.3022
3.0
2.223 µm (using an interval over 2.220-2.224 µm). Linesfrom other species are also present in these intervals.

At 60 pc, TW Hydra (TW Hya) is the closest example of a star with a gas-rich protoplanetary disk, though TW Hya
ABSTRACTf e of the interplay.4 at 2.2µm. The bestmay
fit model
is shownold
in Figure6,
fective
gravity,and magnetic
be relatively(3-15 Myr).
As
such,temperature,
TW Hya issurface
especiallyappealing
to testfieldourg
understanding
Ø
u
n
vg
sm
r
dh
At 60
pc, TW
Hydra(TW Hya)
the closest
examplea stara gas-richprotoplanetary
thoughTW
nd a comparison of models
representing
otherreportedfor
VS11,
and this ofwork
can with
be viewed
in Table
betweenstellaranddiskevolution.
WeisYJV05,
present
a high-resolution
near-infrared
spectrumoff
TW e
Hyadisk,obtainedwith
theHyaGglot
caà
7 SpectrometerJ3(IGRINS)
2. As such,
esults (discussed below)
ontopbeofrelatively
the
IGRINSmay
old data.
(3-15
Myr).
TW Hyatoisre-evaluate
especially appealing
test
understandingof theinterplay
Immersion
GRatingINfraredthe stellartoparametersof TW
comparegourf
e Hya. We
The residualsØ
betweenmodelstheobserveddatastellarand diskevolution.
We present
a high-resolution
near-infrared
spectrumof TW
Hya line
obtained
with
Bhthe
0 and
hG
Ih
t
u of magnetic
these
data
to
synthetic
spectrastars produced
by MoogStokes,
and usesensitive
spectralprofilesto theEbetweenre shown in the bottom
panel.
Immersion
GRating(IGRINS)
to re-evaluate
stellarparameters
of TW
Hya.
the e↵ective
temperature,surface gravity,and magnetic
field. A the
model
with
T = 3800
K, logg=4.2,compareandØ I probe
Bm
OKIRn
tINfrared Spectrometer
I We
data
to fits
synthetic
spectra of magnetic
producedby MoogStokes,
and usetosensitive
spectralprofilesB=these
3.0 kG
best
the near-infrared
spectrum starsof TW
Hya. These
results corresponda spectral
type ofline
M0.5
and toØimi
5. DISCUSSION
AND CONCLUSIONSe↵ectivesurfacegravity,magnetic
an probe
age of the
8 Myr,
whichtemperature,
is well past themedianlife ofandgaseousdisks.field. A model with T = 3800 K, log g = 4.2, and5.1. Comparison to Other
Studies
TWfitsHya
B= 3.0kG of
best
the near-infrared spectrum of TW Hya. These results correspond to a spectral type of M0.5 andThe stellar parameters determined
this workfroman ageof 8inMyr,
which
is wellpast
medianlife of gaseousdisks. — stars: individual (TW Hydra) —Keywords:
infrared:
stars
— the
stars:
fundamental
parameters
he IGRINS K-band spectrum fall firmly withinpreviousstars: pre-main sequenceesults. Using the spectral type to temperature converKeywords: infrared: stars — stars: fundamental parameters — stars: individual (TW Hydra) —ions of Herczeg & Hillenbrand (2014), we conclude thatstars:TW Hya is an M0.5, which is in between the typical
op-pre-main sequence
Note—The results of select 12TW

Figure 2. Parameter sensitivity of R= 45,000 Moog Stokes
spectral synthesis models for three K-band spectral regions.

CHARACTERIZING TW HYDRACHARACTERIZING TW HYDRA

904785v1 [astro-ph.SR] 13 Dec 201785v1 [astro-ph.SR] 13 Dec 201712

Kimberly R. Sokal,1 Casey P. Deen,2 Gregory N. Mace,1 Jae-Joon Lee,3 Heeyoung Oh,3 Hwihyun Kim,4Sokal et al.
Benjamin 2T. Kidder,1 and Daniel
T. Jaffe1 3
1
1
Kimberly R. Sokal, Casey P. Deen, Gregory N. Mace, Jae-Joon Lee, Heeyoung Oh,3 Hwihyun Kim,4Benjamin T. Kidder,1 and Daniel T. Jaffe1
14

3= Sokal et al.

Ø 6 ,
C
R
ØGarching
Cg bei e3
2 Max Planck Institut für Extraterrestrische Physik, Giessenbachstrasse 1,
München, Germany
1 Department of Astronomy, The University of Texas at Austin, Austin, TX, 78712, USA
3 Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu,Ø((
Daejeon 34055, ʼ
Korea
2 Max Planck Institut für Extraterrestrische Physik, Giessenbachstrasse 1, Garching bei München, Germany
4 Gemini
Observatory, Casilla 603, La Serena, ChileeJ
3 Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Korea
SW e
4 Gemini Observatory, Casilla 603, La Serena, Chile(Accepted December 12, 2017)NJ
1 Department of Astronomy, The University of Texas at Austin, Austin, TX, 78712, USA

J
W eJ
=g
W
e

Submitted
to ApJ 12, 2017)(Accepted
DecemberSubmitted to ApJØABSTRACT

Figure 6. The observed IGRINS spectrum (black line) of TW Hya in comparison to MoogStokes synthetic spectra matching
the estimated parameters of this paper,YJV05, and VS11 (colored lines; parameters are given in Table 2). The di↵erence
between the observed and synthetic spectra is shown in the bottom panels, with an increased y-axis scale. Left: the Na interval,
center: the 12 CO interval, right: Ti lines. A full view of the K-band spectrum is included in the online version (Figure 1).

9i

At 60 pc, TW Hydra (TW Hya) is the closest example of a star with a gas-rich
disk, though TW Hya
N protoplanetary
J
ABSTRACT
may be relatively old (3-15 Myr). As such, TW Hya is especially appealing
our understanding
interplayØ to testT= 8 , of the7.Y
1*
important point here is that while theof veilinglines are(TWtoo deep,an e↵ectmostlyclosest
due to theexample
surfaceAte↵ects
60
pc,
TW
Hya)
the
of a starwith a gas-richprotoplanetary
thoughTW
betweenstellarand Hydra
diskevolution.
Weispresent
a high-resolution
near-infrared
spectrumof TW Hyadisk,
obtainedwith
theHyaand surface gravity are often degenerate
in the CO in- TW Hydragravity (albeit with some contribution from the di↵erent
8),J
Characterizing
15
may
be relatively
old
(3-15
Myr).
As such,TW
especially appealing
test our understandingof theinterplayterval, we are able to disentangle
our measurementsbye↵ectivetemperature
as well).
Lastly,themodelHyacorreImmersion
GRatingINfraredSpectrometer(IGRINS)
toisre-evaluate
the stellartoparametersof TW Hya. We
comparedetermining the veiling independently. The best-fit veilsponding
to the alower
temperatureof 3400
K exhibits
Ø
=
5G
p
g
V
p
Y
We
have
presented
highresolution
near-IR
spectrumbetweenstellarandstrongdiskevolution.
We thepresent
aHarhigh-resolution
near-infrared
spectrumof TW
Hya line
obtainedwiththesedatamodel;tosynthetic
spectraofwithmagneticstars
by MoogStokes,
and usesensitive
spectralprofilesto theing is found at 2.2µm for each
MoogStokes
then of TW
lines onbothsides of at
Na 2.7m
I lineproduced
at 2.206
HyaScI
obtained
IGRINStheK
9of TW)peach model is artificially veiled
with
athe
blackbody.
The lanµmSmith(see Figures
3 Spectrometerand6) that gravity,
areObservatory
not observedin theJ.
Telescopeat McDonald
over
Immersion
GRatingINfrared(IGRINS)
to re-evaluate
stellarparameters
Hya.
compareprobe
e↵ectivetemperature,surfaceandmagnetic
field. A the
model
with
Te↵ = 3800
K, log
g =We
4.2,
and
IGRINS
spectrum.
validity of this process is demonstrated by the quality of several
epochs.
We compare these high quality data
123.0 kGdata
to fits
synthetic
spectraofmagneticstars
by MoogStokes,
and useprofilesMO
Stosensitive
Jspectral
best
spectrumofTW
results corresponda spectral
type ofline
M0.5
and tomodel fits of metal lines nearB=the these
CO intervalin Figure
Tonear-infrared
examinethefrom
impactofspectralwhich
resolution
andproduced
theHya. Theseto thesynthetic
spectraMoogStokes,
includes7, which shows that the veiling treatment is satisfactory magnetic
discrepant
results
of
VS11,
we
found
a
moderate
resoe↵ects
while
the emergent
stellare↵ectivetemperature,surfacegravity,andmagnetic
an probe
age of the
8 Myr,
isAfter
well
past
the
life
of
gaseousdisks.field. A model with Te↵ = 3800 K, log g = 4.2, andØwhich5 lutionO
8computing
1-median8
CB1/
out to the 12 CO interval wavelength range (and thus
near-infrared
spectrumtocompareourandspectra.
identifying
spectralregions
to the 8G J
☉ sensitive
over the entire wavelength rangeB=of our3.0
analysis).
We
use an available
InfraredkG bestfitsVS11
thenear-infrared
spectrum
offit TWin parameters.
specific
we find NASAØ changes((
6stellarspectrum,parameters,+fromtotheCovey
0beststel8
J Hya. These results correspond to a spectral type of M0.5 andThe conclusions of VS11 are quite di↵erent from ours
Telescope
Facility(IRTF)
spectrumet☉al.
MoogStokes
syntheticcorresponds
thean ageofprojects.
8 Myr,larwhich
isofwell
past
the
life
of gaseousdisks. — stars: individual (TW Hydra) —infrared:stars—
stars:
fundamental
parameters
despite the use of near-infrared spectra
byKeywords:
both(2010). Thisobtained
2008
parameters
Tspectrum± 100
K, medianlog gin=
4.2 ±with
0.1, thee↵ = 3800wasØ andCBr*(8G
MJ
One contribution to the di↵erences is that VS11 used,
same
instrument(SpeX;
Rayner
et
al.
2003)
as
that
B= 3.0pre-main± 0.2 kG. Our parameterizationof TW Hyastars:
sequencein part, the broad band continuum for spectral typing, doesof
at spectral
nearly thespectralresolution of R
notVS11
rely ontypesameor distancemeasurements.
which can be altered by the combination ofKeywords:
di↵erent This⇠work
2000-3000
is—lower
quality).type
Weof conconfirms(althoughthatstars
TW it
Hya
has
astars:spectral
infrared:fundamental
parameters — stars: individual (TW Hydra) —volve
the MoogStokes
synthetic
spectra corresponding
physical e↵ects (e↵ective temperature, veiling, etc.), and ⇠ M0.5
inagreement
with
Herczeg&
Hillenbrand(2014)
Ø
2
B
H(,
e
a4
ey
W eJ
pre-mainsequence
therefore is less sensitive to individual parameters. Fur- and resolves
tostars:
the findings
of YJV05,
and spectral
this work
to thethe debate
between VS11,
theopticaltype
thermore, it is clear that VS11 was impacted by hav- of K6.5-7
larger(e.g.
resolution
and conflicting
rebin to theobserved
YJV05)(R=3000)
and the solenear-IRM

8
9NASA Exoplanet Science Institute, California Institute of Technology, Pasadena, CA 91125 USA

MORE RAPIDLY ROTATING PMS M DWARFS WITH LIGHT CURVES SUGGESTIVE OF ORBITING
Center for Astrophysics and Space Sciences, University of CLOUDS
California,
Diego, CA 92093-0424, USA
OF SanMATERIAL

Cerro Tololo Inter-American
Observatory,
La Serena
Chile5 , 0000-0001-7124-4094
1John Stauffer, Luisa Casilla
Rebull1,3603,, Trevor
J. David21700000,, Moira Jardine
Andrew Collier Cameron5 , Ann Marie
Cody4 , Lynne A. Hillenbrand2 , David Barrado6 , Julian van Eyken7 , Carl Melis8 , Cesar Briceno9 .

1

ABSTRACT

Spitzer Science Center (SSC), IPAC, California Institute of Technology, Pasadena, CA 91125, USA

2

Astronomy
Department,
California
Technology,
Pasadena, CA
In a previous
paper,
using
dataInstitutefromofK2
Campaign
2, 91125
we USAidentified 11 very low mass members of the3
Infrared Science Archive (IRSA), IPAC, 1200 E. California Blvd, MS 314-6, California Institute of Technology, Pasadena, CA 91125 USA⇢ Oph and4 NASAUpper
Scorpius
region as
havingperiodic
photometricvariability and phased
Ames ResearchCenter,star-forming
Space Sciences and Astrobiology
Division,
MS245-3,
Mo↵ett Field,
CA 94035 USA
5Schoolof Physics multiple
and Astronomy,scallops
University ofor
St. undulations.
Andrews, North Haugh,
St Andrews
KY16922,UK the “scallop-shell” light curve
light curves
showingAllthe stars
with6
Centro de Astrobiologı́a, Dpto. de Astrofı́sica, INTA-CSIC, E-28692, ESAC Campus, Villanueva de la Cañada, Madrid, Spain
morphology
are mid-to-late M dwarfs without evidence of active accretion, and with photometric
7
NASA Exoplanet Science Institute, California Institute of Technology, Pasadena, CA 91125 USA
8periods generally<1 day.andTheirphasedlight
curvesSanhave
much USA
structure to be attributed to nonCenter for Astrophysics
Space Sciences,
Universityof California,
Diego, too
CA 92093-0424,
9
Cerro Tololo distributed
Inter-American Observatory,
Casilla 603, Laspots
Serena 1700000,
Chile 0000-0001-7124-4094
axisymmetricallyphotosphericand rotational
modulation. We have now identified
an additional eight probable members of the samestar-forming region plus three stars in the Taurus
ABSTRACTIn a previous
paper,sameusing data
fromcurve
K2 Campaign
2, we identified
very low mass
thestar-forming region
with thislightmorphology
and11sharing
themembers
same ofperiod
and spectral⇢ Oph and Upper Scorpius star-forming region as having periodic photometric variability and phasedtype range as thelightprevious
group.
Wescallops
describe
the light
curvesof these
new stars
detail and present
curves showing
multipleor undulations.
All thestars withthe “scallop-shell”
lightincurvemorphology
are mid-to-late M We
dwarfswithout
evidencetheof active
accretion,ofandwithphotometric
their general physicalcharacteristics.
also
examineproperties
theoverallset of stars in orderperiods generally <1 day. Their phased light curves have too much structure to be attributed to nonto identify common
features that might help elucidate the causes of their photometric variability.
axisymmetrically distributed photospheric spots and rotational modulation. We have now identified

712.04390v1 [astro-ph.SR] 12 Dec 20177

an additional eight probable members of the same star-forming region plus three stars in the Taurus
star-forming
region with<this same lightandsharing thesame period andsO
2
2 curve
K morphology
22
1Mh
cr
U spectralOtype range as the previous group. We
the light curves of these new stars in detail and present
1. describe
INTRODUCTION
i
O ga
ma
h cr
O
M
their general physical characteristics. We also examine the properties of the overall set of stars in order
CTM
onM
M
Ophotometricephotometric
M U with many
to identify
commonnearlyfeaturesthat stars
might help
elucidatethetypecauses ofof theirvariability. K variability,
If observed with enoughprecision,
all
show
some
short
term

T
p source of thatOSOOShM
U K2 missiondi↵erentuOhphysical cr
mechanisms
as thevariability. NASA’s
Keplermission,andUp
its successor
1. INTRODUCTION(Howell et al. 2014), have produced long duration, continuous, high precision light curves of more than 300,000 stars
If observed with enough precision, nearly all stars show some type of short term photometric variability, with many
which have served tohighlightof theseknown
mechanisms
for producing
variability.
Inevitably, thedi↵erent
physical manymechanisms
as the sourceof thatvariability. NASA’s
Kepler mission, photometricand its successor K2
mission(Howell
et al. 2014),
produced
duration,continuous,
high precision light
more than
300,000 stars
quality and quantityof thoselighthave
curveshaslong
also
resulted
in identification
ofcurves
starsofwhose
photometricvariability is notwhich have served to highlight many of these known mechanisms for producing photometric variability. Inevitably, the1Instituto de Astronomı́a, Universidad Nacional Autónoma de México, Ensenada, B. C., CP 22830, Mexico; 2 INAFThe star-forming
cores inthe centreof thedel
Trifidnebula(M00133
20): Roma,from Herschel
to the Madrid,
Istituto di Astrofisica
e Planetologia
Spaziali,Via Fosso
Cavaliere
100,
Italy; 3 INTA,
near-infrared
Spain
Mauricio Tapia1 , Paolo Persi2 , Carlos Román-Zúñiga1, Davie Elia2 , Franco Giovannelli2 and L SabauE-mail contact:
mt 3at astrosen.unam.mx
Graziati

12
Institutode Astronomı́a,
Universidad
Autónomade México,
Ensenada, (TCs)
B. C., CP
INAFA new detailed
infrared(IR) studyof eight Nacional
star-forming
dense
condensationsin 22830,
M 20,Mexico;
the Trifid
nebula, is
3
Istitutoe Planetologia
Spaziali,properties
Via Fosso delCavaliere00133globules
Roma, Italy;
INTA, Madrid,presented. The
aimdi isAstrofisica
to determine
the physicalof thedust 100,in suchand establish
the presenceSpainand properties of their embedded protostellar and/or young stellar population. For this, we analysed new HerschelE-mailAlto
contact:
mt at astrosen.unam.mx
far-IR and Calar
near-IR
images of the region, combined with Spitzer/IRAC archival observations. We confirm
detailed
infrared(IR) studyof eight
star-forming
dense mid-IR
condensations
(TCs)
M 20,
Trifid innebula,is one ofthe presenceAofnew
severalyoung
stellarobjects(YSOs),
most withcoloursof inClassII thesources
all but
The aimto determine
the physicalproperties
the dust
in such globules
and establish
the presence between
the observedpresented.
cores. Five
TCsis aredominatedin the far-IR
by ofClassI sources
with bolometricluminosities
and properties of their embedded protostellar and/or young stellar population. For this, we analysed new Herschel
100 and 500far-IR
L⊙ . andWe
report the discovery of a possible counterjet to HH 399 and its protostellar engine inside
Calar Alto near-IR images of the region, combined with Spitzer/IRAC archival observations. We confirm
the photodissociation
TC2,
asstellar
well asa bipolarsystem,by IIsymmetricH2butemissionthe presenceregionof several
young
objects(YSOs),outflow
most with
mid-IR signposted
colours of Class
sources in all
one of knots,
embedded intheTC3.
Thecores.
present
compatible
star formation
been active
observed
Fiveresults
TCs areare
dominatedin thewith
far-IRprevious
by Class suggestions
I sources with thatbolometricluminosities has
between
5 report the discovery of a possible counterjet to HH 399 and its protostellar engine inside
500 3L×We⊙ . 10in the region100
forandsome
years, and that the most recent events in some of these TCs may have been triggered
the photodissociation
region We
TC2,also
as well
as a bipolar
outflowvalue
system,by symmetricknots,
by the expansionof the HII region.
obtaineda revisedforsignposted
the distanceto M 20H2ofemission
2.0 ± 0.1
kpc.

embedded in TC3. The present results are compatible with previous suggestions that star formation has been active
the region for some 3 × 105 years, and that the most recent events in some of these TCs may have been triggered
Accepted byinMNRAS
by the expansion of the HII region. We also obtained a revised value for the distance to M 20 of 2.0 ± 0.1 kpc.

yi,
R by MNRAS
R s
R k
91 3Rcae uz
T
k 3 253
Accepted
2MASS
A Young,k J11151597+1937266:
00
9 .
3 F
0
, A Dusty,0Isolated, Planetary-MassH
R Object
gbC with a
Potential
Wide Stellar
Companione r uztpt Dusty, Isolated,
HM Planetary-Masss
A withIa
2MASS J11151597+1937266:
A Young,
ObjectWide1,2
Stellar
RPotential
hRl
M 2R
o
2
Christopher
A.geS
Theissen, AdamCompanion
J. Burgasser, Daniella
C. Bardalez
Gagliuﬃ3 , Kevin K. Hardegree5
6
1,2
2
Ullman4 , Jonathan, SarahJ. Schmidt
andAndrew
West Gagliuﬃ3 , Kevin K. HardegreeChristopherGagné
A. Theissen, AdamJ. Burgasser, Daniella
C.A.
Bardalez1

Ullman4 , Jonathan Gagné5 , Sarah J. Schmidt6 and Andrew A. West2
DepartmentofAstronomy,
BostonUniversity,
725
CommonwealthAvenue,Boston,MA
02215,
USA;
Center for
1
Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston, MA 02215, USA; 2 Center for
Astrophysics and Space Sciences, University of California, San Diego, 9500 Gilman Dr., Mail Code 0424, La Jolla, CA

Astrophysics and Space Sciences, University of California, San Diego, 9500 Gilman Dr., Mail Code 0424, La Jolla, CA

6 NASA Sagan Fellow
7 Leibniz-Institute for 2MASSJ11151597+1937266:
YOUNG,
DUSTY, 16,
ISOLATED,
Astrophysics
Potsdam (AIP),A An
der Sternwarte
D-14482,PLANETARY-MASS
Potsdam, Germany OBJECT WITH A

POTENTIAL WIDE STELLAR COMPANION

4v2 [astro-ph.SR] 13 Dec 2017

ABSTRACT
1, 2
2
3
Christopher A. Theissen,
Adam
J. Burgasser,
Daniella
C. Bardalez
Gagliuffi,
We present 2MASS J11151597+1937266,
a recently
identified
low-surface
gravity
L dwarf,classified
as an L2 based
45, 6
7Kevin optical
K. Hardegree-Ullman,Gagné, spectral
Sarah J.type
Schmidt,
Andrew A. Weston Sloan Digital Sky Survey
spectroscopy. Jonathan
We confirm
thiswithandnear-infrared
spectroscopy, which
provides further evidence that 2MASS J11151597+1937266 is a low-surface gravity L dwarf. This object also shows
significant excess
mid-infrared flux, indicative of circumstellar material; and its strong H↵ emission (EWH↵ = 560 ± 82
1 Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston, MA 02215, USAÅ) is an indicatorof enhanced magnetic activity or weak accretion. Comparison of its spectral energy distribution
2 Center for Astrophysics and Space Sciences, University of California, San Diego, 9500 Gilman Dr., Mail Code 0424, La Jolla, CA 92093,+184
to model photospheres
yieldsane↵ectivetemperatureof1724
38 K. We also provide a revised distance estimate ofUSA
37 ± 6 pc using3 Departmenta spectral
type–luminosity
relationshiplow-surface
objects.
The
3-dimensionalof Astrophysics,
American Museumof Naturalfor
History,
Central Parkgravity
West at 79th
Street, New
York,
NY 10034, USA galactic
4 The University
velocities and positionsof 2MASS
J11151597+1937266
do notknownof Toledo, 2801
West Bancroft Street, Mailstop
111,match
Toledo, any
OH 43606,
USAyoung association or moving group.
5 Carnegie Institution of Washington DTM, 5241 Broad Branch Road NW, Washington, DC 20015, USA
Assuming a probableage in the range of 5–45 Myr, the model-dependent estimated mass of this object is between
6 NASA Sagan Fellow
7–21 MJup , making it a potentially isolated planetary-mass object. We also identify a candidate co-moving, young
7 Leibniz-Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, D-14482, Potsdam, Germany
stellar companion,
2MASS J11131089+2110086.
ABSTRACT
Hu We present
S 2MASS
4MJ11151597+1937266,
T
E stars
50H—
4H
Dstars:ebasedcM
Keywords:brown
dwarfs— circumstellar—
infrared:propermotions—
amatterrecentlycHO
identified
low-surface
gravity
L dwarf,classified
as an L2indiyT
D (2MASS
T2MASS
Ytype with near-infrared
03stars:spectroscopy,
M 50
vidualJ11151597+1937266,—
low-mass4 whichon Sloan
DigitalSky Survey
optical spectroscopy. We
confirm J11131089+2110086)
this spectral
providesfurther52Lr
evidence that 2MASS J11151597+1937266
is a low-surface
dwarf. Thisg O
M
JM gravity LLO
K object also shows- T
significant excess mid-infrared flux, indicative of circumstellar material; and its strong H↵ emission (EWH↵ = 560 ± 82
- 75KMH
y
~
E
L
1
p O
D
Å) is anindicator of enhanced magnetic activity or weak accretion. Comparison of its spectral energy distribution
to model photospheres yields an e↵ective temperature of 1724+184
38 K. We also provide a revised distance estimate of
37 ± 6 pc using a spectral type–luminosity relationship for low-surface gravity objects. The 3-dimensional galactic
velocities and positions of 2MASS J11151597+1937266 do not match any known young association or moving group.
Assuming a probable age in the range of 5–45 Myr, the model-dependent estimated mass of this object is between
7–21 MJup , making it a potentially isolated planetary-mass object. We also identify a candidate co-moving, youngstellar companion, 2MASS J11131089+2110086.