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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

Abstract
Class I protostars are thought to represent an early stage in the lifetime of protoplanetary disks, when they are stillembedded in their natal envelope. Here we measure the disk masses of 10 Class I protostars in the Taurus
Molecular Cloud to constrain the initial mass budget for forming planets in disks. We use radiative transfer
modeling to produce synthetic protostar observations and ﬁt the models to a multi-wavelength data set using a
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 scales
that are expected from protostellar disks and envelopes so as to be able to distinguish each component, as well as
broadband spectral energy distributions compiled from the literature. We ﬁnd a median disk mass of 0.018 M: on
average, more massive than the Taurus Class 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 ishigher than the value quoted here.
Key words: protoplanetary disks – stars: formation
Supporting material: ﬁgure sets
1. Introduction

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-

Disk Masses for Embedded Class I Protostars in the Taurus Molecular Cloud
Patrick D. Sheehan

and Josh A. Eisnerb

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

Abstract
Class I protostars are thought to represent an early stage in the lifetime of protoplanetary disks, when they are stillembedded in their natal envelope. Here we measure the disk masses of 10 Class I protostars in the Taurus
Molecular Cloud to constrain the initial mass budget for forming planets in disks. We use radiative transfer
modeling to produce synthetic protostar observations and ﬁt the models to a multi-wavelength data set using a
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 scales
that are expected from protostellar disks and envelopes so as to be able to distinguish each component, as well as
broadband spectral energy distributions compiled from the literature. We ﬁnd a median disk mass of 0.018 M: on
The disk mass of our best-ﬁt model for IRAS 04166+2706
Because this object has few ﬂux measurements at millimeter
average, more massive than
the Taurus Class II disks, which have median disk mass of ~0.0025 M:. This decreaseis in good agreement with the results from Eisner (2012), but
wavelengths, there have been a lack of studies to determine
in disk
be explained
if dustgrainsgrown
factorthe disk radius we measure is muchsmallermass(180 aucan
comparedparameters
for thesystem,have
and what
has bybeena done
onlyof 75 in grain size, indicating that by the Class
with 450 au). Furlan et al. (2008)
ﬁnd
a
disk
radiusof300
au,considered
the
SED.
Our
results
areingood
agreementwith has occurred. However, there is evidence that
II stage, at a few Myr, a signiﬁcantamount of dust grain processing
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 lowsigniﬁcant
has occurred
duringthean Class
stage,
so it is likely that the initial mass budget is
Kenyon et al. (1993) ﬁnd a smaller
disk (70 au)dust
but a processing
similarinclination
disk with aeven
radius of
50 au andenvelopeIwithainclination (30°). Our millimeter
data
set,
however,ismuchradiusof
10,000au.
Kenyonetal.
(1993)
also
ﬁnd
that
the
disk
higher than the value quoted
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

Supporting material: ﬁgureIRAS
sets04181+2654B is detected in the near- to far-infrared

4.5. IRAS 04169+2702

but has not been detected at millimeter wavelengths. Thisremains true of our own observations, which detect no 1.3 mm
IRAS 04169+2702 has a compact (Rdisk ~ 40 au) disk
hidden in a larger envelope that is about four times more
emission. It seems to be embedded based on CO2 ice
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 arecausesthe 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 withinthought
weighting up the SED produces a ﬁt with a 100 au disk, but
measure for IRAS 04181+2654A.
As that to be disks in which the gas has been depleted and only
circumstellar disk. Viscosity in thetheenvelope
disk wecausesmaterial tocomparable disk masses and inclinations. Furlan et al. (2008) ﬁt
envelope is quite large and massive, it could be thatathis
sourceamount of rocky material remains.
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
Previous
studies have shown this classiﬁcation scheme to bea high inclination, comparable
while Robitaille ettoal. theoretical(2007) found from
+2654Aenvelope.
expectations of planet formation
SED ﬁtting that Rdisk < 150 au and i > 30 , both in agreement
prone to errors. For example, it is possible to mistake an edge-TA disrupted molecular torus around Eta Carinae as seen in
12
CO with ALMANathan Smith,1‹ Adam Ginsburg2,3 † and John Bally4
1 Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721, USA
2 National Radio Astronomy Observatory, Socorro, NM 87801, USA

3 European Southern Observatory, Karl-Schwarzschild-Strae 2, D-85748 Garching bei München, Germany
4 Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309, USA

Accepted 2017 November 17. Received 2017 November 14; in original form 2017 July 14

ABSTRACT

We present Atacama Large Millimeter Array (ALMA) observations of 12 CO 2–1 emission
from circumstellar material around the massive star Eta Carinae (η Car). These observations
reveal new structural details about the cool equatorial torus located ∼4000 au from the star.
The CO torus is not a complete azimuthal loop, but rather, is missing its near side, whichappears to have been cleared away. The missing material matches the direction of apastronin the eccentric binary system, making it likely that η Car’s companion played an importantrole in disrupting portions of the torus soon after ejection. Molecular gas seen in ALMA dataaligns well with the cool dust around η Car previously observed in mid-infrared (IR) maps,
whereas hot dust resides at the inner surface of the molecular torus. The CO also coincides
with the spatial and velocity structure of near-IR H2 emission. Together, these suggest that
the CO torus seen by ALMA is actually the pinched waist of the Homunculus polar lobes,
which glows brightly because it is close to the star and warmer than the poles. The near sideof the torus appears to be a blowout, associated with fragmented equatorial ejecta. We discuss
implications for the origin of various features north-west of the star. CO emission from themain torus implies a total gas mass in the range of 0.2–1 M⊙ (possibly up to 5 M⊙ or more,
although with questionable assumptions). Deeper observations are needed to constrain CO
emission from the cool polar lobes.

A disrupted molecular torus around Eta Carinae as seen in
12
CO with ALMANathan Smith,1‹ Adam Ginsburg2,3 † and John Bally4
1 Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721, USA
2 National Radio Astronomy Observatory, Socorro, NM 87801, USA

3 European Southern Observatory, Karl-Schwarzschild-Strae 2, D-85748 Garching bei München, Germany
4 Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309, USA

Accepted 2017 November 17. Received 2017 November 14; in original form 2017 July 14

ABSTRACT

We present Atacama Large Millimeter Array (ALMA) observations of 12 CO 2–1 emission
from circumstellar material around the massive star Eta Carinae (η Car). These observations
reveal new structural details about the cool equatorial torus located ∼4000 au from the star.
The CO torus is not a complete azimuthal loop, but rather, is missing its near side, whichappears to have been cleared away. The missing material matches the direction of apastronin the eccentric binary system, making it likely that η Car’s companion played an importantrole in disrupting portions of the torus soon after ejection. Molecular gas seen in ALMA dataaligns well with the cool dust around η Car previously observed in mid-infrared (IR) maps,
whereas hot dust resides at the inner surface of the molecular torus. The CO also coincides
with the spatial and velocity structure of near-IR H2 emission. Together, these suggest that
the CO torus seen by ALMA is actually the pinched waist of the Homunculus polar lobes,
which glows brightly because it is close to the star and warmer than the poles. The near sideof the torus appears to be a blowout, associated with fragmented equatorial ejecta. We discuss
implications for the origin of various features north-west of the star. CO emission from themain torus implies a total gas mass in the range of 0.2–1 M⊙ (possibly up to 5 M⊙ or more,
although with questionable assumptions). Deeper observations are needed to constrain CO
emission from the cool polar lobes.

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
providesfurther evidence that 2MASS J11151597+1937266 is a low-surface gravity L dwarf. This object also showsg O
significant excess mid-infrared flux, indicative of circumstellar material; and its strong H↵ emission (EWH↵ = 560 ± 82
Å) is an indicator 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.