J/ApJ/920/99 Ultracool Dwarfs with Spitzer IR Spectrograph. I. (Suarez+, 2021)
Ultracool Dwarfs Observed with the Spitzer Infrared Spectrograph. I.
An Accurate Look at the L-to-T Transition at ∼300Myr from Optical Through MIR
Spectrophotometry.
Suarez G.,Metchev S.,Leggett S.K.,Saumon D.,Marley M.S.
<Astrophys. J., 920, 99 (2021)>
=2021ApJ...920...99S 2021ApJ...920...99S
ADC_Keywords: Stars, brown dwarf; Spectra, infrared
Keywords: Brown dwarfs
Abstract:
We present Spitzer IRS 5-14µm spectra and 16µm and 22µm
photometry of the T2.5 companion to the ∼300Myr old G0V star HN Peg.
We incorporate previous 0.8-5µm observations to obtain the most
comprehensive spectral energy distribution (SED) of an
intermediate-gravity L/T-transition dwarf that, together with an
accurate Gaia EDR3 parallax of the primary, enables us to derive
precise fundamental parameters. We find that young (∼0.1-0.3Gyr)
early-T dwarfs on average have ∼140K lower effective temperatures,
∼20% larger radii, and similar bolometric luminosities compared to
≳1Gyr old field dwarfs with similar spectral types. Our accurate
infrared spectrophotometry offers new detail at wavelengths where the
dominant carbon-bearing molecules have their strongest transitions: at
3.4µm for methane and at 4.6µm for carbon monoxide. We assess
the performance of various widely available photospheric models and
find that models with condensates and/or clouds better reproduce the
full SED of this moderately young early-T dwarf. However, cloud-free
models incorporating a more general convective instability treatment
reproduce at least the low-resolution near-infrared spectrum similarly
well. Our analysis of R∼2300 J-band spectra shows that the
near-infrared potassium absorption lines in HN Peg B have similar
strengths to those seen in both younger and older T2-T3 dwarfs. We
conclude that while alkali lines are well established as surface
gravity indicators for L-type or warmer stars, they are insensitive to
surface gravity in early-T dwarfs.
Description:
Observations are described in table1.dat.
Objects:
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RA (2000) DE Designation(s)
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21 44 28.47 +14 46 07.7 HN Peg B = V* HN Peg B
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 87 8 Summary of observations
fig10.dat 33 1499 Near- and mid-IR spectra of HN Peg B
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See also:
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/ApJ/564/421 : Spectra of T dwarfs. I. (Burgasser+, 2002)
J/AJ/127/3553 : JHK photometry & spectroscopy for L & T dwarfs (Knapp+, 2004)
J/ApJS/159/141 : Spectroscopic properties of cool stars. I. (Valenti+, 2005)
J/ApJ/637/1067 : Near-IR spectral classification of T dwarfs (Burgasser+, 2006)
J/AJ/134/1162 : 11 new T dwarfs in 2MASS (Looper+, 2007)
J/ApJS/173/104 : Stellar population in Chamaeleon I (Luhman, 2007)
J/ApJ/689/1295 : Li test implications for brown dwarfs (Kirkpatrick+, 2008)
J/ApJ/710/1142 : SpeX spectroscopy of low mass binaries. I. (Burgasser+, 2010)
J/ApJS/201/19 : Hawaii Infrared Parallax Program. I. (Dupuy+, 2012)
J/ApJ/810/158 : M,L,T dwarfs fundamental parameters & SEDs (Filippazzo+, 2015)
J/other/Sci/350.64 : 51 Eri b near-infrared spectrum (Macintosh+, 2015)
J/A+A/589/A21 : K-H2 line shapes for cool brown dwarfs spectra (Allard+, 2016)
J/ApJS/225/10 : Kinematic analysis of M7-L8 dwarfs (Faherty+, 2016)
J/ApJS/231/15 : Astrometric monitoring ultracool dwarf binaries (Dupuy+, 2017)
J/ApJ/838/73 : Brown dwarf surface gravity with Keck/NIRSPEC (Martin , 2017)
J/AJ/159/257 : Hawaii IR plx program. IV. L0-T8 BDs with UKIRT (Best+, 2020)
J/ApJ/891/171 : COCONUTS. I. Spectra of a WD & T4 comoving syst (Zhang+, 2020)
J/A+A/648/A73 : Discovery of the directly imaged planet YSES 2b (Bohn+, 2021)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- Obs.Type Type of observation; photometry or spectroscopy
14- 25 A12 --- Inst Instrument used
27- 51 A25 --- Band Band or wavelength observed
53- 59 A7 --- Res Resolution (for spectroscopy)
61- 85 A25 --- Obs Observation date(s)
87 I1 --- Ref Reference used (1)
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Note (1): References as follows:
1 = Chambers+, 2016, II/349
2 = Luhman+, 2007, J/ApJS/173/104
3 = This work
4 = Zhou+, 2018AJ....155..132Z 2018AJ....155..132Z
5 = Leggett+, 2008ApJ...682.1256L 2008ApJ...682.1256L
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Byte-by-byte Description of file: fig10.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Inst Instrument identifier (1)
9- 16 F8.5 um Wave [0.85/14.2] Wavelength
18- 25 E8.2 cW/m2/nm Flux [4e-19/2e-16] Observed flux
27- 33 E7.1 cW/m2/nm e_Flux [0/5e-17] Uncertainty in flux
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Note (1): Instruments as follows:
SpeX = IRTF's SpeX instrument
NIRSPEC = Keck's NIRSPEC instrument
NIRI = Gemini's NIRI instrument
IRS = Spitzer's IRS instrument
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 02-Mar-2023