J/AJ/164/155 K-band spectroscopy of substellar companion VHS1256b (Hoch+, 2022)
Moderate-resolution K-band Spectroscopy of the Substellar Companion VHS 1256 b.
Hoch K.K.W., Konopacky Q.M., Barman T.S., Theissen C.A., Brock L.,
Perrin M.D., Ruffio J.-B., Macintosh B., Marois C.
<Astron. J., 164, 155 (2022)>
=2022AJ....164..155H 2022AJ....164..155H
ADC_Keywords: Exoplanets; Stars, brown dwarf; Spectra, infrared
Keywords: Direct imaging ; Exoplanet atmospheres ; High resolution
spectroscopy ; Exoplanet formation ; Brown dwarfs
Abstract:
We present moderate-resolution (R∼4000) K-band spectra of the
planetary-mass companion VHS1256b. The data were taken with the OSIRIS
integral field spectrograph at the W.M. Keck Observatory. The spectra
reveal resolved molecular lines from H2O and CO. The spectra are
compared to custom PHOENIX atmosphere model grids appropriate for
young, substellar objects. We fit the data using a Markov chain Monte
Carlo forward-modeling method. Using a combination of our
moderate-resolution spectrum and low-resolution broadband data from
the literature, we derive an effective temperature of 1240K, with a
range of 1200-1300K, a surface gravity of logg=3.25, with a range of
3.25-3.75, and a cloud parameter of log(Pcloud)=6, with a range of
6.0-6.6. These values are consistent with previous studies, regardless
of the new, larger system distance from GAIA EDR3 (21.15±0.22pc).
We derive a C/O ratio of 0.590-0.354+0.280 for VHS1256b. Both our
OSIRIS data and spectra from the literature are best modeled when
using a larger 3µm grain size for the clouds than used for hotter
objects, consistent with other sources in the L/T transition region.
VHS1256b offers an opportunity to look for systematics in the modeling
process that may lead to the incorrect derivation of properties like
C/O ratio in the high contrast regime.
Objects:
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RA (2000) DE Designation(s)
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12 56 02.13 -12 57 21.9 VHS 1256 = VHS J1256-1257
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig2.dat 29 1665 OSIRIS K-band spectra of VHS 1256 b
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See also:
II/359 : The VISTA Hemisphere Survey (VHS) catalog DR4.1 (McMahon+, 2013)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/ApJ/723/684 : NIRSPEC ultracool dwarf radial velocity survey (Blake+, 2010)
J/ApJ/777/160 : NIR imaging survey for planets around MG stars (Biller+, 2013)
J/A+A/594/A63 : International Deep Planet Survey results (Galicher+, 2016)
J/ApJ/833/96 : Hawaii IR parallax program. II. Ultracool dwarfs (Liu+, 2016)
J/AJ/155/34 : Analysis of NIR spectra of neighboring L dwarfs (Cruz+, 2018)
J/AJ/158/13 : The first 300 stars observed by the GPIES (Nielsen+, 2019)
J/AJ/160/207 : OSIRIS K-band spectroscopy κAndromedaeb (Wilcomb+, 2020)
J/ApJS/257/45 : BDKP V. Radial & rot. velocities of M, L, T dwarfs (Hsu+, 2021)
J/AJ/162/290 : OSIRIS K-band spectra planets HR8799 b, c, & d (Ruffio+, 2021)
J/ApJ/926/141 : 3-D kinematics of Orion Nebula Cluster (Theissen+, 2022)
Byte-by-byte Description of file: fig2.dat
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Bytes Format Units Label Explanations
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1- 9 E9.3 um Wave [1.96/2.39] Wavelength
11- 19 E9.3 W/m2/um Flux [1e-15/3e-15] Absolute flux density
21- 29 E9.3 W/m2/um e_Flux [1e-16/3e-16] Uncertainty in Flux (1)
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Note (1): The errors are derived from the RMS of the individual spectra at each
wavelength. Such as error includes uncertainties in both the
continuum and the lines, the former of which tends to be larger and
is removed via continuum subtraction in portions of our analysis.
The median uncertainty is ∼7% in flux.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 23-Nov-2022