J/AJ/164/155ivo://CDS.VizieR/J/AJ/164/155doi:10.26093/cds/vizier.51640155CDSHoch K.K.W.Konopacky Q.M.Barman T.S.Theissen C.A.Brock L.,Perrin M.D.Ruffio J.-B.Macintosh B.Marois C.2023-01-17T13:27:06Z2022-12-07T08:03:36ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frexoplanetsbrown-dwarfsinfrared-astronomyspectroscopyWe 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(P_cloud_)=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 3{mu}m 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.2022AJ....164..155Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/164/155CatalogResearchIsServedByTAP VizieR generic servicerelated-toII/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 {kappa}Andromedaeb (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)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/164/155https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/164/155http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/164/155https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/164/155https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/164/155http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/164/155GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapInfrareddefaultJ/AJ/164/155/fig2OSIRIS K-band spectra of VHS 1256 brecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintWave[1.96/2.39] Wavelengthumem.wldoubleFlux[1e-15/3e-15] Absolute flux densityW.m**-2.um**-1phot.flux.density;em.IR.Kdoublee_Flux[1e-16/3e-16] Uncertainty in Flux (1)W.m**-2.um**-1stat.error;phot.fluxdouble