Please use this identifier to cite or link to this item: http://elar.urfu.ru/handle/10995/90214
Title: A new take on the low-mass brown dwarf companions on wide orbits in Upper-Scorpius
Authors: Petrus, S.
Bonnefoy, M.
Chauvin, G.
Babusiaux, C.
Delorme, P.
Lagrange, A. -M.
Florent, N.
Bayo, A.
Janson, M.
Biller, B.
Manjavacas, E.
Marleau, G. -D.
Kopytova, T.
Issue Date: 2020
Publisher: EDP Sciences
Citation: A new take on the low-mass brown dwarf companions on wide orbits in Upper-Scorpius / S. Petrus, M. Bonnefoy, G. Chauvin, C. Babusiaux, et al. . — DOI 10.1051/0004-6361/201935732 // Astronomy and Astrophysics. — 2020. — Iss. 633. — 35732.
Abstract: Context. The Upper-Scorpius association (5 11 Myr) contains a unique population of low-mass (M< 30 MJup) brown dwarfs either free-floating, forming wide pairs, or on wide orbits around solar-type and massive stars. The detailed relative characterization of their physical properties (mass, radius, temperature, composition, and ongoing accretion) offers the opportunity to potentially explore their origin and mechanisms of formation. Aims. In this study, we aim to characterize the chemical and physical properties of three young, late-M brown dwarfs claimed to be companions of the Upper-Scorpius stars USco 161031.9-16191305, HIP 77900, and HIP 78530 using medium-resolution spectroscopy at UV (0:300:56 m; R 3300), optical (0:551:02 m; RA - 5400), and NIR (1:022:48 m; RA - 4300) wavelengths. The spectra of six free-floating analogs from the same association are analyzed for comparison and to explore the potential physical differences between these substellar objects found in different configurations. We also aim to examine and analyze hydrogen emission lines at UV and optical wavelengths to investigate the presence of ongoing accretion processes. Methods. The X-shooter spectrograph at VLT was used to obtain the spectra of the nine young brown dwarfs over the 0:32:5 mrange simultaneously. Performing a forward modeling of the observed spectra with the ForMoSA code, we infer the Teff, log (g), and radius of our objects. The code compares here the BT-SETTL15 models to the observed spectra using the Nested Sampling Bayesian inference method. Mass is determined using evolutionary models, and a new analysis of the physical association is presented based on Gaia-DR2 astrometry. Results. The Teff and log (g) determined for our companions are compatible with those found for free-floating analogs of the Upper-Scorpius association and with evolutionary model predictions at the age of the association. However the final accuracy on the Teff estimates is strongly limited by nonreproducibility of the BT-SETTL15 models in the range of Teff corresponding to the M8 M9 spectral types. We identified Hff, H, H , and Ca II H and K emission lines in the spectrum of several objects. We attribute these lines to chromospheric activity except for the free-floating object USco 1608-2315 for which they are indicative of active accretion ( ?M 1010:76 M yr1). We confirm the four-fold over-luminosity of USco 161031.9-16191305 B down to 0.3 m, which could be explained in part by the activity of this object and if the companion is an unresolved multiple system. © 2020 EDP Sciences. All rights reserved.
Keywords: BROWN DWARFS
PLANETARY SYSTEMS
STARS: ATMOSPHERES
STARS: FUNDAMENTAL PARAMETERS
STARS: LUMINOSITY FUNCTION, MASS FUNCTION
BAYESIAN NETWORKS
CHROMOPHORES
ELECTROMAGNETIC WAVE EMISSION
INFERENCE ENGINES
PHYSICAL PROPERTIES
BAYESIAN INFERENCE
CHEMICAL AND PHYSICAL PROPERTIES
CHROMOSPHERIC ACTIVITY
EVOLUTIONARY MODELS
HYDROGEN EMISSIONS
MECHANISMS OF FORMATION
NON-REPRODUCIBILITY
SUBSTELLAR OBJECTS
STARS
URI: http://elar.urfu.ru/handle/10995/90214
Access: info:eu-repo/semantics/openAccess
cc-by
SCOPUS ID: 85088666391
WOS ID: 000508589100001
PURE ID: 12013708
ISSN: 0004-6361
DOI: 10.1051/0004-6361/201935732
metadata.dc.description.sponsorship: Deutsche Forschungsgemeinschaft, DFG: KU 2849/7-1
Agence Nationale de la Recherche, ANR: ANR-14-CE33-0018
Ministerio de Economía y Competitividad, MINECO: AyA2017-84089
Acknowledgements. The authors thank the ESO staff for conducting the observations. We are grateful to D. Lachapelle for providing the spectra of HIP 78530 B and USco 1610-1913 B. We also thank J. Bouvier for advising us on accretion process and chromospheric activity effects. We acknowledge financial support from the Programme National de Planétologie (PNP), the Programme National de Physique Stellaire (PNPS) of CNRS-INSU in France, and the Agence Nationale de la Recherche (GIPSE project; grant ANR-14-CE33-0018). This research has made use of the SIMBAD database and VizieR catalogue access tool (operated at CDS, Strasbourg, France). This research has made use of NASA’s Astrophysics Data System and of the Extrasolar Planet Encyclopedia (http:// exoplanet.eu/). This publication makes use of VOSA, developed under the Spanish Virtual Observatory project supported from the Spanish MINECO through grant AyA2017-84089. G-DM acknowledges the support of the DFG priority program SPP 1992 “Exploring the Diversity of Extrasolar Planets” (KU 2849/7-1).
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