2020A&A...633A.124P


Query : 2020A&A...633A.124P

2020A&A...633A.124P - Astronomy and Astrophysics, volume 633A, 124-124 (2020/1-1)

A new take on the low-mass brown dwarf companions on wide orbits in Upper-Scorpius.

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. and KOPYTOVA T.

Abstract (from CDS):


Context. The Upper-Scorpius association (5-11Myr) contains a unique population of low-mass (M≤30MJup) 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 (0.30-0.56µm; Rλ∼3300), optical (0.55-1.02µm; Rλ∼5400), and NIR (1.02-2.48µm; Rλ∼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 0.3-2.5µm range 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 Hα, Hβ, Hγ, 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 (dM/dt≤10–10.76M/yr). We confirm the four-fold over-luminosity of USco 161031.9-16191305 B down to 0.3µm, which could be explained in part by the activity of this object and if the companion is an unresolved multiple system. <%K brown dwarfs - stars: atmospheres - stars: fundamental parameters - stars: luminosity function, mass function - planetary systems

Abstract Copyright: © S. Petrus et al. 2020

Journal keyword(s):

Simbad objects: 33

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Number of rows : 33
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 V* FW Tau TT* 04 29 29.703744 +26 16 53.06412       15.85   M5.5 136 0
2 V* DH Tau B LM* 04 29 41.66 +26 32 56.5           M9.25 83 1
3 LSPM J0714+3702 LM* 07 14 03.9421559688 +37 02 46.016599776   20.9   18.3   M8 22 0
4 NAME TW Hya Association As* 11 01.9 -34 42           ~ 942 0
5 V* CT Cha B LM* 11 04 08.44 -76 27 18.0           M8 53 0
6 CD-33 7795B LM* 11 31 55.2500 -34 36 25.200     20.40   15.8 M8.5/9e 124 0
7 TWA 26 LM* 11 39 51.1378374696 -31 59 21.443660124         15.83 M8e 109 0
8 2MASS J11582484+1354456 PM* 11 58 24.8347201248 +13 54 46.025336628       19.642 17.138 M9 5 0
9 TWA 29 LM* 12 45 14.1607780560 -44 29 07.728263340         18.0 M9.5p 49 0
10 CD-40 8434b Pl 14 08 10.1545500744 -41 23 52.573291080           ~ 204 0
11 V* GQ Lup B LM* 15 49 12.05 -35 39 05.1           M9e 132 1
12 HD 142250 * 15 54 30.1089445104 -27 20 19.085902512   6.07 6.10     B7V 113 0
13 HD 142250B LM* 15 54 30.4773546672 -27 19 57.359301384           M8.5-9.5 10 0
14 HD 143567 * 16 01 55.4547295632 -21 58 49.398900888   7.27 7.19 7.87   B9Van 130 0
15 HD 143567B LM* 16 01 55.65696 -21 58 53.0076           M8 39 0
16 2MASS J16025116-2401502 Y*? 16 02 51.1649651376 -24 01 50.297892708         14.65 M7-8 13 0
17 UScoCTIO 108 LM* 16 05 54.0734809368 -18 18 44.376318180           M7 44 0
18 NAME UScoCTIO 108B BD? 16 05 54.09504 -18 18 48.8592           ~ 50 0
19 2MASS J16060629-2335133 BD* 16 06 06.29400 -23 35 13.3656           L0 22 0
20 2MASS J16072382-2211018 LM* 16 07 23.8268923080 -22 11 01.873246380           M11.00 23 0
21 2MASS J16073799-2242468 BD* 16 07 37.99056 -22 42 46.8324           L0 24 0
22 2MASS J16081843-2232248 BD* 16 08 18.43608 -22 32 24.8280           L0 22 0
23 2MASS J16082847-2315103 BD* 16 08 28.4764248744 -23 15 10.371654900           L1 23 0
24 [PGZ2001] J161031.9-191305 Y*O 16 10 31.9513754952 -19 13 06.080941452   15.14 13.56 13.31   K7e 37 0
25 2MASS J16103232-1913085 * 16 10 32.3277488136 -19 13 08.392480032           M8.5-9.5 15 0
26 2MASS J16104714-2239492 LM* 16 10 47.1390030984 -22 39 49.326872040           M9.00 22 0
27 NAME Upper Sco Association As* 16 12 -23.4           ~ 1369 1
28 NAME Upper Sco-Cen As* 16 15 -24.2           ~ 1332 1
29 GSC 06214-00210 TT* 16 21 54.6676915200 -20 43 09.140591496   13.62 12.38 12.11 11.08 M1e 77 0
30 NAME GSC 06214-00210B LM* 16 21 54.678 -20 43 11.33           ~ 87 0
31 2MASS J16224385-1951057 Y*O 16 22 43.8550223256 -19 51 05.741328384       17.0 15.0 M8 23 0
32 EM* SR 12 Or* 16 27 19.5054789229 -24 41 40.414828505     13.28 12.15 10.855 M0IVe 183 1
33 NAME SR 12C LM* 16 27 19.6577175120 -24 41 49.239711024           M9.0 47 0

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