2015ApJ...805...56D


C.D.S. - SIMBAD4 rel 1.7 - 2020.01.27CET10:07:54

2015ApJ...805...56D - Astrophys. J., 805, 56 (2015/May-3)

The mass-luminosity relation in the L/T transition: individual dynamical masses for the new J-band flux reversal binary SDSSJ105213.51+442255.7AB.

DUPUY T.J., LIU M.C., LEGGETT S.K., IRELAND M.J., CHIU K. and GOLIMOWSKI D.A.

Abstract (from CDS):

We have discovered that SDSS J105213.51+442255.7 (T0.5±1.0) is a binary in Keck laser guide star adaptive optics imaging, displaying a large J- to K-band flux reversal ( mag, mag). We determine a total dynamical mass from Keck orbital monitoring (88±5) and a mass ratio by measuring the photocenter orbit from CFHT/WIRCam absolute astrometry (). Combining these provides the first individual dynamical masses for any field L or T dwarfs, 49±3 for the L6.5±1.5 primary and 39±3 for the T1.5±1.0 secondary. Such a low mass ratio for a nearly equal luminosity binary implies a shallow mass-luminosity relation over the L/T transition (). This provides the first observational support that cloud dispersal plays a significant role in the luminosity evolution of substellar objects. Fully cloudy models fail our coevality test for this binary, giving ages for the two components that disagree by 0.2 dex (2.0σ). In contrast, our observed masses and luminosities can be reproduced at a single age by ''hybrid'' evolutionary tracks where a smooth change from a cloudy to cloudless photosphere around 1300 K causes slowing of luminosity evolution. Remarkably, such models also match our observed JHK flux ratios and colors well. Overall, it seems that the distinguishing features SDSS J1052+4422AB, like a J-band flux reversal and high-amplitude variability, are normal for a field L/T binary caught during the process of cloud dispersal, given that the age ( Gyr) and surface gravity ( = 5.0-5.2) of SDSS J1052+4422AB are typical for field ultracool dwarfs.

Abstract Copyright:

Journal keyword(s): astrometry - binaries: close - brown dwarfs - parallaxes - stars: fundamental parameters - stars: individual: SDSS J105213.51+442255.7

Simbad objects: 11

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Number of rows : 11

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 2MASS J01075242+0041563 BD* 01 07 52.422 +00 41 56.40           L8 45 0
2 V* BF Ari BD* 01 51 41.559 +12 44 30.08           T0.0 61 0
3 NAME Orion Nebula Cluster OpC 05 35.0 -05 29           ~ 1924 1
4 2MASSW J0820299+450031 BD* 08 20 29.961 +45 00 31.52           L5V 22 0
5 2MASS J10521350+4422559 BD* 10 52 13.505 +44 22 55.91           L6.5+T1.5 24 0
6 TWA 27B BD* 12 07 33.50 -39 32 54.4           L5 229 1
7 2MASS J14044948-3159330 BD* 14 04 49.484 -31 59 33.06           T1+T5 28 1
8 2MASS J17502385+4222373 BD* 17 50 23.853 +42 22 37.35           T2 13 0
9 * 15 Sge B BD* 20 04 06.2 +17 04 13           L6 30 0
10 Wolf 1084 SB* 20 43 19.2534162835 +55 20 53.541561877   16.46   13.9   M5Ve 76 0
11 2MASS J21140802-2251358 BD* 21 14 08.026 -22 51 35.84           L7+1 70 0

    Equat.    Gal    SGal    Ecl

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2020.01.27-10:07:54

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