2006ApJS..166..585B


Query : 2006ApJS..166..585B

2006ApJS..166..585B - Astrophys. J., Suppl. Ser., 166, 585-612 (2006/October-0)

Hubble space telescope NICMOS observations of T dwarfs: brown dwarf multiplicity and new probes of the L/T transition.

BURGASSER A.J., KIRKPATRICK J.D., CRUZ K.L., REID I.N., LEGGETT S.K., LIEBERT J., BURROWS A. and BROWN M.E.

Abstract (from CDS):

We present the results of a Hubble Space Telescope NICMOS imaging survey of 22 T-type field brown dwarfs. Five are resolved as binary systems with angular separations of 0".05-0".35, and companionship is established on the basis of component F110W-F170M colors (indicative of CH4absorption) and low probabilities of background contamination. Prior ground-based observations show 2MASS 1553+1532AB to be a common proper-motion binary. The properties of these systems–low multiplicity fraction (12+7–4% resolved, as corrected for sample selection biases), close projected separations (ρ=1.8-5.0 AU) and near-unity mass ratios–are consistent with previous results for field brown dwarf binaries. Three of the binaries have components that span the poorly understood transition between L dwarfs and T dwarfs. Spectral decomposition analysis of one of these, SDSS 1021-0304AB, reveals a peculiar flux reversal between its components, as its cooler T5 secondary is ∼30% brighter at 1.05 and 1.27 µm than its T1 primary. This system, 2MASS 0518-2828AB, and SDSS 1534+1615AB all demonstrate that the J-band brightening observed between late-type L to mid-type T dwarfs is an intrinsic feature of this spectral transition, albeit less pronounced than previously surmised. We also find that the resolved binary fraction of L7 to T3.5 dwarfs is twice that of other L and T dwarfs, an anomaly that can be explained by a relatively rapid evolution of brown dwarfs through the L/T transition, perhaps driven by dynamic (nonequilibrium) depletion of photospheric condensates.

Abstract Copyright:

Journal keyword(s): Stars: Binaries: Visual - Stars: Fundamental Parameters - stars: individual (SDSS J042348.57-041403.5) - Stars: Individual: Alphanumeric: 2MASS J05185995-2828372 - stars: individual (SDSS J092615.38+584720.9) - stars: individual (SDSS J102109.69-030420.1) - stars: individual (2MASS J15530228+1532369) - Stars: Low-Mass, Brown Dwarfs

CDS comments: Table 1: 2MASS J1217110-0311131 is a misprint for 2MASS J12171110-0311131.

Simbad objects: 23

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Number of rows : 23
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 BRLT 38 BD* 01 51 41.55936 +12 44 30.0768           T0.5 68 0
2 2MASS J02074284+0000564 BD* 02 07 42.84984 +00 00 56.4408           T4.5 39 0
3 2MASSI J0243137-245329 BD* 02 43 13.71792 -24 53 29.8356           T6.0 50 0
4 2MASS J03480772-6022270 BD* 03 48 07.72104 -60 22 27.0624           T7 32 0
5 2MASSI J0415195-093506 BD* 04 15 19.54368 -09 35 06.6732           T8.0 165 0
6 2MASSI J0423485-041403 BD* 04 23 48.5763811987 -04 14 03.246502948           L6.5+T2 125 0
7 2MASS J05160945-0445499 BD* 05 16 09.45840 -04 45 49.9392           T5.5 25 0
8 2MASS J05185995-2828372 BD* 05 18 59.95656 -28 28 37.2720           L6+T4 37 0
9 2MASSI J0727182+171001 BD* 07 27 18.24600 +17 10 01.2072           T7.0 91 0
10 2MASSI J0755480+221218 BD* 07 55 47.95488 +22 12 16.9416           T5.2 32 0
11 SDSS J083717.21-000018.0 BD* 08 37 17.20032 -00 00 19.3608           T1 51 0
12 2MASS J09261537+5847212 BD* 09 26 15.37752 +58 47 21.2280           T3.5+T5 34 0
13 2MASS J10210969-0304197 BD* 10 21 09.69240 -03 04 19.7904           T1+T4 75 0
14 2MASS J11101001+0116130 BD* 11 10 10.01064 +01 16 13.0872           T5.5 76 0
15 2MASS J12171110-0311131 BD* 12 17 11.10288 -03 11 13.1748           T7.5 85 0
16 2MASS J12545393-0122474 BD* 12 54 53.9040607346 -01 22 47.399401142           T2e: 150 0
17 2MASS J15031961+2525196 BD* 15 03 19.6109033841 +25 25 19.795679019           T5.5 70 0
18 2MASS J15530228+1532369 BD* 15 53 02.28072 +15 32 36.9132           T6.5+T7.5 55 0
19 2MASS J16241436+0029158 BD* 16 24 14.36712 +00 29 15.8172           T6V 145 0
20 2MASS J17503293+1759042 BD* 17 50 32.93832 +17 59 04.2504           T3.5 51 0
21 2MASS J22282889-4310262 BD* 22 28 28.89432 -43 10 26.2740           T6.5 66 0
22 2MASSI J2254188+312349 BD* 22 54 18.92016 +31 23 49.8300           T5.0 70 0
23 2MASSI J2339101+135230 BD* 23 39 10.25160 +13 52 28.4772           T5.4 28 0

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