2004AJ....127.2948V


Query : 2004AJ....127.2948V

2004AJ....127.2948V - Astron. J., 127, 2948-2968 (2004/May-0)

Preliminary parallaxes of 40 L and T dwarfs from the US Naval Observatory infrared astrometry program.

VRBA F.J., HENDEN A.A., LUGINBUHL C.B., GUETTER H.H., MUNN J.A., CANZIAN B., BURGASSER A.J., KIRKPATRICK J.D., FAN X., GEBALLE T.R., GOLIMOWSKI D.A., KNAPP G.R., LEGGETT S.K., SCHNEIDER D.P. and BRINKMANN J.

Abstract (from CDS):

We present preliminary trigonometric parallaxes and proper motions for 22 L dwarfs and 18 T dwarfs measured using the ASTROCAM infrared imager on the US Naval Observatory (USNO) 1.55 m Strand Astrometric Reflector. The results presented here are based on observations obtained between 2000 September and 2002 November; about half of the objects have an observational time baseline of Δt=1.3 yr and half Δt=2.0 yr. Despite these short time baselines, the astrometric quality is sufficient to produce significant new results, especially for the nearer T dwarfs. Seven objects are in common with the USNO optical CCD parallax program for quality control and seven in common with the European Southern Observatory 3.5 m New Technology Telescope parallax program. We compare astrometric quality with both of these programs. Relative to absolute parallax corrections are made by employing Two Micron All Sky Survey and/or Sloan Digital Sky Survey photometry for reference-frame stars. We combine USNO infrared and optical parallaxes with the best available California Institute of Technology (CIT) system photometry to determine M_J_, MH, and MKvalues for 37 L dwarfs between spectral types L0 and L8 and 19 T dwarfs between spectral types T0.5 and T8 and present selected absolute magnitude versus spectral type and color diagrams, based on these results. Luminosities and temperatures are estimated for these objects. Of special interest are the distances of several objects that are at or near the L-T dwarf boundary so that this important transition can be better understood. The previously reported early to mid T dwarf luminosity excess is clearly confirmed and found to be present at J, H, and K. The large number of objects that populate this luminosity-excess region indicate that it cannot be due entirely to selection effects. The T dwarf sequence is extended to MJ~16.9 by 2MASS J041519-0935, which, at d=5.74 pc, is found to be the least luminous [log(L/L)=-5.58] and coldest (Teff~760 K) brown dwarf known. Combining results from this paper with earlier USNO CCD results we find that, in contrast to the L dwarfs, there are no examples of low-velocity (Vtan<20 km/s) T dwarfs. This is consistent with the T dwarfs in this study being generally older than the L dwarfs. We briefly discuss future directions for the USNO infrared astrometry program.

Abstract Copyright:

Journal keyword(s): Astrometry - Stars: Color-Magnitude Diagrams - Stars: Distances - Stars: Late-Type - Stars: Low-Mass, Brown Dwarfs

Simbad objects: 52

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Number of rows : 52
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 2MASSW J0030300-145033 BD* 00 30 30.13224 -14 50 33.3960           L7V 39 0
2 2MASS J00325937+1410371 BD* 00 32 59.37576 +14 10 37.1136           L8V 27 0
3 LSPM J0036+1821 BD* 00 36 16.1118891182 +18 21 10.286665966       18.451 16.053 L3.5 201 0
4 2MASS J01075242+0041563 BD* 01 07 52.42200 +00 41 56.3964           L8 50 0
5 BRLT 38 BD* 01 51 41.55936 +12 44 30.0768           T0.5 65 0
6 DENIS J020529.0-115925 BD* 02 05 29.3651195393 -11 59 29.721210536           L7V 146 0
7 2MASS J02074284+0000564 BD* 02 07 42.84984 +00 00 56.4408           T4.5 37 0
8 2MASSI J0243137-245329 BD* 02 43 13.71792 -24 53 29.8356           T6.0 46 0
9 2MASSI J0328426+230205 BD* 03 28 42.65592 +23 02 05.1900           L9.5 46 0
10 Cl* Melotte 22 KPNO 2 BD* 03 45 43.1616128256 +25 40 23.239779672         17.36 L0V 119 0
11 2MASSI J0415195-093506 BD* 04 15 19.54368 -09 35 06.6732           T8.0 158 0
12 2MASSI J0423485-041403 BD* 04 23 48.5763811987 -04 14 03.246502948           L6.5+T2 117 0
13 SIPS J0539-0059 BD* 05 39 52.0040375405 -00 59 01.491092352           L5V 79 0
14 2MASS J05591914-1404488 BD* 05 59 19.1872549354 -14 04 49.206913185           T4.5 141 0
15 HD 42581B BD* 06 10 34.80 -21 52 00.0           T6.5 486 0
16 2MASSI J0727182+171001 BD* 07 27 18.24600 +17 10 01.2072           T7.0 83 0
17 LSPM J0746+2000 BD* 07 46 42.50553 +20 00 31.9757       17.9 15.034 L0+L1.5 176 1
18 2MASSI J0825196+211552 BD* 08 25 19.6125672818 +21 15 51.549358145       21.97 19.22 L7.5V 110 0
19 2MASS J08300825+4828482 BD* 08 30 08.1496038211 +48 28 47.538657498           L9.5 38 0
20 SDSS J083717.21-000018.0 BD* 08 37 17.20032 -00 00 19.3608           T1 45 0
21 2MASS J08503593+1057156 BD* 08 50 35.93400 +10 57 15.6168       22.466 20.349 L6.5+L8.5 75 0
22 2MASSI J0937347+293142 BD* 09 37 34.87968 +29 31 40.9908           T6 85 0
23 LP 261-75 B BD* 09 51 05.49288 +35 58 02.1288           L6V 56 0
24 2MASS J10210969-0304197 BD* 10 21 09.69240 -03 04 19.7904           T1+T4 71 0
25 2MASSW J1047539+212423 BD* 10 47 53.85456 +21 24 23.4684           T6.5 80 0
26 SIPS J1058-1548 BD* 10 58 47.8366017792 -15 48 17.250428304       20.095 17.764 L3V 90 2
27 2MASS J11463449+2230527 BD* 11 46 34.5341033040 +22 30 54.036482400           L3+L4 86 0
28 2MASS J12171110-0311131 BD* 12 17 11.10288 -03 11 13.1748           T7.5 81 0
29 2MASS J12255432-2739466 BD* 12 25 54.32328 -27 39 46.6776           T5.5+T8 57 0
30 SIPS J1228-1547 BD* 12 28 15.23184 -15 47 34.2312       20.187 18.163 L5.5+L5.5 142 0
31 2MASS J12373919+6526148 BD* 12 37 39.19632 +65 26 14.8092           T6.5 69 0
32 2MASS J12545393-0122474 BD* 12 54 53.9040607346 -01 22 47.399401142           T2e: 142 0
33 NAME Kelu-1 BD* 13 05 40.1642434199 -25 41 05.712165150         16.85 L2+L3.5 245 0
34 2MASS J13262981-0038314 BD* 13 26 29.81880 -00 38 31.4880           L5.5V 38 0
35 2MASS J13285503+2114486 BD* 13 28 55.03776 +21 14 48.6024           L5V 25 0
36 2MASS J13464634-0031501 BD* 13 46 46.34496 -00 31 50.1312           T6 72 0
37 GD 165B BD* 14 24 39.09480 +09 17 10.4352         20.53 L4V 201 0
38 2MASS J14392836+1929149 BD* 14 39 28.1499428599 +19 29 15.908790370           L1V 121 0
39 2MASS J14460061+0024519 BD* 14 46 00.61560 +00 24 51.9660           L5V 33 0
40 2MASSW J1507476-162738 BD* 15 07 47.6758255542 -16 27 40.113982846     22.136 18.928 16.579 L5V 183 0
41 * eta CrB C BD* 15 23 22.63488 +30 14 56.2092           L8V 99 1
42 2MASS J16241436+0029158 BD* 16 24 14.36712 +00 29 15.8172           T6V 137 0
43 2MASS J16322911+1904407 BD* 16 32 29.11416 +19 04 40.7136       22.42 19.98 L8V 126 0
44 LSPM J1658+7027 BD* 16 58 03.8028228991 +70 27 01.695233449       19.0   L1(e) 34 0
45 2MASSI J1711457+223204 BD* 17 11 45.73344 +22 32 04.4052           L5.0+T5.5 34 0
46 2MASSW J1728114+394859 BD* 17 28 11.50056 +39 48 59.3100           L5+L6.5 54 0
47 2MASS J17503293+1759042 BD* 17 50 32.93832 +17 59 04.2504           T3.5 48 0
48 2MASSW J1841086+311727 BD* 18 41 08.61480 +31 17 27.9600           L4Vpec 19 0
49 2MASSW J2101154+175658 BD* 21 01 15.44112 +17 56 58.6860           L7+L8 28 0
50 2MASSW J2224438-015852 BD* 22 24 43.8544128559 -01 58 53.284975671           L4.5V 118 0
51 2MASS J22552907-0034336 LM* 22 55 29.0832187176 -00 34 33.656819808     20.26     M8.6V 29 1
52 2MASSI J2356547-155310 BD* 23 56 54.77040 -15 53 11.1336           T5.8 40 0

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2022.11.26-11:02:44

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