First determination of the dynamical mass of a binary L dwarf

被引:78
作者
Bouy, H
Duchêne, G
Köhler, R
Brandner, W
Bouvier, J
Martín, EL
Ghez, A
Delfosse, X
Forveille, T
Allard, F
Baraffe, I
Basri, G
Close, L
McCabe, CE
机构
[1] Max Planck Inst Extraterr Phys, D-85748 Garching, Germany
[2] European So Observ, D-85748 Garching, Germany
[3] Max Planck Inst Astron, D-69117 Heidelberg, Germany
[4] Observ Grenoble, Astrophys Lab, F-38400 St Martin Dheres, France
[5] Inst Astrofis Canarias, E-38200 San Cristobal la Laguna, Spain
[6] Univ Calif Los Angeles, Div Astron & Astrophys, Los Angeles, CA 90095 USA
[7] Ecole Normale Super Lyon, Ctr Rech Astron Lyon, UML 5574, F-69364 Lyon 07, France
[8] Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA
[9] Univ Arizona, Steward Observ, Tucson, AZ 85721 USA
[10] Canada France Hawaii Telescope Corp, Kamuela, HI 96743 USA
来源
ASTRONOMY & ASTROPHYSICS | 2004年 / 423卷 / 01期
关键词
stars; low-mass; brown dwarfs; star : individual : 2MASSW J0746425+2000321; stars : binary (including multiple): close; techniques : high angular resolution; stars : binaries : visual;
D O I
10.1051/0004-6361:20040551
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present here the results of astrometric, photometric and spectroscopic observations leading to the determination of the orbit and dynamical masses of the binary L dwarf 2MASSW J0746425+2000321. High angular resolution observations spread over almost 4 years and obtained with the Hubble Space Telescope (HST), the ESO Very Large Telescope (VLT), and a the W. M. Keck Observatory (Keck) allow us to cover similar to36% of the period, corresponding to 60% of the orbit, and, for the first time. to derive a precise estimate of the total and individual masses of such a late-type object. We find an orbital period of 3850.9(-767)(+904) days. The corresponding total mass is 0.146(-0.006)(+0.016) M-circle dot with uncertainties depending on the distance. Spatially resolved low resolution optical (550-1025 nm) spectra have been obtained with HST/STIS, allowing us to measure the spectral types of the two components (L0 +/- 0.5 for the primary and L1.5 +/- 0.5 for the secondary). We also present precise photometry of the individual components measured on the high angular resolution images obtained with HST/ACS and WFPC2 (visible), VLT/NACO (J. H and K-S bands) and Keck I (K-S band). These spectral and photometric measurements enable us to estimate their effective temperatures and mass ratio, and to place the object accurately in a H-R diagram. The binary system is most likely formed by a primary with a mass of 0.085 +/- 0.010 M. and a secondary with a mass of 0.066 (sic) 0.006 M., thus clearly substellar. for an age of approximately 300 +/- 150 Myr. Halpha variability indicates chromospheric and/or magnetic activity.
引用
收藏
页码:341 / 352
页数:12
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