TY - JOUR

T1 - Dynamical mass determination for the very low mass stars LHS 1070 B and C

AU - Leinert, Ch

AU - Jahreiß, H.

AU - Woitas, J.

AU - Zucker, S.

AU - Mazeh, T.

AU - Eckart, A.

AU - Köhler, R.

PY - 2001

Y1 - 2001

N2 - We followed the relative orbit of the close pair of very late-type stars in the nearby triple system LHS 1070 during the past seven years. These observations are used to derive the astrometric elements of the orbit. Using the period of 16.1 ± 1.4 years and assuming the distance of 7.39 pc given by van Altena (1995) to be exactly correct, the combined mass of components B and C is 0.138 ± 0.003 M⊙. Otherwise, this mass scales with the third power of the distance, which presently is not known to better than 9%. The dynamical mass would equal the combined mass of 0.161 ± 0.002 M⊙ derived from the theoretical mass-luminosity relation of Baraffe et al. (1998) and Chabrier et al. (2000) for a 5% larger distance of 7.78 pc. A critical comparison with the theoretical relations therefore has to await more precise parallax determinations for this comparatively faint system with visual magnitude V = 15.3. The wide orbit of component A around the center of mass of components B and C cannot yet be determined from our measurements. However, we can show that it is probably co-planar with the close pair orbit and should have a period in the range 60-1000 years.

AB - We followed the relative orbit of the close pair of very late-type stars in the nearby triple system LHS 1070 during the past seven years. These observations are used to derive the astrometric elements of the orbit. Using the period of 16.1 ± 1.4 years and assuming the distance of 7.39 pc given by van Altena (1995) to be exactly correct, the combined mass of components B and C is 0.138 ± 0.003 M⊙. Otherwise, this mass scales with the third power of the distance, which presently is not known to better than 9%. The dynamical mass would equal the combined mass of 0.161 ± 0.002 M⊙ derived from the theoretical mass-luminosity relation of Baraffe et al. (1998) and Chabrier et al. (2000) for a 5% larger distance of 7.78 pc. A critical comparison with the theoretical relations therefore has to await more precise parallax determinations for this comparatively faint system with visual magnitude V = 15.3. The wide orbit of component A around the center of mass of components B and C cannot yet be determined from our measurements. However, we can show that it is probably co-planar with the close pair orbit and should have a period in the range 60-1000 years.

KW - Binaries

KW - Low-mass stars

KW - Mass-luminosity relation

UR - http://www.scopus.com/inward/record.url?scp=0035242847&partnerID=8YFLogxK

U2 - 10.1051/0004-6361:20000408

DO - 10.1051/0004-6361:20000408

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AN - SCOPUS:0035242847

SN - 0004-6361

VL - 367

SP - 183

EP - 188

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

IS - 1

ER -