J/ApJ/466/415 Spectroscopic orbits for three binaries (Mazeh+ 1996)
Spectroscopic orbits for three binaries with low-mass companions and
the distribution of secondary masses near the substellar limit
Mazeh T., Latham D.W., Stefnik R.P.
<Astrophys. J. 466, 415 (1996)>
=1996ApJ...466..415M 1996ApJ...466..415M
ADC_Keywords: Binaries, spectroscopic ; Radial velocities
Keywords: binaries: spectroscopic - stars: low-mass, brown dwarfs -
stars: individual (HD 29587, HD 114762, HD 140913)
Abstract:
We present orbital solutions for three low-amplitude spectroscopic
binaries discovered in a sample of 20 solar-type IAU radial velocity
standard stars observed with the Digital Speedometers at the Harvard-
Smithsonian Center for Astrophysics. We update the orbital solutions
for HD 114762 and HD 140913, and present a preliminary new solution
for HD 29587. For all three orbits, the minimum mass for the secondary
is less than 0.08M☉, the borderline between stellar and
substellar masses. We consider the probability that all three binaries
have small enough inclination angles so that their companions are
above the substellar limit. To do so, we treat the 20 IAU standards as
a sample drawn from a population of binaries with a mass-ratio
distribution that does not allow any substellar companions. We
calculate the probability that such a sample could still have three
binaries, with the low-amplitude orbits actually found within the IAU
sample. We show that this probability is small, depending on the
specific mass-ratio distribution. For example, a flat mass-ratio
distribution that assumes there are no substellar companions can be
excluded at a high confidence level, 99.7%. We further show that our
three detections may imply that the secondary-mass distribution rises
near the substellar limit. However, the observations do not yet allow
us to distinguish whether the unseen companions of HD 114762, HD
140913, and HD 29587 have stellar or substellar masses. In particular,
recent attempts to estimate the mass of the companion of HD 114762
based on assumptions about the intrinsic rotation of the primary are
inconclusive, and the companion could easily have a mass as low as
0.02M☉. We compare our three detections with the null results of
four very precise radial velocity searches for substellar companions.
The difference is indeed puzzling but can be accounted for if just a
small fraction of the solar-type stars, of the order of a few percent,
have companions with masses near the substellar limit.
Objects:
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RA (2000) DE Designation(s)
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04 41 33.9 +42 07 28 HD 29587
13 12 21.7 +17 31 01 HD 114762
15 45 07.7 +28 28 10 HD 140913
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 71 3050 Individual velocities
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Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- HD Henry Draper Catalog number (Cat. III/135)
13- 14 I2 h RAh Right ascension, J2000
16- 17 I2 min RAm Right ascension, J2000
19- 22 F4.1 s RAs Right ascension, J2000
24 A1 --- DE- Declination sign
25- 26 I2 deg DEd Declination, J2000
28- 29 I2 arcmin DEm Declination, J2000
31- 32 I2 arcsec DEs Declination, J2000
34- 46 F13.5 d HJD Heliocentric Julian Date
48- 54 F7.2 km/s RV Barycentric radial velocity
57- 61 F5.2 km/s e_RV Internal estimate of velocity error
63- 66 F4.1 --- TDR Tonry-Davis (1979AJ.....84.1511T 1979AJ.....84.1511T) R value
68- 71 F4.2 --- CC Peak value of the correlation coefficient
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Origin: AAS CD-ROM series, Volume 7, 1996 Lee Brotzman [ADS] 22-Oct-96
(End) [CDS] 03-Feb-1997