J/AJ/132/663 Differential Velocities of very low mass SBs (Basri+, 2006) ================================================================================ A survey for spectroscopic binaries among very low mass stars. Basri G., Reiners A. =2006AJ....132..663B ================================================================================ ADC_Keywords: Binaries, spectroscopic ; Radial velocities Keywords: binaries: close - stars: formation - stars: low-mass, brown dwarfs Abstract: We report on the results of a survey for radial velocity variability in a heterogeneous sample of very low mass stars and brown dwarfs. One distinguishing characteristic of the survey is its time span, which allows an overlap between spectroscopic binaries and those that can be found by high angular resolution imaging. Despite our relatively low velocity precision, we are able to place a new constraint on the total binary fraction in these objects, which suggests that they are more likely the result of extending the same processes at work at higher masses into this mass range, rather than a distinct mode of formation. Description: Our sample was largely determined by the observations discussed in Mohanty & Basri (2003ApJ...583..451M). All observations were conducted with the High Resolution Echelle Spectrometer (HIRES) on the Keck I telescope. The sample consists of a collection of stars M5 and later, which was assembled during the years of discovery of VLMs, and so is rather heterogeneous. They are all field objects and tend to be at the brighter end of the objects discovered. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table2.dat 54 14 Stars with indications for radial velocity variabilities table3.dat 54 39 Stars with probably constant radial velocities table5.dat 28 132 Differential radial velocities for all sets of observations -------------------------------------------------------------------------------- Byte-by-byte Description of file: table[23].dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1 I1 --- sigma [1,2]? 1 or 2 sigma detection (in table2 only) 3- 11 A9 --- Name Object name 12 A1 --- n_Name [f] f for flare star 14- 17 A4 --- SpType MK spectral type 20 I1 --- Nbsp Number of spectra 21 A1 --- n_Nbsp Note on Nbsp (1) 23- 25 F3.1 km/s DRV1 Differential radial velocity between the two exposures, corrected for the barycentric velocity on the two night of observation 27- 29 F3.1 km/s e_DRV1 ? rms uncertainty on DVstar 31- 34 F4.1 km/s DRV2 ?=- Mean absolute virtual shift from the stars in which the reference value of the shift has been derived from telluric bands 35 A1 --- n_DRV2 [c] c: From water bands 37- 39 F3.1 km/s DRV Final radial velocity variation 41- 43 F3.1 km/s e_DRV rms uncertainty on DRVtot 45- 48 I4 d DTmax Time difference between our earliest and latest exposure 50- 54 F5.3 --- Prob Probability that a random measurement of a radial velocity shift DRVtot in a single star is smaller than the one we have measured -------------------------------------------------------------------------------- Note (1): Notes as follows: a = Only orders 41 and 44 b = Only orders 41 and 42 d = Only orders 41, 42, and 45 e = Only order 44 -------------------------------------------------------------------------------- Byte-by-byte Description of file: table5.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 9 A9 --- Name Object name 11- 20 A10 "YYYY/MM/DD" Obs.Date Date of the observation 22- 24 F3.1 km/s DRV Differential radial velocity (1) 26- 28 F3.1 km/s e_DRV Uncertainty in DRV (2) -------------------------------------------------------------------------------- Note (1): In each set, the bluemost observation is arbitrarily given a differential radial velocity of zero, and the other epochs have the difference in velocity relative to that one listed. Note (2): The error given is the same as described in Section 2.1, except that no telluric shift or error has been added. -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Greg Schwarz [AAS], Patricia Vannier [CDS] 11-Jan-2008