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J/ApJ/804/30      Robo-AO observed cool subdwarf companions     (Ziegler+, 2015)

Multiplicity of the Galactic senior citizens: a high-resolution search for cool subdwarf companions. Ziegler C., Law N.M., Baranec C., Riddle R.L., Fuchs J.T. <Astrophys. J., 804, 30 (2015)> =2015ApJ...804...30Z (SIMBAD/NED BibCode)
ADC_Keywords: Stars, subdwarf ; Stars, double and multiple ; Stars, late-type ; Magnitudes Keywords: binaries: close - instrumentation: adaptive optics - methods: data analysis - stars: late-type - subdwarfs - techniques: high angular resolution Abstract: Cool subdwarfs are the oldest members of the low-mass stellar population. Mostly present in the galactic halo, subdwarfs are characterized by their low-metallicity. Measuring their binary fraction and comparing it to solar-metallicity stars could give key insights into the star formation process early in the Milky Way's history. However, because of their low luminosity and relative rarity in the solar neighborhood, binarity surveys of cool subdwarfs have suffered from small sample sizes and incompleteness. Previous surveys have suggested that the binary fraction of red subdwarfs is much lower than for their main-sequence cousins. Using the highly efficient Robo-AO system, we present the largest high-resolution survey of subdwarfs, sensitive to angular separations (ρ≥0.15") and contrast ratios (Δmi≤6) invisible in past surveys. Of 344 target cool subdwarfs, 43 are in multiple systems, 19 of which are newly discovered, for a binary fraction of 12.5±1.9%. We also discovered seven triple star systems for a triplet fraction of 2.0±0.8%. Comparisons to similar surveys of solar-metallicity dwarf stars gives a ∼3σ disparity in luminosity between companion stars, with subdwarfs displaying a shortage of low-contrast companions. We also observe a lack of close subdwarf companions in comparison to similar-mass dwarf multiple systems. Description: We selected targets from the 564 spectral type F- through M-subdwarf candidates studied by Marshall (2007, J/AJ/134/778). These targets were selected from the New Luyten Two-Tenths catalog (NLTT; Luyten, 1979nlcs.book.....L; Luyten & Hughes 1980, Proper-Motion Survey with the Forty-Eight Inch Schmidt Telescope LV First Supplement to the NLTT Catalogue (Minneapolis, MN: Univ. Minnesota Press)) of high proper motion stars (>0.18 arcsec/yr) using a reduced proper motion diagram (RPM). Of the 552 subdwarfs confirmed by Marshall, a randomly selected sample of 348 G-, K-, and M-subdwarfs were observed by Robo-AO when available between other high priority surveys. We obtained high-angular-resolution images of the 348 subdwarfs during 32 separate nights of observations between 2012 September 3 and 2013 August 21 (UT). The observations were performed using the Robo-AO laser adaptive optics system (Riddle et al. 2012SPIE.8447E..2OR; Baranec et al. 2013, J. Visualized Exp. 72 e50021; 2014ApJ...790L...8B) mounted on the Palomar 60 inch telescope. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table5.dat 33 344 Full Robo-AO Observation List
See also: I/98 : NLTT Catalogue (Luyten, 1979) J/ApJ/582/1011 : Revised NLTT Catalog (Salim+, 2003) J/PASP/115/22 : Stellar parameters for 134 cool subdwarfs (Yong+, 2003) J/AJ/134/778 : BVRI photometry of candidate subdwarfs (Marshall, 2007) J/ApJ/799/4 : Robo-AO observations of binary stars (Riddle+, 2015) Byte-by-byte Description of file: table5.dat
Bytes Format Units Label Explanations
1- 5 I5 --- NLTT [69/58812] NLTT number (NNNNN) 7- 10 F4.1 --- Vmag V-band magnitude 12- 22 A11 "date" Date Date of the observation 24- 29 A6 --- Qual [High/Medium/Low ] Observation quality 31- 33 A3 --- Comp [Yes-] Presence of detected companion
History: From electronic version of the journal
(End) Prepared by Tiphaine Pouvreau [CDS] 14-Sep-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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