J/ApJ/804/30ivo://CDS.VizieR/J/ApJ/804/30doi:10.26093/cds/vizier.18040030CDSZiegler C.Law N.M.Baranec C.Riddle R.L.Fuchs J.T.2017-10-26T12:46:48Z2017-09-18T12:50:10ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frsubdwarf-starsmultiple-starslate-type-starsapparent-magnitudeCool 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 ({rho}>=0.15") and contrast ratios ({Delta}_mi_<=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 ~3{sigma} 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.2015ApJ...804...30Zhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/804/30CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/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)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/804/30https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/804/30http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/804/30https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/804/30https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/804/30http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/804/30GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/804/30/table5 (Full Robo-AO Observation List)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/804/30/table5?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/804/30/table5?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/804/30/table5?GETtext/xml+votable180.050000true0.9317792-3.59526940.0055555555555555565/4246 6/118 191 232 243 345 408 419 526 530 537 544 555 571 590 591 4222 4241 4323 4347 4383 4396 4524 4528 4619 4637 4682 4688 4714 4751 4760 4773 4776 8377 8409 8496 8576 8580 8614 8732 8776 8834 8850 8872 12473 12510 12559 12567 12603 12628 12692 12705 12839 12844 12868 12943 16759 16814 16850 16872 16889 16981 17004 17021 17049 17068 17092 17120 17149 17202 17216 17218 17253 17258 17309 17312 17318 17320 17330 17331 17332 17349 17358 17369 17378 17393 17488 17492 17554 17614 17633 17648 17652 17661 17667 17676 17695 17726 17928 17930 17950 17954 17959 17973 18295 18377 18432 18458 18471 18477 18489 18493 18523 18531 18540 18543 18579 18585 18587 18593 18612 18615 18653 18658 18663 18696 18737 18826 18953 18955 18973 19042 19083 19085 19388 19410 19421 19485 19668 19686 19722 19752 19753 19811 19854 19856 19875 19978 19999 20004 20050 21467 21757 21806 21814 21824 21835 22042 22056 22093 22179 22487 22636 22637 22658 22667 22674 22686 22691 22699 22708 22721 22734 22748 22751 22754 22763 22765 22769 22771 22782 22797 22806 22820 22837 22912 22946 23064 23092 23113 23122 23174 23177 23192 23209 23506 23851 23865 23869 23870 23889 23892 23893 23969 23978 24107 24109 24110 24136 24193 24195 24203 24233 25471 25527 25543 25573 25587 25821 25835 25848 25854 26132 26152 26154 26173 26182 26187 26209 26256 26550 26559 26746 26848 26868 26873 26891 26895 26902 26920 26925 26936 26939 26950 26955 27018 27143 27162 27180 27205 27601 27612 27622 27767 27830 27847 27857 27863 27920 27948 27962 27980 28070 28075 28201 28202 28210 28233 28245 28309 28329 28336 29907 30018 30021 30022 30023 30296 30711 31974 31975 32267 32283 32302 32308 32361 36249 36270 36271 36279 36343 36458 36474 36507 36508 36581 36593 36611 36612 36628 36638 36651 36657 36661 36668 36679 36718 36729 36757 36806 36813 36827 36849 40827 40908 40916 40924 40944 40949 40955 40957 48598 48974 48999 49084 49094 49150https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/804/30?format=asciidefaultJ/ApJ/804/30/table5Full Robo-AO Observation ListDateDate of the observationtime.epochnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNLTT[69/58812] NLTT number (NNNNN)meta.id;meta.mainintVmagV-band magnitudephot.mag;em.opt.VfloatQual[High/Medium/Low ] Observation qualitymeta.code.qual;obs.param;obscharComp[Yes-] Presence of detected companionmeta.codecharSimbadSimbad column added by the CDSmeta.ref.urlchar_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.main