A spectroscopic and proper motion search of Sloan Digital Sky Survey: red subdwarfs in binary systems

Zhang, ZH; Pinfield, D. J.; Burningham, B.; Jones, H. R. A.; Gálvez-Ortiz, M. C.; Catalán, S.; Smart, R. L.; Lépine, Sébastien; Clarke, J. R. A.; Pavlenko, Ya. V.; Murray, D. N.; Кузнецов, М. К.; Day-Jones, A. C.; Gomes, Jorge; Marocco, F.; Sipőcz, Brigitta

doi:10.1093/mnras/stt1030

Cited by 35 publications

(37 citation statements)

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“…The new SDSS spectra made public by Savcheva et al (2014) improve our classification too (Covey et al 2007), which does not include low-metallicity M dwarfs. In this work we confirm their low-metallicity (Table 4) • Five candidates in Zhang et al (2013): ID = 7 (usdM6), 33 (sdM6), 43 (esdM6), 67 (esdM6), and 85 (sdM6). These spectral types agree with our final classification for these objects, except for ID = 43 and ID = 85 which we classify as a sdM8.0 and esdM5.5-6.0, respectively…”

Section: New Late-type Subdwarfssupporting

confidence: 72%

“…For our confirmed subdwarfs whose spectral types are not covered above, we inferred their spectrophotometric distances using the polynomial fits of the J-band in Table 2 of Zhang et al (2013). These polynomial are only valid up to spectral types as late as M9.5 so we do not quote distances for our L subdwarfs although we can guess that the two brightest are most likely within 100 pc.…”

Section: Spectroscopic Distances To Our New Subdwarfsmentioning

confidence: 99%

“…After the first spectral classification for M subdwarfs proposed by Gizis (1997), other authors contributed to the increase in the numbers of this type of objects. New M subdwarfs with spectral types later than M7 were published in Gizis & Reid (1997), Schweitzer et al (1999), Lépine et al (2003b), Scholz et al (2004a), Scholz et al (2004b), Lépine & Scholz (2008), Cushing et al (2009), Kirkpatrick et al (2010), Lodieu et al (2012), and Zhang et al (2013). The largest samples come from Lépine & Scholz (2008), Kirkpatrick et al (2010), Lodieu et al (2012), and Zhang et al (2013) and include 23, 15, 20, and 30 new cool subdwarfs, respectively.…”

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confidence: 99%

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New ultracool subdwarfs identified in large-scale surveys using Virtual Observatory tools

Lodieu

Contreras

Osorio

et al. 2017

A&A

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Aims. We aim at developing an efficient method to search for late-type subdwarfs (metal-depleted dwarfs with spectral types ≥ M5) to improve the current statistics. Our objectives are: improve our knowledge of metal-poor low-mass dwarfs, bridge the gap between the late-M and L types, determine their surface density, and understand the impact of metallicity on the stellar and substellar mass function. Methods. We carried out a search cross-matching the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) and the Two Micron All Sky Survey (2MASS), and different releases of SDSS and the United Kingdom InfraRed Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS) using STILTS, Aladin, and Topcat developed as part of the Virtual Observatory tools. We considered different photometric and proper motion criteria for our selection. We identified 29 and 71 late-type subdwarf candidates in each crosscorrelation over 8826 and 3679 square degrees, respectively (2312 square degrees overlap). We obtained our own low-resolution optical spectra for 71 of our candidates. : 26 were observed with the Gran Telescopio de Canarias (GTC; R ∼ 350, λλ5000-10000 Å), six with the Nordic Optical Telescope (NOT; R ∼ 450, λλ5000-10700 Å), and 39 with the Very Large Telescope (VLT; R ∼ 350, λλ6000-11000 Å). We also retrieved spectra for 30 of our candidates from the SDSS spectroscopic database (R ∼ 2000 and λλ 3800-9400 Å), nine of these 30 candidates with an independent spectrum in our follow-up. We classified 92 candidates based on 101 optical spectra using two methods: spectral indices and comparison with templates of known subdwarfs. Results. We developed an efficient photometric and proper motion search methodology to identify metal-poor M dwarfs. We confirmed 86% and 94% of the candidates as late-type subdwarfs from the SDSS vs 2MASS and SDSS vs UKIDSS cross-matches, respectively. These subdwarfs have spectral types ranging between M5 and L0.5 and SDSS magnitudes in the r = 19.4-23.3 mag range. Our new late-type M discoveries include 49 subdwarfs, 25 extreme subdwarfs, six ultrasubdwarfs, one subdwarf/extreme subdwarf, and two dwarfs/subdwarfs. In addition, we discovered three early-L subdwarfs to add to the current compendium of L-type subdwarfs known to date. We doubled the numbers of cool subdwarfs (11 new from SDSS vs 2MASS and 50 new from SDSS vs UKIDSS). We derived a surface density of late-type subdwarfs of 0.040 +0.012 −0.007 per square degree in the SDSS DR7 vs UKIDSS LAS DR10 cross-match (J = 15.9-18.8 mag) after correcting for incompleteness. The density of M dwarfs decreases with decreasing metallicity. We also checked the Wide Field Survey Explorer (AllWISE) photometry of known and new subdwarfs and found that midinfrared colours of M subdwarfs do not appear to differ from their solar-metallicity counterparts of similar spectral types. However, the near-to-mid-infrared colours J − W2 and J − W1 are bluer for lower metallicity dwarfs, results that may be used as a criterion to look for late-type subdwarfs in future sea...

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Section: New Late-type Subdwarfssupporting

confidence: 72%

Section: Spectroscopic Distances To Our New Subdwarfsmentioning

confidence: 99%

mentioning

confidence: 99%

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New ultracool subdwarfs identified in large-scale surveys using Virtual Observatory tools

Lodieu

Contreras

Osorio

et al. 2017

A&A

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“…Recent new proper motion surveys with fainter magnitude limits like SuperBLINK (Lépine & Shara 2005), SuperCOSMOS-RECONS , and SIPS (Deacon et al 2005) have discovered many new metal-deficient high proper motion subdwarf candidates. To confirm that these candidates are, indeed, cool subdwarfs, spectroscopic observations are typically necessary, such as those by (Scholz et al 2004b;Jao et al 2008;Zhang et al 2013). Large sky spectroscopic surveys like SDSS and LAMOST have also provided systematic ways to identify cool subdwarfs (West et al 2004;Zhong et al 2015).…”

Section: Discussion: Observational Differences Between Dwarfs and Submentioning

confidence: 99%

The Solar Neighborhood. XLII. Parallax Results from the CTIOPI 0.9 m Program—Identifying New Nearby Subdwarfs Using Tangential Velocities and Locations on the H–R Diagram

Jao

Henry²,

Winters

et al. 2017

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Parallaxes, proper motions, and optical photometry are presented for 51 systems consisting of 37 cool subdwarf and 14 additional high proper motion systems. Thirty-seven systems have parallaxes reported for the first time, 15 of which have proper motions of at least 1″ yr −1 . The sample includes 22 newly identified cool subdwarfs within 100 pc, of which three are within 25 pc, and an additional five subdwarfs from 100 to 160 pc. Two systems-LSR 1610-0040 AB and LHS 440 AB-are close binaries exhibiting clear astrometric perturbations that will ultimately provide important masses for cool subdwarfs. We use the accurate parallaxes and proper motions provided here, combined with additional data from our program and others, to determine that effectively all nearby stars with tangential velocities greater than 200 km s −1 are subdwarfs. We compare a sample of 167 confirmed cool subdwarfs to nearby main sequence dwarfs and Pleiades members on an observational Hertzsprung-Russell diagram using M V versus(V − K s ) to map trends of age and metallicity. We find that subdwarfs are clearly separated for spectral types K5-M5, indicating that the low metallicities of subdwarfs set them apart in the H-R diagram for (V − K s )=3-6. We then apply the tangential velocity cutoff and the subdwarf region of the H-R diagram to stars with parallaxes from Gaia Data Release 1 and the MEarth Project to identify a total of 29 new nearby subdwarf candidates that fall clearly below the main sequence.

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“…Proper motions measured from the large surveys have enabled us to identify the substellar members of nearby young moving groups (e.g., Gagné et al 2015cGagné et al , 2015bFaherty et al 2016;Liu et al 2016), a population crucial to our understanding of brown dwarf evolution over their first few hundred million years. Proper motions from large catalogs have also identified wide, comoving companions to higher-mass stars, whose ages and metallicities can more easily be determined (e.g., Luhman et al 2012;Burningham et al 2013;Zhang et al 2013;Smith et al 2014a), making the ultracool companions important benchmarks for constraining atmospheric and evolutionary models.…”

Section: Introductionmentioning

confidence: 99%

Photometry and Proper Motions of M, L, and T Dwarfs from the Pan-STARRS1 3 π Survey

Best

Magnier

Liu

et al. 2017

ApJS

119

110

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractWe present a catalog of 9888 M, L and T dwarfs detected in the Pan-STARRS13π Survey (PS1), covering threequarters of the sky. Our catalog contains nearly all known objects of spectral types L0-T2 in the PS1 field, with objects as early as M0 and as late as T9, and includes PS1, 2MASS, AllWISE, and GaiaDR1 photometry. We analyze the different types of photometry reported by PS1 and use two types in our catalog in order to maximize both depth and accuracy. Using parallaxes from the literature, we construct empirical SEDs for field ultracool dwarfs spanning 0.5-12 μm. We determine typical colors of M0-T9 dwarfs and highlight the distinctive colors of subdwarfs and young objects. We combine astrometry from PS1, 2MASS, and GaiaDR1 to calculate new proper motions for our catalog. We achieve a median precision of 2.9mas yr −1 , a factor of ≈3−10 improvement over previous large catalogs. Our catalog contains proper motions for 2405M6-T9 dwarfs and includes the largest set of homogeneous proper motions for L and T dwarfs published to date, 406objects for which there were no previous measurements, and 1176objects for which we improve upon previous literature values. We analyze the kinematics of ultracool dwarfs in our catalog and find evidence that bluer but otherwise generic late-M and Lfield dwarfs (i.e., not subdwarfs) tend to have tangential velocities higher than those of typical field objects. With the public release of the PS1 data, this survey will continue to be an essential tool for characterizing the ultracool dwarf population.

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A spectroscopic and proper motion search of Sloan Digital Sky Survey: red subdwarfs in binary systems

Cited by 35 publications

References 118 publications

New ultracool subdwarfs identified in large-scale surveys using Virtual Observatory tools

New ultracool subdwarfs identified in large-scale surveys using Virtual Observatory tools

The Solar Neighborhood. XLII. Parallax Results from the CTIOPI 0.9 m Program—Identifying New Nearby Subdwarfs Using Tangential Velocities and Locations on the H–R Diagram

Photometry and Proper Motions of M, L, and T Dwarfs from the Pan-STARRS1 3 π Survey

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