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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, Wei-Chun and Henry, Todd J. and Winters, Jennifer G. and Subasavage, John P. and Riedel, Adric R. and Silverstein, Michele L. and Ianna, Philip A. (2017) 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. Astronomical Journal, 154 (5). Art. No. 191. ISSN 1538-3881.

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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.

Item Type:Article
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URLURL TypeDescription Paper
Jao, Wei-Chun0000-0003-0193-2187
Winters, Jennifer G.0000-0001-6031-9513
Subasavage, John P.0000-0001-5912-6191
Riedel, Adric R.0000-0003-1645-8596
Silverstein, Michele L.0000-0003-2565-7909
Additional Information:© 2017 The American Astronomical Society. Received 2017 August 9; revised 2017 September 6; accepted 2017 September 6; published 2017 October 20. The astrometric observations reported here began as part of the NOAO Surveys Program in 1999 and continued on the CTIO 0.9 m via the SMARTS Consortium starting in 2003. We gratefully acknowledge support from the National Science Foundation (grants AST 05-07711, AST 09-08402, and AST 14-12026), NASA's Space Interferometry Mission, and Georgia State University, which together have made this long-term effort possible. We also thank the members of the SMARTS Consortium, who enable the operations of the small telescopes at CTIO, as well as the supporting observers at CTIO, specifically Edgardo Cosgrove, Arturo Gómez, Alberto Miranda, and Joselino Vásquez. The HST-FGS observations were supported under program 11943 by NASA through grants from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This work also has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, Funding for the DPAC has been provided by national institutions, particularly the institutions participating in the Gaia Multilateral Agreement. The Pan-STARRS1 Surveys (PS1) and the PS1 public science archive, which were used for this study, have been made possible through contributions by the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg, the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, the Queen's University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under Grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation through Grant No. AST-1238877, the University of Maryland, Eotvos Lorand University (ELTE), the Los Alamos National Laboratory, and the Gordon and Betty Moore Foundation.
Funding AgencyGrant Number
Georgia State UniversityUNSPECIFIED
Eotvos Lorand University (ELTE)UNSPECIFIED
Los Alamos National LaboratoryUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Subject Keywords:astrometry – solar neighborhood – stars: distances – stars: low-mass – subdwarfs
Issue or Number:5
Record Number:CaltechAUTHORS:20171018-161440565
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Official Citation:Wei-Chun Jao et al 2017 AJ 154 191
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82473
Deposited By: Tony Diaz
Deposited On:18 Oct 2017 23:23
Last Modified:09 Mar 2020 13:19

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