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Exploring the Variable Sky with LINEAR. III. Classification of Periodic Light Curves

Palaversa, Lovro and Ivezić, Željko and Eyer, Laurent and Ruždjak, Domagoj and Sudar, Davor and Galin, Mario and Kroflin, Andrea and Mesarić, Martina and Munk, Petra and Vrbanec, Dijana and Božić, Hrvoje and Loebman, Sarah and Sesar, Branimir and Rimoldini, Lorenzo and Hunt-Walker, Nicholas and VanderPlas, Jacob and Westman, David and Stuart, J. Scott and Becker, Andrew C. and Srdoć, Gregor and Wozniak, Przemysław and Oluseyi, Hakeem (2013) Exploring the Variable Sky with LINEAR. III. Classification of Periodic Light Curves. Astronomical Journal, 146 (4). Art. No. 101. ISSN 0004-6256. doi:10.1088/0004-6256/146/4/101.

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We describe the construction of a highly reliable sample of ~7000 optically faint periodic variable stars with light curves obtained by the asteroid survey LINEAR across 10,000 deg^2 of the northern sky. The majority of these variables have not been cataloged yet. The sample flux limit is several magnitudes fainter than most other wide-angle surveys; the photometric errors range from ~0.03 mag at r = 15 to ~0.20 mag at r = 18. Light curves include on average 250 data points, collected over about a decade. Using Sloan Digital Sky Survey (SDSS) based photometric recalibration of the LINEAR data for about 25 million objects, we selected ~200,000 most probable candidate variables with r < 17 and visually confirmed and classified ~7000 periodic variables using phased light curves. The reliability and uniformity of visual classification across eight human classifiers was calibrated and tested using a catalog of variable stars from the SDSS Stripe 82 region and verified using an unsupervised machine learning approach. The resulting sample of periodic LINEAR variables is dominated by 3900 RR Lyrae stars and 2700 eclipsing binary stars of all subtypes and includes small fractions of relatively rare populations such as asymptotic giant branch stars and SX Phoenicis stars. We discuss the distribution of these mostly uncataloged variables in various diagrams constructed with optical-to-infrared SDSS, Two Micron All Sky Survey, and Wide-field Infrared Survey Explorer photometry, and with LINEAR light-curve features. We find that the combination of light-curve features and colors enables classification schemes much more powerful than when colors or light curves are each used separately. An interesting side result is a robust and precise quantitative description of a strong correlation between the light-curve period and color/spectral type for close and contact eclipsing binary stars (β Lyrae and W UMa): as the color-based spectral type varies from K4 to F5, the median period increases from 5.9 hr to 8.8 hr. These large samples of robustly classified variable stars will enable detailed statistical studies of the Galactic structure and physics of binary and other stars and we make these samples publicly available.

Item Type:Article
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URLURL TypeDescription DOIArticle Paper
Ivezić, Željko0000-0001-5250-2633
Loebman, Sarah0000-0003-3217-5967
Sesar, Branimir0000-0002-0834-3978
Wozniak, Przemysław0000-0002-9919-3310
Additional Information:© 2013 The American Astronomical Society. Received 2013 June 9; accepted 2013 July 30; published 2013 September 16. The authors thank Gaia Coordination Unit 7 (based at ISDC, Department of Astronomy, University of Geneva, Switzerland) for the help and infrastructure used in the calculation of Lomb–Scargle and generalized Lomb–Scargle periods. L.P. acknowledges support from the Gaia Research for European Astronomy Training (GREAT-ITN) Marie Curie network, funded through the European Union Seventh Framework Programme ([FP7/2007-2013] under grant agreement No. 264895). Ž.I. acknowledges support by NSF grants AST-0707901 and AST-1008784 to the University of Washington, by NSF grant AST-0551161 to LSST for design and development activity, and by the Croatian National Science Foundation grant O-1548-2009. The LINEAR program is funded by the National Aeronautics and Space Administration at MIT Lincoln Laboratory under Air Force Contract FA8721-05-C-0002. Opinions, interpretations, conclusions and recommendations are those of the authors and are not necessarily endorsed by the United States Government.
Funding AgencyGrant Number
Marie Curie FellowshipUNSPECIFIED
European Research Council (ERC)264895 GENIUS
Croatian National Science FoundationO-1548-2009
Air ForceFA8721-05-C-0002
Subject Keywords:binaries: eclipsing; blue stragglers; catalogs; Galaxy: halo; stars: statistics; stars: variables: general
Issue or Number:4
Record Number:CaltechAUTHORS:20131015-094234269
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Official Citation:Lovro Palaversa et al. 2013 The Astronomical Journal 146 101 doi:10.1088/0004-6256/146/4/101
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:41915
Deposited By: Tony Diaz
Deposited On:15 Oct 2013 20:31
Last Modified:10 Nov 2021 04:35

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