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Machine-learned Identification of RR Lyrae Stars from Sparse, Multi-band Data: The PS1 Sample

Sesar, B.; Hernitschek, N.; Mitrović, S.; Ivezić, Ž; Rix, H.-W.; Cohen, J.G.; Bernard, E.J.; Grebel, E.K.; Martin, N.F.; Schlafly, E.F.; Burgett, W.S.; Draper, P.W.; Flewelling, H.; Kaiser, N.; Kudritzki, R.P.; Magnier, E.A.; Metcalfe, N.; Tonry, J.L.; Waters, C.

Machine-learned Identification of RR Lyrae Stars from Sparse, Multi-band Data: The PS1 Sample Thumbnail


B. Sesar

N. Hernitschek

S. Mitrović

Ž Ivezić

H.-W. Rix

J.G. Cohen

E.J. Bernard

E.K. Grebel

N.F. Martin

E.F. Schlafly

W.S. Burgett

P.W. Draper

H. Flewelling

N. Kaiser

R.P. Kudritzki

E.A. Magnier

J.L. Tonry

C. Waters


RR Lyrae stars may be the best practical tracers of Galactic halo (sub-)structure and kinematics. The PanSTARRS1 (PS1) $3\pi $ survey offers multi-band, multi-epoch, precise photometry across much of the sky, but a robust identification of RR Lyrae stars in this data set poses a challenge, given PS1's sparse, asynchronous multi-band light curves ($\lesssim 12$ epochs in each of five bands, taken over a 4.5 year period). We present a novel template fitting technique that uses well-defined and physically motivated multi-band light curves of RR Lyrae stars, and demonstrate that we get accurate period estimates, precise to 2 s in $\gt 80 \% $ of cases. We augment these light-curve fits with other features from photometric time-series and provide them to progressively more detailed machine-learned classification models. From these models, we are able to select the widest (three-fourths of the sky) and deepest (reaching 120 kpc) sample of RR Lyrae stars to date. The PS1 sample of ~45,000 RRab stars is pure (90%) and complete (80% at 80 kpc) at high galactic latitudes. It also provides distances that are precise to 3%, measured with newly derived period–luminosity relations for optical/near-infrared PS1 bands. With the addition of proper motions from Gaia and radial velocity measurements from multi-object spectroscopic surveys, we expect the PS1 sample of RR Lyrae stars to become the premier source for studying the structure, kinematics, and the gravitational potential of the Galactic halo. The techniques presented in this study should translate well to other sparse, multi-band data sets, such as those produced by the Dark Energy Survey and the upcoming Large Synoptic Survey Telescope Galactic plane sub-survey.


Sesar, B., Hernitschek, N., Mitrović, S., Ivezić, Ž., Rix, H., Cohen, J., …Waters, C. (2017). Machine-learned Identification of RR Lyrae Stars from Sparse, Multi-band Data: The PS1 Sample. Astronomical Journal, 153(5), Article 204.

Journal Article Type Article
Acceptance Date Mar 7, 2017
Online Publication Date Apr 7, 2017
Publication Date Apr 7, 2017
Deposit Date May 9, 2017
Publicly Available Date May 17, 2017
Journal Astronomical Journal
Print ISSN 0004-6256
Publisher IOP Publishing
Peer Reviewed Peer Reviewed
Volume 153
Issue 5
Article Number 204


Published Journal Article (11.3 Mb)

Copyright Statement
Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

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