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Statistical Searches for Microlensing Events in Large, Non-uniformly Sampled Time-Domain Surveys: A Test Using Palomar Transient Factory Data

Price-Whelan, Adrian M. and Agüeros, Marcel A. and Fournier, Amanda P. and Street, Rachel and Ofek, Eran O. and Covey, Kevin R. and Levitan, David and Laher, Russ R. and Sesar, Branimir and Surace, Jason (2014) Statistical Searches for Microlensing Events in Large, Non-uniformly Sampled Time-Domain Surveys: A Test Using Palomar Transient Factory Data. Astrophysical Journal, 781 (1). Art. No. 35. ISSN 0004-637X.

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Many photometric time-domain surveys are driven by specific goals, such as searches for supernovae or transiting exoplanets, which set the cadence with which fields are re-imaged. In the case of the Palomar Transient Factory (PTF), several sub-surveys are conducted in parallel, leading to non-uniform sampling over its ~20,000 deg^2 footprint. While the median 7.26 deg^2 PTF field has been imaged ~40 times in the R band, ~2300 deg^2 have been observed >100 times. We use PTF data to study the trade off between searching for microlensing events in a survey whose footprint is much larger than that of typical microlensing searches, but with far-from-optimal time sampling. To examine the probability that microlensing events can be recovered in these data, we test statistics used on uniformly sampled data to identify variables and transients. We find that the von Neumann ratio performs best for identifying simulated microlensing events in our data. We develop a selection method using this statistic and apply it to data from fields with >10 R-band observations, 1.1 × 10^9 light curves, uncovering three candidate microlensing events. We lack simultaneous, multi-color photometry to confirm these as microlensing events. However, their number is consistent with predictions for the event rate in the PTF footprint over the survey's three years of operations, as estimated from near-field microlensing models. This work can help constrain all-sky event rate predictions and tests microlensing signal recovery in large data sets, which will be useful to future time-domain surveys, such as that planned with the Large Synoptic Survey Telescope.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Price-Whelan, Adrian M.0000-0003-0872-7098
Agüeros, Marcel A.0000-0001-7077-3664
Street, Rachel0000-0001-6279-0552
Ofek, Eran O.0000-0002-6786-8774
Covey, Kevin R.0000-0001-6914-7797
Laher, Russ R.0000-0003-2451-5482
Sesar, Branimir0000-0002-0834-3978
Surace, Jason0000-0001-7291-0087
Additional Information:© 2014 American Astronomical Society. Received 2013 June 21; accepted 2013 November 13; published 2014 January 6. We thank E. Bowsher, S. Douglas, and S. Tang for their assistance in obtaining spectra for our candidates and M. Modjaz for help in interpreting several of these spectra. We are grateful to the anonymous referee and to our editor, E. Feigelson, for comments that improved the paper. This paper is based upon work supported by a National Science Foundation Graduate Research Fellowship under grant No. 11-44155 and on observations obtained with the Samuel Oschin Telescope as part of the Palomar Transient Factory project, a scientific collaboration between the California Institute of Technology, Columbia University, Las Cumbres Observatory, the Lawrence Berkeley National Laboratory, the National Energy Research Scientific Computing Center, the University of Oxford, and the Weizmann Institute of Science. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the US Department of Energy Office of Science. The SDSS-III Web site is SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, University of Cambridge, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University. This publication makes use of data products from the Widefield Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. This research made use of Astropy, a community-developed core Python package for astronomy (Astropy Collaboration 2013).
Group:Infrared Processing and Analysis Center (IPAC), Palomar Transient Factory
Funding AgencyGrant Number
NSF Graduate Research Fellowship11-44155
Alfred P. Sloan FoundationUNSPECIFIED
Participating InstitutionsUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Subject Keywords:gravitational lensing: micro; methods: statistical; surveys
Issue or Number:1
Record Number:CaltechAUTHORS:20140211-143531840
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Official Citation:Statistical Searches for Microlensing Events in Large, Non-uniformly Sampled Time-Domain Surveys: A Test Using Palomar Transient Factory Data Adrian M. Price-Whelan et al. 2014 ApJ 781 35
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43784
Deposited By: Ruth Sustaita
Deposited On:11 Feb 2014 23:09
Last Modified:09 Mar 2020 13:19

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