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iPTF Archival Search for Fast Optical Transients

Ho, Anna Y. Q. and Kulkarni, S. R. and Nugent, Peter E. and Zhao, Weijie and Rusu, Florin and Cenko, S. Bradley and Ravi, Vikram and Kasliwal, Mansi M. and Perley, Daniel A. and Adams, Scott M. and Bellm, Eric C. and Brady, Patrick R. and Fremling, Christoffer and Gal-Yam, Avishay and Kann, David Alexander and Kaplan, David and Laher, Russ R. and Masci, Frank and Ofek, Eran O. and Sollerman, Jesper and Urban, Alex (2018) iPTF Archival Search for Fast Optical Transients. Astrophysical Journal Letters, 854 (1). Art. No. L13. ISSN 2041-8213.

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There has been speculation about a class of relativistic explosions with an initial Lorentz factor Γ_(init) smaller than that of classical gamma-ray bursts (GRBs). These "dirty fireballs" would lack prompt GRB emission but could be pursued via their optical afterglow, appearing as transients that fade overnight. Here we report a search for such transients (that fade by 5-σ in magnitude overnight) in four years of archival photometric data from the intermediate Palomar Transient Factory (iPTF). Our search criteria yielded 50 candidates. Of these, two were afterglows to GRBs that had been found in dedicated follow-up observations to triggers from the Fermi GRB Monitor. Another (iPTF14yb) was a GRB afterglow discovered serendipitously. Eight were spurious artifacts of reference image subtraction, and one was an asteroid. The remaining 38 candidates have red stellar counterparts in external catalogs. The photometric and spectroscopic properties of the counterparts identify these transients as strong flares from M dwarfs of spectral type M3–M7 at distances of d ≈ 0.15–2.1 kpc; three counterparts were already spectroscopically classified as late-type M stars. With iPTF14yb as the only confirmed relativistic outflow discovered independently of a high-energy trigger, we constrain the all-sky rate of transients that peak at m = 18 and fade by Δm = 2 mag in Δt = 3 hr to be 680 yr^(-1), with a 68% confidence interval of 119-2236, yr^(-1). This implies that the rate of visible dirty fireballs is at most comparable to that of the known population of long-duration GRBs.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Ho, Anna Y. Q.0000-0002-9017-3567
Kulkarni, S. R.0000-0001-5390-8563
Nugent, Peter E.0000-0002-3389-0586
Cenko, S. Bradley0000-0003-1673-970X
Ravi, Vikram0000-0002-7252-5485
Kasliwal, Mansi M.0000-0002-5619-4938
Perley, Daniel A.0000-0001-8472-1996
Adams, Scott M.0000-0001-5855-5939
Bellm, Eric C.0000-0001-8018-5348
Fremling, Christoffer0000-0002-4223-103X
Gal-Yam, Avishay0000-0002-3653-5598
Kaplan, David0000-0001-6295-2881
Masci, Frank0000-0002-8532-9395
Ofek, Eran O.0000-0002-6786-8774
Sollerman, Jesper0000-0003-1546-6615
Additional Information:© 2018 American Astronomical Society. Received 2017 December 5. Accepted 2018 January 24. Published 2018 February 9. It is a pleasure to thank Yi Cao, Jim Davenport, Adam Miller, Yuguang Chen, Harish Vendantham, Lynne Hillenbrand, and Trevor David for helpful discussions and assistance. We are grateful to the anonymous referee for constructive feedback that improved the quality of the paper. A.Y.Q.H. was supported by a National Science Foundation Graduate Research Fellowship under grant No. DGE1144469. D.A.K. acknowledges support from from the Spanish research project AYA 2014-58381-P and the Juan de la Cierva Incorporacíon fellowship IJCI-2015-261. This work was supported by the GROWTH project funded by the National Science Foundation under PIRE grant No. 1545949. The Intermediate Palomar Transient Factory project is a scientific collaboration among the California Institute of Technology, Los Alamos National Laboratory, the University of Wisconsin, Milwaukee, the Oskar Klein Center, the Weizmann Institute of Science, the TANGO Program of the University System of Taiwan, and the Kavli Institute for the Physics and Mathematics of the Universe. This research made use of Astropy, a community-developed core Python package for Astronomy (Astropy Collaboration et al. 2013).
Group:IPTF, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1144469
Ministerio de Educación y Ciencia (MEC)AYA 2014-58381-P
Juan de la Cierva IncorporacíonIJCI-2015-261
Subject Keywords:catalogs; gamma-ray burst: general; stars: activity; stars: flare; stars: jets; surveys
Record Number:CaltechAUTHORS:20180209-095826158
Persistent URL:
Official Citation:Anna Y. Q. Ho et al 2018 ApJL 854 L13
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84762
Deposited By: Ruth Sustaita
Deposited On:09 Feb 2018 23:45
Last Modified:09 Feb 2018 23:45

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