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ZTF20aajnksq (AT 2020blt): A Fast Optical Transient at z ≈ 2.9 with No Detected Gamma-Ray Burst Counterpart

Ho, Anna Y. Q. and Perley, Daniel A. and Beniamini, Paz and Cenko, S. Bradley and Kulkarni, S. R. and Andreoni, Igor and Singer, Leo P. and De, Kishalay and Kasliwal, Mansi M. and Fremling, Christoffer and Bellm, Eric C. and Dekany, Richard and Delacroix, Alexandre and Duev, Dmitry A. and Goldstein, Daniel A. and Golkhou, V. Zach and Goobar, Ariel and Graham, Matthew J. and Hale, David and Kupfer, Thomas and Laher, Russ R. and Masci, Frank J. and Miller, Adam A. and Neill, James D. and Riddle, Reed and Rusholme, Ben and Shupe, David L. and Smith, Roger and Sollerman, Jesper and van Roestel, Jan (2020) ZTF20aajnksq (AT 2020blt): A Fast Optical Transient at z ≈ 2.9 with No Detected Gamma-Ray Burst Counterpart. Astrophysical Journal, 905 (2). Art. No. 98. ISSN 1538-4357. doi:10.3847/1538-4357/abc34d.

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We present ZTF20aajnksq (AT 2020blt), a fast-fading (Δr = 2.3 mag in Δt = 1.3 days) red (g − r ≈ 0.6 mag) and luminous (M_(1626 Å) = −25.9 mag) optical transient at z = 2.9 discovered by the Zwicky Transient Facility (ZTF). AT 2020blt shares several features in common with afterglows to long-duration gamma-ray bursts (GRBs): (1) an optical light curve well-described by a broken power law with a break at t_j = 1 d (observer frame); (2) a luminous (L_(0.3–10 KeV) = 10⁴⁶ erg s⁻¹) X-ray counterpart; and (3) luminous (L_(10 GHz) = 4 × 10³¹ erg s⁻¹ Hz⁻¹) radio emission. However, no GRB was detected in the 0.74 days between the last ZTF nondetection (r > 21.36 mag) and the first ZTF detection (r = 19.60 mag), with an upper limit on the isotropic-equivalent gamma-ray energy release of E_(γ,iso) < 7 × 10⁵² erg. AT 2020blt is thus the third afterglow-like transient discovered without a detected GRB counterpart (after PTF11agg and ZTF19abvizsw) and the second (after ZTF19abvizsw) with a redshift measurement. We conclude that the properties of AT 2020blt are consistent with a classical (initial Lorentz factor Γ₀ ≳ 100) on-axis GRB that was missed by high-energy satellites. Furthermore, by estimating the rate of transients with light curves similar to that of AT 2020blt in ZTF high-cadence data, we agree with previous results that there is no evidence for an afterglow-like phenomenon that is significantly more common than classical GRBs, such as dirty fireballs. We conclude by discussing the status and future of fast-transient searches in wide-field high-cadence optical surveys.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Ho, Anna Y. Q.0000-0002-9017-3567
Perley, Daniel A.0000-0001-8472-1996
Beniamini, Paz0000-0001-7833-1043
Cenko, S. Bradley0000-0003-1673-970X
Kulkarni, S. R.0000-0001-5390-8563
Andreoni, Igor0000-0002-8977-1498
Singer, Leo P.0000-0001-9898-5597
De, Kishalay0000-0002-8989-0542
Kasliwal, Mansi M.0000-0002-5619-4938
Fremling, Christoffer0000-0002-4223-103X
Bellm, Eric C.0000-0001-8018-5348
Dekany, Richard0000-0002-5884-7867
Duev, Dmitry A.0000-0001-5060-8733
Goldstein, Daniel A.0000-0003-3461-8661
Golkhou, V. Zach0000-0001-8205-2506
Goobar, Ariel0000-0002-4163-4996
Graham, Matthew J.0000-0002-3168-0139
Kupfer, Thomas0000-0002-6540-1484
Laher, Russ R.0000-0003-2451-5482
Masci, Frank J.0000-0002-8532-9395
Miller, Adam A.0000-0001-9515-478X
Neill, James D.0000-0002-0466-1119
Riddle, Reed0000-0002-0387-370X
Rusholme, Ben0000-0001-7648-4142
Shupe, David L.0000-0003-4401-0430
Smith, Roger0000-0001-7062-9726
Sollerman, Jesper0000-0003-1546-6615
van Roestel, Jan0000-0002-2626-2872
Additional Information:© 2020 The American Astronomical Society. Received 2020 June 18; revised 2020 October 15; accepted 2020 October 17; published 2020 December 17. It is a pleasure to thank the anonymous referee for a thorough and thoughtful report that greatly improved the quality of the paper. A.Y.Q.H. would like to thank Udi Nakar for pointing out that dirty fireballs will have a longer rise time than clean fireballs, and Chris Bochenek and Vikram Ravi for useful discussions regarding scintillation of radio point sources. She would also like to thank Steve Schulze, Eran Ofek, and Avishay Gal-Yam, and David Kaplan for their detailed reading of the manuscript. A.Y.Q.H. and K.D. were supported by the GROWTH project funded by the National Science Foundation under PIRE grant No. 1545949. A.Y.Q.H. was also supported by the Miller Institute for Basic Research in Science at the University of California Berkeley. A. A. Miller is funded by the Large Synoptic Survey Telescope Corporation, the Brinson Foundation, and the Moore Foundation in support of the LSSTC Data Science Fellowship Program; he also receives support as a CIERA Fellow by the CIERA Postdoctoral Fellowship Program (Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University). C.F. gratefully acknowledges support of his research by the Heising-Simons Foundation (#2018-0907). A. Goobar acknowledges support from the K & A Wallenberg Foundation, the Swedish Research Council (VR), and the GREAT research environment grant 2016-06012. Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. Z.T.F. is supported by the National Science Foundation under grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. SED Machine is based upon work supported by the National Science Foundation under grant No. 1106171. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. Based on observations obtained at the international Gemini Observatory, a program of NSFs OIR Lab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation, on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). Gemini data were processed using the Gemini IRAF package and DRAGONS (Data Reduction for Astronomy from Gemini Observatory North and South). The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. We acknowledge the use of public data from the Swift data archive. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Facilities: Swift - Swift Gamma-Ray Burst Mission, EVLA - , VLA - , Liverpool:2 m - , PO:1.2 m - , PO:1.5 m, Keck:I (LRIS). - Software: CASA (McMullin et al. 2007), astropy (Astropy Collaboration et al. 2013, 2018), matplotlib (Hunter 2007), scipy (Virtanen et al. 2020), DRAGONS.
Group:Astronomy Department, Infrared Processing and Analysis Center (IPAC), Zwicky Transient Facility
Funding AgencyGrant Number
Miller Institute for Basic Research in ScienceUNSPECIFIED
Large Synoptic Survey Telescope CorporationUNSPECIFIED
Brinson FoundationUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA)UNSPECIFIED
Heising-Simons Foundation2018-0907
Northwestern UniversityUNSPECIFIED
Knut and Alice Wallenberg FoundationUNSPECIFIED
Swedish Research Council2016-06012
ZTF partner institutionsUNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:Gamma-ray bursts ; Radio transient sources ; Transient sources ; X-ray transient sources ; Sky surveys ; Surveys
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Gamma-ray bursts (629); Radio transient sources (2008); Transient sources (1851); X-ray transient sources (1852); Sky surveys (1464); Surveys (1671)
Record Number:CaltechAUTHORS:20200824-095838244
Persistent URL:
Official Citation:Anna Y. Q. Ho et al 2020 ApJ 905 98
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105070
Deposited By: Tony Diaz
Deposited On:24 Aug 2020 17:27
Last Modified:16 Nov 2021 18:39

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