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ZTF20aajnksq (AT2020blt): 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 Hale, David and Kupfer, Thomas and Laher, Russ R. and Masci, Frank J. and Miller, A. 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 (AT2020blt): A Fast Optical Transient at z ≈ 2.9 With No Detected Gamma-Ray Burst Counterpart. . (Unpublished)

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We present ZTF20aajnksq (AT2020blt), a fast-fading (Δr = 2.4 mag in Δt = 1.3 days) red (g−r ≈ 0.6 mag) and luminous (M₁₆₂₆ = −25.9) optical transient at z = 2.9 discovered by the Zwicky Transient Facility (ZTF). AT2020blt 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 day (observer-frame); (2) a luminous (L_X = 10⁴⁶ erg s⁻¹) X-ray counterpart; and (3) luminous (L_ν = 4×10³¹ erg sec⁻¹ Hz−1 at 10 GHz) radio emission. However, no GRB was detected in the 0.74d between the last ZTF non-detection (r > 20.64) and the first ZTF detection (r = 19.57), with an upper limit on the isotropic-equivalent gamma-ray energy release of E_(γ,iso) < 7×10⁵² erg. AT2020blt 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 AT2020blt 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 AT2020blt 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. We conclude by discussing the status and future of fast-transient searches in wide-field high-cadence optical surveys.

Item Type:Report or Paper (Discussion Paper)
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
Kupfer, Thomas0000-0002-6540-1484
Laher, Russ R.0000-0003-2451-5482
Masci, Frank J.0000-0002-8532-9395
Miller, A. 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
Sollerman, Jesper0000-0003-1546-6615
van Roestel, Jan0000-0002-2626-2872
Additional Information: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. 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. ZTF 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, Inova çoes e Comunicaçoes (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 Astrofísica de Canarias with financial support from the UK Science and Technology Facilities Council.
Group:Astronomy Department, Infrared Processing and Analysis Center (IPAC), Zwicky Transient Facility
Funding AgencyGrant Number
Large Synoptic Survey Telescope CorporationUNSPECIFIED
Brinson FoundationUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA)UNSPECIFIED
Northwestern UniversityUNSPECIFIED
Heising-Simons Foundation2018-0907
Knut and Alice Wallenberg FoundationUNSPECIFIED
Swedish Research Council2016-06012
ZTF partner institutionsUNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
Record Number:CaltechAUTHORS:20200824-095838244
Persistent URL:
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:24 Aug 2020 17:27

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