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Constraining the X-Ray–Infrared Spectral Index of Second-timescale Flares from SGR 1935+2154 with Palomar Gattini-IR

De, Kishalay and Ashley, Michael C. B. and Andreoni, Igor and Kasliwal, Mansi M. and Soria, Roberto and Srinivasaragavan, Gokul P. and Cai, Ce and Delacroix, Alexander and Greffe, Tim and Hale, David and Hankins, Matthew J. and Li, Chengkui and McKenna, Daniel and Moore, Anna M. and Ofek, Eran O. and Smith, Roger M. and Soon, Jamie and Travouillon, Tony and Zhang, Shuangnan (2020) Constraining the X-Ray–Infrared Spectral Index of Second-timescale Flares from SGR 1935+2154 with Palomar Gattini-IR. Astrophysical Journal Letters, 901 (1). Art. No. L7. ISSN 2041-8213. doi:10.3847/2041-8213/abb3c5.

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The Galactic magnetar SGR 1935+2154 has been reported to produce the first example of a bright millisecond-duration radio burst (FRB 200428) similar to the cosmological population of fast radio bursts (FRBs). The detection of a coincident bright X-ray burst represents the first observed multiwavelength counterpart of an FRB. However, the search for similar emission at optical wavelengths has been hampered by the high inferred extinction on the line of sight. Here, we present results from the first search for second-timescale emission from the source at near-infrared (NIR) wavelengths using the Palomar Gattini-IR observing system in the J band, enabled by a novel detector readout mode that allows short exposure times of ≈0.84 s with 99.9% observing efficiency. With a total observing time of ≈12 hr (≈47,728 images) during its 2020 outburst, we place median 3σ limits on the second-timescale NIR fluence of ≾18 Jy ms (13.1 AB mag). The corresponding extinction-corrected limit is ≾125 Jy ms for an estimated extinction of A_J = 2.0 mag. Our observations were sensitive enough to easily detect an NIR counterpart of FRB 200428 if the NIR emission falls on the same power law as observed across its radio to X-ray spectrum. We report nondetection limits from epochs of four simultaneous X-ray bursts detected by the Insight-HXMT and NuSTAR telescopes during our observations. These limits provide the most stringent constraints to date on fluence of flares at ~10¹⁴ Hz, and constrain the fluence ratio of the NIR emission to coincident X-ray bursts to R_(NIR) ≾0.025 (fluence index ≳0.35).

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
De, Kishalay0000-0002-8989-0542
Andreoni, Igor0000-0002-8977-1498
Kasliwal, Mansi M.0000-0002-5619-4938
Soria, Roberto0000-0002-4622-796X
Hankins, Matthew J.0000-0001-9315-8437
Moore, Anna M.0000-0002-2894-6936
Ofek, Eran O.0000-0002-6786-8774
Smith, Roger M.0000-0001-7062-9726
Additional Information:© 2020 The American Astronomical Society. Received 2020 July 4; revised 2020 August 24; accepted 2020 August 25; published 2020 September 18. We thank the Insight/HXMT team for their kind cooperation in coordinating observations and quickly providing fluence estimates. We thank K. Smith for cooperation regarding the CHIME observability windows. We thank C. Bochenek, W. Lu, V. Ravi, and S. R. Kulkarni for valuable discussions on this work. Palomar Gattini-IR (PGIR) is generously funded by Caltech, Australian National University, the Mt Cuba Foundation, the Heising Simons Foundation, the Bi-national Science Foundation. PGIR is a collaborative project among Caltech, Australian National University, University of New South Wales, Columbia University and the Weizmann Institute of Science. This work was supported by the GROWTH (Global Relay of Observatories Watching Transients Happen) project funded by the National Science Foundation under PIRE grant No 1545949. GROWTH is a collaborative project among the California Institute of Technology (USA), University of Maryland College Park (USA), University of Wisconsin Milwaukee (USA), Texas Tech University (USA), San Diego State University (USA), University of Washington (USA), Los Alamos National Laboratory (USA), Tokyo Institute of Technology (Japan), National Central University (Taiwan), Indian Institute of Astrophysics (India), Indian Institute of Technology Bombay (India), Weizmann Institute of Science (Israel), The Oskar Klein Centre at Stockholm University (Sweden), Humboldt University (Germany), Liverpool John Moores University (UK), and University of Sydney (Australia).
Group:Astronomy Department
Funding AgencyGrant Number
Australian National UniversityUNSPECIFIED
Mt. Cuba Astronomical FoundationUNSPECIFIED
Heising-Simons FoundationUNSPECIFIED
Binational Science Foundation (USA-Israel)UNSPECIFIED
Subject Keywords:Radio transient sources ; Magnetars ; Soft gamma-ray repeaters
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Radio transient sources (2008); Magnetars (992); Soft gamma-ray repeaters (1471)
Record Number:CaltechAUTHORS:20200903-070938939
Persistent URL:
Official Citation:Kishalay De et al 2020 ApJL 901 L7
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105232
Deposited By: Tony Diaz
Deposited On:08 Sep 2020 22:56
Last Modified:16 Nov 2021 18:41

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