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X-ray and radio observations of the magnetar SGR J1935+2154 during its 2014, 2015, and 2016 outbursts

Younes, George and Kouveliotou, Chryssa and Jaodand, Amruta and Baring, Matthew G. and van der Horst, Alexander J. and Harding, Alice K. and Hessels, Jason W. T. and Gehrels, Neil and Gill, Ramandeep and Huppenkothen, Daniela and Granot, Jonathan and Göğüş, Ersin and Lin, Lin (2017) X-ray and radio observations of the magnetar SGR J1935+2154 during its 2014, 2015, and 2016 outbursts. Astrophysical Journal, 847 (2). Art. No. 85. ISSN 1538-4357. doi:10.3847/1538-4357/aa899a.

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We analyzed broadband X-ray and radio data of the magnetar SGR J1935+2154 taken in the aftermath of its 2014, 2015, and 2016 outbursts. The source soft X-ray spectrum <10 keV is well described with a blackbody+power-law (BB+PL) or 2BB model during all three outbursts. Nuclear Spectroscopic Telescope Array observations revealed a hard X-ray tail, with a PL photon index Γ = 0.9, extending up to 50 keV, with flux comparable to the one detected <10 keV. Imaging analysis of Chandra data did not reveal small-scale extended emission around the source. Following the outbursts, the total 0.5–10 keV flux from SGR J1935+2154 increased in concordance to its bursting activity, with the flux at activation onset increasing by a factor of ~7 following its strongest 2016 June outburst. A Swift/X-Ray Telescope observation taken 1.5 days prior to the onset of this outburst showed a flux level consistent with quiescence. We show that the flux increase is due to the PL or hot BB component, which increased by a factor of 25 compared to quiescence, while the cold BB component kT = 0.47 keV remained more or less constant. The 2014 and 2015 outbursts decayed quasi-exponentially with timescales of ~40 days, while the stronger 2016 May and June outbursts showed a quick short-term decay with timescales of about four days. Our Arecibo radio observations set the deepest limits on the radio emission from a magnetar, with a maximum flux density limit of 14 μJy for the 4.6 GHz observations and 7 μJy for the 1.4 GHz observations. We discuss these results in the framework of the current magnetar theoretical models.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Younes, George0000-0002-7991-028X
Kouveliotou, Chryssa0000-0003-1443-593X
Jaodand, Amruta0000-0002-3850-6651
van der Horst, Alexander J.0000-0001-9149-6707
Harding, Alice K.0000-0001-6119-859X
Hessels, Jason W. T.0000-0003-2317-1446
Gill, Ramandeep0000-0003-0516-2968
Huppenkothen, Daniela0000-0002-1169-7486
Granot, Jonathan0000-0001-8530-8941
Göğüş, Ersin0000-0002-5274-6790
Lin, Lin0000-0001-6860-9566
Additional Information:© 2017 The American Astronomical Society. Received 2017 February 14; revised 2017 August 28; accepted 2017 August 29; published 2017 September 25. We thank NuSTAR PI Fiona Harrison and Belinda Wilkes for granting NuSTAR and Chandra DDT observations of SGR J1935+2154 during the 2015 and 2016 outbursts, respectively. We also thank the Swift team for performing the monitoring of the source during all of its outbursts. G.Y. and C.K. acknowledge support by NASA through grant NNH07ZDA001-GLAST. A.J. and J.W.T.H. acknowledge funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007–2013) ERC grant agreement no. 337062 (DRAGNET). The Arecibo Observatory is operated by SRI International under a cooperative agreement with the National Science Foundation (AST-1100968) and in alliance with Ana G. Méndez-Universidad Metropolitana and the Universities Space Research Association. We would like to thank Arecibo observatory scheduler Hector Hernandez for the support during our observations. A.J. thanks Daniele Michilli for helping with the single-pulse search analysis. We thank the anonymous referee for their careful reading and insightful comments that improved the quality of the manuscript. Software: CIAO (, SAS (v14.0.0,, xrtpipeline (v13.2), nustardas (v1.5.1,, HEASOFT (v6.20,, ChaRT ( MARX (, PRESTO (Ransom 2001; Ransom et al. 2002, 2003), XSPEC (v12.9.0k; Arnaud 1996).
Subject Keywords:radio continuum: stars – stars: individual (SGR J1935+2154) – stars: magnetars – stars: neutron – X-rays: stars
Issue or Number:2
Record Number:CaltechAUTHORS:20170222-114618877
Persistent URL:
Official Citation:George Younes et al 2017 ApJ 847 85
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:74469
Deposited By: Joy Painter
Deposited On:22 Feb 2017 19:53
Last Modified:11 Nov 2021 05:27

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