X-Ray Burst and Persistent Emission Properties of the Magnetar SGR 1830-0645 in Outburst
Journal article, 2022
We report on NICER X-ray monitoring of the magnetar SGR 1830-0645 covering 223 days following its 2020 October outburst, as well as Chandra and radio observations. We present the most accurate spin ephemerides of the source so far: nu = 0.096008680(2) Hz, <(nu) over dot> = -6.2(1) x 10(-14) Hz s(-1), and significant second and third frequency derivative terms indicative of nonnegligible timing noise. The phase-averaged 0.8-7 keV spectrum is well fit with a double-blackbody (BB) model throughout the campaign. The BB temperatures remain constant at 0.46 and 1.2 keV. The areas and flux of each component decreased by a factor of 6, initially through a steep decay trend lasting about 46 days, followed by a shallow long-term one. The pulse shape in the same energy range is initially complex, exhibiting three distinct peaks, yet with clear continuous evolution throughout the outburst toward a simpler, single-pulse shape. The rms pulsed fraction is high and increases from about 40% to 50%. We find no dependence of pulse shape or fraction on energy. These results suggest that multiple hot spots, possibly possessing temperature gradients, emerged at outburst onset and shrank as the outburst decayed. We detect 84 faint bursts with NICER, having a strong preference for occurring close to the surface emission pulse maximum-the first time this phenomenon is detected in such a large burst sample. This likely implies a very low altitude for the burst emission region and a triggering mechanism connected to the surface active zone. Finally, our radio observations at several epochs and multiple frequencies reveal no evidence of pulsed or burst-like radio emission.
Author
George Younes
George Washington University
Chin-Ping Hu
National Changhua University of Education
Karishma Bansal
California Institute of Technology (Caltech)
Paul S. Ray
Naval Research Laboratory
Aaron B. Pearlman
McGill University
California Institute of Technology (Caltech)
Franz Kirsten
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Zorawar Wadiasingh
NASA Goddard Space Flight Center
University of Maryland
Ersin Gogus
Sabancı University
Matthew G. Baring
Rice University
Teruaki Enoto
RIKEN
Zaven Arzoumanian
NASA Goddard Space Flight Center
Keith C. Gendreau
NASA Goddard Space Flight Center
Chryssa Kouveliotou
George Washington University
Tolga Guver
Istanbul University
Alice K. Harding
Los Alamos National Laboratory
Walid A. Majid
California Institute of Technology (Caltech)
Harsha Blumer
West Virginia University
Jason W. T. Hessels
University of Amsterdam
Netherlands Institute for Radio Astronomy (ASTRON)
Marcin P. Gawronski
Nicolaus Copernicus University
Vladislavs Bezrukovs
Ventspils University of Applied Sciences
Arturs Orbidans
Ventspils University of Applied Sciences
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 924 2 136Subject Categories
Meteorology and Atmospheric Sciences
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
DOI
10.3847/1538-4357/ac3756