Resumed NICER observations of the magnetar SGR 1830-0645
ATel #14406; George Younes (George Washington University), Tolga Guver (Istanbul Univ.), Paul S. Ray (U. S. Naval Research Laboratory), Zaven Arzoumanian (NASA/GSFC), Teruaki Enoto (RIKEN), Keith Gendreau (NASA/GSFC), Chryssa Kouveliotou (George Washington University), Walid A. Majid (JPL, Caltech), Zorawar Wadiasingh (NASA/GSFC), report on behalf of the NICER magnetar team
on 19 Feb 2021; 00:10 UT
Credential Certification: George Younes (gyounes@email.gwu.edu)
Subjects: X-ray, Neutron Star, Soft Gamma-ray Repeater, Magnetar
Magnetar SGR 1830-0645, which was discovered on 2020 October 10 with Swift/BAT (Page et al. GCN #28594), is again observable with NICER since February 10, after a period of sun-constraint that started on 2020 November 17. We initiated a series of observations that covered the interval of February 10 - 18, with a total exposure of 9.7 ks. During this time SGR 1830-0645 triggered Swift/BAT and Fermi/GBM on a few short hard X-ray bursts (Fletcher et al. GCN #29524, Klingler et al. GCN #29516, Kennea et al. GCN #29500).
The source is detected in all NICER snapshots at a background corrected rate of 2 counts/s. The phase-averaged spectrum in the 1 to 6 keV range is well fit with an absorbed two-blackbody model. After fixing the hydrogen column density to 1.2E22 /cm2, we derive the temperatures of the two components as 0.41(5) and 0.90(6) keV. The total absorption corrected flux (in the 0.5-10 keV range) is 1.07(2)E-11 erg/s/cm2, indicating that the source flux decay has flattened compared to values early in the outburst (Coti-Zelati et al. 2021, ApJ, 907L, 34C). Moreover, several candidate short bursts are seen in the recent NICER observations.
The source spin parameters after the sun-constraint period follow the expectation from the timing model reported in Ray et al. 2020, ATEL #14112.
The above results are preliminary. More detailed analysis will be presented in an upcoming paper. NICER will continue monitoring the source to track its spectral and temporal evolution towards quiescence. Given the continued active period of the source, we encourage multi-wavelength follow-up.
NICER is a 0.2-12 keV X-ray telescope operating on the International Space Station. The NICER mission and portions of the NICER science team activities are funded by NASA.
