Fermi-GBM detection of the new magnetar Swift J1818.0-1607
ATel #13555; C. Malacaria (NASA-MSFC/USRA), O. J. Roberts (USRA), P. Veres (UAH), C. Wilson-Hodge (NASA-MSFC)
on 14 Mar 2020; 23:34 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Christian Malacaria (cmalacaria@usra.edu)
Subjects: X-ray, Neutron Star, Transient, Magnetar
We report on the GBM observation of the new magnetar, Swift J1818.0-1607 (Evans et al. 2020, GCN 27373 and Enoto et al. 2020, ATel 13551).
The GBM targeted search, the most sensitive, coherent search for sub-threshold signals, was run from +/- 30 s around the Swift/BAT trigger time, employing a soft spectral template, and identified a significant counterpart. The False Alarm Rate (FAR) for the GBM Targeted Search detection statistic is 3.9e-05 Hz.
The duration of the burst is approximately 18 ms. The 8-200 keV spectrum is well fit by a single absorbed blackbody with a best-fit temperature value of kT= 5.72+/-0.6 keV for N_H fixed to ~10^23 cm^-2 (see ATel 13551). This value is consistent with that obtained by the Swift/BAT refined analysis (GCN 27384). The fluence in the 8-200 keV band for the best-fit model is (1.4 +/- 0.8)x10^-8 erg/cm^2.
Additional analysis of this event and possible precursors/following flares is ongoing. The results presented above are preliminary.
