TITLE: GCN CIRCULAR NUMBER: 43763 SUBJECT: GRB 260206A: probable hard X-ray burst from 4U 0513-40 DATE: 26/02/16 11:32:52 GMT FROM: Hitoshi Negoro at Nihon University/MAXI team <negoro.hitoshi@nihon-u.ac.jp> H. Negoro, M. Nakajima (Nihon U.), J.A. Kennea (PSU), T. Mihara (RIKEN) This is a cross-posting of ATel 17682. In Swift-XRT followup observations of GRB 260206A detected with the MAXI-GSC (GCN Circ. 43624), the XRT marginally detected a faint, uncatalogued X-ray source near the center of the MAXI error region (Lenava et al. GCN Circ. 43630). The XRT also detected a bright known X-ray source, LSXPS J051406.5-400237, of which a count rate was 7.3 +/- 0.3 cts/s, approximately 70% higher than the mean count rate (Source 1: Evans et al. GCN Circ. 43625). We analyzed the GSC energy spectrum of the burst, and found that a power-law model gave a better fit to the spectrum than a blackbody model. This is because many hard X-ray photons were detected above 10 keV. We fixed the equivalent hydrogen column density to 3.84e20 (obtained with the nH Calculator at NASA/HEASARC for the direction of 4U 0513-40), and obtained a photon index of 1.7 (+0.7, -0.6 at 90% confidence interval) and a blackbody temperature of 1.5 (+0.6, - 0.4) keV in each fit. The burst exhibited a double-peaked-like structure with an e-folding decay time of 5.8 +/- 1.0 sec at 2-20 keV without any collimator response correction. The peak X-ray flux is around 1.22e-8 erg/cm2/s at 2-10 keV, which corresponds to 2.2e38 erg/s if the source is in the globular cluster NGC 1851 hosting 4U 0513-40 (aka X0512-401) (12.2 kpc away). MAXI detected more than ten X-ray bursts with a variety of time profiles originating from the direction of NGC 1851. These strongly suggest that this hard energetic burst also came from 4U 0513-40 (or ABK A, see Homer et al. 2001, ApJ, L155), within the error circle of LSXPS J051406.5-400237, though 4U 0513-40 is just outside the MAXI error box if we take account of the systematic uncertainty of the localization, 0.1 deg (GCN Circ. 43624). View this GCN Circular online at https://gcn.nasa.gov/circulars/43763. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...