//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13895 SUBJECT: GRB 121025A: MAXI/GSC detection DATE: 12/10/25 10:50:20 GMT FROM: Mikio Morii at Tokyo Inst Tech M. Asada, H. Negoro (Nihon U.), M. Serino (RIKEN), M. Morii (Tokyo Tech), Nakahira (JAXA), K. Yamaoka (Waseda U.), S. Ueno, H. Tomida, M. Ishikawa (JAXA), T. Mihara, M. Sugizaki, T. Yamamoto, J. Sugimoto, M. Matsuoka (RIKEN), N. Kawai, R. Usui, K. Ishikawa, T. Yoshii (Tokyo Tech), A. Yoshida (AGU), H. Tsunemi, M. Kimura (Osaka U.), M. Nakajima (Nihon U.), Y. Ueda, K. Hiroi, M. Shidatsu, R. Sato (Kyoto U.), Y. Tsuboi, M. Higa (Chuo U.) M. Yamauchi, Y. Nishimura, T. Hanayama, K. Yoshidome (Miyazaki U.) report on behalf of the MAXI team: At 2012-10-25T07:46:30 UT, the MAXI/GSC nova alert system triggered on a bright uncatalogued X-ray transient source. The transient emission lasted at least 20 seconds within the 44 second long triangular transit response of MAXI/GSC. We identify this event as GRB 121025A. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (248.75 deg, +27.73 deg) = (16 35 00, +27 44 05)(J2000) with a 90% C.L. statistical error of 0.27 deg and an additional systematic uncertainty of 0.1 deg (90% containment radius). The 4-10 keV flux was 129 (+26/-22) mCrab. Within the scan transit, the variability of the source was marginally detected with a chance probability of 0.084 for 4 - 10 keV band. There was no significant excess flux in the previous transit at 06:13 UT and in the next transit at 09:18 UT with an upper limit of 20 mCrab for each. Follow-up observations are encouraged. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13909 SUBJECT: GRB 121025A: Swift-XRT observation DATE: 12/10/27 10:34:49 GMT FROM: Kim Page at U.of Leicester K.L. Page, R.L.C. Starling and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: Swift performed a Target of Opportunity observation of the MAXI-detected GRB 121025A (Asada et al., GCN Circ. 13895), starting 26.1 ks after the trigger. A series of four tiled pointings was performed, in order to cover the MAXI error circle. Within these fields, one > 3 sigma uncatalogued source was detected, at RA, Dec = 248.38182, 27.67189, which is equivalent to: RA(J2000) = 16h 33m 31.64s Dec(J2000) = 27d 40' 18.8" with an uncertainty of 3.8 arcsec (radius, 90% containment). This source has a mean count rate of 0.022 +/- 0.004 count s^-1. A spectrum formed from the 1.8 ks of data can be fitted with an absorbed power-law with a photon spectral index of 2.36 (+0.57,-0.56). The best-fitting absorption column is consistent with the Galactic value of 3.8 x 10^20 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.7 x 10^-11 (4.5 x 10^-11) erg cm^-2 count^-1. It is not possible to determine whether this source is fading at this time and, therefore, whether it is the X-ray afterglow. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13941 SUBJECT: GRB 121025A: Confirmation of the X-ray afterglow DATE: 12/11/02 08:41:47 GMT FROM: Kim Page at U.of Leicester K.L. Page (U. Leicester) reports on behalf of the Swift-XRT team: Swift performed a follow-up observation of the possible X-ray afterglow of MAXI-detected GRB 121025A (Asada et al., GCN Circ. 13895) announced in GCN Circ. 13909 (Page, Starling & Evans). This second observation took place on 2012-10-31, 5.8 days after the burst. The source has now faded by at least an order of magnitude, with an upper limit on the count rate of 0.002 count s^-1 (corresponding to an observed flux of 8.1 x 10^-14 erg cm^-2 s^-1). This source is therefore confirmed as the X-ray afterglow of GRB 121025A. This circular is an official product of the Swift-XRT team.