TITLE: GCN CIRCULAR NUMBER: 44526 SUBJECT: GRB 260510C: MAXI/GSC detection DATE: 26/05/10 21:42:33 GMT FROM: Wataru Iwakiri at Chiba University <iwakiri.wataru.buz@gmail.com> W. Iwakiri (Chiba U.), M. Serino(AGU), H. Negoro, M. Nakajima, K. Saito, T. Yokoyama, M. Wada (Nihon U.), T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, Y. Kawakubo, H. Hiramatsu, A. Yoshida (AGU), Y. Tsuboi, Y. Ishihara, H. Ogaki (Chuo U.), M. Shidatsu, C. Kang, M. Uenishi, T. Usuki, S. Yatsuzuka, H. Aoe (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara, S. Kobayashi (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), T. Kawamuro (Osaka U.), S. Yamada (Tohoku U), S. Ogawa (TUS) report on behalf of the MAXI team: At 17:13:42 UT on 2026 May 10, the MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source. The trigger time and position are consistent with GRB 260510C reported by the Fermi team (GCN #44520) and the SVOM team (GCN #44521). The X-ray flux averaged over the scan was 338 +/- 36 mCrab (4.0-10.0 keV, 1-sigma error). Assuming that the source flux was constant over the transit, we obtain the source position at: (R.A., Dec) = (157.881 deg, 2.824 deg) = (10 31 31, +02 49 26) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.17 deg and 0.14 deg, respectively. The roll angle of the long axis is 73.0 deg counterclockwise from the north. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (157.267, 2.290) deg = (10 29 04, +02 17 24) (J2000) (157.477, 2.117) deg = (10 29 54, +02 07 01) (J2000) (158.505, 3.360) deg = (10 34 01, +03 21 35) (J2000) (158.295, 3.533) deg = (10 33 10, +03 31 58) (J2000) There was no significant excess flux in the previous transit at 15:40 UT with an upper limit of 20 mCrab. View this GCN Circular online at https://gcn.nasa.gov/circulars/44526. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...