TITLE: GCN CIRCULAR NUMBER: 44961 SUBJECT: GRB260616C: MAXI/GSC detection DATE: 26/06/17 03:18:02 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: The MAXI/GSC detected a bright uncatalogued X-ray transient source at 14:47 UT on June 16 2026. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (67.745 deg, 9.294 deg) = (04 30 58, +09 17 38) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.39 deg and 0.3 deg, respectively. The roll angle of long axis from the north direction is 22.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 148 +- 33 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (66.883, 10.254) deg = (04 27 31, +10 15 14) (J2000) (66.471, 9.596) deg = (04 25 53, +09 35 45) (J2000) (68.604, 8.290) deg = (04 34 24, +08 17 23) (J2000) (69.019, 8.945) deg = (04 36 04, +08 56 42) (J2000) A marginal excess of about 50 mCrab may be present in the previous and next MAXI scans at 13:14 UT and 16:20 UT, respectively. However, these scans were obtained during a period of large background variations, and the significance of the excesses is currently unclear. The possible presence of X-ray activity over multiple scans raises the possibility that this event is a new X-ray transient source rather than a GRB. We therefore tentatively name the source MAXI J0430+092. Multi-wavelength follow-up observations are encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/44961. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...