//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29676 SUBJECT: GRB 210320A: MAXI/GSC detection DATE: 21/03/21 02:24:37 GMT FROM: Hitoshi Negoro at Nihon U H. Negoro, M. Nakajima, M. Aoki, K. Kobayashi, R. Takagi, K. Asakura, K. Seino (Nihon U.), T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, H. Nishida, K. Komachi, A. Yoshida (AGU), Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, Y. Okamoto, S. Kitakoga (Chuo U.), M. Shidatsu (Ehime U.), N. Kawai, R. Adachi, M. Niwano, R. Hosokawa (Tokyo Tech), S. Nakahira, Y. Sugawara, S. Ueno, H. Tomida, M. Ishikawa, M. Tominaga, T. Nagatsuka (JAXA), Y. Ueda, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake, Y. Goto, R. Uematsu (Kyoto U.), H. Tsunemi (Osaka U.), M. Yamauchi, K. Kurogi, K. Miike (Miyazaki U.), T. Kawamuro (UDP/NAOJ), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU), M. Sugizaki (NAOC) report on behalf of the MAXI team: The MAXI/GSC detected a bright uncatalogued soft X-ray transient source at 22:15 UT on 2021 March 20. Assuming that the source flux was constant over the transit, at 2-4 keV we obtain the source position at (R.A., Dec) = (4.731 deg, -47.476 deg) = (00 18 55, -47 28 34) (J2000) with a 90% C.L. statistical error of 0.45 deg and an additional systematic uncertainty of 0.1 deg (90% containment radius), and, at 4-10 keV we obtained at (R.A., Dec) = (4.630 deg, -47.423 deg) = (00 18 31, -47 25 22) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.64 deg and 0.61 deg, respectively. The roll angle of long axis from the north direction is 104.0 deg counterclockwise. The 2-4 keV and 4-10 keV X-ray fluxes averaged over the scan were 144 +- 28 mCrab and 59 +- 20 mCrab, respectively. There was no significant excess flux in the previous transit at 20:42 UT and in the next transit at 01:21 UT on March 21 with an upper limit of 20 mCrab for each. (Currently, there are no data at 23:47.) There is no known bright X-ray source within the error regions, and no significant short-term variations during the ~45 sec scan. From the above nature, the source is likely a part of a long gamma-ray burst, but we tentatively name the source MAXI J0018-474. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29682 SUBJECT: MAXI GRB210320.89: Global MASTER-Net observations report DATE: 21/03/21 18:34:14 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University) MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the MAXI GRB210320.89 (trigger No 293849998,00h 18m 55.44s , -47d 28m 33.6s, R=1) errorbox 61827 sec after notice time and 73184 sec after trigger time at 2021-03-21 17:40:45 UT, with upper limit up to 17.2 mag. Observations started at twilight. The observations began at zenith distance = 73 deg. The sun altitude is -11.8 deg. The galactic latitude b = -69 deg., longitude l = 317 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1572732 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 73274 | 2021-03-21 17:40:45 | MASTER-SAAO | (00h 18m 44.65s , -47d 28m 58.3s) | C | 180 | 17.3 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.