//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30113 SUBJECT: GRB 210602A: MAXI/GSC detection DATE: 21/06/02 12:44:38 GMT FROM: Motoko Serino at Aoyama Gakuin U. M. Serino, S. Sugita (AGU), H. Negoro, M. Nakajima, K. Kobayashi, K. Asakura, K. Seino (Nihon U.), T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN), T. Sakamoto, K. Komachi, A. Yoshida (AGU), Y. Tsuboi, W. Iwakiri, H. Kawai, Y. Okamoto, S. Kitakoga (Chuo U.), M. Shidatsu (Ehime U.), N. Kawai, 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, Y. Nonaka, T. Sato, R. Hatsuda, R. Fukuoka (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 nova alert system triggered a bright uncatalogued X-ray transient source at 12:04:02 UT on 2021 June 2. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (44.630 deg, -2.672 deg) = (02 58 31, -02 40 19) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.17 deg and 0.16 deg, respectively. The roll angle of long axis from the north direction is 107.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 393 +- 52 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: (R.A., Dec) = (43.754, -3.549) deg = (02 55 00, -03 32 56) (J2000) (R.A., Dec) = (44.013, -3.735) deg = (02 56 03, -03 44 05) (J2000) (R.A., Dec) = (45.446, -1.751) deg = (03 01 47, -01 45 03) (J2000) (R.A., Dec) = (45.187, -1.565) deg = (03 00 44, -01 33 53) (J2000) There was no significant excess flux in the previous transit at 10:31 UT with an upper limit of 20 mCrab. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30117 SUBJECT: GRB 210602A: CALET Gamma-Ray Burst Monitor detection DATE: 21/06/03 07:04:45 GMT FROM: Valentin Pal'shin at AGU V. Pal'shin, A. Yoshida, T. Sakamoto, S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The bright GRB 210602A (MAXI/GSC detection: Serino et al., GCN Circ. 30113) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 12:04:01.493 UTC on 2 June 2021 (http://cgbm.calet.jp/cgbm_trigger/flight/1306670489/index.html). The burst signal was seen by all CGBM detectors. The burst light curve shows a single pulse which starts at T+0.5 sec, peaks at T+1.4 sec, and ends at T+3.0 sec. The T90 and T50 durations measured by the SGM data are 1.9 +- 0.3 sec and 0.5 +- 0.1 sec (40-1000 keV), respectively. The ground processed light curve is available at http://cgbm.calet.jp/cgbm_trigger/ground/1306670489/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30119 SUBJECT: MAXI GRB210602.50: Global MASTER-Net observations report DATE: 21/06/03 10:17:09 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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the MAXI GRB210602.50 (trigger No 367443743,02h 58m 31.20s , -02d 40m 19.2s, R=1) errorbox 76251 sec after notice time and 77693 sec after trigger time at 2021-06-03 09:39:01 UT, with upper limit up to 17.0 mag. The observations began at zenith distance = 77 deg. The sun altitude is -22.4 deg. The galactic latitude b = -50 deg., longitude l = 180 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1626919 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 77784 | 2021-06-03 09:39:01 | MASTER-OAFA | (02h 56m 34.35s , -03d 25m 33.9s) | C | 180 | 17.0 | 77923 | 2021-06-03 09:42:21 | MASTER-OAFA | (02h 56m 37.84s , -03d 22m 41.9s) | C | 60 | 16.7 | 78003 | 2021-06-03 09:43:40 | MASTER-OAFA | (03h 04m 35.58s , -03d 20m 47.3s) | C | 60 | 16.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30145 SUBJECT: Konus-Wind detection of GRB 210602A DATE: 21/06/07 15:08:45 GMT FROM: Dmitry Frederiks at Ioffe Institute D. Frederiks, S. Golenetskii, A.Lysenko, D. Svinkin, A. Ridnaya, A. Tsvetkova, M. Ulanov, and T. Cline, report: The bright GRB 210602A (MAXI/GSC detection: Serino et al., GCN 30113; CALET Gamma-Ray Burst Monitor detection: Pal'shin et al., GCN 30117) triggered Konus-Wind (KW) at T0=43439.748 s UT (12:03:59.748). The burst light curve shows a single pulse which starts at ~T0-0.5 s, peaks at ~T0+0.512 s, and has the total duration of ~3.1 s (T100, 20-1500 keV). The emission is seen up to ~2 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB210602_T43439/ As observed by Konus-Wind, the burst had a fluence of (6.3 ± 0.6)x10^-6 erg/cm^2 and a 64-ms peak energy flux, measured from T0+0.384, of (9.5 ± 1.0)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 15 MeV range by a power law with exponential cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.25(-0.23,+0.26) and Ep = 188(-33,+58) keV (chi2 = 75/97 dof). Fitting this spectrum by a Band function yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.2 (chi2 = 75/96 dof). All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary.