Gamma-ray Burst 210320A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN NOTICE
  

  TITLE:           GCN/MAXI NOTICE
  NOTICE_DATE:     Sun 21 Mar 21 00:30:08 UT
  NOTICE_TYPE:     MAXI Unknown Source Position
  EVENT_ID_NUM:      9293849998
  EVENT_RA:          4.73d {+00h 18m 55s} (J2000),
                     4.99d {+00h 19m 58s} (current),
                     4.11d {+00h 16m 27s} (1950)
  EVENT_DEC:       -47.48d {-47d 28' 32"} (J2000),
                   -47.36d {-47d 21' 29"} (current),
                   -47.75d {-47d 45' 12"} (1950)
  EVENT_ERROR:     1.0 [deg radius, stat+sys, 90% containment]
  EVENT_FLUX:      144.0 +- 0.0 [mCrab]
  EVENT_DATE:      19293 TJD;    79 DOY;   21/03/20
  EVENT_TIME:      76861.00 SOD {21:21:01.00} UT
  EVENT_TSCALE:    3s
  EVENT_EBAND:     Low, 2-4 keV
  SUN_POSTN:         0.57d {+00h 02m 16s}   +0.25d {+00d 14' 46"}
  SUN_DIST:         47.76 [deg]
  MOON_POSTN:       83.38d {+05h 33m 31s}  +24.26d {+24d 15' 19"}
  MOON_DIST:       100.25 [deg]
  MOON_ILLUM:      44 [%]
  GAL_COORDS:      318.17,-68.68 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      340.24,-44.29 [deg] ecliptic lon,lat of the burst (or transient)
  COMMENTS:        MAXI Unknown Source Position. GRB or unknown X-ray Transient.
  

• GCN Circular #29676
  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.