Gamma-ray Burst 210528B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN NOTICE

TITLE:           GCN/MAXI NOTICE
NOTICE_DATE:     Sat 29 May 21 00:09:47 UT
NOTICE_TYPE:     MAXI Unknown Source Position
EVENT_ID_NUM:      9362758075
EVENT_RA:        239.54d {+15h 58m 09s} (J2000),
                 239.80d {+15h 59m 13s} (current),
                 238.92d {+15h 55m 42s} (1950)
EVENT_DEC:        +5.98d {+05d 58' 58"} (J2000),
                  +5.92d {+05d 55' 22"} (current),
                  +6.13d {+06d 07' 31"} (1950)
EVENT_ERROR:     1.0 [deg radius, stat+sys, 90% containment]
EVENT_FLUX:      170.0 +- 0.0 [mCrab]
EVENT_DATE:      19362 TJD;   148 DOY;   21/05/28
EVENT_TIME:      82315.00 SOD {22:51:55.00} UT
EVENT_TSCALE:    10s
EVENT_EBAND:     Low, 2-4 keV
SUN_POSTN:        66.10d {+04h 24m 24s}  +21.62d {+21d 37' 07"}
SUN_DIST:        151.78 [deg]
MOON_POSTN:      284.88d {+18h 59m 30s}  -25.53d {-25d 31' 41"}
MOON_DIST:        53.89 [deg]
MOON_ILLUM:      91 [%]
GAL_COORDS:       16.14, 40.90 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      235.91, 25.89 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        MAXI Unknown Source Position. GRB or unknown X-ray Transient.

GCN Circular #30094
Y. Sugawara (JAXA), H. Negoro, M. Nakajima, K. Kobayashi, K. Asakura, K. Seino (Nihon U.), T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, 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, 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 22:51:37 UT on 2021 May 28. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (239.539 deg, 5.983 deg) = (15 58 09, +05 58 58) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.26 deg and 0.22 deg, respectively. The roll angle of long axis from the north direction is 133.0 deg counterclockwise. 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:
```
(238.974, 6.826) deg = (15 55 53, +06 49 33) (J2000)
(238.661, 6.518) deg = (15 54 38, +06 31 04) (J2000)
(240.060, 5.113) deg = (16 00 14, +05 06 46) (J2000)
(240.373, 5.421) deg = (16 01 29, +05 25 15) (J2000)
```
The X-ray flux averaged over the scan was 170 +- 28 mCrab (4.0-10.0keV, 1 sigma error). There was no significant excess flux in the previous transit at 21:18 UT and in the next transit at 00:24 on May 29 UT with an upper limit of 20 mCrab for each.
GCN Circular #30095
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-IAC robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Spain (IAC Teide Observatory) started inspect of the MAXI GRB210528.95 (trigger No 362758075,15h 58m 09.36s , +05d 58m 58.8s, R=1) errorbox 10 sec after notice time and 4707 sec after trigger time at 2021-05-29 00:10:22 UT, with upper limit up to 18.8 mag. The observations began at zenith distance = 23 deg. The sun altitude is -39.0 deg.
The galactic latitude b = 40 deg., longitude l = 16 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1623577
We obtain a following upper limits.
```
Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

    4798 | 2021-05-29 00:10:22 |          MASTER-IAC | (15h 57m 01.56s , +06d 02m 14.3s) |  P| |   180 | 18.5 |        
    4798 | 2021-05-29 00:10:22 |          MASTER-IAC | (15h 56m 10.28s , +06d 08m 43.9s) |  P- |   180 | 18.3 |        
    4998 | 2021-05-29 00:13:42 |          MASTER-IAC | (15h 57m 09.19s , +06d 02m 16.4s) |  P| |   180 | 18.7 |        
    4998 | 2021-05-29 00:13:42 |          MASTER-IAC | (15h 56m 17.67s , +06d 08m 46.0s) |  P- |   180 | 18.3 |        
    5198 | 2021-05-29 00:17:02 |          MASTER-IAC | (15h 57m 06.12s , +06d 03m 54.3s) |  P| |   180 | 18.7 |        
    5198 | 2021-05-29 00:17:02 |          MASTER-IAC | (15h 56m 14.54s , +06d 10m 23.3s) |  P- |   180 | 18.4 |        
    5398 | 2021-05-29 00:20:22 |          MASTER-IAC | (15h 57m 06.18s , +06d 02m 37.0s) |  P| |   180 | 18.8 |        
    5398 | 2021-05-29 00:20:22 |          MASTER-IAC | (15h 56m 14.59s , +06d 09m 05.6s) |  P- |   180 | 18.4 |        
```
The observation and reduction will continue. The message may be cited.
GCN Circular #30096
K. L. Murata, R. Hosokawa, M. Niwano, Y. Imai, N. Ito, H. Takamatsu, S. Sato, M. Takaku, R. Noto, R. Yamaguchi, Y. Yatsu, and N. Kawai (TokyoTech) report on behalf of the MITSuME collaboration:
We observed the field of GRB 210528B (Sugawara et al. GCN Circular #30094, Lipunov et al. GCN Circular #30095) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME telescope Akeno. The observation with a series of 60 sec exposures started at 2021-05-29 11:21:57 UT (12.5 hours after the trigger). We stacked the images with good conditions. We did not detect any uncatalogued sources in all three bands within the elliptical error region (Sugawara et al. GCN Circular #30094) determined under the assumption that the source flux was constant over the transit. We obtained the 5-sigma limits of the stacked images as follows.
```
T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
12.5 2021-05-29 12:13 1560 g'>19.9
12.5 2021-05-29 12:13 2040 Rc>20.2
12.5 2021-05-29 12:13 1500 Ic>19.4
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
```
We used the PS1 catalog for flux calibration. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1, Pages 4-24; https://github.com/MNiwano/Eclaire).
GCN Circular #30097
Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), Simone Dichiara (GSFC/UMD), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl Lopez (UNAM), Diego Gonzalez (UNAM), Margarita Pereyra (UNAM), Srihari Ravi (ASU), and Eleonora Troja (GSFC/UMD) report:
We observed the field of the MAXI/GSC GRB 210528B (Sugawara et al., GCN Circ., 30094) with the DDOTI wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Martir (http://ddoti.astroscu.unam.mx) from 2021-05-29 04:07 to 06:53 UTC (from 5.3 to 8.0 hours after the trigger).
We observed a region covering aproximately 7 degrees in RA and 10 degrees in declination (1 instrumental field or about 70 square degrees) including the entire MAXI/GSC uncertainty region centered on 15:58:09 +05:58:58 J2000 (Sugawara et al., GCN Circ., 30094). We obtained 7860 seconds of exposure in the w filter. We obtained AB photometry by calibration against the APASS catalog.
Within the uncertainty region, we detect no likely candidate for the afterglow to our 5-sigma upper limits of w = 21.8.
We thank the staff of the Observatorio Astronomico Nacional in San Pedro Martir.

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Jochen Greiner, last update: 29-May-2021 [Disclaimer]