Gamma-ray Burst 210312B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Fri 12 Mar 21 20:52:28 UT
NOTICE_TYPE:    INTEGRAL Wakeup
TRIGGER_NUM:    9073,   Sub_Num: 0
GRB_RA:         155.8425d {+10h 23m 22s} (J2000),
                156.3184d {+10h 25m 16s} (current),
                154.6976d {+10h 18m 47s} (1950)
GRB_DEC:        +76.8765d {+76d 52' 35"} (J2000),
                +76.7686d {+76d 46' 07"} (current),
                +77.1294d {+77d 07' 46"} (1950)
GRB_ERROR:      2.95 [arcmin, radius, statistical only]
GRB_INTEN:      10.96 [sigma]
GRB_TIME:       75137.36 SOD {20:52:17.36} UT
GRB_DATE:       19285 TJD;    71 DOY;   21/03/12
SC_RA:          151.27 [deg] (J2000)
SC_DEC:          75.77 [deg] (J2000)
SUN_POSTN:      353.11d {+23h 32m 28s}   -2.97d {-02d 58' 27"}
SUN_DIST:       105.62 [deg]   Sun_angle= -10.9 [hr] (East of Sun)
MOON_POSTN:     348.95d {+23h 15m 49s}  -10.17d {-10d 10' 02"}
MOON_DIST:      113.06 [deg]
GAL_COORDS:     132.82, 37.26 [deg] galactic lon,lat of the burst
ECL_COORDS:     113.67, 58.93 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       Time_Scale=2.0000 and Time_Error=2.0000.  
COMMENTS:       Possibly real GRB event

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Fri 12 Mar 21 20:55:30 UT
NOTICE_TYPE:    INTEGRAL Refined
TRIGGER_NUM:    9073,   Sub_Num: 1
GRB_RA:         155.8406d {+10h 23m 22s} (J2000),
                156.3164d {+10h 25m 16s} (current),
                154.6958d {+10h 18m 47s} (1950)
GRB_DEC:        +76.8713d {+76d 52' 17"} (J2000),
                +76.7634d {+76d 45' 48"} (current),
                +77.1242d {+77d 07' 27"} (1950)
GRB_ERROR:      2.72 [arcmin, radius, statistical only]
GRB_INTEN:      15.78 [sigma]
GRB_TIME:       75140.10 SOD {20:52:20.10} UT
GRB_DATE:       19285 TJD;    71 DOY;   21/03/12
SC_RA:          151.27 [deg] (J2000)
SC_DEC:          75.77 [deg] (J2000)
SUN_POSTN:      353.12d {+23h 32m 28s}   -2.97d {-02d 58' 24"}
SUN_DIST:       105.63 [deg]   Sun_angle= -10.9 [hr] (East of Sun)
MOON_POSTN:     348.98d {+23h 15m 54s}  -10.16d {-10d 09' 24"}
MOON_DIST:      113.05 [deg]
GAL_COORDS:     132.83, 37.26 [deg] galactic lon,lat of the burst
ECL_COORDS:     113.68, 58.93 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       Time_Scale=0.1599 and Time_Error=2.0000.  
COMMENTS:       Possibly real GRB event

GCN Circular #29649
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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Integral GRB210312.87 (trigger No 9073,10h 23m 22.09s , +76d 52m 36.7s, R=0.0491667) errorbox 27 sec after notice time and 41 sec after trigger time at 2021-03-12 20:52:58 UT, with upper limit up to 15.9 mag. The observations began at zenith distance = 34 deg. The sun altitude is -49.6 deg.
The galactic latitude b = 38 deg., longitude l = 133 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1567228
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

      46 |   MASTER-Kislovodsk |  P- |    10 | 14.9 |        
      46 |   MASTER-Kislovodsk |  P| |    10 | 15.8 |        
      64 |   MASTER-Kislovodsk |  P- |    10 | 14.9 |        
      64 |   MASTER-Kislovodsk |  P| |    10 | 15.9 |        
```
The observation and reduction will continue. The message may be cited.

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Fri 12 Mar 21 21:39:20 UT
NOTICE_TYPE:    INTEGRAL Offline
TRIGGER_NUM:    9073,   Sub_Num: 2
GRB_RA:         155.8430d {+10h 23m 22s} (J2000),
                156.3188d {+10h 25m 17s} (current),
                154.6983d {+10h 18m 48s} (1950)
GRB_DEC:        +76.8713d {+76d 52' 17"} (J2000),
                +76.7634d {+76d 45' 48"} (current),
                +77.1242d {+77d 07' 27"} (1950)
GRB_ERROR:      2.00 [arcmin, radius, statistical only]
GRB_INTEN:      15.78 [sigma]
GRB_TIME:       75140.10 SOD {20:52:20.10} UT
GRB_DATE:       19285 TJD;    71 DOY;   21/03/12
SC_RA:          151.27 [deg] (J2000)
SC_DEC:          75.77 [deg] (J2000)
SUN_POSTN:      353.14d {+23h 32m 35s}   -2.96d {-02d 57' 40"}
SUN_DIST:       105.61 [deg]   Sun_angle= -10.9 [hr] (East of Sun)
MOON_POSTN:     349.33d {+23h 17m 20s}  -10.01d {-10d 00' 17"}
MOON_DIST:      112.88 [deg]
GAL_COORDS:     132.83, 37.26 [deg] galactic lon,lat of the burst
ECL_COORDS:     113.68, 58.93 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       Time_Scale=0.1599 and Time_Error=2.0000.  
COMMENTS:       refined_coordinates_after_offline_analysis

GCN Circular #29650
S.Mereghetti (INAF, IASF-Milano), D.Gotz (CEA, Saclay), C.Ferrigno, E.Bozzo, V.Savchenko (ISDC, Versoix), L.Ducci (IAAT, Germany and ISDC, Versoix) and J.Borkowski (CAMK, Torun) report:
a gamma ray burst lasting about 5 s has been detected by IBAS in the IBIS/ISGRI data at 20:52:17 UT of March 12, 2021
The refined coordinates (J2000) are:
```
R.A.=  155.8431 deg
DEC.=  +76.8714 deg
```
with an uncertainty of 2 arcmin (90% c.l.).
The burst had a peak flux of about 1.5 ph/cm2/s (20-200 keV, 1-s integration time) and a fluence in the same energy range of about 2e-7 erg/cm2
A plot of the light curve will be posted at http://ibas.iasf-milano.inaf.it/IBAS_Results.html
GCN Circular #29651
M. Jelinek, J. Strobl, S. Trcka, R. Hudec, C. Polasek (ASU CAS Ondrejov) report:
We observed the position of the Integral trigger 9073 (GRB 210312.87 or B) with the D50 robotic telescope of the Astronomical Institute Ondrejov, near Prague, Czech Republic. We performed a series of 10s and 20s unfiltered exposures starting 23.8 s after the trigger.
In the first images we detect a rapidly fading object not present in the DSS catalogue at 10:23:15.312 +76:52:06.96 J2000. The preliminary magnitude of the object in the earliest images was R~18m.
GCN Circular #29652
V. Lipunov, V.Kornilov, E.Gorbovskoy,N.Tiurina,P.Balanutsa,F.Balakin, V.Vladimirov, A.Kuznetsov,K.Zhirkov,D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, A.Chasovnikov,A.Pozdnyakov,V.Topolev, D.Cheryasov(Lomonosov Moscow State University, SAI, Physics Department), D. Buckley (South African Astronomical Observatory), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico FelixAguilar OAFA), R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias), O.A. Gres, N.M. Budnev (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)
MASTER Global robotic net (MASTER-Net:http://observ.pereplet.ru Lipunov et al.,2010,Advances in Astronomy,2010,30L) automatically started (Lipunov et al. GCN 29649) Integral GRB 210312B (Mereghetti et al. GCN 29650,Ttrigger=20:52:17UT) optical observations at MASTER-Kislovodsk at 2021-03-12 20:52:58 UT 27s after notice time(41s after trigger time), and at MASTER-Tunka at 2021-03-12 20:52:58UT with mlim=18.7 at first 10s images. We confirm Jelinek et al. GCN 29651 (Ondrejov) optical counterpart with unfiltered m_OT=18.2 at first image.
This message may be cited.
GCN Circular #29653
D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), C. C. Thoene, M. Blazek, J. F. Agui Fernandez (all HETH/IAA-CSIC), and R. Scarpa (GTC) report:
We observed the afterglow (Jelinek et al., GCN #29651; Lipunov et al., GCN #29652) of INTEGRAL GRB 210312B (Mereghetti et al., GCN #29650) with OSIRIS at the 10.4m Gran Telescopio Canarias (Roque de los Muchachos Observatory, La Palma, Canary Islands, Spain), starting at 2021-03-12 22:57:10.834 UT. We obtained a 60 s finding chart exposure under adverse conditions (2" seeing, bad transparency because of Calima).
In the image, the afterglow is clearly detected. Against a nearby PanSTARRS star, we measure r' = 21.52 +/- 0.06 mag at 2.0898 hr after the trigger (0.08708 days).
GCN Circular #29655
D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), C. C. Thoene, M. Blazek, J. F. Agui Fernandez (all HETH/IAA-CSIC), and R. Scarpa (GTC) report:
We observed the afterglow (Jelinek et al., GCN #29651; Lipunov et al., GCN #29652) of INTEGRAL GRB 210312B (Mereghetti et al., GCN #29650) with OSIRIS at the 10.4m Gran Telescopio Canarias (Roque de los Muchachos Observatory, La Palma, Canary Islands, Spain), starting at 2021-03-12 22:57:10.834 UT under adverse conditions (2" seeing, bad transparency because of Calima). Following the finding chart exposure (Kann et al., GCN #29653), we obtained 2 x 900 s spectroscopic exposures with the R1000B grism, covering the spectral range from 3700 to 7800 AA, before the telescope was shut down due to worsening observing conditions. We detect a faint trace in both images. We resumed observations after an improvement in weather conditions at 2021-03-13 01:41:40.281 UT, obtaining two further finding charts and 4 x 900 s spectra with the same grism.
Using the same comparison star as Kann et al., GCN #29653, we find the afterglow has faded to r' = 22.36 +/- 0.03 mag (AB) at 4.8316 hrs after the GRB trigger.
Combining the first spectral exposure and the latter, for a total exposure of 5 x 900 s, a trace is clearly detected redwards of 4300 AA, as well as several absorption lines. We identify these as FeII, MgII, and MgI, at a mean redshift of z = 1.069. At this redshift, we also detect OII in emission, which allows us to identify this as the redshift of the GRB.
GCN Circular #29716
D. A. Kann (HETH/IAA-CSIC), M. Jelinek (ASU CAS Ondrejov), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), C. C. Thoene, M. Blazek, J. F. Agui Fernandez (all HETH/IAA-CSIC), A. Sota, and R. M. Eloy (both IAA-CSIC) report:
We observed the optical afterglow of GRB 210312B (INTEGRAL detection: Mereghetti et al., GCN #29650) with both the 1.5m T150 and the 0.9m T90 telescopes of the Observatorio de Sierra Nevada (OSN), Granada, Spain. We obtained 5 x 90 s exposures in B, V, Rc, and 6 x 90 s in Ic, followed by 21 x 180 s exposures in Rc with the T150 telescope, and 18 x 180 s in Rc with the T90 telescope in parallel, starting at 2021-03-12 22:51:28.19 UT. The afterglow is detected in multiple combined images from T150, and in the complete combined T90 image. We furthermore obtained 10 x 500 s Rc images in the second night with the T150. The afterglow is detected in the combined image.
From three stacked images observed from 0.09577 to 0.14106 days after the GRB, we detect a potential plateau phase, measuring Rc ~ 21.69 mag (AB mag, vs. a nearby Pan-STARRS star converted to Rc following the Lupton transformations, then transformed back to AB mag; errors range from 0.04 to 0.11 mag). Then at 1.0850 days, we find the afterglow has significantly decayed to Rc = 23.04 +/- 0.07 mag (AB).
Using photometry from our GTC observations (Kann et al., GCNs #29653, #29655) as well as earlier photometry from the Ondrejov D50, we find a broken power-law decay with a late slope of alpha ~ 2.2. The second-day OSN detection is in excess of the extrapolated decay, indicating that the host galaxy may contribute already, or that another rebrightening has taken place.

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Jochen Greiner, last update: 13-Mar-2021 [Disclaimer]