Gamma-ray Burst 210120A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 20 Jan 21 07:11:18 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      58
TRIGGER_NUM:     632819449
GRB_RA:          164.367d {+10h 57m 28s} (J2000),
                 164.644d {+10h 58m 35s} (current),
                 163.707d {+10h 54m 50s} (1950)
GRB_DEC:         +14.067d {+14d 04' 00"} (J2000),
                 +13.954d {+13d 57' 13"} (current),
                 +14.334d {+14d 20' 04"} (1950)
GRB_ERROR:       10.80 [deg radius, statistical plus systematic]
GRB_INTEN:       143 [cnts/sec]
DATA_SIGNIF:     14.10 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        19234 TJD;    20 DOY;   21/01/20
GRB_TIME:        25844.70 SOD {07:10:44.70} UT
GRB_PHI:         154.00 [deg]
GRB_THETA:        80.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.66
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      96%  GRB
2nd_MOST_LIKELY:   3%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 0,0,0, 0,1,1, 0,0,
SUN_POSTN:       302.65d {+20h 10m 36s}  -20.05d {-20d 03' 05"}
SUN_DIST:        139.48 [deg]   Sun_angle= 9.2 [hr] (West of Sun)
MOON_POSTN:       24.03d {+01h 36m 08s}   +5.45d {+05d 27' 12"}
MOON_DIST:       136.36 [deg]
MOON_ILLUM:      45 [%]
GAL_COORDS:      233.37, 60.41 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      160.19,  6.84 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210120299/quicklook/glg_lc_medres34_bn210120299.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 23.03,-3.45 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 20 Jan 21 07:11:09 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      45
TRIGGER_NUM:     632819449
GRB_RA:          169.733d {+11h 18m 56s} (J2000),
                 170.007d {+11h 20m 02s} (current),
                 169.082d {+11h 16m 20s} (1950)
GRB_DEC:         +11.717d {+11d 43' 00"} (J2000),
                 +11.601d {+11d 36' 05"} (current),
                 +11.990d {+11d 59' 25"} (1950)
GRB_ERROR:       18.33 [deg radius, statistical plus systematic]
GRB_INTEN:       85 [cnts/sec]
DATA_SIGNIF:     7.90 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        19234 TJD;    20 DOY;   21/01/20
GRB_TIME:        25844.70 SOD {07:10:44.70} UT
GRB_PHI:         151.00 [deg]
GRB_THETA:        75.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.48
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      95%  GRB
2nd_MOST_LIKELY:   4%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 0,0,0, 0,1,1, 0,0,
SUN_POSTN:       302.65d {+20h 10m 35s}  -20.05d {-20d 03' 05"}
SUN_DIST:        133.81 [deg]   Sun_angle= 8.8 [hr] (West of Sun)
MOON_POSTN:       24.03d {+01h 36m 07s}   +5.45d {+05d 27' 10"}
MOON_DIST:       142.10 [deg]
MOON_ILLUM:      45 [%]
GAL_COORDS:      243.80, 63.38 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      165.96,  6.71 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210120299/quicklook/glg_lc_medres34_bn210120299.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 23.03,-3.45 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 20 Jan 21 07:11:29 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     632819449
GRB_RA:          166.390d {+11h 05m 34s} (J2000),
                 166.666d {+11h 06m 40s} (current),
                 165.734d {+11h 02m 56s} (1950)
GRB_DEC:         +13.010d {+13d 00' 36"} (J2000),
                 +12.896d {+12d 53' 46"} (current),
                 +13.280d {+13d 16' 49"} (1950)
GRB_ERROR:       4.96 [deg radius, statistical only]
DATA_SIGNIF:     14.60 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        19234 TJD;    20 DOY;   21/01/20
GRB_TIME:        25844.70 SOD {07:10:44.70} UT
GRB_PHI:         153.00 [deg]
GRB_THETA:        78.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       302.65d {+20h 10m 36s}  -20.05d {-20d 03' 05"}
SUN_DIST:        137.31 [deg]   Sun_angle= 9.1 [hr] (West of Sun)
MOON_POSTN:       24.03d {+01h 36m 08s}   +5.45d {+05d 27' 14"}
MOON_DIST:       138.59 [deg]
MOON_ILLUM:      45 [%]
GAL_COORDS:      237.37, 61.51 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      162.43,  6.62 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210120299/quicklook/glg_lc_medres34_bn210120299.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_632819449.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 20 Jan 21 07:12:11 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      1
TRIGGER_NUM:     632819449
GRB_RA:          164.830d {+10h 59m 19s} (J2000),
                 165.109d {+11h 00m 26s} (current),
                 164.167d {+10h 56m 40s} (1950)
GRB_DEC:         +16.840d {+16d 50' 24"} (J2000),
                 +16.727d {+16d 43' 36"} (current),
                 +17.108d {+17d 06' 30"} (1950)
GRB_ERROR:       4.23 [deg radius, statistical only]
DATA_SIGNIF:     20.40 [sigma]
DATA_INTERVAL:   10.240 [sec]
GRB_DATE:        19234 TJD;    20 DOY;   21/01/20
GRB_TIME:        25844.70 SOD {07:10:44.70} UT
GRB_PHI:         152.00 [deg]
GRB_THETA:        82.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       302.65d {+20h 10m 36s}  -20.05d {-20d 03' 05"}
SUN_DIST:        139.67 [deg]   Sun_angle= 9.2 [hr] (West of Sun)
MOON_POSTN:       24.04d {+01h 36m 09s}   +5.46d {+05d 27' 23"}
MOON_DIST:       135.58 [deg]
MOON_ILLUM:      45 [%]
GAL_COORDS:      228.75, 62.13 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      159.52,  9.57 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210120299/quicklook/glg_lc_medres34_bn210120299.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_632819449.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This is likely a Long GRB.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 20 Jan 21 07:12:35 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      2
TRIGGER_NUM:     632819449
GRB_RA:          165.950d {+11h 03m 48s} (J2000),
                 166.229d {+11h 04m 55s} (current),
                 165.286d {+11h 01m 09s} (1950)
GRB_DEC:         +18.760d {+18d 45' 36"} (J2000),
                 +18.646d {+18d 38' 46"} (current),
                 +19.030d {+19d 01' 47"} (1950)
GRB_ERROR:       4.08 [deg radius, statistical only]
DATA_SIGNIF:     20.00 [sigma]
DATA_INTERVAL:   12.288 [sec]
GRB_DATE:        19234 TJD;    20 DOY;   21/01/20
GRB_TIME:        25844.70 SOD {07:10:44.70} UT
GRB_PHI:         150.00 [deg]
GRB_THETA:        83.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       302.65d {+20h 10m 36s}  -20.05d {-20d 03' 05"}
SUN_DIST:        138.97 [deg]   Sun_angle= 9.1 [hr] (West of Sun)
MOON_POSTN:       24.04d {+01h 36m 10s}   +5.46d {+05d 27' 28"}
MOON_DIST:       135.62 [deg]
MOON_ILLUM:      45 [%]
GAL_COORDS:      225.91, 63.91 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      159.75, 11.75 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210120299/quicklook/glg_lc_medres34_bn210120299.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_632819449.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This is likely a Long GRB.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 20 Jan 21 07:20:03 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     632819449
GRB_RA:          163.370d {+10h 53m 29s} (J2000),
                 163.650d {+10h 54m 36s} (current),
                 162.704d {+10h 50m 49s} (1950)
GRB_DEC:         +17.090d {+17d 05' 24"} (J2000),
                 +16.978d {+16d 58' 39"} (current),
                 +17.356d {+17d 21' 23"} (1950)
GRB_ERROR:       3.79 [deg radius, statistical only]
GRB_DATE:        19234 TJD;    20 DOY;   21/01/20
GRB_TIME:        25844.70 SOD {07:10:44.70} UT
GRB_PHI:         153.00 [deg]
GRB_THETA:        83.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       302.65d {+20h 10m 37s}  -20.05d {-20d 03' 01"}
SUN_DIST:        141.10 [deg]   Sun_angle= 9.3 [hr] (West of Sun)
MOON_POSTN:       24.10d {+01h 36m 24s}   +5.48d {+05d 28' 59"}
MOON_DIST:       134.15 [deg]
MOON_ILLUM:      45 [%]
GAL_COORDS:      226.99, 60.98 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      158.12,  9.25 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210120299/quicklook/glg_lc_medres34_bn210120299.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210120299/quicklook/glg_locplot_all_bn210120299.png
COMMENTS:        Fermi-GBM Final Position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file should be available by the time this FINAL notice is produced.  
COMMENTS:        This notice was generated completely by automated pipeline processing.
COMMENTS:        This is likely a Long GRB.

GCN Circular #29334
The Fermi GBM team reports the detection of a likely LONG GRB
At 07:10:44 UT on 20 Jan 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210120A (trigger 632819449.704302 / 210120299).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 163.4, Dec = 17.1 (J2000 degrees, equivalent to J2000 10h 53m, 17d 06'), with a statistical uncertainty of 3.8 degrees.
The angle from the Fermi LAT boresight is 83.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210120299/quicklook/glg_skymap_all_bn210120299.png
The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210120299/quicklook/glg_healpix_all_bn210120299.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210120299/quicklook/glg_lc_medres34_bn210120299.gif
GCN Circular #29335
B. Biltzinger, F. Kunzweiler, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 632819449 at 07:10:44 on 20 Jan. 2021 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60).
The best-fit position (1 sigma statistical errors) is:
```
RA(2000.0) = 163.5+/-2.8 deg
Decl.(2000.0) = 17.0+/-2.2 deg
```
We estimate an additional systematic error of 1 deg.
Further details are available at: https://grb.mpe.mpg.de/grb/GRB210120299/
The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB210120299/healpix
The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB210120299/json
GCN Circular #29336
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 Fermi GRB 210120A ( Fermi GBM team, GCN 29334) errorbox 80 sec after notice time and 143 sec after trigger time at 2021-01-20 07:13:07 UT, with upper limit up to 19.5 mag. The observations began at zenith distance = 50 deg. The sun altitude is -27.8 deg.
The galactic latitude b = 61 deg., longitude l = 228 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1529824
We obtain a following upper limits.
```
Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

     158 | 2021-01-20 07:13:07 |         MASTER-OAFA | (11h 02m 27.64s , +18d 11m 39.0s) |   C |    30 | 18.3 |        
     214 | 2021-01-20 07:13:58 |         MASTER-OAFA | (11h 02m 27.67s , +18d 10m 13.7s) |   C |    40 | 18.4 |        
     279 | 2021-01-20 07:14:58 |         MASTER-OAFA | (11h 02m 30.93s , +18d 11m 51.7s) |   C |    50 | 19.0 |        
     353 | 2021-01-20 07:16:07 |         MASTER-OAFA | (11h 02m 25.55s , +18d 10m 58.1s) |   C |    60 | 18.8 |        
     646 | 2021-01-20 07:20:30 |         MASTER-OAFA | (10h 52m 05.03s , +16d 29m 39.0s) |   C |   120 | 19.2 |        
     795 | 2021-01-20 07:22:49 |         MASTER-OAFA | (10h 52m 11.15s , +16d 29m 48.7s) |   C |   140 | 19.4 |        
     974 | 2021-01-20 07:25:29 |         MASTER-OAFA | (10h 52m 07.89s , +16d 31m 35.3s) |   C |   180 | 19.5 |        
    1174 | 2021-01-20 07:28:48 |         MASTER-OAFA | (10h 52m 07.90s , +16d 30m 04.6s) |   C |   180 | 19.4 |
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #29338
Z. H. An, C. Cai, G. Chen, W. Chen, M. Gao, M. Y. Ge, K. Gong, D. Y. Guo, J. J. He, Y. Huang, B. Li, C. Li, C. Y. Li, J. H. Li, M. S. Li, Q. X. Li, X. B. Li, X. Q. Li, Y. G. Li, X. H. Liang, J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu, Q. Luo, X. Ma, G. Ou, W. X. Peng, R. Qiao, J. Y. Shi, D. L. Shi, L. M. Song, X. Y. Song, G. X. Sun, X. L. Sun, Y. L. Tuo, J. Z. Wang, C. W. Wang, P. Wang, W. S. Wang, X. Y. Wen, S. Xiao, S. L. Xiong, Y. B. Xu, Y. P. Xu, W. C. Xue, S. Yang, M. Yao, Q. B. Yi, K. Zhang, P. Zhang, D. L. Zhang, F. Zhang, H. M. Zhang, S. N. Zhang, Y. Q. Zhang, Z. Zhang, S. Y. Zhao, X. Y. Zhao, Y. Zhao, C. Zheng, S. J. Zheng (IHEP), L. Chang, W. W. Chen, Y. M. Chen, L. Dong, X. B. Han, J. Huang, J. Huang, C. Y. Ji, Y. C. Ji, F. Li, M. Y. Li, Z. D. Li, Y. F. Lu, Y. Pang, J. L. Qi, J. G. Rong, Q. Q. Wang, Z. Wang, Y. Yang, J. P. Yu, S. M. Yu, K. K. Zhang, D. K. Zhou (IAMCAS), M. Bai, T. Hu, Z. Ji, Y. R. Liu, J. Su, C. X. Tian, J. Z. Tong, H. Y. Wu, Q. S. Yu, J. Zhong, Z. M. Zou (NSSC), X. X. Feng (AIR), (The GECAM Mission Team) report:
During the commissioning phase, one satellite of GECAM mission, GECAM-B, was triggered by a long GRB 210120A at 2021-01-20T07:10:48.550 (T0), which was also observed by Fermi/GBM (GCN #29334, 29335).
This burst was triggered, localized and classified as unknown source by the GECAM In-Flight Trigger and Localization Software and then its alert data was promptly downlinked to the ground through the short message service of BeiDou Navigation Satellite System (BDS). The time latency of the first BeiDou message (including in-flight trigger and location results) relative to the trigger time is about 60 seconds. All other messages (including light curves data) for this trigger arrived within about 10 minutes.
We made the quick-look light curve and the on-ground localization using the alert data. The quick-look light curve shows that this burst mainly consists of a single peak with a duration of about 20 s. Although the in-flight calibration of energy response and localization has not been finalized yet, the quick-look location is generally consistent with the position given by Fermi/GBM within the error. As the detailed science data are downloaded, all analyses including localization would be further improved.
The GECAM quick-look light curve could be found here: http://twiki.ihep.ac.cn/pub/GECAM/GRBList/utn210120_071048_GECAMb.png
The GECAM quick-look location (preliminary) could be found here: http://twiki.ihep.ac.cn/pub/GECAM/GRBList/utn210120_071048_GECAMb_Localization.png
Please note that all GECAM results here are preliminary. The final analysis will be published in journal papers or GECAM online catalog.
This is the first GECAM GRB which was triggered and localized in-flight with alert data promptly downlinked to ground successfully.
Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time), which was funded by the Chinese Academy of Sciences (CAS).
GCN Circular #29339
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), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico FelixAguilar OAFA), R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), 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, Yu. Sergienko (Blagoveschensk Educational StateUniversity)
MASTER-OAFA robotic telescope (MASTER-Net: http://observ.pereplet.ru Lipunov et al.,2010,Advances in Astronomy,2010,30L) automatically was pointed (Lipunov et al. GCN 29336) to Fermi GRB210120A (Trigger=07:10:44UT, Fermi GCN 29334, BALROG localization Biltzinger et al. GCN 29335, Barthelmy https://gcn.gsfc.nasa.gov/other/210120A.gcn3 ) 80s after notice time (143s after trigger time) at 2021-01-20 07:13:07UT
At first images MASTER auto-detection system found fast changing optical transient MASTER OT J105242.66+152355.0 / AT2021axc at (RA, Dec) = 10h 52m 42.66s +15d 23m 55.0s at 2021-01-20 07:20:30UT with unfiltered m_OT=18.6 at the beginning stage.
The OT is seen at several images. There is no any sources at this place in MASTER database since 2004.
The nearest source in VIZIER is SDSS galaxy in 4.9" with rmag(as most closest to MASTER unfiltered)=22.217 (22.088 in PanSTARRS)
The reduction will be continued. This message may be cited.
GCN Circular #29341
S. Belkin (IKI), A. Pozanenko (IKI), N. Pankov (HSE), E. Klunko (ISTP) report on behalf of GRB IKI FuN:
We observed the MASTER OT J105242.66+152355.0 / AT2021axc (Lipunov et al., GCN 29339) in the field of Fermi GRB 210120A (Fermi GBM Team, GCN 29334; Biltzinger et al. GCN 29335) with AZT-33IK telescope of Sayan observatory (Mondy) starting on 2021-01-20 (UT) 20:57:41. The candidate in optical afterglow (Lipunov et al., GCN 29339) is well detected in our R-filter stacked image at R = 22.14 +/- 0.27 with 3 sigma upper limit of the field for point-like source R=22.3. We confirm fading nature of the transient and support it for afterglow candidate of GRB 210112A.
Preliminary photometry of the optical transient in the stacked image is following
```
Date       UT start   t-T0       Filter Exp.    OT    Err.  UL(3sigma)
                       (mid, days)        (s)

2021-01-20 20:57:41   0.59510    R      30*120  22.14 0.27  22.3
```
The photometry is based on the nearby USNO-B1.0 stars
```
USNO-B1.0_id R2
1053-0195054 16.13
1053-0195003 18.57
```
GCN Circular #29345
Dimple (ARIES), A. Ghosh (ARIES), R. Gupta (ARIES), A. Kumar (ARIES), K. Misra (ARIES), S.B. Pandey (ARIES) report:
We carried out the follow-up observations of the MASTER OT J105242.66+152355.0 / AT2021axc (Lipunov et al., GCN #29339) in the field of Fermi GRB 210120A (Fermi GBM Team, GCN 29334; Biltzinger et al., GCN #29335) with 1.3m Devasthal Fast Optical Telescope (DFOT) at Devasthal observatory of Aryabhatta Research Institute of observational sciencES (ARIES), India. The observations started on 2021-01-21 at 20:51:55 in R-band. We observed a set of 18 images with an exposure time of 300 seconds each, centered at 1.5937 days after the burst. We clearly detect the optical afterglow candidate reported by Lipunov et al., GCN #29339 in the stacked image with a magnitude of 22.60+-0.16. The object is fading with time (S. Belkin et al. GCN #29341; Lipunov et al., GCN #29339) which supports it as an afterglow candidate for GRB 210120A.
The magnitude is not corrected for the Galactic extinction in the direction of the burst. The photometric calibration is performed using the standard stars from the USNO-B1.0 catalog.
GCN Circular #29361
S. Lesage (UAH), R. Dunwoody (UCD), J. Mangan (UCD), C. Meegan (UAH) report on behalf of the Fermi GBM Team:
"At 07:10:44.70 UT on 20 January 2021, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 210120A (trigger 632819449 / 210120.299), the optical counterpart for which was detected by MASTER (Lipunov et al. 2021, GCN 29339) and confirmed (Pozanenko et al. 2021, GCN 29341; Dimple et al. 2021, GCN 29345). The GBM Fermi GBM Final Real-time Localization (GCN 29334) is consistent with the MASTER OT follow-up observations.
The angle from the Fermi LAT boresight at the GBM trigger time is 82 degrees.
The GBM light curve consists of a single peak with a duration (T90) of about 22.2 s (50-300 keV). The time-averaged spectrum from T0-0.32 s to T0+22.21 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.62 +/- 0.12 and the cutoff energy, parameterized as Epeak, is 94 +/- 6 keV
The event fluence (10-1000 keV) in this time interval is (2.9 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+ 2.6 s in the 10-1000 keV band is 3.6 +/- 0.2 ph/s/cm^2.
A Band function fits the spectrum equally well with Epeak= 95 +/- 6 keV, alpha = -0.63 +/- 0.12 and beta = -29 +/- 6E12.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"

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Jochen Greiner, last update: 27-Jan-2021 [Disclaimer]