Gamma-ray Burst 201104B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 08 Dec 20 06:03:48 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      46
TRIGGER_NUM:     629100208
GRB_RA:          155.933d {+10h 23m 44s} (J2000),
                 156.170d {+10h 24m 41s} (current),
                 155.369d {+10h 21m 29s} (1950)
GRB_DEC:         -33.833d {-33d 49' 59"} (J2000),
                 -33.940d {-33d 56' 22"} (current),
                 -33.580d {-33d 34' 46"} (1950)
GRB_ERROR:       11.83 [deg radius, statistical plus systematic]
GRB_INTEN:       69 [cnts/sec]
DATA_SIGNIF:     6.30 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        19191 TJD;   343 DOY;   20/12/08
GRB_TIME:        21803.25 SOD {06:03:23.25} UT
GRB_PHI:         240.00 [deg]
GRB_THETA:        15.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.09
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      98%  GRB
2nd_MOST_LIKELY:   2%  Generic SGR
DETECTORS:       0,0,0, 0,0,0, 1,0,0, 1,0,0, 0,0,
SUN_POSTN:       255.46d {+17h 01m 50s}  -22.76d {-22d 45' 45"}
SUN_DIST:         84.69 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:      172.52d {+11h 30m 05s}   +9.01d {+09d 00' 31"}
MOON_DIST:        45.67 [deg]
MOON_ILLUM:      48 [%]
GAL_COORDS:      270.92, 19.70 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      173.28,-40.21 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201208252/quicklook/glg_lc_medres34_bn201208252.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 12.67,-2.03 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 08 Dec 20 06:03:57 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      58
TRIGGER_NUM:     629100208
GRB_RA:          149.883d {+09h 59m 32s} (J2000),
                 150.105d {+10h 00m 25s} (current),
                 149.354d {+09h 57m 25s} (1950)
GRB_DEC:         -38.333d {-38d 19' 59"} (J2000),
                 -38.434d {-38d 26' 02"} (current),
                 -38.093d {-38d 05' 34"} (1950)
GRB_ERROR:       8.38 [deg radius, statistical plus systematic]
GRB_INTEN:       170 [cnts/sec]
DATA_SIGNIF:     11.40 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        19191 TJD;   343 DOY;   20/12/08
GRB_TIME:        21803.25 SOD {06:03:23.25} UT
GRB_PHI:         240.00 [deg]
GRB_THETA:        20.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      0.47
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      95%  GRB
2nd_MOST_LIKELY:   4%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 1,0,0, 1,0,0, 0,0,
SUN_POSTN:       255.46d {+17h 01m 50s}  -22.76d {-22d 45' 45"}
SUN_DIST:         87.18 [deg]   Sun_angle= 7.0 [hr] (West of Sun)
MOON_POSTN:      172.52d {+11h 30m 06s}   +9.01d {+09d 00' 29"}
MOON_DIST:        51.84 [deg]
MOON_ILLUM:      48 [%]
GAL_COORDS:      269.62, 13.18 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      170.43,-46.52 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201208252/quicklook/glg_lc_medres34_bn201208252.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 12.67,-2.03 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 08 Dec 20 06:04:09 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      69
TRIGGER_NUM:     629100208
GRB_RA:          149.567d {+09h 58m 16s} (J2000),
                 149.787d {+09h 59m 09s} (current),
                 149.040d {+09h 56m 10s} (1950)
GRB_DEC:         -38.917d {-38d 55' 00"} (J2000),
                 -39.017d {-39d 01' 01"} (current),
                 -38.677d {-38d 40' 37"} (1950)
GRB_ERROR:       7.33 [deg radius, statistical plus systematic]
GRB_INTEN:       185 [cnts/sec]
DATA_SIGNIF:     16.50 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        19191 TJD;   343 DOY;   20/12/08
GRB_TIME:        21803.25 SOD {06:03:23.25} UT
GRB_PHI:         240.00 [deg]
GRB_THETA:        20.00 [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, 1,0,0, 1,0,0, 0,0,
SUN_POSTN:       255.46d {+17h 01m 50s}  -22.76d {-22d 45' 45"}
SUN_DIST:         87.13 [deg]   Sun_angle= 7.0 [hr] (West of Sun)
MOON_POSTN:      172.53d {+11h 30m 06s}   +9.01d {+09d 00' 26"}
MOON_DIST:        52.47 [deg]
MOON_ILLUM:      48 [%]
GAL_COORDS:      269.80, 12.57 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      170.55,-47.15 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201208252/quicklook/glg_lc_medres34_bn201208252.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 12.67,-2.03 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 08 Dec 20 06:04:07 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     629100208
GRB_RA:          158.110d {+10h 32m 26s} (J2000),
                 158.352d {+10h 33m 25s} (current),
                 157.533d {+10h 30m 08s} (1950)
GRB_DEC:         -31.090d {-31d 05' 23"} (J2000),
                 -31.198d {-31d 11' 53"} (current),
                 -30.832d {-30d 49' 55"} (1950)
GRB_ERROR:       7.44 [deg radius, statistical only]
DATA_SIGNIF:     8.10 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        19191 TJD;   343 DOY;   20/12/08
GRB_TIME:        21803.25 SOD {06:03:23.25} UT
GRB_PHI:         234.00 [deg]
GRB_THETA:        12.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       255.46d {+17h 01m 50s}  -22.76d {-22d 45' 45"}
SUN_DIST:         84.10 [deg]   Sun_angle= 6.5 [hr] (West of Sun)
MOON_POSTN:      172.53d {+11h 30m 06s}   +9.01d {+09d 00' 27"}
MOON_DIST:        42.44 [deg]
MOON_ILLUM:      48 [%]
GAL_COORDS:      270.91, 23.00 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      173.71,-36.93 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201208252/quicklook/glg_lc_medres34_bn201208252.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_629100208.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
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:     Tue 08 Dec 20 06:05:07 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      0
TRIGGER_NUM:     629100208
GRB_RA:          150.280d {+10h 01m 07s} (J2000),
                 150.508d {+10h 02m 02s} (current),
                 149.736d {+09h 58m 57s} (1950)
GRB_DEC:         -34.740d {-34d 44' 23"} (J2000),
                 -34.841d {-34d 50' 28"} (current),
                 -34.499d {-34d 29' 55"} (1950)
GRB_ERROR:       1.00 [deg radius, statistical only]
DATA_SIGNIF:     25.60 [sigma]
DATA_INTERVAL:   5.120 [sec]
GRB_DATE:        19191 TJD;   343 DOY;   20/12/08
GRB_TIME:        21803.25 SOD {06:03:23.25} UT
GRB_PHI:         230.00 [deg]
GRB_THETA:        18.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       255.46d {+17h 01m 50s}  -22.76d {-22d 45' 45"}
SUN_DIST:         88.52 [deg]   Sun_angle= 7.0 [hr] (West of Sun)
MOON_POSTN:      172.53d {+11h 30m 08s}   +9.00d {+09d 00' 13"}
MOON_DIST:        48.54 [deg]
MOON_ILLUM:      48 [%]
GAL_COORDS:      267.56, 16.18 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      168.35,-43.23 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201208252/quicklook/glg_lc_medres34_bn201208252.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_629100208.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
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:     Tue 08 Dec 20 06:12:48 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     629100208
GRB_RA:          156.660d {+10h 26m 38s} (J2000),
                 156.902d {+10h 27m 37s} (current),
                 156.082d {+10h 24m 20s} (1950)
GRB_DEC:         -29.310d {-29d 18' 35"} (J2000),
                 -29.417d {-29d 25' 01"} (current),
                 -29.055d {-29d 03' 17"} (1950)
GRB_ERROR:       1.94 [deg radius, statistical only]
GRB_DATE:        19191 TJD;   343 DOY;   20/12/08
GRB_TIME:        21803.25 SOD {06:03:23.25} UT
GRB_PHI:         212.00 [deg]
GRB_THETA:        11.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       255.47d {+17h 01m 52s}  -22.76d {-22d 45' 47"}
SUN_DIST:         85.96 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:      172.60d {+11h 30m 25s}   +8.97d {+08d 58' 27"}
MOON_DIST:        41.26 [deg]
MOON_ILLUM:      47 [%]
GAL_COORDS:      268.69, 23.77 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      171.32,-35.91 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201208252/quicklook/glg_lc_medres34_bn201208252.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201208252/quicklook/glg_locplot_all_bn201208252.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:        In the LAT Field-of-view.  
COMMENTS:        This is likely a Long GRB.

GCN Circular #28998
The Fermi GBM team reports the detection of a likely LONG GRB
At 06:03:23 UT on 8 Dec 2020, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 201208A (trigger 629100208.248204 / 201208252).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 156.7, Dec = -29.3 (J2000 degrees, equivalent to J2000 10h 26m, -29d 18'), with a statistical uncertainty of 1.9 degrees.
The angle from the Fermi LAT boresight is 11.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201208252/quicklook/glg_skymap_all_bn201208252.png
The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201208252/quicklook/glg_healpix_all_bn201208252.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201208252/quicklook/glg_lc_medres34_bn201208252.gif
GCN Circular #28999
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 201208A ( Fermi GBM team, GCN 28998) errorbox 129 sec after notice time and 199 sec after trigger time at 2020-12-08 06:06:42 UT, with upper limit up to 18.3 mag. The observations began at zenith distance = 47 deg. The sun altitude is -31.2 deg.
The galactic latitude b = 24 deg., longitude l = 269 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1497931
We obtain a following upper limits.
```
Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

     229 | 2020-12-08 06:06:42 |         MASTER-OAFA | (10h 22m 26.04s , -30d 34m 40.3s) |   C |    60 | 18.3 |        
     308 | 2020-12-08 06:08:01 |         MASTER-OAFA | (10h 35m 33.22s , -32d 34m 16.4s) |   C |    60 | 18.3 |        
     388 | 2020-12-08 06:09:21 |         MASTER-OAFA | (10h 16m 42.48s , -32d 36m 29.2s) |   C |    60 | 18.2 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #29001
D. Nadella (NITK), A. Marathe (NITK), G. Waratkar (IITB), V. Shenoy (IITB), V. Bhalerao (IITB), A. Vibhute (IUCAA), S. Gupta (IUCAA), D. Bhattacharya (IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al, 2020, arXiv:2011.07067) showed detection of a long GRB 201208A, which was also detected by Fermi GBM Final Real-time (GCN #28998).
The source was clearly detected in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2020-12-08 06:03:32.500 UT. The measured peak count rate associated with the burst is 383 (+53, -58) cts/s above the background in the combined data of four quadrants, with a total of 2992 (+511, -554) cts. The local mean background count rate was 757 (+3, -5) cts/s. Using cumulative rates, we measure a T90 of 39.75 (+5, -14) s. A weak signal was also seen in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range.
CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 08 Dec 20 23:39:12 UT
NOTICE_TYPE:     Fermi-LAT Offline Position
TRIGGER_NUM:     201208252 
GRB_RA:          158.314d {+10h 33m 15s} (J2000),
                 158.559d {+10h 34m 14s} (current),
                 157.730d {+10h 30m 55s} (1950)
GRB_DEC:         -28.750d {-28d 45' 00"} (J2000),
                 -28.858d {-28d 51' 29"} (current),
                 -28.492d {-28d 29' 30"} (1950)
GRB_ERROR:       12.00 [arcmin radius, 90% containment, statistical only]
GRB_DATE:        19191 TJD;   343 DOY;   20/12/08
GRB_TIME:        21803.00 SOD {06:03:23.00} UT
TRIGGER_ID:      0x20000000
MISC:            0x40000000
SUN_POSTN:       256.26d {+17h 05m 03s}  -22.84d {-22d 50' 05"}
SUN_DIST:         85.46 [deg]   Sun_angle= 6.5 [hr] (West of Sun)
MOON_POSTN:      181.94d {+12h 07m 46s}   +4.82d {+04d 49' 27"}  
MOON_DIST:        40.50 [deg] 
MOON_ILLUM:      39 [%] 
GAL_COORDS:      269.65, 25.05 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      172.59,-34.76 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi LAT Offline position.
COMMENTS:        This Notice was ground-generated -- not flight-generated.
COMMENTS:        It is the result of human-in-the-loop processing.
COMMENTS:        This is a human generated position of a LAT ground detection.
COMMENTS:        This source corresponds to GBM trigger.

GCN Circular #29002
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the Fermi/LAT GRB 201208A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021405
Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the Fermi/LAT event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
GCN Circular #29003
F. Dirirsa (LAPP), N. Omodei (Stanford University), F. Longo (University and INFN Trieste), D. Kocevski (NASA/MSFC), M. Ohno (Hiroshima Univ. & Eotvos Univ.) and M. Axelsson (KTH and Stockholm Univ.) report on behalf of the Fermi-LAT Collaboration:
On December 08, 2020, Fermi-LAT detected high-energy emission from GRB 201208A, which was also detected by Fermi-GBM (trigger 201208252, GCN 28998) and AstroSat CZTI (GCN 29001).
The best LAT on-ground location is found to be
RA, Dec 158.3, -28.8 (degrees, J2000)
with an error radius of 0.16 deg (90% containment, statistical error only). This was 11 deg from the LAT boresight at the time of the GBM trigger:
T0 = 06:03:23 UT.
The data from the Fermi-LAT show a significant increase in the event rate after the GBM trigger that is spatially correlated with the GBM emission with high significance. The photon flux above 100 MeV in the time interval 0-3000 s after the GBM trigger is (9.7+/-5.8)e-07 ph/cm2/s.
The estimated photon index above 100 MeV is -1.6 +/- 0.3.
The highest-energy photon is a 6.2 GeV event which is observed 1320 seconds after the GBM trigger.
A Swift ToO has been approved for this burst.
The Fermi-LAT point of contact for this burst is Feraol Fana Dirirsa (ffdirirsa@gmail.com).
The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
GCN Circular #29015
L. Izzo (DARK/NBI) and D. B. Malesani (DTU Space) report:
We observed the field of GRB 201208A (Fermi-GBM team, GCN #28998, Nadella et al., GCN #29001, Dirirsa et al., GCN #29003) with the Sinistro instrument mounted on the 1-m telescope of the LCO network located at the McDonald Observatory (Texas). Observations started on December 9 at 12:09:55 UT (1.25 days after the GRB trigger). We obtained a series of 5x120s images in r filter.
Within the XRT best candidate afterglow position at RA (J2000) = 10:33:17.64, Dec. (J2000) = -28:43:11.6, and with an error of 3.1" (see Evans, GCN #29002) we do not detect any optical afterglow candidate. In our stacked image we measure an upper limit value of r > 23 (AB mag), calibrated against nearby Pan-STARRS catalog stars.
This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 730890.
GCN Circular #29017
R,Dunwoody (UCD), J.Mangan (UCD) and C. Meegan (UAH) report on behalf of the Fermi GBM Team:
At 06:03:23.25 UT on 08 December 2020, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 201208A (trigger 629100208 / 201208252) which was also detected by the Fermi/LAT (F. Dirirsa et al. 2020, GCN 29003) The Fermi GBM Final Real-time Localization (GCN 28998) is consistent with the Fermi/LAT position. This source was also detected by AstroSat (D. Nadella et al. 2020, GCN29001).
The angle from the Fermi LAT boresight at the GBM trigger time is 11 degrees.
The GBM light curve consists of one main pulse with a duration (T90) of about 45 s (50-300 keV). The time-averaged spectrum from T0-14 s to T0+34 s is best fit by a power law with an exponential high-energy cutoff. The power law index is -0.87 +/- 0.07 and the cutoff energy, parameterized as Epeak, is 254 +/- 24.
The event fluence (10-1000 keV) in this time interval is (1.07 +/- 0.22)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+12 s in the 10-1000 keV band is 5.1 +/- 0.3 ph/s/cm^2.
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/"
GCN Circular #29018
A. D'Ai (INAF-IASFPA), D.N. Burrows (PSU), J. D. Gropp (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAB), T. Sbarrato (INAF-OAB) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the Fermi/LAT-detected burst GRB 201208A (Dirirsa et al. GCN Circ. 29003), collecting 5.0 ks of Photon Counting (PC) mode data between T0+70.4 ks and T0+111.4 ks.
Four uncatalogued X-ray sources are detected, of which one ("Source 2") is above the 2SXPS 3-sigma upper limit at this position, and is therefore likely the GRB afterglow. Using 2046 s of PC mode data and 2 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 158.32352, -28.71989 which is equivalent to:
```
RA (J2000): 10h 33m 17.64s
Dec(J2000): -28d 43' 11.6"
```
with an uncertainty of 3.1 arcsec (radius, 90% confidence). This position is 112 arcsec from the Fermi/LAT position. The results of the XRT-team automatic analysis of the likely afterglow are at https://www.swift.ac.uk/ToO_GRBs/00021405/Source2.php. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021405.
This circular is an official product of the Swift-XRT team.

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Jochen Greiner, last update: 09-Dec-2020 [Disclaimer]