Gamma-ray Burst 200325B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 25 Mar 20 14:53:40 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      47
TRIGGER_NUM:     606840801
GRB_RA:          161.900d {+10h 47m 36s} (J2000),
                 162.173d {+10h 48m 42s} (current),
                 161.224d {+10h 44m 54s} (1950)
GRB_DEC:         +22.033d {+22d 01' 60"} (J2000),
                 +21.926d {+21d 55' 34"} (current),
                 +22.297d {+22d 17' 51"} (1950)
GRB_ERROR:       17.87 [deg radius, statistical plus systematic]
GRB_INTEN:       113 [cnts/sec]
DATA_SIGNIF:     7.00 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        18933 TJD;    85 DOY;   20/03/25
GRB_TIME:        53596.04 SOD {14:53:16.04} UT
GRB_PHI:         213.00 [deg]
GRB_THETA:        95.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      1.53
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      85%  GRB
2nd_MOST_LIKELY:  14%  Generic SGR
DETECTORS:       0,0,0, 0,0,0, 0,0,1, 0,0,1, 0,0,
SUN_POSTN:         4.98d {+00h 19m 55s}   +2.15d {+02d 09' 13"}
SUN_DIST:        147.19 [deg]   Sun_angle= -10.5 [hr] (East of Sun)
MOON_POSTN:       19.09d {+01h 16m 21s}   +2.90d {+02d 53' 51"}
MOON_DIST:       136.21 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      216.36, 61.46 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      154.86, 13.28 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200325620/quicklook/glg_lc_medres34_bn200325620.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 78.75,2.63 [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 25 Mar 20 14:53:50 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      58
TRIGGER_NUM:     606840801
GRB_RA:          162.750d {+10h 51m 00s} (J2000),
                 163.027d {+10h 52m 06s} (current),
                 162.065d {+10h 48m 16s} (1950)
GRB_DEC:         +27.850d {+27d 51' 00"} (J2000),
                 +27.742d {+27d 44' 32"} (current),
                 +28.115d {+28d 06' 55"} (1950)
GRB_ERROR:       10.90 [deg radius, statistical plus systematic]
GRB_INTEN:       542 [cnts/sec]
DATA_SIGNIF:     18.00 [sigma]
INTEG_TIME:      0.512 [sec]
GRB_DATE:        18933 TJD;    85 DOY;   20/03/25
GRB_TIME:        53596.04 SOD {14:53:16.04} UT
GRB_PHI:         216.00 [deg]
GRB_THETA:       100.00 [deg]
DATA_TIME_SCALE: 0.5120 [sec]
HARD_RATIO:      0.75
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      97%  GRB
2nd_MOST_LIKELY:   2%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 0,0,1, 0,0,1, 0,0,
SUN_POSTN:         4.98d {+00h 19m 55s}   +2.15d {+02d 09' 13"}
SUN_DIST:        143.40 [deg]   Sun_angle= -10.5 [hr] (East of Sun)
MOON_POSTN:       19.09d {+01h 16m 22s}   +2.90d {+02d 53' 53"}
MOON_DIST:       133.71 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      204.34, 63.35 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      153.21, 18.92 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200325620/quicklook/glg_lc_medres34_bn200325620.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 78.75,2.63 [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 25 Mar 20 15:02:36 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     606840801
GRB_RA:          166.900d {+11h 07m 36s} (J2000),
                 167.172d {+11h 08m 41s} (current),
                 166.228d {+11h 04m 55s} (1950)
GRB_DEC:         +26.160d {+26d 09' 36"} (J2000),
                 +26.050d {+26d 03' 01"} (current),
                 +26.431d {+26d 25' 51"} (1950)
GRB_ERROR:       3.28 [deg radius, statistical only]
GRB_DATE:        18933 TJD;    85 DOY;   20/03/25
GRB_TIME:        53596.04 SOD {14:53:16.04} UT
GRB_PHI:         212.00 [deg]
GRB_THETA:       101.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:         4.98d {+00h 19m 56s}   +2.16d {+02d 09' 22"}
SUN_DIST:        146.95 [deg]   Sun_angle= -10.8 [hr] (East of Sun)
MOON_POSTN:       19.16d {+01h 16m 38s}   +2.93d {+02d 55' 37"}
MOON_DIST:       137.61 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      209.38, 66.82 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      157.51, 18.88 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200325620/quicklook/glg_lc_medres34_bn200325620.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200325620/quicklook/glg_locplot_all_bn200325620.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 NOTICE

 
TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 25 Mar 20 14:55:04 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      2
TRIGGER_NUM:     606840801
GRB_RA:          169.080d {+11h 16m 19s} (J2000),
                 169.351d {+11h 17m 24s} (current),
                 168.410d {+11h 13m 38s} (1950)
GRB_DEC:         +28.440d {+28d 26' 24"} (J2000),
                 +28.329d {+28d 19' 46"} (current),
                 +28.713d {+28d 42' 47"} (1950)
GRB_ERROR:       2.51 [deg radius, statistical only]
DATA_SIGNIF:     30.90 [sigma]
DATA_INTERVAL:   15.360 [sec]
GRB_DATE:        18933 TJD;    85 DOY;   20/03/25
GRB_TIME:        53596.04 SOD {14:53:16.04} UT
GRB_PHI:         212.00 [deg]
GRB_THETA:       104.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:         4.98d {+00h 19m 55s}   +2.15d {+02d 09' 14"}
SUN_DIST:        146.02 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       19.10d {+01h 16m 24s}   +2.90d {+02d 54' 08"}
MOON_DIST:       137.67 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      203.81, 68.96 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      158.38, 21.76 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200325620/quicklook/glg_lc_medres34_bn200325620.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_606840801.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 25 Mar 20 14:55:09 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      3
TRIGGER_NUM:     606840801
GRB_RA:          169.000d {+11h 16m 00s} (J2000),
                 169.271d {+11h 17m 05s} (current),
                 168.328d {+11h 13m 19s} (1950)
GRB_DEC:         +29.850d {+29d 51' 00"} (J2000),
                 +29.739d {+29d 44' 22"} (current),
                 +30.123d {+30d 07' 23"} (1950)
GRB_ERROR:       2.33 [deg radius, statistical only]
DATA_SIGNIF:     31.50 [sigma]
DATA_INTERVAL:   18.432 [sec]
GRB_DATE:        18933 TJD;    85 DOY;   20/03/25
GRB_TIME:        53596.04 SOD {14:53:16.04} UT
GRB_PHI:         213.00 [deg]
GRB_THETA:       105.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:         4.98d {+00h 19m 55s}   +2.15d {+02d 09' 14"}
SUN_DIST:        144.75 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       19.10d {+01h 16m 24s}   +2.90d {+02d 54' 09"}
MOON_DIST:       136.65 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      199.89, 68.89 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      157.66, 23.01 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200325620/quicklook/glg_lc_medres34_bn200325620.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_606840801.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 25 Mar 20 14:54:00 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     606840801
GRB_RA:          164.690d {+10h 58m 46s} (J2000),
                 164.968d {+10h 59m 52s} (current),
                 164.001d {+10h 56m 00s} (1950)
GRB_DEC:         +32.960d {+32d 57' 36"} (J2000),
                 +32.851d {+32d 51' 05"} (current),
                 +33.228d {+33d 13' 41"} (1950)
GRB_ERROR:       6.39 [deg radius, statistical only]
DATA_SIGNIF:     20.30 [sigma]
DATA_INTERVAL:   1.024 [sec]
GRB_DATE:        18933 TJD;    85 DOY;   20/03/25
GRB_TIME:        53596.04 SOD {14:53:16.04} UT
GRB_PHI:         218.00 [deg]
GRB_THETA:       105.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:         4.98d {+00h 19m 55s}   +2.15d {+02d 09' 13"}
SUN_DIST:        140.21 [deg]   Sun_angle= -10.7 [hr] (East of Sun)
MOON_POSTN:       19.09d {+01h 16m 22s}   +2.90d {+02d 53' 55"}
MOON_DIST:       131.85 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      192.58, 65.01 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      152.59, 24.27 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200325620/quicklook/glg_lc_medres34_bn200325620.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_606840801.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 Circular #27441
The Fermi GBM team reports the detection of a likely LONG GRB
At 14:53:16 UT on 25 Mar 2020, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 200325B (trigger 606840801.036936 / 200325620).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 166.9, Dec = 26.2 (J2000 degrees, equivalent to J2000 11h 07m, 26d 11'), with a statistical uncertainty of 3.3 degrees.
The angle from the Fermi LAT boresight is 101.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200325620/quicklook/glg_skymap_all_bn200325620.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/bn200325620/quicklook/glg_healpix_all_bn200325620.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200325620/quicklook/glg_lc_medres34_bn200325620.gif
GCN Circular #27446
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(Lomonosov Moscow State University, SAI, Physics Department), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), R. Podesta, C.Lopez, F. Podesta, C.Francile(Observatorio Astronomico Felix Aguilar OAFA), H.Levato(Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE), 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), V. Yurkov, A. Gabovich, Yu. Sergienko(Blagoveschensk Educational State University)
MASTER OT J111012.51+274912.8 discovery - new OT inside Fermi GRB 200325B (trigger 606840801)
MASTER Global Robotic Net inspected GRB 200325B: Fermi trigger 606840801, Ttr=2020-03-05 14:53:16 UT, GCN #27441, MASTER report GCN #27442, MASTER map and OT position. During inspection MASTER-Kislovodsk auto-detection system ( Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 30L ) discovered new OT source at (RA, Dec) = 11h 10m 12.51s +27d 49m 12.8s on 2020-03-25 16:21:15 UT. The OT unfiltered magnitude is 16.1m (mlim=17.8). The OT is seen in 2 inspect images (MASTER has 2 tubes at each observatory and works with large error-fields like Fermi in open mode, that gives 8 square degrees, i.e. 2x4sq.deg.). There is no minor planet at this place and no any sources in VIZIER database (22mag limit in POSS history).
We have reference images on 2010-03-13.87244 UT with unfiltered mlim= 20.2m, on 2020-02-21 21:54:40UT with mlim=20.3. Spectral observations are required. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/111012.51274912.8.png
GCN Circular #27450
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the Fermi/GBM GRB 200325B. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00020978
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/GBM 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 #27452
A. Pozanenko (IKI), E. Klunko (ISTP), A. Sosnovskij (CrAO), M. Eselevich (ISTP), V. Rumyantsev (CrAO), S. Belkin (IKI), E. Mazaeva (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN:
We observed the field of Fermi-GBM GRB 200325B (Fermi GBM team, GCN 27441) with AZT-33VM 1.5-m telescope of Sayan observatory (Mondy) starting on 2020-03-26 (UT) 15:08:10 and and ZTSh 2.6m telescope of CrAO starting on 2020-03-26 (UT) 20:11:20. We clearly detected the OT discovered by MASTER (Lipunov et al., GCN 27446). Coordinates of the OT are (J2000) 11:10:12.54 +27:49:11.7 with uncertainty of 0.5 arcses. The R magnitude of the OT is 19.8 +/- 0.15 at 2020-03-26 (UT) 15:08:10. Observations and data reduction is ongoing.
GCN Circular #27455
S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), A. Sosnovskij (CrAO), R. Ya. Inasaridze (AbAO), V. Rumyantsev (CrAO), M. Eselevich (ISTP), E. Mazaeva (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN:
We observed the MASTER OT J111012.51+274912.8 (Lipunov et al., GCN 27446) as a candidate in afterglow of the Fermi GRB 200325B (Fermi GBM team, GCN 27441) with AZT-33VM 1.5-m telescope of Sayan observatory (Mondy) starting on 2020-03-26 (UT) 15:08:10, ZTSh 2.6m telescope of CrAO starting on 2020-03-26 (UT) 20:11:20 (Pozanenko et al., GCN 27452), and AS-32 0.7m telescope of Abastumani observatory starting on 2020-03-26 (UT) 20:27:39. Below we present refined photometry of the OT. Preliminary photometry of the object is following.
```
Date UT start       t-T0  Filter Exp. OT Err UL(3sigma)   telescope
                         (mid, days) (s)
2020-03-26 15:08:10 1.0263   R 23*120  19.89 0.05  22.6 AZT-33VM
2020-03-26 20:11:20 1.2306   R 14*120  20.07 0.08  22.3 ZTSh
2020-03-26 20:27:39 1.2444   R 35*60    n/d  n/d   20.0 AS-32
```
the photometry is based on nearby SDSS-DR12 stars
```
RA DEC               R(Lupton transformations)
167.569191 27.848262 16.015
167.513655 27.832992 16.930
167.510507 27.850424 15.261
```
We note that coordinates of the OT (Lipunov et al., GCN 27446; Pozanenko et al., GCN 27452) coincide with only one XRT source (https://www.swift.ac.uk/ToO_GRBs/00020978/ ) found in the error localization of GBM/Fermi. Taking into account the XRT source and fading OT we suggest the MASTER OT J111012.51+274912.8 is an afterglow GRB 200325B.
GCN Circular #27456
R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration:
We observed Fermi GRB 200325A (Fermi GBM Team, GCN 27441) with the LCO 1-m Sinistro instrument at the Siding Spring Observatory, Australia site, on March 27, from 12:08 to 12:48 UT (corresponding to 45.25 to 45.92 hours from the GRB trigger time) with the Bessel R and I filters.
We performed a series of 5x240s exposures in R and I. We detect a source consistent with other optical detections (Lipunov et al., GCN 27446, Pozanenko et al., GCN 27452) in stacked images. Using the USNO-B.1 catalog as reference, we obtain the following magnitudes:
R = 21.36 +/- 0.11
I = 20.52 +/- 0.13
These magnitudes are not corrected for Galactic Extinction.
R.S. is funded by NSF AST grant #1831682
GCN Circular #27457
P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), A. Melandri (INAF-OAB), T. Sbarrato (INAF-OAB), S. R. Oates (U. of Birmingham), M. H. Siegel (PSU), F. E. Marshall (NASA/GSFC), S. Dichiara (NASA/GSFC/UMCP) and P.A. Evans (U.Leicester) report on behalf of the Swift-XRT and UVOT teams:
Swift-XRT has performed follow-up observations of the Fermi-detected burst GRB 200325B (Fermi GBM team, GCN Cir. 27441), collecting 1.1 ks of Photon Counting (PC) mode data between T0+102.4 ks and T0+124.8 ks in a single pointing covering the region of the candidate GRB optical counterpart initially reported by Lipunov et al. (GCN Circ. 27446).
An uncatalogued X-ray source has been detected:
Source 1:
```
 RA (J2000.0):  167.55381  =  11:10:12.91
 Dec (J2000.0):  +27.8196  =  +27:49:10.5
 Error: 4.9 arcsec (radius, 90% conf. [Enhanced position])
 Count-rate: 0.020 [+/-0.005] ct s^-1   
 Flux: (7.2 [+/-1.8])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)
```
The source is below the RASS limit and, due to the limited amount of data available so far, shows no signs of fading.
The position of this source is consistent with the one reported for the GRB optical afterglow (Lipunov et al., GCN Circ. 27446; Pozanenko et al., GCN Circ. 27452; Belkin et al., GCN Circ. 27455; Strausbaugh & Cucchiara, GCN Circ. 27456). We therefore conclude that this is the X-ray afterglow of GRB 200325B.
The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/00020978
.
The Swift/UVOT began settled observations of the field of GRB 200325B 102ks after the Fermi/GBM trigger. An optical source consistent with the GRB optical afterglow (Lipunov et al., GCN Circ. 27446; Pozanenko et al., GCN Circ. 27452; Belkin et al., GCN Circ. 27455; Strausbaugh & Cucchiara, GCN Circ. 27456) is detected in the initial UVOT white exposure. A preliminary magnitude in white using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) is:
```
Filter         T_start(ks)   T_stop(ks)      Exp(s)         Mag

white             102.39       124.75         1044        21.27 � 0.24
```
This magnitude is not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #27460
C. Malacaria (NASA-MSFC/USRA) and C. Meegan (UAH) report on behalf of the Fermi GBM Team:
"At 14:53:16.04 UT on 25 March 2020, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 200325B (trigger 606840801 / 200325620), which was also detected by the Swift/XRT (GCN 27457). The optical counterpart was detected by MASTER (GCN 27446), Mondy (GCN 27452), and LCO (GCN 27457).
The angle from the Fermi LAT boresight at the GBM trigger time is 102.5 degrees.
The GBM light curve shows a broad peak with several spikes overimposed, with a duration (T90) of about 36.6 s (50-300 keV). The time-averaged spectrum from T0-8.1 s to T0+36.9 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.33 +/- 0.04 and the cutoff energy, parameterized as Epeak, is 150.1 +/- 12.8 keV.
The event fluence (10-1000 keV) in this time interval is (1.12 +/- 0.04)e-5 erg/cm^2. The 1-sec peak photon flux measured starting from T0+10.7 s in the 10-1000 keV band is 9.1 +/- 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 #27464
S. Klose, B. Stecklum, A. Nicuesa Guelbenzu, S. Melnikov, and F. Ludwig (all Tautenburg) report:
We observed the field of GRB 200325B (Ferni GBM team, GCN 27441) with the Tautenburg 1.34m Schmidt telescope equipped with the TAUKAM 6k x 6k CCD camera and the wide V-band filter (VB). The transmission curve of this filter closely follows the Gaia GBP filter. Observations were performed during several epochs starting 1.2 days after the burst.
The optical transient discovered by the MASTER Global Robotic Net (Lipunov et al., GCN 27446) is clearly detected (see also Pozanenko et al., GCN 27452; Belkin et al., GCN 27455; Strausbaugh et al., GCN 27456; D'Avanzo et al., GCN 27457). Aperture photometry was performed using several Gaia DR2 stars in the field. Between dt = 1.2 and 2.4 days the optical transient was fading by 1.3 mag. During our last observation (2.4 days post burst) it had reached VB = 20.7 +/- 0.2 mag.
GCN Circular #27465
S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), M. Eselevich (ISTP), E. Mazaeva (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN:
We observed the MASTER OT J111012.51+274912.8 (Lipunov et al., GCN 27446) afterglow of the Fermi GRB 200325B (Fermi GBM team, GCN 27441) with AZT-33IK 1.5-m telescope of Sayan observatory (Mondy) starting on 2020-03-27 (UT) 14:07:34. Preliminary photometry of the OT is following.
```
Date UT start       t-T0  Filter Exp. OT Err UL(3sigma)
                         (mid, days) (s)
2020-03-27 14:07:34 1.9877   R 28*120  21.15  0.06  23.1
```
the photometry is based on nearby SDSS-DR12 stars
```
RA DEC               R(Lupton transformations)
167.569191 27.848262 16.015
167.513655 27.832992 16.930
167.510507 27.850424 15.261
```
The photometry presented above corroborates the photometry presented by LCO (Strausbaugh et al. GCN 27456) at about the same time.
GCN Circular #27467
S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), M. Eselevich (ISTP), E. Mazaeva (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN:
We observed the MASTER OT J111012.51+274912.8 (Lipunov et al., GCN 27446) afterglow of the Fermi GRB 200325B (Fermi GBM team, GCN 27441) with AZT-33IK 1.5-m telescope of Sayan observatory (Mondy) starting on 2020-03-28 (UT) 14:50:17. Preliminary photometry of the OT is following.
```
Date UT start       t-T0  Filter Exp. OT Err UL(3sigma)
                          (mid, days) (s)
2020-03-28 14:50:17 3.01182  R 20*120  21.82  0.13  23.4
```
the photometry is based on nearby SDSS-DR12 stars
```
RA DEC               R(Lupton transformations)
167.569191 27.848262 16.015
167.513655 27.832992 16.930
167.510507 27.850424 15.261
```
GCN Circular #27468
S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), M. Eselevich (ISTP), E. Mazaeva (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN:
We observed the MASTER OT J111012.51+274912.8 (Lipunov et al., GCN 27446) afterglow of the Fermi GRB 200325B (Fermi GBM team, GCN 27441) with AZT-33IK 1.5-m telescope of Sayan observatory (Mondy) starting on 2020-03-29 (UT) 13:47:58. Preliminary photometry of the OT is following.
```
Date UT start       t-T0  Filter Exp. OT Err UL(3sigma)
                          (mid, days) (s)
2020-03-29 13:47:58 3.96785  R 19*120  22.30  0.25  22.4
```
the photometry is based on nearby SDSS-DR12 stars
```
RA DEC               R(Lupton transformations)
167.569191 27.848262 16.015
167.513655 27.832992 16.930
167.510507 27.850424 15.261
```
GCN Circular #27471
A. D'Ai (INAF-IASFPA), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), D.N. Burrows (PSU), J.P. Osborne (U. Leicester), 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 further follow-up observations of the GBM-detected burst GRB 200325B (Fermi GBM team, GCN Cir. 27441), collecting overall 4.6 ks of Photon Counting (PC) mode data between T0+102.4 ks and T0+505.5 ks.
The uncatalogued X-ray source (Source 1) reported in D'Avanzo et al. (GCN Circ. 27457) has faded with alpha >1.2, confirming that this is the GRB afterglow.
The results of the XRT-team automatic analysis of the afterglow are at https://www.swift.ac.uk/ToO_GRBs/00020978/Source1.php. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00020978.
This circular is an official product of the Swift-XRT team.
GCN Circular #27473
A. Kumar (ARIES), A. Aryan (ARIES), S. B. Pandey (ARIES), R. Gupta (ARIES), A. Ghosh (ARIES), Dimple (ARIES), and K. Misra (ARIES) report:
We observed the optical afterglow field of the Fermi GRB 200325B (Fermi GBM team, GCN 27441, Lipunov et al., GCN 27446) with 1.3m Devsthal Fast Optical Telescope (DFOT) at Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital (India), from 2020-03-30 UT 19:37:08 to 2020-03-30 UT 20:59:28. We observed 16 frames each of 300 seconds in Bessell I filter. No new optical source was detected within the Swift XRT enhanced error circle in any individual as well as stacked frame.
The 3-sigma upper limit is as follows:
```
T_start-T0 (days)   Start Date (UTC)            End Date (UTC)      Filter        3-sigma upper limit (mag)
---------------------------------------------------------------------------------------------------------------
5.21                2020-03-30 19:37:08       2020-03-30 20:59:28        I               >23.2
```
Photometry is done based on the standard star PB 2256 and USNO-B1.0 catalog. The quoted magnitude is not corrected for Galactic extinction.
GCN Circular #27481
S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), M. Eselevich (ISTP), E. Mazaeva (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN:
We continued observations of the MASTER OT J111012.51+274912.8 (Lipunov et al., GCN 27446) which is now is confirmed afterglow (Pozanenko et al., GCN 27452; Strausbaugh et al., GCN 27456; Klose et al., GCN 27464; D'Ai et al., GCN 27471) of the Fermi GRB 200325B (Fermi GBM team, GCN 27441) with AZT-33IK 1.5-m telescope of Sayan observatory (Mondy). Preliminary photometry of the OT is following.
```
Date UT start       t-T0  Filter Exp. OT Err UL(3sigma)
                          (mid, days) (s)

2020-03-30  15:07:22 5.03063  R 30*120  22.40  0.20  22.7
2020-03-31  17:09:44 6.11561  R 30*120  22.45  0.17  22.8
2020-04-01  16:40:59 7.10254  R 40*120  n/d    n/d   22.6
```
the photometry is based on nearby SDSS-DR12 stars
```
RA         DEC       R(Lupton transformations)
167.569191 27.848262 16.015
167.513655 27.832992 16.930
167.510507 27.850424 15.261
```
A light curve of the GRB 200325B afterglow based on our observations (Belkin et al., GCNs 27455, 27465, 27467, 27468) can be found at http://grb.rssi.ru/GRB200325B/GRB200325B_lc.png

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Jochen Greiner, last update: 03-Apr-2020 [Disclaimer]