Gamma-ray Burst 200522A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 22 May 20 11:41:52 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     973628,   Seg_Num: 0
GRB_RA:            5.667d {+00h 22m 40s} (J2000),
                   5.928d {+00h 23m 43s} (current),
                   5.026d {+00h 20m 06s} (1950)
GRB_DEC:          -0.282d {-00d 16' 53"} (J2000),
                  -0.169d {-00d 10' 06"} (current),
                  -0.559d {-00d 33' 31"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       916 [cnts]    Image_Peak=116 [image_cnts]
TRIGGER_DUR:     0.128 [sec] 
TRIGGER_INDEX:   122     E_range: 25-100 keV
BKG_INTEN:       21448 [cnts]
BKG_TIME:        42079.01 SOD {11:41:19.01} UT
BKG_DUR:         8 [sec]
GRB_DATE:        18991 TJD;   143 DOY;   20/05/22
GRB_TIME:        42094.12 SOD {11:41:34.12} UT
GRB_PHI:         170.50 [deg]
GRB_THETA:        24.82 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     30.62 [sigma]
IMAGE_SIGNIF:    9.79 [sigma]
MERIT_PARAMS:     +1  +0  +0  -3  +2  +0  +0  +0 -55  +0 
SUN_POSTN:        59.74d {+03h 58m 58s}  +20.53d {+20d 31' 39"}
SUN_DIST:         56.50 [deg]   Sun_angle= 3.6 [hr] (West of Sun)
MOON_POSTN:       57.50d {+03h 49m 59s}  +17.34d {+17d 20' 07"}
MOON_DIST:        53.67 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      107.32,-62.28 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:        5.09, -2.51 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 353.33,-8.35 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 22 May 20 11:43:12 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     973628,   Seg_Num: 0
POINT_RA:          5.666d {+00h 22m 40s} (J2000)
POINT_DEC:        -0.284d {-00d 17' 00"} (J2000)
IMG_START_DATE:  18991 TJD;   143 DOY;   20/05/22
IMG_START_TIME:  42177.52 SOD {11:42:57.52} UT,   83.4 [sec] since BAT Trigger Time
COUNTS:          15    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        2    Max_iter_allowed= 4
ERROR_CODE:      1
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        No source found in the image.

GCN NOTICE

 
TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 22 May 20 11:45:23 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve 
TRIGGER_NUM:     973628,   Seg_Num: 0
GRB_RA:            5.667d {+00h 22m 40s} (J2000),
                   5.928d {+00h 23m 43s} (current),
                   5.026d {+00h 20m 06s} (1950)
GRB_DEC:          -0.282d {-00d 16' 53"} (J2000),
                  -0.169d {-00d 10' 06"} (current),
                  -0.559d {-00d 33' 31"} (1950)
GRB_DATE:        18991 TJD;   143 DOY;   20/05/22
GRB_TIME:        42094.12 SOD {11:41:34.12} UT
TRIGGER_INDEX:   122
GRB_PHI:         170.50 [deg]
GRB_THETA:        24.82 [deg]
DELTA_TIME:      -70.00 [sec]
TRIGGER_DUR:     0.128 [sec]
SOLN_STATUS:     0x3
RATE_SIGNIF:     30.62 [sigma]
IMAGE_SIGNIF:    9.79 [sigma]
LC_URL:          sw00973628000msb.lc
SUN_POSTN:        59.75d {+03h 58m 59s}  +20.53d {+20d 31' 41"}
SUN_DIST:         56.51 [deg]   Sun_angle= 3.6 [hr] (West of Sun)
MOON_POSTN:       57.53d {+03h 50m 07s}  +17.34d {+17d 20' 38"}
MOON_DIST:        53.70 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      107.32,-62.28 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:        5.09, -2.51 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Lightcurve.
COMMENTS:         
COMMENTS:        The next comments were copied from the BAT_POS Notice:
COMMENTS:        This is a rate trigger. 
COMMENTS:        A point_source was found.
COMMENTS:        This does not match any source in the on-board catalog.
COMMENTS:        This does not match any source in the ground catalog.
COMMENTS:        This is a GRB.
COMMENTS:        This trigger occurred at longitude,latitude = 353.33,-8.35 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 19 May 20 11:45:12 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     973140,   Seg_Num: 0
POINT_RA:        255.354d {+17h 01m 25s} (J2000)
POINT_DEC:       -30.379d {-30d 22' 44"} (J2000)
ROLL:            117.585d
IMG_START_DATE:  18988 TJD;   140 DOY;   20/05/19
IMG_START_TIME:  41693.83 SOD {11:34:53.83} UT,   870.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     611580918
X_OFFSET:        715 [pixels]
Y_OFFSET:        981 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       875
Y_GRB_POS:       1141
BINNING_INDEX:   1
IM_URL:          sw00973140000msuni0895.fits
SUN_POSTN:        56.74d {+03h 46m 57s}  +19.92d {+19d 55' 26"}
SUN_DIST:        159.95 [deg]   Sun_angle= 10.7 [hr] (West of Sun)
MOON_POSTN:       22.85d {+01h 31m 24s}   +4.41d {+04d 24' 49"}
MOON_DIST:       123.95 [deg]
MOON_ILLUM:      10 [%]
GAL_COORDS:      353.39,  7.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      257.29, -7.58 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 22 May 20 11:55:01 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     973628,   Seg_Num: 0
POINT_RA:          5.667d {+00h 22m 40s} (J2000)
POINT_DEC:        -0.285d {-00d 17' 05"} (J2000)
POINT_ROLL:      65.017d
IMG_START_DATE:  18991 TJD;   143 DOY;   20/05/22
IMG_START_TIME:  42542.41 SOD {11:49:02.41} UT,   448.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        9.193
N_STARS:         15
X_OFFSET:        471 [pixels]
Y_OFFSET:        531 [pixels]
X_MAX:           1430 [pixels]
Y_MAX:           1490 [pixels]
DET_THRESH:      27
PHOTO_THRESH:    17
SL_URL:          sw00973628000msufc0448.fits
SUN_POSTN:        59.75d {+03h 59m 00s}  +20.53d {+20d 31' 45"}
SUN_DIST:         56.51 [deg]   Sun_angle= 3.6 [hr] (West of Sun)
MOON_POSTN:       57.61d {+03h 50m 26s}  +17.37d {+17d 22' 04"}
MOON_DIST:        53.78 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      107.32,-62.28 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        5.09, -2.51 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 22 May 20 11:55:15 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     973628,   Seg_Num: 0
POINT_RA:          5.667d {+00h 22m 40s} (J2000)
POINT_DEC:        -0.285d {-00d 17' 05"} (J2000)
POINT_ROLL:      65.017d
IMG_START_DATE:  18991 TJD;   143 DOY;   20/05/22
IMG_START_TIME:  42542.41 SOD {11:49:02.41} UT,   448.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        9.193
N_STARS:         15
X_OFFSET:        471 [pixels]
Y_OFFSET:        531 [pixels]
X_MAX:           1430 [pixels]
Y_MAX:           1490 [pixels]
DET_THRESH:      27
PHOTO_THRESH:    17
SL_URL:          sw00973628000msufc0448.fits
SUN_POSTN:        59.75d {+03h 59m 00s}  +20.53d {+20d 31' 45"}
SUN_DIST:         56.51 [deg]   Sun_angle= 3.6 [hr] (West of Sun)
MOON_POSTN:       57.61d {+03h 50m 27s}  +17.37d {+17d 22' 06"}
MOON_DIST:        53.78 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      107.32,-62.28 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        5.09, -2.51 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 22 May 20 11:54:38 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     973628,   Seg_Num: 0
GRB_RA:            5.6820d {+00h 22m 43.68s} (J2000),
                   5.9432d {+00h 23m 46.36s} (current),
                   5.0417d {+00h 20m 10.00s} (1950)
GRB_DEC:          -0.2825d {-00d 16' 56.9"} (J2000),
                  -0.1696d {-00d 10' 10.4"} (current),
                  -0.5597d {-00d 33' 34.8"} (1950)
GRB_ERROR:       4.9 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  18991 TJD;   143 DOY;   20/05/22
IMG_START_TIME:  42500.00 SOD {11:48:20.00} UT,   405.9 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        59.75d {+03h 59m 00s}  +20.53d {+20d 31' 45"}
SUN_DIST:         56.50 [deg]   Sun_angle= 3.6 [hr] (West of Sun)
MOON_POSTN:       57.61d {+03h 50m 26s}  +17.37d {+17d 22' 00"}
MOON_DIST:        53.76 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      107.35,-62.28 [deg] galactic lon,lat of the burst
ECL_COORDS:        5.10, -2.52 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 1.1% < P(seren) < 2.8%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 22 May 20 11:56:49 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     973628,   Seg_Num: 0
POINT_RA:          5.667d {+00h 22m 40s} (J2000)
POINT_DEC:        -0.285d {-00d 17' 05"} (J2000)
ROLL:            65.017d
IMG_START_DATE:  18991 TJD;   143 DOY;   20/05/22
IMG_START_TIME:  42542.41 SOD {11:49:02.41} UT,   448.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     611840967
X_OFFSET:        790 [pixels]
Y_OFFSET:        850 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       950
Y_GRB_POS:       1010
BINNING_INDEX:   1
IM_URL:          sw00973628000msuni0473.fits
SUN_POSTN:        59.75d {+03h 59m 01s}  +20.53d {+20d 31' 46"}
SUN_DIST:         56.52 [deg]   Sun_angle= 3.6 [hr] (West of Sun)
MOON_POSTN:       57.63d {+03h 50m 30s}  +17.37d {+17d 22' 20"}
MOON_DIST:        53.80 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      107.32,-62.28 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        5.09, -2.51 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 22 May 20 11:56:56 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     973628,   Seg_Num: 0
POINT_RA:          5.667d {+00h 22m 40s} (J2000)
POINT_DEC:        -0.285d {-00d 17' 05"} (J2000)
ROLL:            65.017d
IMG_START_DATE:  18991 TJD;   143 DOY;   20/05/22
IMG_START_TIME:  42542.41 SOD {11:49:02.41} UT,   448.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     611840967
X_OFFSET:        790 [pixels]
Y_OFFSET:        850 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       950
Y_GRB_POS:       1010
BINNING_INDEX:   1
IM_URL:          sw00973628000msuni0473.fits
SUN_POSTN:        59.75d {+03h 59m 01s}  +20.53d {+20d 31' 46"}
SUN_DIST:         56.52 [deg]   Sun_angle= 3.6 [hr] (West of Sun)
MOON_POSTN:       57.63d {+03h 50m 30s}  +17.37d {+17d 22' 21"}
MOON_DIST:        53.80 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      107.32,-62.28 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        5.09, -2.51 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 22 May 20 11:55:52 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     973628,   Seg_Num: 0
GRB_RA:            5.6822d {+00h 22m 43.72s} (J2000),
                   5.9434d {+00h 23m 46.41s} (current),
                   5.0419d {+00h 20m 10.04s} (1950)
GRB_DEC:          -0.2823d {-00d 16' 56.2"} (J2000),
                  -0.1694d {-00d 10' 09.7"} (current),
                  -0.5595d {-00d 33' 34.1"} (1950)
GRB_ERROR:       3.9 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  18991 TJD;   143 DOY;   20/05/22
IMG_START_TIME:  42500.00 SOD {11:48:20.00} UT,   405.9 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        59.75d {+03h 59m 01s}  +20.53d {+20d 31' 46"}
SUN_DIST:         56.50 [deg]   Sun_angle= 3.6 [hr] (West of Sun)
MOON_POSTN:       57.62d {+03h 50m 28s}  +17.37d {+17d 22' 11"}
MOON_DIST:        53.77 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      107.35,-62.28 [deg] galactic lon,lat of the burst
ECL_COORDS:        5.10, -2.52 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        This position was enhanced using UVOT field astrometry.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 1.1% < P(seren) < 2.8%.

GCN Circular #27778
P. A. Evans (U Leicester), J.D. Gropp (PSU), S. Laha (GSFC/UMBC/CRESST), A. Y. Lien (GSFC/UMBC) and K. L. Page (U Leicester) report on behalf of the Neil Gehrels Swift Observatory Team:
At 11:41:34 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 200522A (trigger=973628). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 5.667, -0.282 which is
```
   RA(J2000) = 00h 22m 40s
   Dec(J2000) = -00d 16' 53"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 1 sec. The peak count rate was ~5000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 11:42:57.5 UT, 83.4 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 5.6823, -0.2824 which is equivalent to:
```
   RA(J2000)  = 00h 22m 43.76s
   Dec(J2000) = -00d 16' 56.7"
```
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This location is 55 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event data does not constrain the column density.
No UVOT analysis is available at this time.
Burst Advocate for this burst is P. A. Evans (pae9 AT star.le.ac.uk). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)
GCN Circular #27779
W. Fong, K. Paterson (Northwestern) and E. Berger (Harvard) report:
"We searched the location of the short GRB 200522A (GCN 27778; Evans et al.) in the SDSS DR12 and PS1-3Pi surveys at the XRT afterglow candidate position. The current XRT position fully encompasses a catalogued galaxy in both SDSS and PS1-3Pi, with a position of RA = 0:22:43.717, Dec = -0:16:57.52 (Alam et al. 2015, Chambers et al. 2016). This galaxy has SDSS magnitudes* of u = 22.55, g = 22.11, r = 21.17, i = 20.87, z = 20.69 mag. The SDSS photometric redshift estimate is z_phot = 0.4 +/- 0.1.
Adopting r=21.17 mag and the XRT positional uncertainty, we estimate a probability of chance coincidence of ~0.01. If the association to this galaxy is correct, pending the precise position of the GRB afterglow, this would place GRB 200522A in lower 35% of the Swift short GRB redshift distribution (c.f., Fong et al. 2017, Gompertz et al. 2020).
Follow-up, where possible, is highly encouraged."
* Information pulled from SDSS: http://skyserver.sdss.org/DR12//en/tools/explore/summary.aspx?id=1237663783662977850
GCN Circular #27780
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.
Using 235 s of XRT Photon Counting mode data and 1 UVOT images for GRB 200522A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 5.68182, -0.28273 which is equivalent to:
```
RA (J2000): 00h 22m 43.64s
Dec (J2000): -00d 16' 57.8"
```
with an uncertainty of 3.2 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN Circular #27783
N. P. M. Kuin (UCL-MSSL) and P. A. Evans (U. Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 200522A 448 s after the BAT trigger (Evans et al., GCN Circ. 27778). No optical afterglow consistent with the XRT position (Evans et al. GCN Circ. 27778) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           448          598          147         >19.5
white              448          598          147         >19.5
v                  605          624           19         >17.2
```
The magnitudes in the table are 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 #27784
Y.-D. Hu, E. Fernandez-Garcia, A. J. Castro-Tirado (IAA-CSIC), I. Carrasco and C. Perez del Pulgar (Univ. de Malaga), M. D. Caballero-Garcia (ASU-CAS, CZ) and R. Querel (NIWA), on behalf of a larger collaboration, report:
The 60cm BOOTES-3/YA robotic telescope at NIWA Lauder in Otago (New Zealand) responded to the Swift trigger of GRB 200522A (Evans et al. GCNC 27778). The first image (clear filter) was obatined at high airmass starting at 18:31:37 UT(~ 6.8 hr after trigger). In the co-added image (15 exposures 60s each), no source is found at the position reported by Swift/XRT (Beardmore et al. GCNC 27780) down to 18.2 mag. Further observations are ongoing.
We thank the staff at NIWA for its excellent support.
GCN Circular #27785
A.P. Beardmore (U. Leicester), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M. Perri (ASDC), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), J.P. Osborne (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 6.1 ks of XRT data for GRB 200522A (Evans et al. GCN Circ. 27778), from 406 s to 35.1 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN Circ. 27780).
The light curve can be modelled with a power-law decay with a decay index of alpha=0.64 (+0.13, -0.14).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.6 (+0.5, -0.4). The best-fitting absorption column is 6 (+14, -4) x 10^20 cm^-2, consistent with the Galactic value of 2.9 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.3 x 10^-11 (4.7 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     6 (+14, -4) x 10^20 cm^-2
Galactic foreground: 2.9 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.6 (+0.5, -0.4)
```
If the light curve continues to decay with a power-law decay index of 0.64, the count rate at T+24 hours will be 3.9 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.7 x 10^-13 (1.8 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00973628.
This circular is an official product of the Swift-XRT team.
GCN Circular #27786
G. Schroeder, W. Fong, and K. D. Alexander (Northwestern) report:
"We observed the position of GRB 200522A (Evans et al., GCN 27778; Beardmore et al., GCN 27780) with the Karl G. Jansky Very Large Array (VLA) beginning on 2020 May 22.709 UT (5.33 hr post-burst) at a mean frequency of 6 GHz.
We detect a faint radio source with a significance of ~4-sigma at the position:
```
RA(J2000) = 00:22:43.72
Dec(J2000) = -00:16:57.9
```
with an uncertainty of ~1" in each coordinate. This position is consistent with the putative host galaxy (Fong et al., GCN 27779), and toward the outskirts of the updated XRT position. Further observations are planned to understand the nature of this source and whether it is the radio afterglow or emission from the host galaxy.
We thank the VLA staff immensely for quickly approving and executing these observations."
GCN Circular #27789
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),
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),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 200522A ( P. A. Evans et al., GCN 27778) errorbox 52336 sec after notice time and 52358 sec after trigger time at 2020-05-23 02:14:12 UT, with upper limit up to 19.7 mag. The observations began at zenith distance = 73 deg. The sun altitude is -40.2 deg.
The galactic latitude b = -62 deg., longitude l = 109 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1363025
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   52448 |         MASTER-SAAO |   C |   180 | 17.1 |        
   52448 |         MASTER-SAAO |   C |   180 | 17.4 |        
   53065 |         MASTER-SAAO |   C |   180 | 16.4 |        
   53065 |         MASTER-SAAO |   C |   180 | 17.3 |        
   53265 |         MASTER-SAAO |   C |   180 | 16.4 |        
   53265 |         MASTER-SAAO |   C |   180 | 16.9 |        
   55058 |         MASTER-SAAO |   C |    60 | 19.3 |        
   55138 |         MASTER-SAAO |   C |    60 | 19.3 |        
   55278 |         MASTER-SAAO |   C |   180 | 19.7 |        
   55697 |         MASTER-SAAO |   C |    60 | 19.1 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #27792
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 Swift GRB 200522A (Evans et al., GCN 27778) with the LCO 1-m Sinistro instrument at the South African Astronomical Observatory site, on May 23, from 03:20 to 04:20 UT (corresponding to 15.65 to 16.65 hours from the GRB trigger time) with the Bessel R and I filters.
We performed a series of 5x180s exposures in R and I. We detect an optical source in R band, but not I band, in stacked images at the Swift XRT enhanced position (Beardmore et al., GCN 27780). Using the USNO-B.1 catalog as reference, we calculate the following magnitude and upper limit:
R = 21.49 +/- 0.16
I > 20.39
These magnitudes are not corrected for galactic extinction.
R.S. is funded by NSF AST grant #1831682
GCN Circular #27793
T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), P. A. Evans (U Leicester), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 200522A (trigger #973628) (Evans et al., GCN Circ. 27778). The BAT ground-calculated position is RA, Dec = 5.668, -0.264 deg which is
```
   RA(J2000)  =  00h 22m 40.3s
   Dec(J2000) = -00d 15' 49.9"
```
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 86%.
The mask-weighted light curve shows a multi-peaked structure that starts at ~ T-0.3 s and ends at ~T+0.7 s. The main peak occur at ~T0. T90 (15-350 keV) is 0.62 +- 0.08 sec (estimated error including systematics).
The time-averaged spectrum from T-0.02 to T+0.67 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.45 +- 0.17. The fluence in the 15-150 keV band is 1.1 +- 0.1 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.17 sec in the 15-150 keV band is 1.5 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/973628/BA/
GCN Circular #27794
R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration:
Upon further analysis, the LCO observations reported in GCN 27792 clearly show two possible sources consistent with the XRT enhanced position (Beardmore et al., GCN 27780). One source is located at ra, dec=(00:22:43.66,-00:16:58.59), 0.72 arc seconds from the center of the XRT enhanced position. The magnitudes of this source are the following:
```
R = 22.57 +/- 0.29
I > 20.39
```
A second source, which is located at ra, dec=(00:22:43.69,-00:16:57.37), 1.08 arcesonds from the center of the XRT localization is likely consistent with the potential host galaxy and magnitude were reported in GCN 27792.
At this moment it is not possible to determine if any of these objects is related to the short GRB 200522A, but further observations have been scheduled to determine possible variability.
We apologize for any confusion our earlier analysis may have caused.
R.S. is funded by NSF AST grant #1831682
GCN Circular #27822
S.Dichiara (UMD, NASA-GSFC), B. O'Connor (GWU, UMD) , E. Troja (UMD, NASA-GSFC) report on behalf of a larger collaboration:
We observed the field of GRB 200522A (Evans et al., GCN Circ. 27778) with the Gemini North telescope beginning 2020-05-24 14:36:32 UT, approximately 2.12 days post-burst. We obtained 7x90s exposures in r-band performed with poor weather conditions and at an airmass of 2.9.
We measure an AB magnitude of r=21.37 +/- 0.10 for the putative host galaxy (Fong et al., GCN Circ. 27779; Strausbaugh et al., GCN Circ. 27792).
No other object is detected within the enhanced Swift-XRT position (Beardmore et al., GCN Circ. 27780) down to a 3-sigma limit r>22.3 AB. Magnitudes are calibrated against the SDSS catalog and not corrected for Galactic extinction.
Further observations are on-going.
A Chandra ToO has been approved for this burst.
We thank the Gemini North staff for efficiently executing these observations in these difficult times.
GCN Circular #27826
W. Fong (Northwestern), E. Berger (Harvard), J. Rastinejad (Northwestern) and C. D. Kilpatrick (UCSC) report on behalf of a larger collaboration:
"We initiated Hubble Space Telescope (HST) observations of the field of GRB 200522A (Evans et al., GCN 27778; Beardmore et al., GCN 27780) under Program 15964 (PI: Berger). We obtained WFC3/IR imaging in the F160W band, at a mid-time on 2020 May 26.077 UT (3.6 days post-burst). A total of 5223-sec of exposure time was obtained.
Coincident with the XRT position (90% confidence), we detect two clearly extended sources, Sources A and B. We perform absolute astrometry with SDSS DR12 and use WFC3 tabulated zeropoints to determine the following:
Source A:
```
RA(J2000) = 00:22:43.72
Dec(J2000) = -00:16:57.46
m(F160W) = 20.7 AB mag
```
Source B:
```
RA(J2000) = 00:22:43.82
Dec(J2000) = -00:16:59.54
m(F160W) = 23.7 AB mag.
```
Source A is the catalogued SDSS galaxy (Fong et al., GCN 27786) and exhibits a disturbed morphology, while Source B is considerably fainter. The angular offsets from the XRT positional center are ~2.0" and ~2.1", and the light of both galaxies are ~50% encompassed by the XRT position (90% confidence). Using NIR number counts, we estimate Pchance ~ 0.01 and 0.11 for Sources A and B, respectively.
We do not detect any additional sources, point-like or extended, within the XRT position or at the position of the additional LCO optical source (Strausbaugh et al., GCN 27794) to a 3-sigma limiting magnitude of m(F160W)>27.2 mag.
Assuming an optical decline rate of F~t^-1 from the time of the LCO faint source detection (R~22.57; Strausbaugh et al., GCNs 27792, 27794) to 3.6 days, and typical afterglow colors, the expected afterglow magnitude is m(F160W)~23.6 mag, which is >3 mag brighter than the HST limit. If we assume that a jet break occurred at t~1 day, this still results in expected afterglow magnitudes of ~25.5 mag, >1 mag brighter than the HST limit. We thus conclude that either the LCO source is not real, or that the afterglow exhibited a very steep decline of t^-3.5 or steeper beyond ~1 day.
At the redshift of the putative host galaxy of z~0.4 (Fong et al., GCN 27786), F160W roughly corresponds to rest-frame J-band. Scaling the J-band kilonova light curve of GW170817 (Villar et al. 2017: ApJL, 851, L21) to z~0.4, we find that the HST limit is slightly deeper than the kilonova of GW170817 at the same time.
The results of WFC3/F125W observations, which have been taken but are not yet available, will be discussed in an upcoming circular. We thank the HST staff for quickly implementing these observations."
GCN Circular #27827
W. Fong (Northwestern), C. D. Kilpatrick (UCSC), J. Rastinejad (Northwestern) and E. Berger (Harvard) report on behalf of a larger collaboration:
"We report on further HST/WFC3 observations of GRB200522A (Evans et al., GCN 27778) taken under Program 15964 in the F125W filter. A total of 5223-sec of exposure time was obtained roughly at the same mid-time of ~3.6 days. We detect sources A and B (Fong et al., GCN 27826), as well as an additional point-like source C at:
```
RA(J2000) = 00:22:43.62
Dec(J2000) = -00:16:57.56
```
This position is ~1.2" away from the center of the LCO faint source position (Strausbaugh et al., GCN 27794), ~1.5" offset from Source A, and at the edge of the XRT position (90% confidence). While there is some contamination from the host galaxy that introduces uncertainty, we estimate a magnitude for Source C of m(F125W)~26.8 +/- 0.3 AB mag. Regarding the LCO source, the positional offset, coupled with the fact that Source C is considerably fainter than extrapolations based on afterglow evolution, suggests that the potential LCO source and Source C are not related.
The color of Source C is blue, with F125W-F160W < -0.4 mag. This color is more consistent with those of afterglows (-0.3 mag) than the corresponding redder color of the kilonova of GW170817 (~0.2-0.4 mag; comparing to rest-frame z-J assuming z~0.4). However, further observations are necessary to determine the nature of this source, assess its variability, and its relation to GRB 200522A."
GCN Circular #27904
C. D. Kilpatrick (UCSC), J. Rastinejad, W. Fong (Northwestern), and E. Berger (Harvard) report on behalf of a larger collaboration:
"We report on further HST/WFC3 IR observations (PI: Berger; Program 15964) of the short GRB 200522A (Evans et al., GCN 27778). Subsequent to the previous F125W observations obtained 3.6 days post-burst (Fong et al., GCN 27826), we initiated a second epoch in the F125W filter starting on 2020 June 7.805 UT. A total of 4823-sec of exposure time was obtained (approximately 7 minutes shallower than the previous epoch), at a mid-time of ~16.4 days.
The previously-identified point-like Source C (Fong et al., GCN 27827) has an estimated m_f125W ~ 26.8 AB mag, fully consistent with our previous estimate. This indicates that this source has not faded and is unlikely to be related to the GRB.
To constrain the presence of any transient sources, we performed image subtraction between the two F125W epochs using the HOTPANTS software (Becker 2015). The difference image reveals low significance (<3 sigma) residuals, the brightest of which is located at RA = 00:22:43.62, Dec = -00:16:58.90 (J2000) with m_f125w = 28.1 AB mag. This position is close to the LCO candidate (e.g., Strausbaugh et al., GCN 27792) but inconsistent with the VLA candidate (Fong et al., GCN 27786).
There are otherwise no obvious high-significance residuals consistent with the VLA or LCO candidates, or around the XRT position. We caution that the difference image is contaminated by the center of the bright galaxy, and analysis is ongoing. Firm conclusions will require a deep template observation.
We thank the HST staff for quickly implementing these observations."
GCN Circular #28038
S.Dichiara (UMD, NASA-GSFC), B. O'Connor (GWU, UMD) , E. Troja (UMD, NASA-GSFC) report on behalf of a larger collaboration:
We obtained a spectrum of the putative host galaxy (Fong et al., GCN Circ. 27779; Strausbaugh et al., GCN Circ. 27792) of the short GRB 200522A (Evans et al., GCN Circ. 27778) with the Gemini Multi-Object Spectrograph mounted on the Gemini North telescope. Observations began at 13:22 UT on June 27, 2020 (36 days after the Swift trigger) and cover the wavelength range from 5000-9900 A.
The spectra shows several well detected emission lines which we interpret as [OII] 3727, H-beta, and [OIII] 5007 at a common redshift of z=0.554.
We thank the Gemini North staff for efficiently executing these observations in these difficult times.
GCN Circular #28100
B. O'Connor (GWU, UMD), S. Dichiara (UMD, NASA-GSFC), E. Troja (UMD, NASA-GSFC), S.B. Cenko (UMD, NASA-GSFC) report on behalf of a larger collaboration:
We report on further observations of the short GRB 200522A (Evans et al., GCN Circ. 27778) taken at 3.1 and 9.1 d post-burst in the r-band filter with the Gemini Multi-Object Spectrograph (GMOS) mounted on the 8.1m Gemini North telescope. Image subtraction with HOTPANTS (Becker 2015) identifies a low significance residual close to the candidate host galaxy's center (Fong et al., GCN Circ. 27779; Strausbaugh et al., GCN Circ. 27792), and at the edge of the XRT enhanced position (Beardmore et al., GCN Circ. 27780). We independently reanalyzed the HST images (Fong et al., GCN Circ. 27827; Kilpatrick et al., GCN Circ. 27904), and performed image subtraction between the two epochs at 3.5 and 16.3 d. Although the analysis is complicated by the presence of a bright galaxy's nucleus, a residual signal of brightness F125W ~ 25.6 AB mag is present at the location of the Gemini optical candidate. We suggest this to be the candidate optical/nIR counterpart of GRB 200522A. The observed magnitude is much brighter than expected for a kilonova like AT2017gfo, and suggests that the afterglow emission is the dominant component. The projected offset from the galaxy's nucleus is ~0.23 arcseconds, corresponding to 1.5 kpc at redshift z = 0.554 (Dichiara et al., GCN Circ. 28038). This physical offset is low yet not unprecedented, falling in the bottom 15% of the short GRB offset distribution (Fong & Berger, 2013).
We thank the Gemini North staff for efficiently executing these observations.
GCN Circular #28127
W. Fong (Northwestern), C. D. Kilpatrick (UCSC), J. Rastinejad (Northwestern), T. Laskar (U. Bath), and E. Berger (Harvard) report on behalf of a larger collaboration:
We report on new HST/WFC3 IR observations (PI: Berger; Program 15964) of the short GRB 200522A (Evans et al., GCN 27778) in the F125W and F160W filters at approximately 55 days post-burst. A total of 5223-s was obtained in both filters and the resulting images are deep enough to provide adequate templates for all previous epochs (F125W at 3.6 and 16.4 days, and F160W at 3.6 days; Fong et al., GCN 27826; Kilpatrick et al., GCN 27904). An independent analysis of the first two epochs of data resulted in a candidate afterglow (O’Connor et al., GCN 28100).
To constrain the presence of any transient sources, we first performed image subtraction between the observations in each filter taken at 3.6 days and the new 55-day templates using the HOTPANTS software (Becker 2015). In the difference images, we detect a high-significance residual within the XRT position (Beardmore et al., GCN 27780) and close to the host galaxy center in both filters. Given the contamination from residuals as a result of the core of the host galaxy, accurate photometry of the source will require further analysis.
We also perform image subtraction between the F125W observations at 16.4 days and 55 days. The source is no longer detected to a 3-sigma limit of m_F125W>27.3 AB mag. The fading behavior, coupled with the detection at 3.6 days in both filters, confirms the source as the counterpart to GRB 200522A. Based on our preliminary analysis, we cannot distinguish between whether the emission is resulting from the afterglow alone, or a combination of afterglow and kilonova emission.
We thank the HST staff for scheduling and implementing these observations.
Fong et al. 2021, ApJ 906, 127: broad-band afterglow etc.
https://iopscience.iop.org/article/10.3847/1538-4357/abc74a

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