Gamma-ray Burst 210527A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 27 May 21 07:09:35 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1051453,   Seg_Num: 0
GRB_RA:          172.355d {+11h 29m 25s} (J2000),
                 172.638d {+11h 30m 33s} (current),
                 171.690d {+11h 26m 46s} (1950)
GRB_DEC:         +31.618d {+31d 37' 06"} (J2000),
                 +31.500d {+31d 30' 00"} (current),
                 +31.894d {+31d 53' 38"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       0 [cnts]    Image_Peak=2546 [image_cnts]
TRIGGER_DUR:     96.000 [sec] 
TRIGGER_INDEX:   20000     E_range: 15-50 keV
BKG_INTEN:       0 [cnts]
BKG_TIME:        0.00 SOD {00:00:00.00} UT
BKG_DUR:         0 [sec]
GRB_DATE:        19361 TJD;   147 DOY;   21/05/27
GRB_TIME:        25668.91 SOD {07:07:48.91} UT
GRB_PHI:         -168.55 [deg]
GRB_THETA:        25.89 [deg]
SOLN_STATUS:     0x13
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    10.78 [sigma]
MERIT_PARAMS:     +1  +0  +0  +7  +1  +0  +0  +0  +5  +0 
SUN_POSTN:        64.36d {+04h 17m 27s}  +21.35d {+21d 20' 44"}
SUN_DIST:         93.38 [deg]   Sun_angle= -7.2 [hr] (East of Sun)
MOON_POSTN:      256.98d {+17h 07m 54s}  -23.55d {-23d 33' 14"}
MOON_DIST:        97.57 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:      193.90, 71.61 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      159.68, 25.84 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is an image trigger.  (The RATE_SIGNIF & BKG_{INTEN, TIME, DUR} are undefined.)  
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 = 279.31,14.89 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 27 May 21 07:12:18 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1051453,   Seg_Num: 0
GRB_RA:          172.355d {+11h 29m 25s} (J2000),
                 172.638d {+11h 30m 33s} (current),
                 171.690d {+11h 26m 46s} (1950)
GRB_DEC:         +31.618d {+31d 37' 06"} (J2000),
                 +31.500d {+31d 30' 00"} (current),
                 +31.894d {+31d 53' 38"} (1950)
GRB_DATE:        19361 TJD;   147 DOY;   21/05/27
GRB_TIME:        25668.91 SOD {07:07:48.91} UT
TRIGGER_INDEX:   20000
GRB_PHI:         -168.55 [deg]
GRB_THETA:        25.89 [deg]
DELTA_TIME:      0.00 [sec]
TRIGGER_DUR:     96.000 [sec] 
SOLN_STATUS:     0x13
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    10.78 [sigma]
LC_URL:          sw01051453000msb.lc
SUN_POSTN:        64.36d {+04h 17m 27s}  +21.35d {+21d 20' 45"}
SUN_DIST:         93.37 [deg]   Sun_angle= -7.2 [hr] (East of Sun)
MOON_POSTN:      257.01d {+17h 08m 01s}  -23.56d {-23d 33' 32"}
MOON_DIST:        97.59 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:      193.90, 71.61 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      159.68, 25.84 [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 an image 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 = 279.31,14.89 [deg].

GCN Circular #30081
S. Laha (GSFC/UMBC/CRESST), P. A. Evans (U Leicester), K. L. Page (U Leicester) and B. Sbarufatti (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 07:07:48 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 210527A (trigger=1051453). Swift did not slew immediately due to an observing constraint. The BAT on-board calculated location is RA, Dec 172.355, +31.618 which is
```
   RA(J2000) = 11h 29m 25s
   Dec(J2000) = +31d 37' 06"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is normal for an image trigger, the BAT light curve does not show any significant structure.
Due to an observing constraint, Swift will not slew until T0+49.6 minutes. There will be no XRT or UVOT data until this time.
Burst Advocate for this burst is S. Laha (sib.laha AT gmail.com). 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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 27 May 21 08:00:42 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     1051453,   Seg_Num: 0
POINT_RA:        172.326d {+11h 29m 18s} (J2000)
POINT_DEC:       +31.618d {+31d 37' 06"} (J2000)
IMG_START_DATE:  19361 TJD;   147 DOY;   21/05/27
IMG_START_TIME:  28828.44 SOD {08:00:28.44} UT,   3159.5 [sec] since BAT Trigger Time
COUNTS:          2    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        1    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:     Thu 27 May 21 08:04:26 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1051453,   Seg_Num: 0
POINT_RA:        172.326d {+11h 29m 18s} (J2000)
POINT_DEC:       +31.618d {+31d 37' 06"} (J2000)
POINT_ROLL:      297.499d
IMG_START_DATE:  19361 TJD;   147 DOY;   21/05/27
IMG_START_TIME:  28831.68 SOD {08:00:31.68} UT,   3162.8 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.654
N_STARS:         16
X_OFFSET:        377 [pixels]
Y_OFFSET:        716 [pixels]
X_MAX:           1336 [pixels]
Y_MAX:           1675 [pixels]
DET_THRESH:      20
PHOTO_THRESH:    12
SL_URL:          sw01051453000msufc3162.fits
SUN_POSTN:        64.40d {+04h 17m 36s}  +21.35d {+21d 21' 06"}
SUN_DIST:         93.32 [deg]   Sun_angle= -7.2 [hr] (East of Sun)
MOON_POSTN:      257.59d {+17h 10m 22s}  -23.65d {-23d 39' 16"}
MOON_DIST:        98.13 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:      193.91, 71.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      159.66, 25.83 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 27 May 21 08:04:29 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1051453,   Seg_Num: 0
GRB_RA:          172.3231d {+11h 29m 17.54s} (J2000),
                 172.6069d {+11h 30m 25.66s} (current),
                 171.6586d {+11h 26m 38.05s} (1950)
GRB_DEC:         +31.6240d {+31d 37' 26.3"} (J2000),
                 +31.5059d {+31d 30' 21.1"} (current),
                 +31.8997d {+31d 53' 58.8"} (1950)
GRB_ERROR:       7.3 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  19361 TJD;   147 DOY;   21/05/27
IMG_START_TIME:  28837.00 SOD {08:00:37.00} UT,   3168.1 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        64.40d {+04h 17m 36s}  +21.35d {+21d 21' 06"}
SUN_DIST:         93.32 [deg]   Sun_angle= -7.2 [hr] (East of Sun)
MOON_POSTN:      257.59d {+17h 10m 23s}  -23.65d {-23d 39' 16"}
MOON_DIST:        98.13 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:      193.90, 71.58 [deg] galactic lon,lat of the burst
ECL_COORDS:      159.65, 25.84 [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 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 27 May 21 08:04:41 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1051453,   Seg_Num: 0
POINT_RA:        172.326d {+11h 29m 18s} (J2000)
POINT_DEC:       +31.618d {+31d 37' 06"} (J2000)
POINT_ROLL:      297.499d
IMG_START_DATE:  19361 TJD;   147 DOY;   21/05/27
IMG_START_TIME:  28831.68 SOD {08:00:31.68} UT,   3162.8 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.654
N_STARS:         16
X_OFFSET:        377 [pixels]
Y_OFFSET:        716 [pixels]
X_MAX:           1336 [pixels]
Y_MAX:           1675 [pixels]
DET_THRESH:      20
PHOTO_THRESH:    12
SL_URL:          sw01051453000msufc3162.fits
SUN_POSTN:        64.40d {+04h 17m 36s}  +21.35d {+21d 21' 06"}
SUN_DIST:         93.32 [deg]   Sun_angle= -7.2 [hr] (East of Sun)
MOON_POSTN:      257.60d {+17h 10m 23s}  -23.66d {-23d 39' 18"}
MOON_DIST:        98.13 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:      193.91, 71.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      159.66, 25.83 [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:     Thu 27 May 21 08:05:54 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1051453,   Seg_Num: 0
POINT_RA:        172.326d {+11h 29m 18s} (J2000)
POINT_DEC:       +31.618d {+31d 37' 06"} (J2000)
ROLL:            297.499d
IMG_START_DATE:  19361 TJD;   147 DOY;   21/05/27
IMG_START_TIME:  28831.68 SOD {08:00:31.68} UT,   3162.8 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     643795258
X_OFFSET:        696 [pixels]
Y_OFFSET:        1035 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       856
Y_GRB_POS:       1195
BINNING_INDEX:   1
IM_URL:          sw01051453000msuni3190.fits
SUN_POSTN:        64.40d {+04h 17m 36s}  +21.35d {+21d 21' 07"}
SUN_DIST:         93.32 [deg]   Sun_angle= -7.2 [hr] (East of Sun)
MOON_POSTN:      257.61d {+17h 10m 26s}  -23.66d {-23d 39' 26"}
MOON_DIST:        98.14 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:      193.91, 71.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      159.66, 25.83 [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:     Thu 27 May 21 08:06:01 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1051453,   Seg_Num: 0
POINT_RA:        172.326d {+11h 29m 18s} (J2000)
POINT_DEC:       +31.618d {+31d 37' 06"} (J2000)
ROLL:            297.499d
IMG_START_DATE:  19361 TJD;   147 DOY;   21/05/27
IMG_START_TIME:  28831.68 SOD {08:00:31.68} UT,   3162.8 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     643795258
X_OFFSET:        696 [pixels]
Y_OFFSET:        1035 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       856
Y_GRB_POS:       1195
BINNING_INDEX:   1
IM_URL:          sw01051453000msuni3190.fits
SUN_POSTN:        64.40d {+04h 17m 36s}  +21.35d {+21d 21' 07"}
SUN_DIST:         93.32 [deg]   Sun_angle= -7.2 [hr] (East of Sun)
MOON_POSTN:      257.61d {+17h 10m 27s}  -23.66d {-23d 39' 26"}
MOON_DIST:        98.14 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:      193.91, 71.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      159.66, 25.83 [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:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.

GCN Circular #30082
J.P. Osborne (U. Leicester), D.N. Burrows (PSU), J.A. Kennea (PSU), G. Tagliaferri (INAF-OAB), S. Campana (INAF-OAB) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:
The XRT began observing the field of GRB 210527A at 08:00:28.4 UT, 3159.5 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 172.32169, 31.62421 which is equivalent to:
```
   RA(J2000)  = 11h 29m 17.21s
   Dec(J2000) = +31d 37' 27.2"
```
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This location is 104 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 gives a column density consistent with the Galactic value of 1.85 x 10^20 cm^-2 (Willingale et al. 2013).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 27 May 21 08:41:09 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1051453,   Seg_Num: 0
GRB_RA:          172.3216d {+11h 29m 17.18s} (J2000),
                 172.6054d {+11h 30m 25.30s} (current),
                 171.6571d {+11h 26m 37.69s} (1950)
GRB_DEC:         +31.6242d {+31d 37' 27.1"} (J2000),
                 +31.5061d {+31d 30' 21.8"} (current),
                 +31.8999d {+31d 53' 59.5"} (1950)
GRB_ERROR:       3.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  19361 TJD;   147 DOY;   21/05/27
IMG_START_TIME:  28837.00 SOD {08:00:37.00} UT,   3168.1 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        64.43d {+04h 17m 42s}  +21.36d {+21d 21' 21"}
SUN_DIST:         93.29 [deg]   Sun_angle= -7.2 [hr] (East of Sun)
MOON_POSTN:      258.01d {+17h 12m 02s}  -23.72d {-23d 43' 13"}
MOON_DIST:        98.49 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:      193.90, 71.58 [deg] galactic lon,lat of the burst
ECL_COORDS:      159.65, 25.84 [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:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN Circular #30083
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
Using 1707 s of XRT Photon Counting mode data and 4 UVOT images for GRB 210527A, 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 = 172.32085, +31.62621 which is equivalent to:
```
RA (J2000): 11h 29m 17.00s
Dec (J2000): +31d 37' 34.3"
```
with an uncertainty of 2.3 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 #30084
Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jes�s Gonz�lez (UNAM), Carlos Rom�n-Z��iga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report:
We observed the field of GRB 210527A (Laha, et al., GCN 30081) with the Reionization and Transients Infrared Camera (RATIR) on the 1.5m Harold Johnson Telescope at the Observatorio Astron�mico Nacional on Sierra San Pedro M�rtir from 2021/05 27.30 to 2021/05 27.32 UTC (0.01 to 0.56 hours after the BAT trigger), obtaining a total of 0.19 hours exposure in the r and i bands and 0.25 hours exposure in the Z, Y, J, and H bands.
We find no new sources within the refined XRT error region (Evans, et al., GCN 30083). In comparison with the SDSS DR9 and 2MASS catalogs, we obtain the following upper limits (3-sigma):
```
  r     > 21.67
  i     > 21.70
  Z     > 21.54
  Y     > 21.32
  J     > 20.78
  H     > 20.42
```
These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB.
We thank the staff of the Observatorio Astron�mico Nacional in San Pedro M�rtir.
GCN Circular #30085
V. D'Elia (SSDC & INAF-OAR), A. D'Ai (INAF-IASFPA), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A. Melandri (INAF-OAB) and report on behalf of the Swift-XRT team: report on behalf of the Swift-XRT team:
We have analysed 7.1 ks of XRT data for GRB 210527A, from 3.2 ks to 27.7 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode.
The light curve can be modelled with a power-law decay with a decay index of alpha=0.90 (+0.23, -0.20).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 3.1 (+0.6, -0.5). The best-fitting absorption column is 6.6 (+2.6, -2.1) x 10^21 cm^-2, in excess of the Galactic value of 1.8 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 2.6 x 10^-11 (1.3 x 10^-10) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     6.6 (+2.6, -2.1) x 10^21 cm^-2
Galactic foreground: 1.8 x 10^20 cm^-2
Excess significance: 5.0 sigma
Photon index:	     3.1 (+0.6, -0.5)
```
If the light curve continues to decay with a power-law decay index of 0.90, the count rate at T+24 hours will be 4.0 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x 10^-13 (5.1 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/01051453.
This circular is an official product of the Swift-XRT team.
GCN Circular #30086
V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University)
MASTER-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 210527A ( S. Laha et al., GCN 30081) errorbox 41282 sec after notice time and 41473 sec after trigger time at 2021-05-27 18:39:02 UT, with upper limit up to 19.2 mag. The observations began at zenith distance = 30 deg. The sun altitude is -17.1 deg.
The galactic latitude b = 72 deg., longitude l = 195 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1622598
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   41564 |   MASTER-Kislovodsk |   C |   180 | 18.5 |        
   41564 |   MASTER-Kislovodsk |   C |   180 | 19.2 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #30087
Y. Imai, R. Hosokawa, K. L. Murata, M. Niwano, N. Ito, H. Takamatsu, S. Sato, M. Takaku, R. Noto, R. Yamaguchi, Y. Yatsu, and N. Kawai (TokyoTech) report on behalf of the MITSuME collaboration:
We observed the field of GRB 210527A (S. Laha et al. GCN Circular #30081, J.P. Osborne et al. GCN Circular #30082, P.A. Evans et al. GCN Circular #30083, Nat Butler et al. GCN Circular #30084, V. D'Elia et al. GCN Circular #30085, V. Lipunov et al. GCN Circular #30086) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope Akeno. The observation with a series of 60 sec exposures started at 2021-05-27 10:23:37 UT (3.3 hours after the triggers). We stacked the images with good conditions. We did not detect any sources within the enhanced XRT error region (P.A. Evans et al. GCN Circular #30083) in all three bands. We obtained the 5-sigma limits of the stacked images as follows.
```
T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
3.3 2021-05-27 15:28 1980 g'>18.0, Rc>18.6, Ic>18.1
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
```
We used the PS1 catalog for flux calibration. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1, Pages 4-24; https://github.com/MNiwano/Eclaire).
GCN Circular #30088
H. Kumar(IITB), U. Stanzin (IAO), G. C. Anupama(IIA), V. Bhalerao(IITB), S. Barway(IIA) report on behalf of the GIT team:
We observed GRB 210527A detected by Swift-BAT (S. Laha et al., GCN #30081) with the 0.7m GROWTH-India Telescope (GIT). We obtained 10 exposures, each of 300 sec, in the r' filter starting at ~467 mins after the trigger. We did not detect any new source in our stacked image within a 3 arcmin circle around R.A. = 11h 29m 25s Dec(J2000) = +31d 37' 06" (GCN #30081). The obtained upper limit follows as:
-------------------------------------------------------------------------
JD (mid) | T_mid-T0(hrs) | Exposure(sec) | Filter | Lim_mag (5-sigma) |
-------------------------------------------------------------------------
2459362.1416 | ~8.27 | 3000 (stacked) | r' | > 21.98 |
-------------------------------------------------------------------------
Our upper limit is consistent with Nat Butler et al., GCN #30084; V. Lipunov et al., GCN #30086; Y. Imai et al., GCN #30087. The magnitude is calibrated against PanSTARRS (Flewelling et al., 2018) and not corrected for Galactic extinction.
The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7 degree field of view, set up by the Indian Institute of Astrophysics and the Indian Institute of Technology Bombay with support from the Indo-US Science and Technology Forum (IUSSTF) and the Science and Engineering Research Board (SERB) of the Department of Science and Technology (DST), Government of India (https://sites.google.com/view/growthindia/). It is located at the Indian Astronomical Observatory (Hanle), operated by the Indian Institute of Astrophysics (IIA).
GCN Circular #30089
M. H. Siegel (PSU) and S. L. Laha (GSFC/UMBC/CRESST) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 210527A 3164 s after the BAT trigger (Laha et al., GCN Circ. 30081). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 30083) 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          3164         3313          147         >20.2
white             3164         3932          344         >21.2
v                 4143         4343          197         >19.4
b                 3528         3727          197         >20.4
u                 3322         4895          331         >20.4
w1                4553         4753          197         >20.2
m2                4348         4548          197         >20.0
w2                3938         4138          197         >20.5
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.023 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #30092
M. Stamatikos (OSU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), T. N. Ukwatta (LANL) (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 210527A (trigger #1051453) (Laha et al., GCN Circ. 30081). The BAT ground-calculated position is RA, Dec = 172.346, 31.627 deg which is
```
   RA(J2000)  =  11h 29m 23.0s
   Dec(J2000) = +31d 37' 37.0"
```
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 90%.
The BAT light curve showed a complex structure with a duration of about ~70 sec. T90 (15-350 keV) is 63.21 +- 11.15 sec (estimated error including systematics).
The time-averaged spectrum from T-17.07 to T+62.45 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.33 +- 0.26. The fluence in the 15-150 keV band is 6.5 +- 1.0 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+17.86 sec in the 15-150 keV band is 0.4 +- 0.1 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/1051453/BA/

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Jochen Greiner, last update: 29-May-2021 [Disclaimer]