Gamma-ray Burst 160625A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Jun 16 22:40:52 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     701503,   Seg_Num: 0
GRB_RA:          176.937d {+11h 47m 45s} (J2000),
                 177.138d {+11h 48m 33s} (current),
                 176.331d {+11h 45m 20s} (1950)
GRB_DEC:         -65.114d {-65d 06' 49"} (J2000),
                 -65.205d {-65d 12' 19"} (current),
                 -64.836d {-64d 50' 08"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4858 [cnts]    Image_Peak=218 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   137     E_range: 15-50 keV
BKG_INTEN:       30015 [cnts]
BKG_TIME:        81615.53 SOD {22:40:15.53} UT
BKG_DUR:         8 [sec]
GRB_DATE:        17564 TJD;   177 DOY;   16/06/25
GRB_TIME:        81631.46 SOD {22:40:31.46} UT
GRB_PHI:          26.19 [deg]
GRB_THETA:        32.67 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     15.36 [sigma]
IMAGE_SIGNIF:    8.86 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +1  -1  +0  +1 +30  +0 
SUN_POSTN:        95.21d {+06h 20m 50s}  +23.35d {+23d 21' 01"}
SUN_DIST:        107.80 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      342.65d {+22h 50m 35s}   -7.02d {-07d 00' 59"}
MOON_DIST:       106.98 [deg]
MOON_ILLUM:      70 [%]
GAL_COORDS:      296.29, -3.07 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      218.99,-57.27 [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 = 104.70,-20.02 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(15.0<100sec) coincident with the FERMI_GBM event (trignum=488587220).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Jun 16 22:43:57 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     701503,   Seg_Num: 0
GRB_RA:          176.937d {+11h 47m 45s} (J2000),
                 177.138d {+11h 48m 33s} (current),
                 176.331d {+11h 45m 20s} (1950)
GRB_DEC:         -65.114d {-65d 06' 49"} (J2000),
                 -65.205d {-65d 12' 19"} (current),
                 -64.836d {-64d 50' 08"} (1950)
GRB_DATE:        17564 TJD;   177 DOY;   16/06/25
GRB_TIME:        81631.46 SOD {22:40:31.46} UT
TRIGGER_INDEX:   137
GRB_PHI:          26.19 [deg]
GRB_THETA:        32.67 [deg]
DELTA_TIME:      7.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     15.36 [sigma]
IMAGE_SIGNIF:    8.86 [sigma]
LC_URL:          sw00701503000msb.lc
SUN_POSTN:        95.21d {+06h 20m 50s}  +23.35d {+23d 21' 01"}
SUN_DIST:        107.80 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      342.68d {+22h 50m 42s}   -7.01d {-07d 00' 28"}
MOON_DIST:       106.99 [deg]
MOON_ILLUM:      70 [%]
GAL_COORDS:      296.29, -3.07 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      218.99,-57.27 [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 = 104.70,-20.02 [deg].

GCN Circular #19577
A. Maselli (INAF-IASFPA), S. D. Barthelmy (GSFC), A. D'Ai (INAF-IASFPA), N. Gehrels (NASA/GSFC), C. Gronwall (PSU), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), J. L. Racusin (NASA/GSFC) and T. N. Ukwatta (LANL) report on behalf of the Swift Team:
At 22:40:31 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 160625A (trigger=701503). Swift did not slew to the burst due to an observing constraint. The BAT on-board calculated location is RA, Dec 176.937, -65.114, which is
```
   RA(J2000)  =  11h 47m 45s
   Dec(J2000) = -65d 06' 49"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows several peaks in the first 40 sec and then a large peak at T+170 sec structure with a duration of at least 180 sec. The peak count rate was ~14000 counts/sec (15-350 keV), at ~175 sec after the trigger.
Due to an observing constraint, Swift will not slew until T0+20.3 minutes. There will be no XRT or UVOT data until this time.
Burst Advocate for this burst is A. Maselli (maselli AT ifc.inaf.it). 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/too.html.)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Jun 16 23:02:44 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     701503,   Seg_Num: 0
POINT_RA:        176.903d {+11h 47m 37s} (J2000)
POINT_DEC:       -65.113d {-65d 06' 47"} (J2000)
IMG_START_DATE:  17564 TJD;   177 DOY;   16/06/25
IMG_START_TIME:  82956.84 SOD {23:02:36.84} UT,   1325.4 [sec] since BAT Trigger Time
COUNTS:          1    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        0    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:     Sat 25 Jun 16 23:41:06 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     701503,   Seg_Num: 0
GRB_RA:          176.9141d {+11h 47m 39.38s} (J2000),
                 177.1150d {+11h 48m 27.59s} (current),
                 176.3089d {+11h 45m 14.13s} (1950)
GRB_DEC:         -65.1436d {-65d 08' 36.9"} (J2000),
                 -65.2352d {-65d 14' 06.8"} (current),
                 -64.8657d {-64d 51' 56.4"} (1950)
GRB_ERROR:       5.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  17564 TJD;   177 DOY;   16/06/25
IMG_START_TIME:  83380.00 SOD {23:09:40.00} UT,   1748.5 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        95.25d {+06h 21m 00s}  +23.35d {+23d 20' 56"}
SUN_DIST:        107.79 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      343.20d {+22h 52m 47s}   -6.85d {-06d 50' 52"}
MOON_DIST:       107.18 [deg]
MOON_ILLUM:      70 [%]
GAL_COORDS:      296.29, -3.10 [deg] galactic lon,lat of the burst
ECL_COORDS:      219.02,-57.30 [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 Circular #19578
D.N. Burrows (PSU), J.A. Kennea (PSU), S. Campana (INAF-OAB), G. Cusumano (INAF-IASF PA), P.A. Evans (U. Leicester) and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team:
The XRT began observing the field of GRB 160625A at 23:02:36.8 UT, 1325.3 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 176.91418, -65.14362 which is equivalent to:
```
   RA(J2000)  = 11h 47m 39.40s
   Dec(J2000) = -65d 08' 37.0"
```
with an uncertainty of 5.8 arcseconds (radius, 90% containment). This location is 112 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 http://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. No spectrum from the promptly downlinked event data is yet available to determine the column density.
GCN Circular #19579
D. A. Kann (TLS Tautenburg) speculates:
Swift just triggered on GRB 160625A (Swift Trigger 701503, Maselli et al., GCN #19577). They reported several rather small peaks followed by very strong emission ca. three minutes later.
This burst is seen to be extremely powerful in INTEGRAL SPI ACS and CALET GBM. It seems to have begun with a short spike at about the same time as the Swift BAT trigger (Fermi GBM trigger 488587220).
Three minutes later, Fermi LAT sent out a flight position at:
```
RA = 308.267
Dec. = +6.900
```
with an error of 0.5 degrees.
This position differs very strongly from the Swift BAT position. (Dec. of -65!)
Additionally, Swift BAT has recently slewed to the BAT position and found a faint X-ray afterglow (Burrows et al., GCN 19578), which is in contrast to the very bright one one would expect from the extreme burst seen by INTEGRAL and CALET.
I suggest that these are two different events, with the bright GRB seen through side of the Swift spacecraft.
The Fermi LAT position is affected by a relatively low amount of extinction (E_(B-V)=0.1), in contrast to the Swift position (E_(B-V)=1.3).
I strongly urge observations of the LAT position by Swift to determine an XRT position, and by optical observatories as well. Judging from the INTEGRAL SPI ACS light curve, this GRB is of similar intensity to GRB 160623A.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 26 Jun 16 00:45:20 UT
NOTICE_TYPE:     Swift-UVOT Source List 
TRIGGER_NUM:     701503,   Seg_Num: 0  
POINT_RA:        176.899d {+11h 47m 36s} (J2000)
POINT_DEC:       -65.113d {-65d 06' 45"} (J2000)
POINT_ROLL:      287.561d 
IMG_START_DATE:  17565 TJD;   178 DOY;   16/06/26
IMG_START_TIME:  2414.88 SOD {00:40:14.88} UT,   7183.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        0.473
N_STARS:         190 
X_OFFSET:        393 [pixels]
Y_OFFSET:        655 [pixels]  
X_MAX:           1352 [pixels]  
Y_MAX:           1614 [pixels] 
DET_THRESH:      6
PHOTO_THRESH:    3
SL_URL:          sw00701503000msufc7183.fits
SUN_POSTN:        95.30d {+06h 21m 11s}  +23.35d {+23d 20' 50"}
SUN_DIST:        107.75 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      343.78d {+22h 55m 08s}   -6.67d {-06d 40' 03"}
MOON_DIST:       107.45 [deg] 
MOON_ILLUM:      69 [%] 
GAL_COORDS:      296.28, -3.07 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      218.97,-57.28 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

 
TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 26 Jun 16 00:45:51 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     701503,   Seg_Num: 0 
POINT_RA:        176.899d {+11h 47m 36s} (J2000)
POINT_DEC:       -65.113d {-65d 06' 45"} (J2000)
POINT_ROLL:      287.561d 
IMG_START_DATE:  17565 TJD;   178 DOY;   16/06/26
IMG_START_TIME:  2414.88 SOD {00:40:14.88} UT,   7183.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        0.473
N_STARS:         190 
X_OFFSET:        393 [pixels]
Y_OFFSET:        655 [pixels]
X_MAX:           1352 [pixels]
Y_MAX:           1614 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    3
SL_URL:          sw00701503000msufc7183.fits
SUN_POSTN:        95.30d {+06h 21m 11s}  +23.35d {+23d 20' 50"}
SUN_DIST:        107.75 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      343.79d {+22h 55m 09s}   -6.67d {-06d 39' 58"}
MOON_DIST:       107.46 [deg] 
MOON_ILLUM:      69 [%] 
GAL_COORDS:      296.28, -3.07 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      218.97,-57.28 [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:     Sun 26 Jun 16 00:48:06 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     701503,   Seg_Num: 0
POINT_RA:        176.899d {+11h 47m 36s} (J2000)
POINT_DEC:       -65.113d {-65d 06' 45"} (J2000)
ROLL:            287.561d
IMG_START_DATE:  17565 TJD;   178 DOY;   16/06/26
IMG_START_TIME:  2414.88 SOD {00:40:14.88} UT,   7183.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     488594431
X_OFFSET:        712 [pixels]
Y_OFFSET:        974 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       872 
Y_GRB_POS:       1134
BINNING_INDEX:   1
IM_URL:          sw00701503000msuni7200.fits
SUN_POSTN:        95.30d {+06h 21m 12s}  +23.35d {+23d 20' 50"}
SUN_DIST:        107.75 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      343.81d {+22h 55m 14s}   -6.66d {-06d 39' 35"}
MOON_DIST:       107.46 [deg] 
MOON_ILLUM:      69 [%] 
GAL_COORDS:      296.28, -3.07 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      218.97,-57.28 [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:     Sun 26 Jun 16 00:48:06 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     701503,   Seg_Num: 0
POINT_RA:        176.899d {+11h 47m 36s} (J2000)
POINT_DEC:       -65.113d {-65d 06' 45"} (J2000)
ROLL:            287.561d
IMG_START_DATE:  17565 TJD;   178 DOY;   16/06/26
IMG_START_TIME:  2414.88 SOD {00:40:14.88} UT,   7183.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     488594431
X_OFFSET:        712 [pixels]
Y_OFFSET:        974 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       872
Y_GRB_POS:       1134
BINNING_INDEX:   1
IM_URL:          sw00701503000msuni7200.fits
SUN_POSTN:        95.30d {+06h 21m 12s}  +23.35d {+23d 20' 50"}
SUN_DIST:        107.75 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      343.81d {+22h 55m 14s}   -6.66d {-06d 39' 35"}
MOON_DIST:       107.46 [deg]
MOON_ILLUM:      69 [%]
GAL_COORDS:      296.28, -3.07 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      218.97,-57.28 [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 Circular #19583
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
Using 830 s of XRT Photon Counting mode data and 3 UVOT images for GRB 160625A, 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 = 176.91548, -65.14460 which is equivalent to:
```
RA (J2000): 11h 47m 39.72s
Dec (J2000): -65d 08' 40.6"
```
with an uncertainty of 2.5 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 #19591
P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), T.G.R. Roegiers (PSU), L.M. McCauley (PSU), J.A. Kennea (PSU), S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and A. Maselli report on behalf of the Swift-XRT team:
We have analysed 6.4 ks of XRT data for GRB 160625A (Maselli et al. GCN Circ. 19577), from 1.3 ks to 48.7 ks after the BAT trigger. The data comprise 1.7 ks in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 19583).
The late-time light curve (from T0+7.4 ks) can be modelled with a power-law decay with a decay index of alpha=0.71 (+0.31, -0.28).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.2 (+/-0.5). The best-fitting absorption column is 2.2 (+0.9, -0.7) x 10^22 cm^-2, in excess of the Galactic value of 1.0 x 10^22 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 5.8 x 10^-11 (1.6 x 10^-10) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.2 (+0.9, -0.7) x 10^22 cm^-2
Galactic foreground: 1.0 x 10^22 cm^-2
Excess significance: 2.8 sigma
Photon index:	     2.2 (+/-0.5)
```
If the light curve continues to decay with a power-law decay index of 0.71, the count rate at T+24 hours will be 9.8 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.7 x 10^-13 (1.6 x 10^-12) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00701503.
This circular is an official product of the Swift-XRT team.
GCN Circular #19592
S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), A. Maselli (INAF-IASFPA), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from the recent telemetry downlinks, we report further analysis of BAT GRB 160625A (trigger #701503) (Maselli, et al., GCN Circ. 19577). The BAT ground-calculated position is RA, Dec = 176.939, -65.142 deg, which is
```
   RA(J2000)  =  11h 47m 45.3s 
   Dec(J2000) = -65d 08' 30.9" 
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 57%.
The mask-weighted light curve shows at least 7 peaks, the first starting at ~T-35 sec, the brightest peak at ~T+36 sec, and the last peak ending at ~T+70 sec. The peak mentioned in GCN Circ 19577 at T+170 sec is due to GRB 160625B (as suggested by Kann, Circ 19579) and confirmed by our analysis. T90 (15-350 keV) is 53.9 +- 3.1 sec (estimated error including systematics).
The time-averaged spectrum from T-15.04 to T+47.41 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.08 +- 0.07. The fluence in the 15-150 keV band is 3.3 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+35.07 sec in the 15-150 keV band is 3.0 +- 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/701503/BA/
GCN Circular #19593
M. De Pasquale (UCL-MSSL) and A. Maselli (INAF-IASFPA) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 160625A 7183 s after the BAT trigger (Maselli et al., GCN Circ. 19577). No optical afterglow consistent with the XRT position (Burrows et al. GCN Circ. 19578) is detected in the UVOT exposures. We note the presence of a source approximately 3'' from the XRT position. This source is present in the USNO catalogue. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white             7183         7952          344         >20.8
v                 8163         8363          197         >19.0
b                 7548         7747          197         >19.9
u                 7342         7542          197         >19.4
m2                8368         8483          113         >18.9
w2                7958         8158          197         >19.6
```
The magnitudes in the table are not corrected for the substantial Galactic extinction due to the reddening of E(B-V) = 1.51 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #19629
T. Schweyer, T.-W. Chen, and J. Greiner (all MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 160625A (Swift trigger 701503; Maselli et al., GCN #19577) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile).
Observations started at 22:55 UT on 2016-06-26, 24.24 hrs after the GRB trigger. They were performed through cirrus at an average seeing of 1.4" and at an average airmass of 1.2.
We do not detect any source within the Swift-XRT error circle reported by Burrows et al. (GCN #19578) down to
```
g' > 22.6 mag,
r' > 23.9 mag,
i' > 22.5 mag,
z' > 22.6 mag,
J  > 19.9 mag,
H  > 19.4 mag,
K  > 19.5 mag.
```
Given magnitudes are calibrated against USNO as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=1.2 mag in the direction of the burst (Schlafly and Finkbeiner 2011).

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Jochen Greiner, last update: 30-Jun-2016 [Disclaimer]