Gamma-ray Burst 160525A

(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:     Wed 25 May 16 01:35:19 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     687492,   Seg_Num: 0
GRB_RA:          103.530d {+06h 54m 07s} (J2000),
                 103.740d {+06h 54m 58s} (current),
                 102.890d {+06h 51m 34s} (1950)
GRB_DEC:          -0.173d {-00d 10' 24"} (J2000),
                  -0.195d {-00d 11' 41"} (current),
                  -0.110d {-00d 06' 35"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       0 [cnts]    Image_Peak=1202 [image_cnts]
TRIGGER_DUR:     64.000 [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:        17533 TJD;   146 DOY;   16/05/25
GRB_TIME:        5639.68 SOD {01:33:59.68} UT
GRB_PHI:         -67.35 [deg]
GRB_THETA:        10.91 [deg]
SOLN_STATUS:     0x13
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    7.19 [sigma]
MERIT_PARAMS:     +1  +0  +0  +6  +1  -3 -100  +1 -69  +0 
SUN_POSTN:        62.31d {+04h 09m 14s}  +21.00d {+20d 59' 58"}
SUN_DIST:         45.67 [deg]   Sun_angle= -2.8 [hr] (East of Sun)
MOON_POSTN:      280.98d {+18h 43m 56s}  -18.35d {-18d 21' 16"}
MOON_DIST:       161.25 [deg]
MOON_ILLUM:      90 [%]
GAL_COORDS:      213.39,  0.52 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      104.72,-22.92 [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 = 206.42,11.70 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 25 May 16 01:39:04 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     687492,   Seg_Num: 0
GRB_RA:          103.530d {+06h 54m 07s} (J2000),
                 103.740d {+06h 54m 58s} (current),
                 102.890d {+06h 51m 34s} (1950)
GRB_DEC:          -0.173d {-00d 10' 24"} (J2000),
                  -0.195d {-00d 11' 41"} (current),
                  -0.110d {-00d 06' 35"} (1950)
GRB_DATE:        17533 TJD;   146 DOY;   16/05/25
GRB_TIME:        5639.68 SOD {01:33:59.68} UT
TRIGGER_INDEX:   20000
GRB_PHI:         -67.35 [deg]
GRB_THETA:        10.91 [deg]
DELTA_TIME:      0.00 [sec]
TRIGGER_DUR:     64.000 [sec] 
SOLN_STATUS:     0x13
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    7.19 [sigma]
LC_URL:          sw00687492000msb.lc
SUN_POSTN:        62.31d {+04h 09m 15s}  +21.00d {+20d 59' 59"}
SUN_DIST:         45.67 [deg]   Sun_angle= -2.8 [hr] (East of Sun)
MOON_POSTN:      281.02d {+18h 44m 04s}  -18.35d {-18d 21' 11"}
MOON_DIST:       161.26 [deg]
MOON_ILLUM:      90 [%]
GAL_COORDS:      213.39,  0.52 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      104.72,-22.92 [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 = 206.42,11.70 [deg].

GCN Circular #19458
M. Stamatikos (OSU/NASA/GSFC), A. D'Ai (INAF-IASFPA), C. Gronwall (PSU), A. Maselli (INAF-IASFPA) and D. M. Palmer (LANL) report on behalf of the Swift Team:
At 01:33:59 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 160525A (trigger=687492). Swift could not slew to the burst due to an observing constraint. The BAT on-board calculated location is RA, Dec 103.530, -0.173 which is
```
   RA(J2000) = 06h 54m 07s
   Dec(J2000) = -00d 10' 24"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is typical for an image trigger, there is no obvious variation in the immediately available lightcurve.
Due to a Sun observing constraint, Swift cannot slew to the BAT position until 12:15 UT on 2016 August 19. There will thus be no XRT or UVOT data for this trigger before this time.
Although the observing constraint prevents a confirmation of this untriggered event, its significance (7.2 sigma) makes it most likely to be a real astrophysical event. A more definite determination will require the full downlinked dataset.
Burst Advocate for this burst is M. Stamatikos (Michael.Stamatikos-1 AT nasa.gov). 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 Circular #19461
T. N. Ukwatta (LANL), 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), 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+903 sec from recent telemetry downlinks, we report further analysis of BAT GRB 160525A (trigger #687492) (Stamatikos, et al., GCN Circ. 19458). The BAT ground-calculated position is RA, Dec = 103.575, -0.199 deg, which is
```
   RA(J2000)  =  06h 54m 17.9s 
   Dec(J2000) = -00d 11' 55.6" 
```
with an uncertainty of 3.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 98%.
The mask-weighted light curve shows a weak peak starting at ~T+5 sec and ending at ~T+65 sec.
The time-averaged spectrum from T+0.00 to T+64.00 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.58 +- 0.54. The fluence in the 15-150 keV band is 1.9 +- 0.7 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.00 sec in the 15-150 keV band is 0.06 +- 0.02 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
Given the low significance of the peak in the image domain (5.2 sigma) in the ground analysis and the lack of XRT data (Sun constrained), it is not possible to know with certainty if this is a GRB, but it seems likely.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/687492/BA/

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Jochen Greiner, last update: 25-May-2016 [Disclaimer]