Gamma-ray Burst 150901A

(All information courtesy of the instrument teams.)

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 01 Sep 15 15:31:25 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     654042,   Seg_Num: 0
GRB_RA:          183.586d {+12h 14m 21s} (J2000),
                 183.784d {+12h 15m 08s} (current),
                 182.953d {+12h 11m 49s} (1950)
GRB_DEC:         +25.038d {+25d 02' 19"} (J2000),
                 +24.951d {+24d 57' 05"} (current),
                 +25.316d {+25d 18' 59"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       26310 [cnts]    Image_Peak=347 [image_cnts]
TRIGGER_DUR:     8.192 [sec] 
TRIGGER_INDEX:   455     E_range: 15-50 keV
BKG_INTEN:       194583 [cnts]
BKG_TIME:        55504.92 SOD {15:25:04.92} UT
BKG_DUR:         64 [sec]
GRB_DATE:        17266 TJD;   244 DOY;   15/09/01
GRB_TIME:        55595.67 SOD {15:26:35.67} UT
GRB_PHI:         -62.98 [deg]
GRB_THETA:        33.72 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     10.34 [sigma]
IMAGE_SIGNIF:    7.11 [sigma]
MERIT_PARAMS:     +1  +0  +0  +3  +1  -3 -100  +0 -88  +0 
SUN_POSTN:       160.49d {+10h 41m 58s}   +8.24d {+08d 14' 14"}
SUN_DIST:         27.80 [deg]   Sun_angle= -1.6 [hr] (East of Sun)
MOON_POSTN:       18.17d {+01h 12m 40s}   +6.09d {+06d 05' 38"}
MOON_DIST:       145.95 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      224.94, 81.42 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      172.67, 24.26 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This Notice was delayed by more than 60 sec past the end of the trigger integration interval;  
COMMENTS:        probably due to it occurring during a Malindi downlink session.  
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 = 12.19,-5.60 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 01 Sep 15 15:32:04 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     654042,   Seg_Num: 0
GRB_RA:          183.586d {+12h 14m 21s} (J2000),
                 183.784d {+12h 15m 08s} (current),
                 182.953d {+12h 11m 49s} (1950)
GRB_DEC:         +25.038d {+25d 02' 19"} (J2000),
                 +24.951d {+24d 57' 05"} (current),
                 +25.316d {+25d 18' 59"} (1950)
GRB_DATE:        17266 TJD;   244 DOY;   15/09/01
GRB_TIME:        55595.67 SOD {15:26:35.67} UT
TRIGGER_INDEX:   455
GRB_PHI:         -62.98 [deg]
GRB_THETA:        33.72 [deg]
DELTA_TIME:      45.00 [sec]
TRIGGER_DUR:     8.192 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     10.34 [sigma]
IMAGE_SIGNIF:    7.11 [sigma]
LC_URL:          sw00654042000msb.lc
SUN_POSTN:       160.49d {+10h 41m 58s}   +8.24d {+08d 14' 14"}
SUN_DIST:         27.80 [deg]   Sun_angle= -1.6 [hr] (East of Sun)
MOON_POSTN:       18.17d {+01h 12m 42s}   +6.10d {+06d 05' 45"}
MOON_DIST:       145.94 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      224.94, 81.42 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      172.67, 24.26 [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 = 12.19,-5.60 [deg].

GCN Circular #18225
B. Sbarufatti (INAF-OAB/PSU), S. D. Barthelmy (GSFC), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA) and T. N. Ukwatta (LANL) report on behalf of the Swift Team:
At 15:26:35 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 150901A (trigger=654042). Swift did not slew due Sun observing constraint. The BAT on-board calculated location is RA, Dec 183.586, +25.038, which is
```
   RA(J2000)  =  12h 14m 21s
   Dec(J2000) = +25d 02' 19"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak with a duration of about 25 sec. The peak count rate was ~700 counts/sec (15-350 keV), at ~1 sec after the trigger.
Due to a Sun observing constraint, Swift cannot slew to the BAT position until 00:01 UT on 2015 October 28. There will thus be no XRT or UVOT data for this trigger before this time.
Burst Advocate for this burst is B. Sbarufatti (boris.sbarufatti AT brera.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 Circular #18232
J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), B. Sbarufatti (INAF-OAB/PSU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-254 to T+640 sec from the recent telemetry downlink, we report further analysis of BAT GRB 150901A (trigger #654042) (Sbarufatti, et al., GCN Circ. 18225). The BAT ground-calculated position is RA, Dec = 183.609, 25.076 deg which is
```
  RA(J2000)  =  12h 14m 26.1s
  Dec(J2000) = +25d 04' 35.2"
```
with an uncertainty of 2.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 41%.
The mask-weighted light curve shows some weak emissions that start at ~ T-70 s, followed by the main structure with several overlapping pulses from ~T0 to ~T+18 s. T90 (15-350 keV) is 64.0 +- 35.8 sec (estimated error including systematics).
The time-averaged spectrum from T-61.8 to T+18.2 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.72 +- 0.53. The fluence in the 15-150 keV band is 4.5 +- 1.3 x 10^-7 erg/cm2. The 1-s peak photon flux is unconstrained due to the weakness of the burst. 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/654042/BA/

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Jochen Greiner, last update: 03-Sep-2015 [Disclaimer]