Gamma-ray Burst 070427

(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:     Fri 27 Apr 07 08:31:24 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     277356,   Seg_Num: 0
GRB_RA:           28.862d {+01h 55m 27s} (J2000),
                  28.945d {+01h 55m 47s} (current),
                  28.291d {+01h 53m 10s} (1950)
GRB_DEC:         -27.633d {-27d 37' 57"} (J2000),
                 -27.597d {-27d 35' 49"} (current),
                 -27.877d {-27d 52' 38"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4855 [cnts]    Image_Peak=248 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   146     E_range: 15-50 keV
BKG_INTEN:       31675 [cnts]
BKG_TIME:        30654.08 SOD {08:30:54.08} UT
BKG_DUR:         8 [sec]
GRB_DATE:        14217 TJD;   117 DOY;   07/04/27
GRB_TIME:        30668.93 SOD {08:31:08.93} UT
GRB_PHI:         -27.71 [deg]
GRB_THETA:        14.80 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     11.78 [sigma]
IMAGE_SIGNIF:    8.85 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +1  +9 -100  +0 -74  +1 
SUN_POSTN:        34.38d {+02h 17m 32s}  +13.76d {+13d 45' 23"}
SUN_DIST:         41.69 [deg]   Sun_angle= 0.4 [hr] (West of Sun)
MOON_POSTN:      163.13d {+10h 52m 31s}   +7.56d {+07d 33' 34"}
MOON_DIST:       132.32 [deg]
MOON_ILLUM:      79 [%]
GAL_COORDS:      218.65,-75.79 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       15.00,-36.56 [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 = 73.69,-18.94 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 27 Apr 07 08:34:42 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     277356,   Seg_Num: 0
GRB_RA:           28.862d {+01h 55m 27s} (J2000),
                  28.945d {+01h 55m 47s} (current),
                  28.291d {+01h 53m 10s} (1950)
GRB_DEC:         -27.633d {-27d 37' 57"} (J2000),
                 -27.597d {-27d 35' 49"} (current),
                 -27.877d {-27d 52' 38"} (1950)
GRB_DATE:        14217 TJD;   117 DOY;   07/04/27
GRB_TIME:        30668.93 SOD {08:31:08.93} UT
TRIGGER_INDEX:   146
GRB_PHI:         -27.71 [deg]
GRB_THETA:        14.80 [deg]
DELTA_TIME:      -43.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     11.78 [sigma]
IMAGE_SIGNIF:    8.85 [sigma]
LC_URL:          sw00277356000msb.lc
SUN_POSTN:        34.38d {+02h 17m 32s}  +13.76d {+13d 45' 26"}
SUN_DIST:         41.69 [deg]   Sun_angle= 0.4 [hr] (West of Sun)
MOON_POSTN:      163.15d {+10h 52m 37s}   +7.55d {+07d 32' 48"}
MOON_DIST:       132.33 [deg]
MOON_ILLUM:      79 [%]
GAL_COORDS:      218.65,-75.79 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       15.00,-36.56 [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 = 73.69,-18.94 [deg].

GCN Circular #6352
G. Sato (GSFC/ISAS), S. Campana (INAF-OAB), P. A. Evans (U Leicester), C. Guidorzi (Univ Bicocca&INAF-OAB), C. B. Markwardt (GSFC/UMD), P. T. O'Brien (U Leicester), J. P. Osborne (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), R. L. C. Starling (U Leicester) and H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team:
At 08:31:08 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 070427 (trigger=277356). This burst was too close to the Sun (42 degrees) for Swift to slew to it. The BAT on-board calculated location is RA, Dec 28.862, -27.633 which is
```
   RA(J2000) = 01h 55m 27s
   Dec(J2000) = -27d 37' 57"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multiple-peaked structure with a duration of about 15 sec. The peak count rate was ~3500 counts/sec (15-350 keV), at ~5 sec after the trigger.
The GRB will become observable by the XRT and UVOT on May 5.
GCN Circular #6354
G. Sato (GSFC/ISAS), L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) on behalf of the Swift-BAT team:
Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 070427 (trigger #277356) (Sato, et al., GCN Circ. 6352). The BAT ground-calculated position is RA, Dec = 28.871, -27.603 deg which is
```
   RA(J2000) = 1h 55m 29.1s 
   Dec(J2000) = -27d 36' 11.2" 
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%.
The mask weighted light curve steeply rises at ~ T+0 sec, exhibiting some multi-peak sub structure, falling more gradually until ~T+20 sec, with trivial emission above 100 keV. T90 (15-350 keV) is 11 +- 1 sec (estimated error including systematics).
The time-averaged spectrum from T-0.2 to T+13.7 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.08 +- 0.10. The fluence in the 15-150 keV band is 7.2 +- 0.4 x 10^-07 erg/cm^2. The 1-sec peak photon flux measured from T+6.79 sec in the 15-150 keV band is 1.3 +- 0.1 ph/cm^2/sec. All the quoted errors are at the 90% confidence level.
GCN Report 50.1
GCN_Report 50.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_50_1.pdf by G. Sato at GSFC titled: "Swift observations of GRB 070427"

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Jochen Greiner, last update: 28-Apr-2007 [Disclaimer]