Gamma-ray Burst 070923

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 23 Sep 07 19:15:46 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     292004,   Seg_Num: 0
GRB_RA:          184.626d {+12h 18m 30s} (J2000),
                 184.728d {+12h 18m 55s} (current),
                 183.969d {+12h 15m 53s} (1950)
GRB_DEC:         -38.268d {-38d 16' 03"} (J2000),
                 -38.311d {-38d 18' 37"} (current),
                 -37.990d {-37d 59' 23"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       726 [cnts]    Image_Peak=91 [image_cnts]
TRIGGER_DUR:     0.032 [sec] 
TRIGGER_INDEX:   10318     E_range: 25-100 keV
BKG_INTEN:       37263 [cnts]
BKG_TIME:        69309.75 SOD {19:15:09.75} UT
BKG_DUR:         8 [sec]
GRB_DATE:        14366 TJD;   266 DOY;   07/09/23
GRB_TIME:        69323.51 SOD {19:15:23.51} UT
GRB_PHI:         -92.32 [deg]
GRB_THETA:        20.16 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     45.96 [sigma]
IMAGE_SIGNIF:    9.29 [sigma]
MERIT_PARAMS:     +1  +0  +0  -5  +2 +15 -100  +0 -78  +1 
SUN_POSTN:       180.35d {+12h 01m 24s}   -0.15d {-00d 09' 05"}
SUN_DIST:         38.37 [deg]   Sun_angle= -0.3 [hr] (East of Sun)
MOON_POSTN:      322.49d {+21h 29m 58s}  -16.39d {-16d 23' 22"}
MOON_DIST:       112.48 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      295.85, 24.15 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      201.26,-32.89 [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 = 275.83,-6.26 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 23 Sep 07 19:19:03 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     292004,   Seg_Num: 0
GRB_RA:          184.626d {+12h 18m 30s} (J2000),
                 184.728d {+12h 18m 55s} (current),
                 183.969d {+12h 15m 53s} (1950)
GRB_DEC:         -38.268d {-38d 16' 03"} (J2000),
                 -38.311d {-38d 18' 37"} (current),
                 -37.990d {-37d 59' 23"} (1950)
GRB_DATE:        14366 TJD;   266 DOY;   07/09/23
GRB_TIME:        69323.68 SOD {19:15:23.68} UT
TRIGGER_INDEX:   10318
GRB_PHI:         -92.32 [deg]
GRB_THETA:        20.16 [deg]
DELTA_TIME:      47.00 [sec]
TRIGGER_DUR:     0.032 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     45.96 [sigma]
IMAGE_SIGNIF:    9.29 [sigma]
LC_URL:          sw00292004000msb.lc
SUN_POSTN:       180.35d {+12h 01m 25s}   -0.15d {-00d 09' 08"}
SUN_DIST:         38.37 [deg]   Sun_angle= -0.3 [hr] (East of Sun)
MOON_POSTN:      322.52d {+21h 30m 05s}  -16.38d {-16d 22' 36"}
MOON_DIST:       112.51 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      295.85, 24.15 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      201.26,-32.89 [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 = 275.83,-6.26 [deg].

GCN Circular #6818
M. C. Stroh (PSU), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), N. Gehrels (NASA/GSFC), D. Grupe (PSU), H. A. Krimm (GSFC/USRA), D. M. Palmer (LANL), A. M. Parsons (GSFC), J. L. Racusin (PSU), R. L. C. Starling (U Leicester) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:
At 19:15:23 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 070923 (trigger=292004). The BAT on-board calculated location is RA, Dec 184.626, -38.268 which is
```
   RA(J2000)  =  12h 18m 30s
   Dec(J2000) = -38d 16' 03"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single spike with a duration of about 100 msec. The peak count rate was ~8000 counts/sec (15-350 keV), at ~0.0 sec after the trigger.
Because Swift is in the process of returning to normal operations, automatic slewing to GRBs is currently disabled. Therefore, there are no prompt XRT or UVOT observations of this burst. This burst is 38 deg from the Sun and so is too close for later XRT observations.
Burst Advocate for this burst is M. C. Stroh (stroh AT astroh.org). 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 #6819
D.B. Fox (Penn State) and E. Ofek (Caltech) report:
"We note the presence of two 2MASS-cataloged galaxies within the BAT localization region for the short-hard burst GRB 070923 (Stroh et al., GCN 6818). The galaxy coordinates, distances (D) from the center of the BAT error circle in arcmin, and total broadband magnitudes (J, H, Ks) as given by the NASA/IPAC Extragalactic Database* are:
```
            RA (J2000)   Dec (J2000)   D      J      H     Ks
   =================================================================
   2MASS-A  12:18:29.35  -38:16:44.1  0.7   15.01  14.77  13.73
   2MASS-B  12:18:21.87  -38:18:24.0  2.8   15.35  14.44  13.88
   =================================================================
```
Although neither galaxy has a measured redshift, the somewhat more distant galaxy 2MASX J12180474-3818108 (D=5.4 arcmin) and 2MASX J12175556-3818208 (D=7.2 arcmin) both have z~0.076 according to the 6dF redshift survey (Jones et al. 2004)."
*This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
GCN Circular #6821
J. Cummings (GSFC/UMBC), L. Barbier (GSFC), S. D. Barthelmy (GSFC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), M. C. Stroh (PSU), J. Tueller (GSFC), T. Ukwatta (GWU) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+230 sec from the recent telemetry downlink, we report further analysis of BAT GRB 070923 (trigger #292004) (Stroh, et al., GCN Circ. 6818). The BAT ground-calculated position is RA, Dec = 184.623, -38.294 deg which is
```
    RA(J2000)  = 12h 18m 29.5s
    Dec(J2000) = -38d 17' 38"
```
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 75%.
The mask weighted light curve shows a single peak of duration ~50 msec. T90 (15-350 keV) is 0.05 +- 0.01 sec (estimated error including systematics).
The time-averaged spectrum from T+0.16 to T+0.37 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.02 +- 0.29. The fluence in the 15-150 keV band is 5.0 +- 0.9 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from T-0.40 sec in the 15-150 keV band is 2.4 +- 0.4 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
GCN Circular #6831
P. Chandra (UVA/NRAO) and D. A. Frail (NRAO) report on behalf of the Caltech-NRAO-Carnegie GRB Collaboration:
"We observed the field centered on the BAT position of the Swift short hard burst GRB 070923 (GCN#6818) using the VLA at a frequency of 8.46 GHz and starting at 18.70 UT on Sept 28, 2007, about 5 days after the burst. There is no detection of the afterglow at the GRB Swift-BAT position (GCN#6821 )with 2-sigma upper limit of 90 microJy on its flux density.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc."

Back to JG's homepage

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