Gamma-ray Burst 050915B

(All information courtesy of the instrument teams.)

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Results of Observations

GCN/BACODINE POSITION NOTICE


TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 15 Sep 05 21:24:21 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     155284,   Seg_Num: 0
GRB_RA:          219.096d {+14h 36m 23s} (J2000),
                 219.217d {+14h 36m 52s} (current),
                 218.040d {+14h 32m 10s} (1950)
GRB_DEC:         -67.405d {-67d 24' 16"} (J2000),
                 -67.429d {-67d 25' 45"} (current),
                 -67.187d {-67d 11' 13"} (1950)
GRB_ERROR:       4.00 [arcmin radius, statistical only]
GRB_INTEN:       0 [cnts]    Image_Peak=9110 [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:        13628 TJD;   258 DOY;   05/09/15
GRB_TIME:        76984.26 SOD {21:23:04.26} UT
GRB_PHI:          88.31 [deg]
GRB_THETA:        24.54 [deg]
SOLN_STATUS:     0x13
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    23.35 [sigma]
MERIT_PARAMS:     +1  +0  +0  +6  +1  +8  +0  +1 -22  +1 
SUN_POSTN:       173.69d {+11h 34m 45s}   +2.73d {+02d 43' 43"}
SUN_DIST:         77.02 [deg]
MOON_POSTN:      326.17d {+21h 44m 41s}  -17.82d {-17d 49' 06"}
MOON_DIST:        79.86 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      312.78, -6.56 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      243.17,-48.65 [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.

red DSS finding chart ps-file

GCN/SWIFT NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 15 Sep 05 21:25:35 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     155284,   Seg_Num: 0
POINT_RA:        219.084d {+14h 36m 20s} (J2000)
POINT_DEC:       -67.396d {-67d 23' 44"} (J2000)
GRB_DATE:        13628 TJD;   258 DOY;   05/09/15
GRB_TIME:        77119.98 SOD {21:25:19.98} UT
COUNTS:          179    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        4    Max_iter_allowed= 4
ERROR_CODE:      2
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        Algorithm did not converge; too many interations.

GCN/SWIFT NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 15 Sep 05 21:27:23 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     155284,   Seg_Num: 0
GRB_RA:          219.096d {+14h 36m 23s} (J2000),
                 219.217d {+14h 36m 52s} (current),
                 218.040d {+14h 32m 10s} (1950)
GRB_DEC:         -67.405d {-67d 24' 16"} (J2000),
                 -67.429d {-67d 25' 45"} (current),
                 -67.187d {-67d 11' 13"} (1950)
GRB_DATE:        13628 TJD;   258 DOY;   05/09/15
GRB_TIME:        76984.26 SOD {21:23:04.26} UT
TRIGGER_INDEX:   20000
GRB_PHI:          88.31 [deg]
GRB_THETA:        24.54 [deg]
DELTA_TIME:      0.00 [sec]
TRIGGER_DUR:     64.000 [sec] 
LC_URL:          sw00155284000msb.lc
SUN_POSTN:       173.69d {+11h 34m 45s}   +2.73d {+02d 43' 43"}
SUN_DIST:         77.02 [deg]
MOON_POSTN:      326.17d {+21h 44m 41s}  -17.82d {-17d 49' 06"}
MOON_DIST:        79.86 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      312.78, -6.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      243.17,-48.65 [deg] ecliptic lon,lat of the pointing direction
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.

GCN/SWIFT NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 15 Sep 05 21:30:04 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     155284,   Seg_Num: 0
POINT_RA:        219.084d {+14h 36m 20s} (J2000)
POINT_DEC:       -67.395d {-67d 23' 42"} (J2000)
POINT_ROLL:      313.102d
GRB_DATE:        13628 TJD;   258 DOY;   05/09/15
GRB_TIME:        77117.95 SOD {21:25:17.95} UT
FILTER:          3, V
BKG_MEAN:        1.000000
N_STARS:         190
X_OFFSET:        476 [pixels]
Y_OFFSET:        555 [pixels]
X_MAX:           1435 [pixels]
Y_MAX:           1514 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00155284000msufc.fits
SUN_POSTN:       173.69d {+11h 34m 45s}   +2.73d {+02d 43' 41"}
SUN_DIST:         77.01 [deg]
MOON_POSTN:      326.19d {+21h 44m 46s}  -17.81d {-17d 48' 34"}
MOON_DIST:        79.89 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      312.78, -6.55 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      243.16,-48.64 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN/SWIFT NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 15 Sep 05 21:30:40 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     155284,   Seg_Num: 0
POINT_RA:        219.084d {+14h 36m 20s} (J2000)
POINT_DEC:       -67.395d {-67d 23' 42"} (J2000)
POINT_ROLL:      313.102d
GRB_DATE:        13628 TJD;   258 DOY;   05/09/15
GRB_TIME:        77117.95 SOD {21:25:17.95} UT
FILTER:          3, V
BKG_MEAN:        1.000000
N_STARS:         190
X_OFFSET:        476 [pixels]
Y_OFFSET:        555 [pixels]
X_MAX:           1435 [pixels]
Y_MAX:           1514 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00155284000msufc.fits
SUN_POSTN:       173.69d {+11h 34m 45s}   +2.73d {+02d 43' 41"}
SUN_DIST:         77.01 [deg]
MOON_POSTN:      326.19d {+21h 44m 46s}  -17.81d {-17d 48' 34"}
MOON_DIST:        79.89 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      312.78, -6.55 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      243.16,-48.64 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_srclist.fits file does not exist; skipping the attachment.

GCN/SWIFT NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 15 Sep 05 21:31:59 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     155284,   Seg_Num: 0
POINT_RA:        219.084d {+14h 36m 20s} (J2000)
POINT_DEC:       -67.395d {-67d 23' 42"} (J2000)
ROLL:            313.102d
GRB_DATE:        13628 TJD;   258 DOY;   05/09/15
GRB_TIME:        77117.95 SOD {21:25:17.95} UT
FILTER:          3, V
EXPOSURE_ID:     2266
X_OFFSET:        796 [pixels]
Y_OFFSET:        875 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       956
Y_GRB_POS:       1035
BINNING_INDEX:   1
IM_URL:          sw00155284000msuni.fits
SUN_POSTN:       173.69d {+11h 34m 45s}   +2.73d {+02d 43' 41"}
SUN_DIST:         77.01 [deg]
MOON_POSTN:      326.19d {+21h 44m 46s}  -17.81d {-17d 48' 34"}
MOON_DIST:        79.89 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      312.78, -6.55 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      243.16,-48.64 [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/SWIFT NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 15 Sep 05 21:32:16 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     155284,   Seg_Num: 0
POINT_RA:        219.084d {+14h 36m 20s} (J2000)
POINT_DEC:       -67.395d {-67d 23' 42"} (J2000)
ROLL:            313.102d
GRB_DATE:        13628 TJD;   258 DOY;   05/09/15
GRB_TIME:        77117.95 SOD {21:25:17.95} UT
FILTER:          3, V
EXPOSURE_ID:     2266
X_OFFSET:        796 [pixels]
Y_OFFSET:        875 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       956
Y_GRB_POS:       1035
BINNING_INDEX:   1
IM_URL:          sw00155284000msuni.fits
SUN_POSTN:       173.69d {+11h 34m 45s}   +2.73d {+02d 43' 41"}
SUN_DIST:         77.01 [deg]
MOON_POSTN:      326.19d {+21h 44m 46s}  -17.81d {-17d 48' 34"}
MOON_DIST:        79.89 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      312.78, -6.55 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      243.16,-48.64 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_image.fits file does not exist; skipping the attachment.

GCN notice #3987
A. Falcone (PSU), A. Beardmore (U. Leicester), D. Burrows (PSU), J. Cummings (GSFC/NRC), D. Fox (PSU), N. Gehrels (GSFC), S. T. Holland (GSFC/UMBC), J. Kennea (PSU), H. Krimm (GSFC/USRA), C. Pagani (PSU), D. Palmer (LANL), A. Parsons (GSFC), E. Rol (U. Leicester), P. Roming (PSU), P. Shady (MSSL), on behalf of the Swift team:
At 21:23:04 UT, Swift-BAT triggered and located GRB050915B (trigger=155284). The spacecraft slewed immediately. The BAT on-board calculated location is RA,Dec 219.096d,-67.405d {14h 36m 23s, -67d 24' 16"} (J2000), with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys). The BAT light curve showed two broad bright peaks from T-10 to T+40 sec. The peak count rate was ~2800 counts/sec (15-350 keV), at T-2 sec.
XRT began observing at 21:25:20 UT, 136 seconds after the BAT trigger. XRT was not able to centroid on any point source, but the downlinked lightcurve shows that a bright, fading X-ray source was present in the XRT field of view.
The UVOT began observing at 21:25:18 UT, 134 seconds after the BAT trigger. No new source, with respect to the DSS, is detected in the initial 100 sec V-band image. The 5-sigma limiting magnitude, in a circular aperture of radius 6.0 arcseconds is V_lim = 17.7 mag. This magnitude is based on the preliminary V-band zero-point, measured in orbit and will require refinement with further calibration. It has not been corrected for extinction. The estimated Galactic extinction in this direction is A_V = 1.29. The UVOT image covers 25% of the 3 arcminute BAT error circle. The field is crowded.
We are currently in the portion of the orbits where the spacecraft does not pass over the Malindi downlink station. Therefore, it will be ~3 hours before we have access to the full data set for the refined analyses.
GCN notice #3988
B. E. Cobb and C. D. Bailyn (Yale), part of the larger SMARTS consortium, report:
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained optical/IR imaging of the error region of GRB 050915b (GCN 3987, Falcone et al.), starting 2.0 hours after the burst at 2005-09-15 23:23 UT. Our optical images, in V and I, have a field of view of 6'x6' and, therefore, cover the entire GRB error circle. Our IR images, in J and K, have a smaller field of view, covering a region totaling ~6 square arcminutes in the middle of the quoted error region.
Visual comparison of the optical images to the SDSS and the IR images to 2MASS frames does not reveal any new sources. Preliminary image differencing, using the ISIS image subtraction program, also does not reveal any significant variable source within the GRB error region.
Analysis of this data is ongoing.
GCN notice #3989
A. D. Falcone, D. N. Burrows, J. A. Kennea (PSU), W. Voges (MPE), F. Marshall (GSFC) report on behalf of the Swift XRT team:
The Swift XRT began observing the long bright burst GRB 050915B (Falcone et al., GCN 3987) at 21:25:20 UT, but was unable to obtain an on-board centroid. Analysis of the initial ground-processed data finds a bright, fading, and uncataloged source at coordinates:
```
RA(J2000) = 14:36:26.5
Dec(J2000) = -67:24:36.5
```
We estimate an uncertainty of 8 arcseconds (90% containment). This position lies 56 arcseconds from the BAT position reported in GCN 3987.
GCN notice #3992
GRB 050915B: Swift/UVOT Upper Limits
S. T. Holland (GSFC/USRA), A. Falcone (PSU), M. Carter (UCL/MSSL), P. Smith (UCL/MSSL), and N. Gehrels (GSFC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began observing the field of GRB 050915B 121 seconds after the BAT trigger (Falcone et al. GCN 3987). No new source is detected at the position of the XRT error circle (Falcone et al. GCN 3989) in the initial 100 second V-band image down to a 5-sigma upper limit of 17.5, or in summed exposures with any of the filters down to the following 5-sigma magnitude upper limits:
```
Filter  T_range (s)     Exp (s)  5sig UL

V       133 - 25,406     1824     19.2
B       279 - 35,461     2983     20.4
U       265 - 31,288     2381     20.2
UVW1    251 - 30,503     2972     21.0
UVM2    237 - 29,595     3006     20.7
UVW2    294 - 35,995     2609     20.8
```
The magnitudes are uncorrected for extinction.
GCN notice #3993
J. Cummings (GSFC/NRC), M. Ajello (MPE), L. Barbier (GSFC), S. Barthelmy (GSFC), E. Fenimore (LANL), R. Fink (GSFC), N. Gehrels (GSFC), D. Hullinger (UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), J. Tueller (GSFC), on behalf of the Swift-BAT team:
Using the full data set from T-90 to T+300 sec from the recent telemetry downlinks, we report further analysis of Swift-BAT GRB 050915B (trigger #155284) (Falcone, et al., GCN 3987). The refined BAT ground position is (RA,Dec) = 219.112, -67.412 degrees {14h 36m 26.8, -67d 24' 43"} (J2000) +-0.7 arcmin, (radius, sys+stat, 90% containment). This is within 8 arcseconds of the XRT counterpart (Falcone et al. GCN 3989). The partial coding was 53% including projection effects.
The mask-weighted light curve shows a rise from T-10 seconds to a peak at T-4, dropping off to a lumpy plateau spanning T+0 to T+25, then steadily declining to zero at T+50. No further instances of emission are apparent on a 1 second timescale out to T+1200 sec. T90 (15-350 keV) is (40 +- 1) sec (estimated error including systematics).
The time-averaged spectrum is well-fit by a power law with photon index 1.89 +- 0.06. The fluence in the 15-150 keV band is (3.4 +- 0.1) x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T-3.1 sec in the 15-150 keV band is (2.3 +- 0.2) ph/cm2/sec. All quoted errors are at the 90% confidence level.
GCN notice #3994
B. E. Cobb and C. D. Bailyn (Yale), part of the larger SMARTS consortium, report:
Our ANDICAM observations reported in GCN 3988 were re-examined following the detection of the X-ray afterglow of GRB 050915b (GCN 3989, Falcone et al.). The position of the X-ray afterglow was captured in both our optical and IR images.
Three sources are detected within the X-ray afterglow error region:
```
        RA           DEC
A) 14:36:26.04  -67:24:41.4
B) 14:36:26.35  -67:24:32.2
C) 14:36:27.30  -67:24:39.3
```
The first source (A) has a stellar profile and has previously been clearly detected in both the SDSS and 2MASS surveys. The other two sources (B and C) appear only slightly above the detection limits of our ANDICAM images. Sources B and C are also weakly detected in the SDSS (and possibly in 2MASS). These two sources, particularly source B, might be extended, though this is uncertain due to the low significance of their detection.
The brightness of these sources does not vary significantly over our period of observation.
Total summed exposure times amounted to 30 minutes in I and V and 24 minutes in J and K, with a mid-exposure time of 2005-09-15 00:01 UT (~2.6 hours post-burst). The preliminary limiting magnitudes of our images are as follows:
```
V < 21.4 +/- 0.1
I < 21.3 +/- 0.1
J < 18.3 +/- 0.2
K < 17.8 +/- 0.2
```
GCN Circular #5821
D. Malesani (SISSA/ISAS & NBI-DARK), S. Covino (INAF/OABr), S. Piranomonte (INAF/OAR), L.A. Antonelli (INAF/OAR), G. Chincarini (Univ. Milano-Bicocca & INAF-OABr), P. D'Avanzo (INAF/OABr), L. Stella (INAF/OAR), and G. Tagliaferri (INAF/OABr), report on behalf of the MISTICI collaboration:
We observed the field of one-year-old GRB 050915B (Falcone et al., GCNs 3987, 389) with the ESO-VLT UT2 equipped with FORS1. Observations started on 2005 Sep 16.01065 UT (2.87 hr after the GRB) and consisted in a series of 24 R-band images lasting 1 minute each. The field was observed again, in the R band, with the ESO-NTT equipped with the SuSI2 imager, with mean time 2005 Oct 1.0261 UT (15.13 days after the GRB). The field is very crowded and reddened due to the low Galactic latitude (b = -6.6 deg).
Inside the XRT error circle (Moretti et al. 2006, A&A, 448, L9) there are three sources, but only two are consistent with the boresight-corrected position (Butler 2006, astro-ph/0611031 + priv. comm.), which has a 90% error radius of 1.4". One of them is clearly fading between the VLT and NTT exposures, being undetectable in the NTT images. Its coordinates (J2000) are:
```
alpha = 14:36:26.17
delta = -67:24:32.5
```
It is remarkable, however, that no fading is seen for this source over the course of the VLT observation (2.87-3.66 hr after the GRB). PSF-matched profile photometry revealed that the source was constant (
= 21.68 +- 0.03) to within ~0.1 mag, with no trend for decline. In the SuSI2 image (15 days after the burst), it has R > 23.4 (3-sigma upper limit).
The other object consistent with the X-ray position has coordinates
```
alpha = 14:36:26.39
delta = -67:24:31.6
```
and is constant between the FORS1 and SuSI2 exposures at R = 21.2. This source, which is just 1.5" away from the afterglow, might be consistent with source "B" reported by Cobb & Bailyn. (GCN 3994).
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Jochen Greiner, last update: 13-Nov-2006 [Disclaimer]