Gamma-ray Burst 080915

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 15 Sep 08 00:03:33 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     324744,   Seg_Num: 0
GRB_RA:           18.004d {+01h 12m 01s} (J2000),
                  18.055d {+01h 12m 13s} (current),
                  17.710d {+01h 10m 50s} (1950)
GRB_DEC:         -76.014d {-76d 00' 51"} (J2000),
                 -75.968d {-75d 58' 05"} (current),
                 -76.279d {-76d 16' 45"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       20073 [cnts]    Image_Peak=379 [image_cnts]
TRIGGER_DUR:     4.096 [sec] 
TRIGGER_INDEX:   298     E_range: 25-100 keV
BKG_INTEN:       187162 [cnts]
BKG_TIME:        116.90 SOD {00:01:56.90} UT
BKG_DUR:         40 [sec]
GRB_DATE:        14724 TJD;   259 DOY;   08/09/15
GRB_TIME:        169.95 SOD {00:02:49.95} UT
GRB_PHI:         -170.27 [deg]
GRB_THETA:        27.40 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     8.18 [sigma]
IMAGE_SIGNIF:    7.13 [sigma]
MERIT_PARAMS:     +1  +0  +0  +3  +2  +0  +0  +0 +26  +1 
SUN_POSTN:       173.14d {+11h 32m 33s}   +2.97d {+02d 57' 55"}
SUN_DIST:        105.65 [deg]   Sun_angle= 10.3 [hr] (West of Sun)
MOON_POSTN:      347.72d {+23h 10m 54s}   -2.60d {-02d 35' 47"}
MOON_DIST:        75.34 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      301.29,-41.05 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      305.91,-66.93 [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 = 289.26,-2.42 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 15 Sep 08 00:06:30 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     324744,   Seg_Num: 0
GRB_RA:           18.004d {+01h 12m 01s} (J2000),
                  18.055d {+01h 12m 13s} (current),
                  17.710d {+01h 10m 50s} (1950)
GRB_DEC:         -76.014d {-76d 00' 51"} (J2000),
                 -75.968d {-75d 58' 05"} (current),
                 -76.279d {-76d 16' 45"} (1950)
GRB_DATE:        14724 TJD;   259 DOY;   08/09/15
GRB_TIME:        169.95 SOD {00:02:49.95} UT
TRIGGER_INDEX:   298
GRB_PHI:         -170.27 [deg]
GRB_THETA:        27.40 [deg]
DELTA_TIME:      -25.00 [sec]
TRIGGER_DUR:     4.096 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     8.18 [sigma]
IMAGE_SIGNIF:    7.13 [sigma]
LC_URL:          sw00324744000msb.lc
SUN_POSTN:       173.14d {+11h 32m 33s}   +2.96d {+02d 57' 52"}
SUN_DIST:        105.65 [deg]   Sun_angle= 10.3 [hr] (West of Sun)
MOON_POSTN:      347.75d {+23h 11m 00s}   -2.58d {-02d 35' 01"}
MOON_DIST:        75.35 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      301.29,-41.05 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      305.91,-66.93 [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 = 289.26,-2.42 [deg].

GCN Circular #8227
S. R. Oates (UCL-MSSL), A. P. Beardmore (U Leicester), J. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester), C. Gronwall (PSU), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC), R. L. C. Starling (U Leicester) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:
At 00:02:49 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080915 (trigger=324744). The BAT on-board calculated location is RA, Dec 18.004, -76.014 which is
```
   RA(J2000) = 01h 12m 01s
   Dec(J2000) = -76d 00' 51"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 20 sec. The peak count rate was ~700 counts/sec (15-350 keV), at ~2 sec after the trigger.
Due to an observing constraint, Swift will not slew until T0+62.4 minutes. There will be no XRT or UVOT data until this time.
Burst Advocate for this burst is S. R. Oates (sro AT mssl.ucl.ac.uk). 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 #8228
W. Rujopakarn (Steward), H. Swan (U Mich), T. Guver (U Arizona) report on behalf of the ROTSE collaboration:
ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to GRB 080915 (Swift trigger 324744; Oates et al., GCN 8227), producing images beginning 11.2 s after the GCN notice time. An automated response took the first image at 00:03:42.2 UT, 52.2 s after the burst, under cloudy conditions. These observations were affected by the full moon. We took 10 5-sec, and 1 20-sec exposures. These unfiltered images are calibrated relative to USNO A2.0 (R). Imaging is on going.
Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma Swift/BAT error circle. Individual images have limiting magnitudes ranging from 14.0-14.3; we set the following specific limit.
```
start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
00:03:42.2   00:03:47.2         5     14.2           52.2       N
```

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 15 Sep 08 01:07:23 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     324744,   Seg_Num: 0
POINT_RA:         18.041d {+01h 12m 10s} (J2000)
POINT_DEC:       -76.029d {-76d 01' 44"} (J2000)
IMG_START_DATE:  14724 TJD;   259 DOY;   08/09/15
IMG_START_TIME:  4037.02 SOD {01:07:17.02} UT,   3867.1 [sec] since BAT Trigger Time
COUNTS:          1    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        0    Max_iter_allowed= 4
ERROR_CODE:      1
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        No source found in the image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 15 Sep 08 01:10:52 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     324744,   Seg_Num: 0
POINT_RA:         18.041d {+01h 12m 10s} (J2000)
POINT_DEC:       -76.029d {-76d 01' 45"} (J2000)
POINT_ROLL:      154.151d
IMG_START_DATE:  14724 TJD;   259 DOY;   08/09/15
IMG_START_TIME:  4041.38 SOD {01:07:21.38} UT,   3871.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.777
N_STARS:         50
X_OFFSET:        354 [pixels]
Y_OFFSET:        622 [pixels]
X_MAX:           1313 [pixels]
Y_MAX:           1581 [pixels]
DET_THRESH:      18
PHOTO_THRESH:    11
SL_URL:          sw00324744000msufc3871.fits
SUN_POSTN:       173.18d {+11h 32m 43s}   +2.95d {+02d 56' 50"}
SUN_DIST:        105.62 [deg]   Sun_angle= 10.3 [hr] (West of Sun)
MOON_POSTN:      348.29d {+23h 13m 09s}   -2.30d {-02d 18' 16"}
MOON_DIST:        75.58 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      301.28,-41.03 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      305.87,-66.94 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 15 Sep 08 01:11:22 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     324744,   Seg_Num: 0
POINT_RA:         18.041d {+01h 12m 10s} (J2000)
POINT_DEC:       -76.029d {-76d 01' 45"} (J2000)
POINT_ROLL:      154.151d
IMG_START_DATE:  14724 TJD;   259 DOY;   08/09/15
IMG_START_TIME:  4041.38 SOD {01:07:21.38} UT,   3871.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.777
N_STARS:         50
X_OFFSET:        354 [pixels]
Y_OFFSET:        622 [pixels]
X_MAX:           1313 [pixels]
Y_MAX:           1581 [pixels]
DET_THRESH:      18
PHOTO_THRESH:    11
SL_URL:          sw00324744000msufc3871.fits
SUN_POSTN:       173.18d {+11h 32m 43s}   +2.95d {+02d 56' 50"}
SUN_DIST:        105.62 [deg]   Sun_angle= 10.3 [hr] (West of Sun)
MOON_POSTN:      348.29d {+23h 13m 10s}   -2.30d {-02d 18' 08"}
MOON_DIST:        75.58 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      301.28,-41.03 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      305.87,-66.94 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 15 Sep 08 01:12:46 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     324744,   Seg_Num: 0
POINT_RA:         18.041d {+01h 12m 10s} (J2000)
POINT_DEC:       -76.029d {-76d 01' 45"} (J2000)
ROLL:            154.151d
IMG_START_DATE:  14724 TJD;   259 DOY;   08/09/15
IMG_START_TIME:  4041.38 SOD {01:07:21.38} UT,   3871.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     243133644
X_OFFSET:        673 [pixels]
Y_OFFSET:        941 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       833
Y_GRB_POS:       1101
BINNING_INDEX:   1
IM_URL:          sw00324744000msuni3871.fits
SUN_POSTN:       173.18d {+11h 32m 43s}   +2.95d {+02d 56' 48"}
SUN_DIST:        105.62 [deg]   Sun_angle= 10.3 [hr] (West of Sun)
MOON_POSTN:      348.30d {+23h 13m 13s}   -2.30d {-02d 17' 47"}
MOON_DIST:        75.59 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      301.28,-41.03 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      305.87,-66.94 [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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 15 Sep 08 01:13:12 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     324744,   Seg_Num: 0
POINT_RA:         18.041d {+01h 12m 10s} (J2000)
POINT_DEC:       -76.029d {-76d 01' 45"} (J2000)
ROLL:            154.151d
IMG_START_DATE:  14724 TJD;   259 DOY;   08/09/15
IMG_START_TIME:  4041.38 SOD {01:07:21.38} UT,   3871.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     243133644
X_OFFSET:        673 [pixels]
Y_OFFSET:        941 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       833
Y_GRB_POS:       1101
BINNING_INDEX:   1
IM_URL:          sw00324744000msuni3871.fits
SUN_POSTN:       173.18d {+11h 32m 43s}   +2.95d {+02d 56' 48"}
SUN_DIST:        105.62 [deg]   Sun_angle= 10.3 [hr] (West of Sun)
MOON_POSTN:      348.31d {+23h 13m 13s}   -2.29d {-02d 17' 40"}
MOON_DIST:        75.59 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      301.28,-41.03 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      305.87,-66.94 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_sources_image.fits.gz file does not exist; skipping the attachment.

GCN Circular #8230
T. Ukwatta (GWU), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), S. R. Oates (UCL-MSSL), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from recent telemetry downlinks, we report further analysis of BAT GRB 080915 (trigger #324744) (Oates, et al., GCN Circ. 8227). The BAT ground-calculated position is RA, Dec = 17.911, -76.042 deg, which is
```
   RA(J2000)  =  01h 11m 38.5s 
   Dec(J2000) = -76d 02' 29.9" 
```
with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 89%.
The mask-weighted light curve shows a single FRED-like peak starting at ~T-5 sec, peaking at ~T+4 sec and ending at ~T+25 sec. T90 (15-350 keV) is 14 +- 5 sec (estimated error including systematics).
The time-averaged spectrum from T-1.2 to T+16.2 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.64 +- 0.29. The fluence in the 15-150 keV band is 2.3 +- 0.5 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+3.03 sec in the 15-150 keV band is 0.5 +- 0.1 ph/cm2/sec. 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/324744/BA/
GCN Circular #8231
P.A. Evans (U. Leicester) and S.R. Oates (MSSL/UCL) report on behalf of the Swift-XRT team.
We have analysed 1.7 ks of XRT data on GRB080915 (Oates et al, GCN Circ 8227), beginning 4.9 ks after the GRB trigger. Swift did not slew immediately to the burst due to an Earth limb constraint.
We find a faint, fading source with a mean count rate ~0.01 counts per second at a position of RA, Dec=17.9473, -76.0204 degrees, which is equivalent to:
```
RA (J2000):  01h 11m 47.35s
Dec (J2000): -76d 01' 13.4"
```
with an uncertainy of 6.5 arcsec (radius, 90% containment). This position is 54 arcsec from the BAT position, within the BAT error circle.
The light curve shows a power-law decay with an index of 0.94 (+1.19/-0.58); the large uncertainty arises because the light curve contains only 2 points.
A spectrum formed from the PC data can be modelled with an absorbed power-law. The absorption column is poorly constained, but consistent with the Galactic value of 6.7 x 10^20 cm^-2 (Kalberla et al. 2005), and the photon index is 2.3 (+2.6, -1.3).
If the light curve continues to decay at alpha=0.94 we predict a count rate at T0+24 hrs of 0.0018 counts per second. This corresponds to an observed (unabsorbed) 0.3-10 keV flux of 6.36 x 10^-14 (1.22 x 10^-13) erg cm^-2 s^-1.
This circular is an official product of the Swift-XRT team.
GCN Circular #8232
A. Breeveld (MSSL-UCL) and S.R. Oates (MSSL-UCL) report on behalf of the Swift/UVOT team:
The Swift/UVOT observed the field of GRB 080915 (Oates et al., GCN Circ. 8227) with settled exposures starting 3872s after the trigger. We do not find a source in any of the UVOT observations inside the XRT error circle (Evans et al., GCN Circ. 8231). The 3-sigma upper limits in the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for detecting a source in the first white finding chart exposure and subsequent co-added exposures are:
```
Filter          T_start T_stop  Exp     Mag (3-sigma UL)
                  (s)     (s)     (s)
=========================================================
white (FC)      3872    3972    98.2    > 19.9
white           5004    5204    196.6   > 20.5
v               3979    4179    196.6   > 18.8
v               9633    10539   885.1   > 19.7
b               4799    4999    196.6   > 19.6
u               4594    4794    196.6	> 19.1
uvw1            4389    4589    196.6	> 19.3
uvm2            4184    11087   731.3   > 20.4
uvw2            5210    5329    117.3	> 19.6
```
The values quoted above are not corrected for the expected Galactic extinction corresponding to a reddening of E(B-V) = 0.049 mag in the direction of the burst (Schlegel et al. 1998).
GCN Circular #8233
S. Covino, P. D'Avanzo, L.A. Antonelli, D. Malesani, D. Fugazza, L. Calzoletti, S. Campana, G. Chincarini, M.L. Conciatore, S. Cutini, V. D'Elia, F. D'Alessio, F. Fiore, P. Goldoni, D. Guetta, C. Guidorzi, G.L. Israel, E. Maiorano, N. Masetti, A. Melandri, E. Meurs, L. Nicastro, E. Palazzi, E. Pian, S. Piranomonte, L. Stella, G. Stratta, G. Tagliaferri, G. Tosti, V.Testa, S.D. Vergani, F. Vitali report on behalf of the REM team:
The robotic 60-cm REM telescope located at La Silla (Chile) observed automatically the field of the GRB 080915 (Oates et al. GCN 8227) on Sep 15 starting from about 2 min after the GRB time for 30 min. In the XRT error circle (Evans et al. GCN 8231) we see no sources fainter than the 2MASS limits in the J, H and K bands.
GCN Circular #8248
B. E. Cobb (UC Berkeley), reports:
Using the ANDICAM instrument on the SMARTS 1.3m telescope at CTIO, we obtained optical/IR imaging of the error region of GRB 080915a (GCN 8227, Oates et al.) with a mid-exposure time of 2008-09-15 01:54 UT (~1.9 hrs post-burst). We then re-observed the field at 2008-09-16 6:12 UT (~30.2 hrs post-burst). Total summed exposure times for each observation amounted to 36 minutes in I and 30 minutes in J.
A comparison of our two epochs of imaging reveals no variable source at the position of the X-ray afterglow reported by Evans et al. (GCN 8231). Our limiting magnitudes are I>21.9 and J>20.1. (Optical photometry is calibrated against Landolt standard stars and IR photometry is calibrated against 2MASS stars in the field.)
GCN Circular #8268
A. Rossi (Tautenburg Obs.), T. Kruehler, J. Greiner, A. Yoldas, C. Clemens, R. Filgas (all MPE Garching), A. Kupcu Yoldas (ESO) and G. Szokoly (Eoetvoes Univ., Budapest), report on behalf of the GROND team:
GROND (Greiner et al. 2008, PASP 120, 405), mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile), started observations of the field of GRB 080915A (Oates et al. GCN #8227) in g'r'i'z'JHK at 00:07:25 UT on 2008-09-15, 4.6 minutes after the burst and continued for 130 minutes.
The observations were resumed in the following night, starting at 05:18:45 UT and continued for 70 minutes.
We detect 2 sources, one inside the XRT error circle (Evans et al.GCN #8231) at coordinates RA, DEC (J2000) = 01:11:47.83, -76:01:13.7, the other at the edge of the XRT error circle at coordinates RA, DEC (J2000) = 01:11:45.4, -76:01:10.5.
A comparison of the two observing runs does not reveal any evidence for variability. We conclude that most likely none of them is associated with GRB 080915A.
The co-added images from the first run then yield the following upper limits measured at a mid-time of 0.038 days after the trigger and calibrated on the SDSS standard star SA95-190:
```
g' > 23.8
r' > 23.7
i' > 23.5
z' > 23.1
J  > 20.5
H  > 19.3
K  > 18.3
```
GCN Report 168.1
GCN_Report 168.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_168_1.pdf by S.R. Oates at MSSL-UCL titled: "Final Swift report on GRB 080915A"

Back to JG's homepage

Jochen Greiner, last update: 14-Oct-2008 [Disclaimer]