Gamma-ray Burst 120815A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 15 Aug 12 02:14:21 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     531003,   Seg_Num: 0
GRB_RA:          273.955d {+18h 15m 49s} (J2000),
                 274.207d {+18h 16m 50s} (current),
                 272.957d {+18h 11m 50s} (1950)
GRB_DEC:         -52.134d {-52d 08' 02"} (J2000),
                 -52.129d {-52d 07' 44"} (current),
                 -52.151d {-52d 09' 02"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4733 [cnts]    Image_Peak=194 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   140     E_range: 15-50 keV
BKG_INTEN:       30366 [cnts]
BKG_TIME:        8022.46 SOD {02:13:42.46} UT
BKG_DUR:         8 [sec]
GRB_DATE:        16154 TJD;   228 DOY;   12/08/15
GRB_TIME:        8038.78 SOD {02:13:58.78} UT
GRB_PHI:          19.66 [deg]
GRB_THETA:        43.79 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     16.03 [sigma]
IMAGE_SIGNIF:    9.23 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +1  +0  +0  +0 +56  +0 
SUN_POSTN:       145.01d {+09h 40m 03s}  +13.96d {+13d 57' 33"}
SUN_DIST:        124.53 [deg]   Sun_angle= -8.6 [hr] (East of Sun)
MOON_POSTN:      112.68d {+07h 30m 42s}  +17.98d {+17d 58' 45"}
MOON_DIST:       142.89 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      342.04,-15.99 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      272.77,-28.73 [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 = 54.88,-17.12 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 15 Aug 12 02:18:00 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     531003,   Seg_Num: 0
GRB_RA:          273.955d {+18h 15m 49s} (J2000),
                 274.207d {+18h 16m 50s} (current),
                 272.957d {+18h 11m 50s} (1950)
GRB_DEC:         -52.134d {-52d 08' 02"} (J2000),
                 -52.129d {-52d 07' 44"} (current),
                 -52.151d {-52d 09' 02"} (1950)
GRB_DATE:        16154 TJD;   228 DOY;   12/08/15
GRB_TIME:        8038.78 SOD {02:13:58.78} UT
TRIGGER_INDEX:   140
GRB_PHI:          19.66 [deg]
GRB_THETA:        43.79 [deg]
DELTA_TIME:      -31.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     16.03 [sigma]
IMAGE_SIGNIF:    9.23 [sigma]
LC_URL:          sw00531003000msb.lc
SUN_POSTN:       145.02d {+09h 40m 04s}  +13.96d {+13d 57' 30"}
SUN_DIST:        124.53 [deg]   Sun_angle= -8.6 [hr] (East of Sun)
MOON_POSTN:      112.71d {+07h 30m 50s}  +17.97d {+17d 58' 21"}
MOON_DIST:       142.88 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      342.04,-15.99 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      272.77,-28.73 [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 = 54.88,-17.12 [deg].

GCN Circular #13645
C. Pagani (U Leicester), S. D. Barthelmy (GSFC), N. Gehrels (NASA/GSFC), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL) and M. Stamatikos (OSU/NASA/GSFC) report on behalf of the Swift Team:
At 02:13:58 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 120815A (trigger=531003). Swift will execute a delayed slew due to Earth-limb observing constraint. The BAT on-board calculated location is RA, Dec 273.955, -52.134, which is
```
   RA(J2000)  =  18h 15m 49s
   Dec(J2000) = -52d 08' 02"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single pulse with a duration of about 10 sec. The peak count rate was ~1500 counts/sec (15-350 keV), at ~1 sec after the trigger.
Due to an observing constraint, Swift will not slew until T0+40.6 minutes. There will be no XRT or UVOT data until this time.
Burst Advocate for this burst is C. Pagani (cp232 AT star.le.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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 15 Aug 12 02:58:54 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     531003,   Seg_Num: 0
POINT_RA:        273.924d {+18h 15m 42s} (J2000)
POINT_DEC:       -52.130d {-52d 07' 46"} (J2000)
IMG_START_DATE:  16154 TJD;   228 DOY;   12/08/15
IMG_START_TIME:  10725.57 SOD {02:58:45.57} UT,   2686.8 [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:     Wed 15 Aug 12 03:03:12 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     531003,   Seg_Num: 0
POINT_RA:        273.924d {+18h 15m 42s} (J2000)
POINT_DEC:       -52.129d {-52d 07' 44"} (J2000)
POINT_ROLL:      246.214d
IMG_START_DATE:  16154 TJD;   228 DOY;   12/08/15
IMG_START_TIME:  10728.92 SOD {02:58:48.92} UT,   2690.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.039
N_STARS:         190
X_OFFSET:        338 [pixels]
Y_OFFSET:        515 [pixels]
X_MAX:           1297 [pixels]
Y_MAX:           1474 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00531003000msufc2690.fits
SUN_POSTN:       145.05d {+09h 40m 11s}  +13.95d {+13d 56' 55"}
SUN_DIST:        124.49 [deg]   Sun_angle= -8.6 [hr] (East of Sun)
MOON_POSTN:      113.12d {+07h 32m 28s}  +17.89d {+17d 53' 19"}
MOON_DIST:       142.66 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      342.04,-15.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      272.75,-28.73 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 15 Aug 12 03:03:54 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     531003,   Seg_Num: 0
POINT_RA:        273.924d {+18h 15m 42s} (J2000)
POINT_DEC:       -52.129d {-52d 07' 44"} (J2000)
POINT_ROLL:      246.214d
IMG_START_DATE:  16154 TJD;   228 DOY;   12/08/15
IMG_START_TIME:  10728.92 SOD {02:58:48.92} UT,   2690.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.039
N_STARS:         190
X_OFFSET:        338 [pixels]
Y_OFFSET:        515 [pixels]
X_MAX:           1297 [pixels]
Y_MAX:           1474 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00531003000msufc2690.fits
SUN_POSTN:       145.05d {+09h 40m 11s}  +13.95d {+13d 56' 54"}
SUN_DIST:        124.49 [deg]   Sun_angle= -8.6 [hr] (East of Sun)
MOON_POSTN:      113.12d {+07h 32m 30s}  +17.89d {+17d 53' 15"}
MOON_DIST:       142.66 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      342.04,-15.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      272.75,-28.73 [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:     Wed 15 Aug 12 03:04:04 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     531003,   Seg_Num: 0
GRB_RA:          273.9585d {+18h 15m 50.04s} (J2000),
                 274.2103d {+18h 16m 50.47s} (current),
                 272.9605d {+18h 11m 50.52s} (1950)
GRB_DEC:         -52.1297d {-52d 07' 46.9"} (J2000),
                 -52.1247d {-52d 07' 28.9"} (current),
                 -52.1465d {-52d 08' 47.4"} (1950)
GRB_ERROR:       3.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  16154 TJD;   228 DOY;   12/08/15
IMG_START_TIME:  10742.00 SOD {02:59:02.00} UT,   2703.2 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       145.05d {+09h 40m 11s}  +13.95d {+13d 56' 54"}
SUN_DIST:        124.51 [deg]   Sun_angle= -8.6 [hr] (East of Sun)
MOON_POSTN:      113.13d {+07h 32m 30s}  +17.89d {+17d 53' 13"}
MOON_DIST:       142.67 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      342.05,-15.99 [deg] galactic lon,lat of the burst
ECL_COORDS:      272.77,-28.73 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 15 Aug 12 03:04:41 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     531003,   Seg_Num: 0
POINT_RA:        273.924d {+18h 15m 42s} (J2000)
POINT_DEC:       -52.129d {-52d 07' 44"} (J2000)
ROLL:            246.214d
IMG_START_DATE:  16154 TJD;   228 DOY;   12/08/15
IMG_START_TIME:  10728.92 SOD {02:58:48.92} UT,   2690.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     366692338
X_OFFSET:        657 [pixels]
Y_OFFSET:        834 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       817
Y_GRB_POS:       994
BINNING_INDEX:   1
IM_URL:          sw00531003000msuni2700.fits
SUN_POSTN:       145.05d {+09h 40m 11s}  +13.95d {+13d 56' 54"}
SUN_DIST:        124.49 [deg]   Sun_angle= -8.6 [hr] (East of Sun)
MOON_POSTN:      113.13d {+07h 32m 31s}  +17.89d {+17d 53' 09"}
MOON_DIST:       142.66 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      342.04,-15.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      272.75,-28.73 [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:     Wed 15 Aug 12 03:05:00 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     531003,   Seg_Num: 0
POINT_RA:        273.924d {+18h 15m 42s} (J2000)
POINT_DEC:       -52.129d {-52d 07' 44"} (J2000)
ROLL:            246.214d
IMG_START_DATE:  16154 TJD;   228 DOY;   12/08/15
IMG_START_TIME:  10728.92 SOD {02:58:48.92} UT,   2690.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     366692338
X_OFFSET:        657 [pixels]
Y_OFFSET:        834 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       817
Y_GRB_POS:       994
BINNING_INDEX:   1
IM_URL:          sw00531003000msuni2700.fits
SUN_POSTN:       145.05d {+09h 40m 11s}  +13.95d {+13d 56' 53"}
SUN_DIST:        124.49 [deg]   Sun_angle= -8.6 [hr] (East of Sun)
MOON_POSTN:      113.13d {+07h 32m 32s}  +17.89d {+17d 53' 07"}
MOON_DIST:       142.66 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      342.04,-15.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      272.75,-28.73 [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:        All 4 attachments are included.

GCN Circular #13646
Klotz A. (IRAP-CNRS-OMP), Gendre B. (ASDC/INAF-OAR), Boer M. (UNS-CNRS-OCA), Atteia J.L. (IRAP-CNRS-OMP) report:
We imaged the field of GRB 120815A detected by SWIFT (trigger 531003) with the TAROT robotic telescope (D=25cm) located at the European Southern Observatory, La Silla observatory, Chile.
The observations started 34.7s after the GRB trigger (15.4s after the notice). The elevation of the field decreased from 65 degrees above horizon and weather conditions were good.
The first image is trailed with a duration of 60.0s (see the description in Klotz et al., 2006, A&A 451, L39). We do not detect any OT with a limiting magnitude of: t0+34.7s to t0+94.7s : R > 16.3
The second image is 30.0s exposure in tracking mode: t0+108.0s to t0+138.0s : R > 18.4
We co-added a series of exposures from t0+108s to t0+1605s. Due to the annouced slew delay announced by Pagani et al. (GCNC 13645), we analyze the BAT error box. We compared the co-added TAROT images with the NOMAD1 catalog sources. Three non catalogued sources could be an optical counterpart candidate:
```
ID ra(J2000)    dec(J2000)  Rmag
T1 18:15:57.33 -52:07:35.6  18.5
T2 18:15:58.58 -52:07:27.5  19.0
T3 18:15:35.22 -52:05:21.4  18.3
```
These sources does not appear in the R filtered DSS image. The sources does not show any significant brightness variation durong 20 min. but they are close to the limiting magnitude in the individual images. Few other fainter sources are also present in the TAROT image.
More informations can be found at the following URL:
http://cador.obs-hp.fr/grb120815a
Magnitudes are not corrected for galactic dust extinction.
N.B. Galactic coordinates are lon=342.0422 lat=-15.9869 and the galactic extinction in R band is about 0.3 magnitudes estimated from D. Schlegel et al. 1998ApJ...500..525S.
This message may be cited.
GCN Circular #13647
J.A. Kennea (PSU), G. Cusumano (INAF-IASF PA), M. Perri (ASDC), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester) and D.N. Burrows (PSU) report on behalf of the Swift-XRT team:
The XRT began observing the field of GRB 120815A at 02:58:45.5 UT, 2686.8 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 273.95896, -52.12978 which is equivalent to:
```
   RA(J2000)  = 18h 15m 50.15s
   Dec(J2000) = -52d 07' 47.2"
```
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This location is 17 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (8.55 x 10^20 cm^-2, Kalberla et al. 2005), with an excess column of 1.6 (+1.61/-1.45) x 10^21 cm^-2 (90% confidence).
GCN Circular #13648
V. Sudilovsky (MPE Garching), D. A. Kann (TLS Tautenburg) and J. Greiner (MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 120815A (Swift trigger 531003; Pagani et al., GCN 13645) simultaneously in g'r'i'z'JHKs with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla Observatory (Chile). Observations started 150 seconds after the BAT trigger, and were obtained at airmass 1.1 and a mean seeing of 1".3.
Based on exposures of 142 seconds in g'r'i'z' and 240 seconds in JHK centered 348 seconds after the trigger, we detect an uncataloged source in all bands at
```
RA (J2000): 18:15:49.82
DEC (J2000): -52:07:52.1
```
with an uncertainty of 0.3".
This position is close to the Swift XRT position (J. A. Kennea et al., GCN 13647).
We measure a preliminary magnitude:
i' ~ 17.6
The magnitudes are derived based on GROND zeropoints (g'r'i'z') and 2MASS stars (JHK).
GCN Circular #13649
D. Malesani (DARK/NBI), S. Schulze (PUC and MCSS), A. de Ugarte Postigo (IAA/CSIC and DARK/NBI), D. Xu (WIS), V. D'Elia (INAF/Roma and ASI/ASDC), J. P. U. Fynbo (DARK/NBI), N. R. Tanvir (Univ. Leicester), report on behalf of a larger collaboration:
We observed the field of GRB 120815A (Pagani et al., GCN 13645) with the VLT/X-shooter spectrograph. We confirm the presence of a bright, uncatalogued object consisent with the GROND position (Sudilovsky et al., GCN 13648). From the acquisition images, we measure R = 18.9 for the afterglow at an epoch of 1.67 hr after the GRB (calibrated to nearby USNO stars).
Our spectra cover the wavelength range 3000-25000 AA, and were taken starting on 2012 Aug 15.163 UT (1.69 hr after the GRB), for a total of 40 min exposure. Continuum from the afterglow is detected with high S/N in all of the UVB, VIS, and NIR arms.
The spectrum shows a wide trough and a multitude of strong absorption lines, which we interpret as due to a DLA and metal transitions of N V, S II, Si II, O I, C IV, Si IV, Fe II, Al II, Al III, Mn II, Mg II, Mg I, among others, at a common redshift z = 2.358. At the same redshift, we also detect fine-structure lines of Ni II and Fe II, thus confirming conclusively that this is the GRB redshift. We also detect intervening systems at z = 1.539, 1.693, and 2.00. In particular, the system at z = 1.539 displays exceptionally strong Mg II, Mg I, and Fe II absorption.
We acknowledge the expert support of the VLT observing staff at Paranal, in particular Maja Vuckovic. We also thank Alex Kann for discussion on the afterglow identification.
GCN Circular #13650
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 1694 s of XRT Photon Counting mode data and 6 UVOT images for GRB 120815A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 273.95807, -52.13142 which is equivalent to:
```
RA (J2000): 18h 15m 49.94s
Dec (J2000): -52d 07' 53.1"
```
with an uncertainty of 1.6 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN Circular #13652
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. Pagani (U Leicester), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (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 120815A (trigger #531003) (Pagani, et al., GCN Circ. 13645). The BAT ground-calculated position is RA, Dec = 273.976, -52.125 deg, which is
```
   RA(J2000)  =  18h 15m 54.4s 
   Dec(J2000) = -52d 07' 29.0" 
```
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 28%.
The mask-weighted light curve shows a FRED pulse starting at ~T-0.3 sec, peaking at ~T+0.5 sec, and ending at ~T+30 sec. T90 (15-350 keV) is 9.7 +- 2.5 sec (estimated error including systematics).
The time-averaged spectrum from T-0.24 to T+11.97 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.29 +- 0.23. The fluence in the 15-150 keV band is 4.9 +- 0.7 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.17 sec in the 15-150 keV band is 2.2 +- 0.3 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/531003/BA/
GCN Circular #13653
C. Pagani (U Leicester) reports on behalf of the Swift-XRT team:
We have analysed 8.5 ks of XRT data for GRB 120815A (Pagani et al. GCN Circ. 13645), from 2.7 ks to 39.5 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN. Circ 13650).
The light curve can be modelled with a power-law decay with a decay index of alpha=0.89 (+/-0.07).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.85 (+0.12, -0.11). The best-fitting absorption column is 5.5 (+4.2, -3.8) x 10^21 cm^-2, at a redshift of 2.358, in addition to the Galactic value of 8.6 x 10^20 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.0 x 10^-11 (5.0 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Galactic foreground: 8.6 x 10^20 cm^-2
Intrinsic column:    5.5 (+4.2, -3.8) x 10^21 cm^-2 at z=2.358
Photon index:	     1.85 (+0.12, -0.11)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00531003.
This circular is an official product of the Swift-XRT team.
GCN Circular #13666
S. T. Holland (STScI) and C. Pagani (U Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT observed the field of GRB 120815A starting 2672 s after the BAT trigger (Pagani et al., 2012, GCNC 13645). Settled observations started at 2690 s. We detect an uncatalogued source inside the UVOT-enhanced XRT error circle (Goad et al., 2012, GCNC 13650) with preliminary coordinates
```
   RA (J2000.0)  18:15:49.88  =  273.95783 (deg)
  Dec (J2000.0) -52:07:52.1   =  -52.13114 (deg)
```
and an estimated uncertainty of 0.6 arcsec (radius, 90% confidence, statistical + systematic). The UVOT detection is consistent with the optical afterglow reported by Sudilovsky et al. (2012, GCNC 13648) Source magnitudes and 3-sigma upper limits at this location are given below. The afterglow is 4.27 arcsec northeast of the USNO-B1.0 source 0378-0977505, so the following photometry should be considered preliminary.
```
Filter       TSTART   TSTOP   Exp Time       Mag  Err  Sigma
------------------------------------------------------------
    v         2847     3046        100     19.34 0.29    3.9
    b         3667     4120        226     20.11 0.24    4.7
    u         3462     3661        100    >20.5
 uvw1         3257     3457        100    >20.2
 uvm2         3052     3252        100    >19.9
 uvw2         4330     4530        100    >20.3
white         2690     2840         75     19.94 0.19    5.8
------------------------------------------------------------
```
The quoted magnitudes and upper limits have not been corrected for the Galactic extinction along the line of sight to this burst of E_{B-V} = 0.10 mag (Schlafly et al. 2011, ApJS, 737, 103).
GCN Circular #13677
H. Levato and C. Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)
C. Mallamaci, C. Lopez and F. Podest Observatorio Astronomico Felix Aguilar (OAFA)
E. Gorbovskoy, V. Lipunov, V. Kornilov, D. Denisenko, A. Kuznetsov, D. Kuvshinov, A. Belinski, N. Tyurina, N. Shatskiy, P. Balanutsa, D. Zimnukhov, V.V. Chazov Lomonosov Moscow State University, Sternberg Astronomical Institute
A. Tlatov, A.V. Parhomenko, D. Dormidontov, V. Sennik Kislovodsk Solar Station of the Pulkovo Observatory
K. Ivanov, S. Yazev, N.M. Budnev, O. Gres, O. Chuvalaev, V.A. Poleshchuk Irkutsk State University
V. Yurkov, Yu. Sergienko, D. Varda, E. Sinyakov Blagoveschensk Educational State University, Blagoveschensk
V. Krushinski, I. Zalozhnich, A. Popov, A. Bourdanov, A. Punanova Ural Federal University
MASTER-ICATE robotic very wide field cameras (FOV=2x384 square degrees, D=72mm, f/1.2, 1 pix = 22 arcsec, http://observ.pereplet.ru) located in Argentina (Observatorio Astronomico Felix Aguilar, http://93.180.27.230:8080/) were pointed to the GRB120815A (C. Pagani, GCN 13645) 37 s after notice time and 60 s after GRB time at 2012-08-15 02:13:58 UT. We haven`t found optical transient within SWIFT error-box our first (5 s exposure) set. The 5-sigma upper limit has been about 12.0 mag The 5-sigma upper limit on coadd first 30 images is about 13.0 mag.
Our cameras are continuously imaging the sky with 5 sec exposures.
This message can be cited.
GCN Report 387.1
GCN_Report 387.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_387_1.pdf by C. Pagani at PSU titled: "Swift Observations of GRB 120815A"
1304.7003 from 29 Apr 13
T. Kr�hler et al.: Molecular Hydrogen in the Damped Lyman-alpha System towards GRB 120815A at z=2.36
[Abridged] Molecular hydrogen H_2 is a key requirement for star-formation, frequently observed along sightlines in the Galaxy and to the Magellanic Clouds, but notoriously hard to detect directly beyond z ~ 0. In the DLAs associated with long gamma-ray bursts (GRBs), which are tightly linked to vigorous star-formation, H_2 has remained largely elusive, and has been unequivocally detected only towards GRB 080607 and possibly towards GRB 060206. Here, we present the discovery of H_2-rich gas, including the presence of vibrationally-excited H_2^* in the optical spectrum of the afterglow of GRB 120815A at z=2.36 obtained with X-shooter at the VLT. The galactic environment of GRB 120815A is characterized by a strong DLA with log(N(H)/cm^-2) = 21.95 +/- 0.10, prominent H_2 absorption in the Lyman-Werner bands (log(N(H_2)/cm^-2) = 20.53 +/- 0.04) and thus a molecular gas fraction log f(H_2)=-1.14 +/- 0.10. The distance d between the absorbing neutral gas and GRB 120815A is constrained via photo-excitation modeling of fine-structure and meta-stable transitions of FeII and NiII to d = 0.5 +/- 0.1 kpc. The DLA metallicity ([Zn/H] = -1.15 +/- 0.11), visual extinction (A_V < 0.15 mag) and dust depletion ([Zn/Fe] = 1.01 +/- 0.09) are intermediate between the values of well-studied, H_2-deficient GRB-DLAs observed at high spectral resolution, and the approximately solar metallicity, highly-obscured and H_2-rich GRB 080607 sightline. With respect to N(H), metallicity, as well as dust-extinction and depletion, GRB 120815A is fairly representative of the average properties of GRB-DLAs. This demonstrates that molecular hydrogen is present in at least a fraction of the more typical GRB-DLAs, and H_2 and H_2^* are probably more wide-spread among GRB-selected systems than the few examples of previous detections would suggest.

Back to JG's homepage

Jochen Greiner, last update: 29-Apr-2013 [Disclaimer]