Gamma-ray Burst 120805A

(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 05 Aug 12 21:29:12 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     530031,   Seg_Num: 0
GRB_RA:          216.533d {+14h 26m 08s} (J2000),
                 216.690d {+14h 26m 46s} (current),
                 215.910d {+14h 23m 38s} (1950)
GRB_DEC:          +5.802d {+05d 48' 08"} (J2000),
                  +5.746d {+05d 44' 46"} (current),
                  +6.027d {+06d 01' 37"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       35896 [cnts]    Image_Peak=438 [image_cnts]
TRIGGER_DUR:     8.192 [sec] 
TRIGGER_INDEX:   336     E_range: 25-100 keV
BKG_INTEN:       266154 [cnts]
BKG_TIME:        77198.49 SOD {21:26:38.49} UT
BKG_DUR:         64 [sec]
GRB_DATE:        16144 TJD;   218 DOY;   12/08/05
GRB_TIME:        77289.88 SOD {21:28:09.88} UT
GRB_PHI:         -46.55 [deg]
GRB_THETA:        38.41 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     8.18 [sigma]
IMAGE_SIGNIF:    8.44 [sigma]
MERIT_PARAMS:     +1  +0  +0  +3  +2  -1  +0  +0 -19  +0 
SUN_POSTN:       136.31d {+09h 05m 14s}  +16.67d {+16d 40' 18"}
SUN_DIST:         79.17 [deg]   Sun_angle= -5.4 [hr] (East of Sun)
MOON_POSTN:      358.52d {+23h 54m 06s}   +4.17d {+04d 10' 21"}
MOON_DIST:       140.62 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:      353.76, 58.98 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      212.19, 19.17 [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 = 263.02,-18.00 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 05 Aug 12 21:30:20 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     530031,   Seg_Num: 0
POINT_RA:        216.538d {+14h 26m 09s} (J2000)
POINT_DEC:        +5.795d {+05d 47' 44"} (J2000)
IMG_START_DATE:  16144 TJD;   218 DOY;   12/08/05
IMG_START_TIME:  77413.01 SOD {21:30:13.01} UT,   123.1 [sec] since BAT Trigger Time
COUNTS:          11    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        1    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:     Sun 05 Aug 12 21:32:39 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     530031,   Seg_Num: 0
POINT_RA:        216.537d {+14h 26m 09s} (J2000)
POINT_DEC:        +5.795d {+05d 47' 44"} (J2000)
POINT_ROLL:      285.908d
IMG_START_DATE:  16144 TJD;   218 DOY;   12/08/05
IMG_START_TIME:  77416.56 SOD {21:30:16.56} UT,   126.7 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.799
N_STARS:         35
X_OFFSET:        552 [pixels]
Y_OFFSET:        563 [pixels]
X_MAX:           1511 [pixels]
Y_MAX:           1522 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    6
SL_URL:          sw00530031000msufc0126.fits
SUN_POSTN:       136.31d {+09h 05m 14s}  +16.67d {+16d 40' 15"}
SUN_DIST:         79.17 [deg]   Sun_angle= -5.4 [hr] (East of Sun)
MOON_POSTN:      358.55d {+23h 54m 13s}   +4.18d {+04d 11' 00"}
MOON_DIST:       140.64 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:      353.75, 58.98 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      212.19, 19.16 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 05 Aug 12 21:33:10 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     530031,   Seg_Num: 0
POINT_RA:        216.537d {+14h 26m 09s} (J2000)
POINT_DEC:        +5.795d {+05d 47' 44"} (J2000)
POINT_ROLL:      285.908d
IMG_START_DATE:  16144 TJD;   218 DOY;   12/08/05
IMG_START_TIME:  77416.56 SOD {21:30:16.56} UT,   126.7 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.799
N_STARS:         35
X_OFFSET:        552 [pixels]
Y_OFFSET:        563 [pixels]
X_MAX:           1511 [pixels]
Y_MAX:           1522 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    6
SL_URL:          sw00530031000msufc0126.fits
SUN_POSTN:       136.31d {+09h 05m 14s}  +16.67d {+16d 40' 15"}
SUN_DIST:         79.17 [deg]   Sun_angle= -5.4 [hr] (East of Sun)
MOON_POSTN:      358.56d {+23h 54m 14s}   +4.19d {+04d 11' 06"}
MOON_DIST:       140.64 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:      353.75, 58.98 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      212.19, 19.16 [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:     Sun 05 Aug 12 21:33:58 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     530031,   Seg_Num: 0
POINT_RA:        216.537d {+14h 26m 09s} (J2000)
POINT_DEC:        +5.795d {+05d 47' 44"} (J2000)
ROLL:            285.908d
IMG_START_DATE:  16144 TJD;   218 DOY;   12/08/05
IMG_START_TIME:  77416.56 SOD {21:30:16.56} UT,   126.7 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     365895026
X_OFFSET:        871 [pixels]
Y_OFFSET:        882 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1031
Y_GRB_POS:       1042
BINNING_INDEX:   1
IM_URL:          sw00530031000msuni0136.fits
SUN_POSTN:       136.31d {+09h 05m 14s}  +16.67d {+16d 40' 14"}
SUN_DIST:         79.17 [deg]   Sun_angle= -5.4 [hr] (East of Sun)
MOON_POSTN:      358.56d {+23h 54m 15s}   +4.19d {+04d 11' 15"}
MOON_DIST:       140.65 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:      353.75, 58.98 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      212.19, 19.16 [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:     Sun 05 Aug 12 21:34:14 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     530031,   Seg_Num: 0
POINT_RA:        216.537d {+14h 26m 09s} (J2000)
POINT_DEC:        +5.795d {+05d 47' 44"} (J2000)
ROLL:            285.908d
IMG_START_DATE:  16144 TJD;   218 DOY;   12/08/05
IMG_START_TIME:  77416.56 SOD {21:30:16.56} UT,   126.7 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     365895026
X_OFFSET:        871 [pixels]
Y_OFFSET:        882 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1031
Y_GRB_POS:       1042
BINNING_INDEX:   1
IM_URL:          sw00530031000msuni0136.fits
SUN_POSTN:       136.31d {+09h 05m 14s}  +16.67d {+16d 40' 14"}
SUN_DIST:         79.17 [deg]   Sun_angle= -5.4 [hr] (East of Sun)
MOON_POSTN:      358.57d {+23h 54m 16s}   +4.19d {+04d 11' 18"}
MOON_DIST:       140.65 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:      353.75, 58.98 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      212.19, 19.16 [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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 05 Aug 12 21:34:05 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     530031,   Seg_Num: 0
GRB_RA:          216.533d {+14h 26m 08s} (J2000),
                 216.690d {+14h 26m 46s} (current),
                 215.910d {+14h 23m 38s} (1950)
GRB_DEC:          +5.802d {+05d 48' 08"} (J2000),
                  +5.746d {+05d 44' 46"} (current),
                  +6.027d {+06d 01' 37"} (1950)
GRB_DATE:        16144 TJD;   218 DOY;   12/08/05
GRB_TIME:        77289.88 SOD {21:28:09.88} UT
TRIGGER_INDEX:   336
GRB_PHI:         -46.55 [deg]
GRB_THETA:        38.41 [deg]
DELTA_TIME:      -18.00 [sec]
TRIGGER_DUR:     8.192 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     8.18 [sigma]
IMAGE_SIGNIF:    8.44 [sigma]
LC_URL:          sw00530031000msb.lc
SUN_POSTN:       136.31d {+09h 05m 14s}  +16.67d {+16d 40' 14"}
SUN_DIST:         79.16 [deg]   Sun_angle= -5.4 [hr] (East of Sun)
MOON_POSTN:      358.56d {+23h 54m 15s}   +4.19d {+04d 11' 17"}
MOON_DIST:       140.65 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:      353.76, 58.98 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      212.19, 19.17 [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 = 263.02,-18.00 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 05 Aug 12 21:54:04 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     530031,   Seg_Num: 0
GRB_RA:          216.5405d {+14h 26m 09.72s} (J2000),
                 216.6976d {+14h 26m 47.43s} (current),
                 215.9171d {+14h 23m 40.10s} (1950)
GRB_DEC:          +5.8257d {+05d 49' 32.5"} (J2000),
                  +5.7694d {+05d 46' 09.9"} (current),
                  +6.0503d {+06d 03' 01.0"} (1950)
GRB_ERROR:       4.3 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  16144 TJD;   218 DOY;   12/08/05
IMG_START_TIME:  78488.00 SOD {21:48:08.00} UT,   1198.1 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       136.32d {+09h 05m 18s}  +16.67d {+16d 40' 00"}
SUN_DIST:         79.15 [deg]   Sun_angle= -5.4 [hr] (East of Sun)
MOON_POSTN:      358.73d {+23h 54m 55s}   +4.25d {+04d 15' 05"}
MOON_DIST:       140.78 [deg]
MOON_ILLUM:      84 [%]
GAL_COORDS:      353.80, 58.99 [deg] galactic lon,lat of the burst
ECL_COORDS:      212.19, 19.19 [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 1.1% < P(seren) < 2.8%.

GCN Circular #13588
E. Troja (NASA/GSFC/ORAU), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), N. Gehrels (NASA/GSFC), C. Gronwall (PSU), S. T. Holland (STScI), J. A. Kennea (PSU), O. M. Littlejohns (U Leicester), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Swift Team:
At 21:28:09 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 120805A (trigger=530031). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 216.533, +5.802 which is
```
   RA(J2000) = 14h 26m 08s
   Dec(J2000) = +05d 48' 08"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 50 sec. The peak count rate was ~500 counts/sec (15-350 keV), at ~2 sec after the trigger.
The XRT began observing the field at 21:30:13.0 UT, 123.1 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 216.54056, 5.82571 which is equivalent to:
```
   RA(J2000)  = 14h 26m 09.73s
   Dec(J2000) = +05d 49' 32.6"
```
with an uncertainty of 4.3 arcseconds (radius, 90% containment). This location is 89 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. We cannot determine whether the source is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 2.22 x 10^20 cm^-2 (Kalberla et al. 2005).
UVOT took a finding chart exposure of 90 seconds with the White filter starting 126 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.03.
Burst Advocate for this burst is E. Troja (eleonora.troja AT nasa.gov). 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 #13589
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 120805A detected by SWIFT (trigger 530031) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France.
The observations started 77.2s after the GRB trigger (19.3s after the notice). The elevation of the field decreased from 20 degrees above horizon and weather conditions were moonlight.
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 in the BAT error box with a limiting magnitude of: t0+77.2s to t0+137.2s : R > 15.9
The second image is 30.0s exposure in tracking mode: t0+152.6s to t0+182.6s : R > 16.2
We co-added a series of exposures: t0+152.6s to t0+851s : R > 17.4
Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction.
N.B. Galactic coordinates are lon=353.7578 lat=+58.9832 and the galactic extinction in R band is about 0.1 magnitude estimated from D. Schlegel et al. 1998ApJ...500..525S.
This message may be cited.
GCN Circular #13590
David Bersier (LJMU), Drejc Kopac (Ljubljana) report
The Liverpool Telescope (La Palma) started robotic observations of GRB 120805A 3 minutes after detection by Swift (Troja et al, GCN 13588). We find no credible afterglow candidate in the XRT error circle. We find upper limits of 18.9 in the r band 30 minutes after burst and 18.7 in the i band 47 minutes after burst.
GCN Circular #13591
J. Gorosabel (IAA-CSIC), N. Huelamo (CAB-CSIC), R. Sanchez-Ramirez (IAA-CSIC), A. de Ugarte Postigo (IAA-CSIC, DARK), T. Kruehler (DARK), A.J. Castro-Tirado (IAA-CSIC), J.C. Tello (IAA-CSIC), M. Jelinek (IAA-CSIC), report on behalf of a larger collaboration:
"I-band observations conducted with the Calar Alto 1.23m telescope at 21:41:19.1--22:04:02.4 UT (obs started ~13 minutes post GRB) for GRB 120805A reveal no object inside the XRT position (GCN Circ. 13588) down to I~18 (Vega). However, we note the presence an object located at RA(J2000)=14:26:09.12, DEC(J2000)=05:49:31.7 (error of ~0.5" in both coordinates) with a magnitude of I~17.5 which seems not to be at the SDSS. Given the lack of a refined XRT position yet, we are cautious about the possible relation of this object with the GRB 120805A optical afterglow."
GCN Circular #13592
D.N. Burrows (PSU), C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), B. Sbarufatti (INAF-OAB/PSU), G. Stratta (ASDC), P. D'Avanzo (INAF-OAB), J.A. Kennea (PSU), M.C. Stroh (PSU) and E. Troja report on behalf of the Swift-XRT team:
We have analysed 6.1 ks of XRT data for GRB 120805A (Troja et al. GCN Circ. 13588), from 126 s to 13.6 ks after the BAT trigger. The data comprise 115 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The refined XRT position is RA, Dec = 216.5411, +5.82554 which is equivalent to:
```
RA (J2000): 14 26 09.86
Dec(J2000): +05 49 31.9
```
with an uncertainty of 3.6 arcsec (radius, 90% confidence).
The light curve can be modelled with a series of power-law decays. The light curve initially rises, with an index alpha=-1.497 (+0.951, -0.003). At T+191 s it breaks to an alpha of 2.33 (+0.14, -0.12) before breaking again at T+2805 s to a final decay with index alpha=0.3 (+/-0.7).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.43 (+0.22, -0.20). The best-fitting absorption column is 2.1 (+0.9, -0.8) x 10^21 cm^-2, in excess of the Galactic value of 2.2 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 5.1 x 10^-11 (6.0 x 10^-11) erg cm^-2 count^-1.
A summary of the WT-mode spectrum is thus:
```
Total column:	     2.1 (+0.9, -0.8) x 10^21 cm^-2
Galactic foreground: 2.2 x 10^20 cm^-2
Excess significance: 3.7 sigma
Photon index:	     1.43 (+0.22, -0.20)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00530031.
This circular is an official product of the Swift-XRT team.
GCN Circular #13594
S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (OSU), E. Troja (NASA/GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+330 sec from the recent telemetry downlink, we report further analysis of BAT GRB 120805A (trigger #530031) (Troja, et al., GCN Circ. 13588). The BAT ground-calculated position is RA, Dec = 216.536, 5.853 deg, which is
```
   RA(J2000)  =  14h 26m 08.5s 
   Dec(J2000) = +05d 51' 09.7" 
```
with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 37%.
The mask-weighted light curve shows several overlapping peaks starting at ~T-8 sec, peaking at ~T+8 sec, and returning to baseline around T+110 sec. T90 (15-350 keV) is 48.00 +- 22.63 sec (estimated error including systematics).
The time-averaged spectrum from T-15.39 to T+32.61 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.20 +- 0.28. The fluence in the 15-150 keV band is 8.2 +- 1.4 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+8.11 sec in the 15-150 keV band is 0.37 +- 0.2 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/530031/BA/
GCN Circular #13598
C. A. Swenson (PSU) and E. Troja (NASA/GSFC/ORAU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 120805A 127 s after the BAT trigger (Troja et al., GCN Circ. 13588). No optical afterglow consistent with the refined XRT position (Burrows et al., GCN Circ. 13592) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white              127         7557          579         >22.0
v                 1339        11924         1248         >20.8
b                 1265         7352          490         >21.5
u                 1240         7146          490         >20.5
w1                1216        13611         1253         >21.3
m2                1364        12829         1141         >21.6
w2                1487         7763          432         >21.6
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #13638
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
We have reinvestigated the XRT position of GRB 120805A. Using 2.6 ks of XRT Photon Counting mode data and 2 UVOT images, 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 = 216.53836, 5.82525 which is equivalent to:
```
RA (J2000):  14 26 09.21
Dec (J2000): +05 49 30.9
```
with an uncertainty of 2.7 arcsec (radius, 90% confidence). This position is 10" from the unenhanced XRT position reported in GCN Circ. 13592. The size of the astrometric correction, which is responsible for this shift, was such that the enhanced position was initially rejected and not circulated automatically. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This corrected position is our best XRT position, and is 1.5 arcsec from the optical counterpart proposed in GCN Circ. 13591, supporting the identification of that source as the afterglow. We thank Daniele Malesani for drawing this to our attention.
This circular is an official product of the Swift-XRT team.
GCN Circular #13639
D. Malesani, T. Kruehler (DARK/NBI), A. de Ugarte Postigo (IAA/CSIC and DARK/NBI), D. Xu (WIS), N. R. Tanvir (Univ. Leicester), J. Gorosabel (IAA/CSIC), P. Jakobsson (Univ. Iceland), S. Geier (NOT and DARK/NBI), T. Pursimo (NOT), report on behalf of a larger collaboration.
We observed the field of GRB 120805A (Troja et al., GCN 13588) on two epochs with the NOT optical telescope, located in La Palma (Canary Islands). The two observations were carried out on mean dates Aug 5.936 and 13.896 UT, that is 1.0 hr and 8.0 days after the GRB, respectively.
The source first noticed by Gorosabel et al. (GCN 13591) is detected in both our images, and it varied significantly between the two epochs, as well as compared to the CAHA report (Gorosabel et al., GCN 13591). We note that the object position is now fully consistent with the revised XRT error circle (Evans, GCN 13638). We thus conclude that this source is the optical afterglow of GRB 120805A.
The source varied by only about 2 mag between the two NOT epochs (corresponding to a power-law decay slope of ~0.3), suggesting that in the later image the host galaxy could be contributing to the total light.
A picture showing the two NOT epochs is posted at this URL:
http://www.astro.ku.dk/~malesani/GRB/120805A/GRB120805A_comparison.jpg
We thank Phil Evans for discussion about the XRT localization of this afterglow.
GCN Circular #13651
C. Guidorzi (U. Ferrara) and C.G. Mundell (LJMU) report on behalf of a large collaboration:
The Liverpool Telescope automatically observed GRB 120805A (Troja et al. GCN Circ. 13588) as previously reported (Bersier et al GCN Circ. 13590). We also detected the optical candidate identified by Gorosabel et al. (GCN Circ. 13591) at the following position, within the UVOT-enhanced XRT error circle (Evans et al. GCN Circ. 13638):
```
RA(J2000) =  14:26:09.11
Dec(J2000)=  +05:49:32.1
```
with an uncertainty of 1". The optical afterglow candidate is detected in both r' and i' filters with the following magnitudes:
```
Mid time from  Total Exp   Filter    Magnitude
trigger (min)   (s)
------------------------------------------------
16.0            6x10        r'       20.9 +- 0.3
50.0           3x120        i'       20.9 +- 0.2
------------------------------------------------
```
Magnitudes are calibrated against nearby USNOB-1 stars.
1503.05323 from 18 Mar 15
cites Kruehler et al. (2015; subm.) with photometric redshift of 3.1
arXiv:1505.06743 X-shooter Ly-alpha break redshift: 3.1+-0.1

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Jochen Greiner, last update: 25-Jun-2015 [Disclaimer]