Gamma-ray Burst 090727

(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 27 Jul 09 22:42:51 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     358520,   Seg_Num: 0
GRB_RA:          315.972d {+21h 03m 53s} (J2000),
                 316.016d {+21h 04m 04s} (current),
                 315.744d {+21h 02m 59s} (1950)
GRB_DEC:         +64.916d {+64d 54' 58"} (J2000),
                 +64.954d {+64d 57' 16"} (current),
                 +64.716d {+64d 42' 58"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       8409 [cnts]    Image_Peak=272 [image_cnts]
TRIGGER_DUR:     2.048 [sec] 
TRIGGER_INDEX:   473     E_range: 25-100 keV
BKG_INTEN:       88372 [cnts]
BKG_TIME:        81707.05 SOD {22:41:47.05} UT
BKG_DUR:         24 [sec]
GRB_DATE:        15039 TJD;   208 DOY;   09/07/27
GRB_TIME:        81738.02 SOD {22:42:18.02} UT
GRB_PHI:         147.05 [deg]
GRB_THETA:        21.07 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     7.48 [sigma]
IMAGE_SIGNIF:    8.11 [sigma]
MERIT_PARAMS:     +1  +0  +0  +1  +2  -2  +0  +0 +10  +0 
SUN_POSTN:       127.37d {+08h 29m 28s}  +19.01d {+19d 00' 42"}
SUN_DIST:         95.77 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      199.76d {+13h 19m 02s}  -14.02d {-14d 00' 56"}
MOON_DIST:       113.65 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      101.65, 11.94 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       16.44, 71.47 [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 = 118.07,17.23 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 27 Jul 09 22:43:56 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     358520,   Seg_Num: 0
POINT_RA:        315.975d {+21h 03m 54s} (J2000)
POINT_DEC:       +64.924d {+64d 55' 27"} (J2000)
IMG_START_DATE:  15039 TJD;   208 DOY;   09/07/27
IMG_START_TIME:  81825.97 SOD {22:43:45.97} UT,   87.9 [sec] since BAT Trigger Time
COUNTS:          6    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:     Mon 27 Jul 09 22:45:44 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     358520,   Seg_Num: 0
GRB_RA:          315.972d {+21h 03m 53s} (J2000),
                 316.016d {+21h 04m 04s} (current),
                 315.744d {+21h 02m 59s} (1950)
GRB_DEC:         +64.916d {+64d 54' 58"} (J2000),
                 +64.954d {+64d 57' 16"} (current),
                 +64.716d {+64d 42' 58"} (1950)
GRB_DATE:        15039 TJD;   208 DOY;   09/07/27
GRB_TIME:        81738.02 SOD {22:42:18.02} UT
TRIGGER_INDEX:   473
GRB_PHI:         147.05 [deg]
GRB_THETA:        21.07 [deg]
DELTA_TIME:      -56.00 [sec]
TRIGGER_DUR:     2.048 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     7.48 [sigma]
IMAGE_SIGNIF:    8.11 [sigma]
LC_URL:          sw00358520000msb.lc
SUN_POSTN:       127.37d {+08h 29m 28s}  +19.01d {+19d 00' 40"}
SUN_DIST:         95.77 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      199.78d {+13h 19m 08s}  -14.03d {-14d 01' 33"}
MOON_DIST:       113.65 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      101.65, 11.94 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       16.44, 71.47 [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 = 118.07,17.23 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 27 Jul 09 22:47:33 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     358520,   Seg_Num: 0
GRB_RA:          315.9613d {+21h 03m 50.71s} (J2000),
                 316.0047d {+21h 04m 01.13s} (current),
                 315.7334d {+21h 02m 56.00s} (1950)
GRB_DEC:         +64.9243d {+64d 55' 27.4"} (J2000),
                 +64.9626d {+64d 57' 45.4"} (current),
                 +64.7245d {+64d 43' 28.3"} (1950)
GRB_ERROR:       4.0 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  15039 TJD;   208 DOY;   09/07/27
IMG_START_TIME:  81842.00 SOD {22:44:02.00} UT,   104.0 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       127.37d {+08h 29m 28s}  +19.01d {+19d 00' 39"}
SUN_DIST:         95.77 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      199.80d {+13h 19m 12s}  -14.03d {-14d 01' 56"}
MOON_DIST:       113.64 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      101.65, 11.95 [deg] galactic lon,lat of the burst
ECL_COORDS:       16.45, 71.48 [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.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 27 Jul 09 22:48:00 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     358520,   Seg_Num: 0
POINT_RA:        315.974d {+21h 03m 54s} (J2000)
POINT_DEC:       +64.924d {+64d 55' 27"} (J2000)
POINT_ROLL:      8.176d
IMG_START_DATE:  15039 TJD;   208 DOY;   09/07/27
IMG_START_TIME:  81829.67 SOD {22:43:49.67} UT,   91.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.331
N_STARS:         113
X_OFFSET:        410 [pixels]
Y_OFFSET:        575 [pixels]
X_MAX:           1369 [pixels]
Y_MAX:           1534 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00358520000msufc0091.fits
SUN_POSTN:       127.37d {+08h 29m 29s}  +19.01d {+19d 00' 39"}
SUN_DIST:         95.76 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      199.80d {+13h 19m 13s}  -14.03d {-14d 02' 02"}
MOON_DIST:       113.65 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      101.66, 11.94 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       16.46, 71.47 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 27 Jul 09 22:48:27 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     358520,   Seg_Num: 0
POINT_RA:        315.974d {+21h 03m 54s} (J2000)
POINT_DEC:       +64.924d {+64d 55' 27"} (J2000)
POINT_ROLL:      8.176d
IMG_START_DATE:  15039 TJD;   208 DOY;   09/07/27
IMG_START_TIME:  81829.67 SOD {22:43:49.67} UT,   91.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.331
N_STARS:         113
X_OFFSET:        410 [pixels]
Y_OFFSET:        575 [pixels]
X_MAX:           1369 [pixels]
Y_MAX:           1534 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00358520000msufc0091.fits
SUN_POSTN:       127.37d {+08h 29m 29s}  +19.01d {+19d 00' 39"}
SUN_DIST:         95.76 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      199.81d {+13h 19m 14s}  -14.04d {-14d 02' 07"}
MOON_DIST:       113.65 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      101.66, 11.94 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       16.46, 71.47 [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 27 Jul 09 22:48:00 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     358520,   Seg_Num: 0
POINT_RA:        315.974d {+21h 03m 54s} (J2000)
POINT_DEC:       +64.924d {+64d 55' 27"} (J2000)
POINT_ROLL:      8.176d
IMG_START_DATE:  15039 TJD;   208 DOY;   09/07/27
IMG_START_TIME:  81829.67 SOD {22:43:49.67} UT,   91.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.331
N_STARS:         113
X_OFFSET:        410 [pixels]
Y_OFFSET:        575 [pixels]
X_MAX:           1369 [pixels]
Y_MAX:           1534 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00358520000msufc0091.fits
SUN_POSTN:       127.37d {+08h 29m 29s}  +19.01d {+19d 00' 39"}
SUN_DIST:         95.76 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      199.80d {+13h 19m 13s}  -14.03d {-14d 02' 02"}
MOON_DIST:       113.65 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      101.66, 11.94 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       16.46, 71.47 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN Circular #9718
P. A. Evans (U Leicester), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), M. M. Chester (PSU), S. T. Holland (CRESST/USRA/GSFC), N. P. M. Kuin (MSSL), C. B. Markwardt (CRESST/GSFC/UMD), K. L. Page (U Leicester), A. Rowlinson (U Leicester), M. H. Siegel (PSU), M. A. Stark (PSU) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:
At 22:42:18 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 090727 (trigger=358520). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 315.972, +64.916 which is
```
   RA(J2000) = 21h 03m 53s
   Dec(J2000) = +64d 54' 58"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single peak with a duration of about 25 sec. The peak count rate was ~1000 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 22:43:46.0 UT, 87.9 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 315.96139, 64.92438 which is equivalent to:
```
   RA(J2000)  = 21h 03m 50.73s
   Dec(J2000) = +64d 55' 27.8"
```
with an uncertainty of 4.0 arcseconds (radius, 90% containment). This location is 34 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 consistent with the Galactic value of 2.48e+21 cm^-2 (Kalberla et al. 2005).
UVOT took a finding chart exposure of nominal 150 seconds with the White filter starting 91 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. Data from the 2.7'x2.7' sub-image are not available at this time. 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 0.54.
Burst Advocate for this burst is P. A. Evans (pae9 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 Circular #9719
R.J. Smith, C.G. Mundell (Liverpool JMU) on behalf of a large collaboration report:
The 2-m Liverpool Telescope robotically reacted to GRB 090727 (SWIFT trigger 358520, Evans et al, GCN Circ. 9718), starting observing at 22:44:59UTC. A source which is not visible in the digitized sky survey is detected in both SDSS r' and i' filters at position 21:03:50.6 +64:55:30 J2000. This lies within the XRT error circle reported by Evans et al, GCN Circ. 9718. The approximate magnitude, calibrated with respect to nearby USNOB stars is R=21.3 +/- 0.2 and I = 20.2 +/- 0.2. The target is slightly crowded by brighter stellar sources and analysis is ongoing to determine if the OT candidate is fading.
GCN Circular #9721
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 5314 s of XRT Photon Counting mode data and 7 UVOT images for GRB 090727, 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 = 315.96078, +64.92481 which is equivalent to:
```
RA (J2000): 21h 03m 50.59s
Dec (J2000): +64d 55' 29.3"
```
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, arXiv:0812.3662).
This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN Circular #9722
R.J. Smith, C.G. Mundell, I.A. Steele, A. Melandri, S. Kobayashi, C.J. Mottram, D.F. Bersier, Z. Cano (Liverpool JMU), A. Gomboc (Ljubljana), C. Guidorzi (INAF-OAB) report:
"Further analysis of the optical light curves of the uncatalogued optical source, at RA(J2000)=21:03:50.6, Dec(J2000)= +64:55:30, reported by Smith & Mundell (GCN Circ. 9719) show significant variability and confirm this object as the optical afterglow of GRB 090727 (SWIFT trigger 358520, Evans et al, GCN Circ. 9718; Goad et al. GCN Circ. 9721).
Within the first 100 mins, the optical light curve shows an early-time flare, peaking at r'=19.4 mag, followed by a plateau and break - features that are the same as suggested by the partially sampled XRT light curve.
Observations are ongoing."
GCN Circular #9723
P. A. Evans (U Leicester) reports on behalf of the Swift-XRT team:
We have analysed 11 ks of XRT data for GRB 090727 (Evans et al. GCN Circ. 9718), from 91 s to 29.2 ks after the BAT trigger. The data comprise 40 s in Windowed Timing (WT) mode from T+260 s to T+300 s, with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN. Circ 9721).
The XRT initially observed the GRB for only 210 s before slewing away, and the data in this interval are dominated by a flare, making it impossible to determine the underlying decay rate. Fitting only the data from the second snapshot onwards (beginning at T+3.9 ks) we find a power-law decay with an index of alpha=0.73 (+/-0.19).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.60 (+0.20, -0.14). The best-fitting absorption column is consistent with the Galactic value of 2.5 x 10^21 cm^-2 (Kalberla et al. 2005).
If the light curve continues to decay with a power-law decay index of 0.73, the count rate at T+24 hours will be 0.0043 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.3 x 10^-13 (2.9 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00358520.
This circular is an official product of the Swift-XRT team.
GCN Circular #9724
C. B. Markwardt (GSFC/UMD), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), P. A. Evans (U Leicester), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from recent telemetry downlinks, we report further analysis of BAT GRB 090727 (trigger #358520) (Evans, et al., GCN Circ. 9718). The BAT ground-calculated position is RA, Dec = 315.917, 64.937 deg, which is
```
   RA(J2000)  =  21h 03m 40.0s 
   Dec(J2000) = +64d 56' 12.7" 
```
with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 83%.
The mask-weighted light curve shows an initial FRED-like peak starting at ~T-5 sec, peaking at ~T_zero, and ending at ~T+20 sec. The second, weaker, peak starts at ~T+130 to ~T+150 sec. The third peak starts at ~T+180 sec, peaks at ~T+270 sec, and ends at ~T+320 sec. This third peak corresponds to the flare mentioned in Circ 9723 (Evans). T90 (15-350 keV) is 302 +- 23 sec (estimated error including systematics).
The time-averaged spectrum from T-1.3 to T+318.9 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.24 +- 0.24. The fluence in the 15-150 keV band is 1.4 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+0.12 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/358520/BA/
GCN Circular #9728
J. Gorosabel (IAA-CSIC, Spain), N. Huelamo (LAEFF-CAB/INTA-CSIC, Spain), M. Fernandez (IAA-CSIC, Spain), M. Jelinek (IAA-CSIC, Spain), P. Kubanek (IAA-CSIC, Spain), A. de Ugarte Postigo (OAB-INAF, Italy), A.J. Castro-Tirado (IAA-CSIC, Spain), R.J. Smith (JMU, Liverpool, UK), C.G. Mundell (JMU, Liverpool, UK), on behalf of a larger collaboration, report:
"We carried out I-band observations of the GRB 090727 XRT optical afterglow (Smith et al. GCN Circ. 9719; GCN Circ. 9722) with the 1.23m Calar Alto telescope. The observations were carried out on July 27.9646-28.0063 UT (0.45-1.45 hours post GRB) with an exposure time of 3600s. Very preliminary photometry yields I ~ 19.4 (Vega system) for the afterglow, against USNO B1.0 star with I=18.72 placed at (RA_J2000, DEC_J2000) = (21:03:49.099, +64:55:58.23)."
GCN Circular #9731
M.M. Chester (PSU) and P. A. Evans (U Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 090727 92 s after the BAT trigger (Evans et al., GCN Circ. 9718). We do not find any new source at the position of the XRT afterglow (Goad et al., GCN Circ. 9721). Preliminary 3-sigma upper limits for the white finding chart and the co-added images, using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627), are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC            92          241          147         >20.6
white               92         5987          541         >21.5
v                 4760        57429         3737         >21.1
b                 4145        46543         1752         >21.3
u                 3939        52323         4261         >21.8
w1                5171        51651         4625         >22.1
m2                4965        57845         4989         >22.3
w2                4556        56519         3825         >21.7
```
The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.54 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #9733
A. Moskvitin, A. Valeev, T. Fatkhullin, O. Sholukhova & S. Fabrika (SAO-RAS Niznijh Arkhyz, Russia), on behalf of a larger colaboration, report:
We observed the GRB090727 optical afterglow (Smith et al. GCN Circ. 9719, GCN Circ. 9722; J. Gorosabel et al. GCN Circ 9728 ) with the SAO RAS 6-m telescope in Caucasus. The observations were carried out in the R band with a total exposure of 158 sec. The weather was cloudy with a sufficient atmospheric extinction. We estimated the brightness of the object as R = 21.53 +/- 0.17 at the middle epoch of 23:21:12 27 July 2009 UT (2334 sec after the trigger). Calibration was done aganist 10 USNO B1.0 stars.
This message may be cited.
GCN Circular #9735
T. Sakamoto (UMBC/GSFC), D. Donato (ORAU/GSFC), N. Gehrels (GSFC), T. Okajima (JHU/GSFC), T.N. Ukwatta (GWU/GSFC), Y. Urata (NCU), C.A. Wallace (FGCU)
We observed the field of GRB 090727 detected by Swift (trigger #358520; Evans et al., GCN Circ. 9718) with the 14-inch Goddard Robotic Telescope (GRT) located at the Goddard Geophysical and Astronomical Observatory (http://cddisa.gsfc.nasa.gov/ggao/).
77 set of 30 sec exposures (excluding the bad quality images) were taken in the R filter starting from July 28 01:57:45 (UT) about 3.2 hours after the trigger and stopped on July 28 02:40:50 (UT). We do not detect the optical afterglow (Smith et al., GCN Circ. 9719; Gorosabel et al., GCN Circ. 9728; Moskvitin et al., GCN Circ. 9733) both in the individual images and the combined image. The estimated three sigma upper limit of the combined image (total exposure of 2310 sec) is ~16.6 mag using the USNO-B1 catalog.
GCN Report 243.1
GCN_Report 243.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_243_1.pdf by P.A. Evans at U.Leicester titled: "Final Results on Swift GRB 090727"

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Jochen Greiner, last update: 11-Sep-2009 [Disclaimer]