Gamma-ray Burst 090305

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 05 Mar 09 05:20:12 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     345127,   Seg_Num: 0
GRB_RA:          241.756d {+16h 07m 02s} (J2000),
                 241.902d {+16h 07m 36s} (current),
                 240.966d {+16h 03m 52s} (1950)
GRB_DEC:         -31.567d {-31d 34' 00"} (J2000),
                 -31.591d {-31d 35' 27"} (current),
                 -31.433d {-31d 26' 00"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       1965 [cnts]    Image_Peak=132 [image_cnts]
TRIGGER_DUR:     0.384 [sec] 
TRIGGER_INDEX:   482     E_range: 50-350 keV
BKG_INTEN:       27946 [cnts]
BKG_TIME:        19179.45 SOD {05:19:39.45} UT
BKG_DUR:         8 [sec]
GRB_DATE:        14895 TJD;    64 DOY;   09/03/05
GRB_TIME:        19191.03 SOD {05:19:51.03} UT
GRB_PHI:         -13.75 [deg]
GRB_THETA:        42.85 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     16.21 [sigma]
IMAGE_SIGNIF:    9.11 [sigma]
MERIT_PARAMS:     +1  +0  +0  -1  +3  +0  +0  +0 +15  +0 
SUN_POSTN:       345.97d {+23h 03m 53s}   -6.00d {-05d 59' 55"}
SUN_DIST:         98.70 [deg]   Sun_angle= 6.9 [hr] (West of Sun)
MOON_POSTN:       86.24d {+05h 44m 57s}  +26.83d {+26d 49' 57"}
MOON_DIST:       158.28 [deg]
MOON_ILLUM:      60 [%]
GAL_COORDS:      344.60, 15.06 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      245.79,-10.47 [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 = 58.28,19.72 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:        GCN/SIMBAD_NED NOTICE
NOTICE_DATE:  Thu Mar  5 05:20:19 UTC 2009
NOTICE_TYPE:  Swift-BAT Position search
TRIGGER_NUM:  345127
RA:           241.7564 (J2000)
DEC:          -31.5669 (J2000)
 
SIMBAD search for BAT_RA,Dec=241.7564,-31.5669,radius=10.0arcmin
 
Num   RA         Dec                    Name                        Type  Num_Pub  Distance

 1 241.76334167 -31.54763889       1RXS J160703.2-313251                X   0      1.21
 2 241.76334167 -31.54763889       1RXS J160703.2-313251                X   0      1.21
 3 241.74083333 -31.51361111             IRAS 16038-3122               IR   0      3.29
 4 241.81739708 -31.58604111          CCDM J16073-3135AB               **   1      3.32
 5 241.64160333 -31.58036028             TYC 7330-2188-1               IR   0      5.92
 6 241.66791667 -31.45277778     2MASX J16064053-3127092                G   1      8.21
 
 
 
NED search for BAT_RA,Dec=241.7564,-31.5669,radius=10.0arcmin
 
Num    RA           Dec       Name                           Type      Distance

 1   241.754917   -31.638389  NVSS J160701-313818           , RadioS   4.30
 2   241.812333   -31.463361  NVSS J160714-312748           , RadioS   6.80
 3   241.899708   -31.513444  NVSS J160735-313048           , RadioS   8.00
 4   241.668833   -31.452556  2MASX J16064053-3127092       , IrS      8.20
 5   241.926500   -31.531278  2MASX J16074236-3131525       , IrS      9.00
 6   241.922292   -31.512889  2MASX J16074134-3130465       , IrS      9.10
 7   241.825542   -31.420167  2MASX J16071813-3125125       , IrS      9.50
 8   241.931125   -31.630083  NVSS J160743-313748           , RadioS   9.70

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Thu 05 Mar 09 05:20:28 UT
NOTICE_TYPE:    INTEGRAL SPI ACS Trigger
TRIGGER_NUM:    5477,   Sub_Num: 0
GRB_INTEN:      9.87 [sigma]
GRB_TIME:       19191.67 SOD {05:19:51.67} UT
GRB_DATE:       14895 TJD;    64 DOY;   09/03/05
COMMENTS:       INTEGRAL SPI_ACS GRB Trigger.
COMMENTS:
+ftp://isdcarc.unige.ch/arc/FTP/ibas/spiacs/2009-03-05T05-19-51.4840-29268-00007-0.lc

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 05 Mar 09 05:21:31 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     345127,   Seg_Num: 0
POINT_RA:        241.760d {+16h 07m 02s} (J2000)
POINT_DEC:       -31.572d {-31d 34' 19"} (J2000)
IMG_START_DATE:  14895 TJD;    64 DOY;   09/03/05
IMG_START_TIME:  19283.77 SOD {05:21:23.77} UT,   92.7 [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:     Thu 05 Mar 09 05:23:33 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     345127,   Seg_Num: 0
GRB_RA:          241.756d {+16h 07m 02s} (J2000),
                 241.902d {+16h 07m 36s} (current),
                 240.966d {+16h 03m 52s} (1950)
GRB_DEC:         -31.567d {-31d 34' 00"} (J2000),
                 -31.591d {-31d 35' 27"} (current),
                 -31.433d {-31d 26' 00"} (1950)
GRB_DATE:        14895 TJD;    64 DOY;   09/03/05
GRB_TIME:        19191.03 SOD {05:19:51.03} UT
TRIGGER_INDEX:   482
GRB_PHI:         -13.75 [deg]
GRB_THETA:        42.85 [deg]
DELTA_TIME:      -37.00 [sec]
TRIGGER_DUR:     0.384 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     16.21 [sigma]
IMAGE_SIGNIF:    9.11 [sigma]
LC_URL:          sw00345127000msb.lc
SUN_POSTN:       345.97d {+23h 03m 53s}   -6.00d {-05d 59' 52"}
SUN_DIST:         98.70 [deg]   Sun_angle= 6.9 [hr] (West of Sun)
MOON_POSTN:       86.27d {+05h 45m 06s}  +26.83d {+26d 49' 52"}
MOON_DIST:       158.25 [deg]
MOON_ILLUM:      60 [%]
GAL_COORDS:      344.60, 15.06 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      245.79,-10.47 [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 = 58.28,19.72 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 05 Mar 09 05:25:22 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     345127,   Seg_Num: 0
POINT_RA:        241.760d {+16h 07m 02s} (J2000)
POINT_DEC:       -31.572d {-31d 34' 18"} (J2000)
POINT_ROLL:      102.689d
IMG_START_DATE:  14895 TJD;    64 DOY;   09/03/05
IMG_START_TIME:  19287.11 SOD {05:21:27.11} UT,   96.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.320
N_STARS:         190
X_OFFSET:        446 [pixels]
Y_OFFSET:        553 [pixels]
X_MAX:           1405 [pixels]
Y_MAX:           1512 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00345127000msufc0096.fits
SUN_POSTN:       345.97d {+23h 03m 54s}   -6.00d {-05d 59' 50"}
SUN_DIST:         98.69 [deg]   Sun_angle= 6.9 [hr] (West of Sun)
MOON_POSTN:       86.29d {+05h 45m 11s}  +26.83d {+26d 49' 49"}
MOON_DIST:       158.24 [deg]
MOON_ILLUM:      60 [%]
GAL_COORDS:      344.60, 15.05 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      245.80,-10.47 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 05 Mar 09 05:26:01 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     345127,   Seg_Num: 0
POINT_RA:        241.760d {+16h 07m 02s} (J2000)
POINT_DEC:       -31.572d {-31d 34' 18"} (J2000)
POINT_ROLL:      102.689d
IMG_START_DATE:  14895 TJD;    64 DOY;   09/03/05
IMG_START_TIME:  19287.11 SOD {05:21:27.11} UT,   96.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.320
N_STARS:         190
X_OFFSET:        446 [pixels]
Y_OFFSET:        553 [pixels]
X_MAX:           1405 [pixels]
Y_MAX:           1512 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00345127000msufc0096.fits
SUN_POSTN:       345.97d {+23h 03m 54s}   -6.00d {-05d 59' 49"}
SUN_DIST:         98.70 [deg]   Sun_angle= 6.9 [hr] (West of Sun)
MOON_POSTN:       86.30d {+05h 45m 12s}  +26.83d {+26d 49' 48"}
MOON_DIST:       158.23 [deg]
MOON_ILLUM:      60 [%]
GAL_COORDS:      344.60, 15.05 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      245.80,-10.47 [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:     Thu 05 Mar 09 05:25:22 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     345127,   Seg_Num: 0
POINT_RA:        241.760d {+16h 07m 02s} (J2000)
POINT_DEC:       -31.572d {-31d 34' 18"} (J2000)
POINT_ROLL:      102.689d
IMG_START_DATE:  14895 TJD;    64 DOY;   09/03/05
IMG_START_TIME:  19287.11 SOD {05:21:27.11} UT,   96.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.320
N_STARS:         190
X_OFFSET:        446 [pixels]
Y_OFFSET:        553 [pixels]
X_MAX:           1405 [pixels]
Y_MAX:           1512 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00345127000msufc0096.fits
SUN_POSTN:       345.97d {+23h 03m 54s}   -6.00d {-05d 59' 50"}
SUN_DIST:         98.69 [deg]   Sun_angle= 6.9 [hr] (West of Sun)
MOON_POSTN:       86.29d {+05h 45m 11s}  +26.83d {+26d 49' 49"}
MOON_DIST:       158.24 [deg]
MOON_ILLUM:      60 [%]
GAL_COORDS:      344.60, 15.05 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      245.80,-10.47 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 05 Mar 09 05:26:38 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     345127,   Seg_Num: 0
POINT_RA:        241.760d {+16h 07m 02s} (J2000)
POINT_DEC:       -31.572d {-31d 34' 18"} (J2000)
ROLL:            102.689d
IMG_START_DATE:  14895 TJD;    64 DOY;   09/03/05
IMG_START_TIME:  19287.11 SOD {05:21:27.11} UT,   96.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     257923291
X_OFFSET:        765 [pixels]
Y_OFFSET:        872 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       925
Y_GRB_POS:       1032
BINNING_INDEX:   1
IM_URL:          sw00345127000msuni0101.fits
SUN_POSTN:       345.97d {+23h 03m 54s}   -6.00d {-05d 59' 49"}
SUN_DIST:         98.70 [deg]   Sun_angle= 6.9 [hr] (West of Sun)
MOON_POSTN:       86.31d {+05h 45m 14s}  +26.83d {+26d 49' 47"}
MOON_DIST:       158.22 [deg]
MOON_ILLUM:      60 [%]
GAL_COORDS:      344.60, 15.05 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      245.80,-10.47 [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:     Thu 05 Mar 09 05:26:57 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     345127,   Seg_Num: 0
POINT_RA:        241.760d {+16h 07m 02s} (J2000)
POINT_DEC:       -31.572d {-31d 34' 18"} (J2000)
ROLL:            102.689d
IMG_START_DATE:  14895 TJD;    64 DOY;   09/03/05
IMG_START_TIME:  19287.11 SOD {05:21:27.11} UT,   96.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     257923291
X_OFFSET:        765 [pixels]
Y_OFFSET:        872 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       925
Y_GRB_POS:       1032
BINNING_INDEX:   1
IM_URL:          sw00345127000msuni0101.fits
SUN_POSTN:       345.97d {+23h 03m 54s}   -6.00d {-05d 59' 48"}
SUN_DIST:         98.70 [deg]   Sun_angle= 6.9 [hr] (West of Sun)
MOON_POSTN:       86.31d {+05h 45m 15s}  +26.83d {+26d 49' 46"}
MOON_DIST:       158.22 [deg]
MOON_ILLUM:      60 [%]
GAL_COORDS:      344.60, 15.05 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      245.80,-10.47 [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 #8932
A. P. Beardmore (U Leicester), J. R. Cummings (NASA/UMBC), S. T. Holland (CRESST/USRA/GSFC), C. B. Markwardt (CRESST/GSFC/UMD), C. Pagani (PSU), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Swift Team:
At 05:19:51 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 090305 (trigger=345127). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 241.756, -31.567 which is
```
   RA(J2000) = 16h 07m 02s
   Dec(J2000) = -31d 34' 00"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single short spike with a duration of about 0.4 sec. The peak count rate was ~2500 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 05:21:23.8 UT, 92.7 seconds after the BAT trigger. No source was detected in the promptly available XRT data in an exposure time of 92.8 seconds before Swift slewed away. We are waiting for the full dataset to detect and localise the XRT counterpart.
UVOT took a finding chart exposure of 102 seconds with the White filter starting 96 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. Because part of the 2.7'x2.7' sub-image was not received, the overlap with the BAT error circle is uncertain. The overlap is at most 25%. The coverage of the BAT error circle by the 8'x8' region for the list of sources generated on-board is uncertain because the large number of sources filled the available telemetry. No correction has been made for the expected extinction corresponding to E(B-V) of 0.22.
We note the presence of a ROSAT survey source, 1RXS J160703.2-313251, within the BAT error circle. Further data are required to determine whether this object is related to the burst.
Burst Advocate for this burst is A. P. Beardmore (apb 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 #8933
S. B. Cenko, B. E. Cobb, D. A. Perley, and J. S. Bloom (UC Berkeley) report on behalf of a larger collaboration:
We have imaged the field of the short GRB 090305 (Beardmore et al., GCN 8932) with GMOS mounted on the Gemini South telescope beginning approximately 27 minutes after the burst. Observations were taken in the Sloan g', r', and i' filters and cover nearly the entire BAT error circle.
Inside the BAT error circle, we find a fading point source at the location (J2000.0):
```
   RA: 16:07:07.61
   Dec: -31:33:21.9
```
Calibrating with respect to the USNO-B1 object at 16:07:06.58, -31:33:37.9 (R2=18.99), we measure an initial magnitude of R ~ 23.3. The source fades by approximately 1.1 mag over the next two hours, corresponding to a power-law decay index of ~ 0.6 (assuming no contribution from an underlying host galaxy). At this point we tentatively consider this source the afterglow of GRB090305, although we await confirmation from the XRT.
We wish to thank the staff at Gemini South, in particular Peter Pessev, for performing our target of opportunity observations.
GCN Circular #8934
E. Berger (Harvard) and D. Kelson (OCIW) report:
"We imaged the BAT error circle of the short GRB 090305 (GCN 8932) with IMACS on the Magellan/Baade 6.5-m telescope. Observations were taken in R band on 2009 March 5 at 06:48 and 09:11 UT (88 and 231 min after the burst, respectively). We confirm the existence of the fading source reported by Cenko et al. from Gemini South observations (GCN 8933) and consider this source to be the afterglow of GRB 090305."
GCN Circular #8936
H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), C. B. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), 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-61 to T+242 sec from the recent telemetry downlink, we report further analysis of BAT GRB 090305 (trigger #345127) (Beardmore et al., GCN 8932). The BAT ground-calculated position is RA, Dec = 241.764, -31.572 deg which is
```
  RA(J2000)  =  16h 07m 03.5s
  Dec(J2000) = -31d 34' 20.9"
```
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment). This position is 1.3 arcmin from the optical afterglow reported by Cenko et al. (GCN Circ 8933). The partial coding was 50%.
The lightcurve consists of two pulses, the first about 0.08 seconds long and the second about 0.28 seconds long. T90 (15-350 keV) is 0.4 +- 0.1 sec (estimated error including systematics). There was very little emission seen in the BAT low energy band, 15-25 keV.
The time-averaged spectrum from T+0.0 to T+0.4 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 0.86 +- 0.33. The fluence in the 15-150 keV band is 7.5 +- 1.3 x 10^-08 erg/cm2. The 1-sec peak photon flux measured from T-0.29 sec in the 15-150 keV band is 1.9 +- 0.4 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/345127/BA/
GCN Circular #8937
A.P. Beardmore, K. L. Page, P.A. Evans (U. Leicester), C. Pagani, J. Kennea, D.N. Burrows (PSU) report on behalf of the Swift-XRT team :
The Swift-XRT began observing the field of the short GRB 090305 (Beardmore et al. GCN Circ. 8932) in photon counting mode at 2009-03-05T05:21:37, 103.4 s after the trigger. The first orbit of data lasted only 90 s before the spacecraft slewed to another target because of an observing constraint.
The default data processing does not reveal any X-ray source during the first orbit (103.4 to 193.5 s post trigger), either within the BAT refined error circle (Krimm et al. GCN Circ. 8936) or at the location of the optical afterglow (Cenko et al. GCN Circ. 8933) - the latter occurring close to a bad-column on the XRT CCD. However, by relaxing the default screening criteria we find 8 counts in a 10 pixel radius circle extraction region at the location of the optical afterglow, compared with a predicted background level of 1.0 count (where an annulus with radii 15 to 100 pixels was used to sample the local background level), implying a greater than 99.99 percent confidence detection (Kraft, Burrows, and Nousek 1991, Ap. J., 374, 344). The clustering of the counts, their proximity to the location of the optical afterglow and their detection significance allow us to conclude the afterglow was detected by the XRT at this time. The estimated count rate is 0.112 +0.051 -0.041 count/s (where a systematic error of 5 percent has been included in the 1 sigma error estimate to account for the PSF correction uncertainty). Applying a canonical GRB count to observed flux conversion factor of 5e-11 erg cm^-2 count^-1 (for a photon index of 1.98, Evans et al. 2009, MNRAS, submitted. arXiv:0812.3662, http://www.swift.ac.uk/xrt_spectra), we estimate the observed 0.3-10 keV flux was (5.5 +2.6 -2.0)e-12 erg cm^-2 s^-1.
A further 2.05 ks of data was taken in orbit two, from 3.92 to 5.97 ks after the trigger, where the optical afterglow position was located away from the XRT CCD bad column. This showed the source was no longer detected and a 3 sigma upper limit to the count rate of 7.0e-3 count/s was obtained. Using all of the available data after the first orbit (i.e. presently an exposure of 12.64 ks from 3.92 to 46.1 ks post trigger) reduces the 3 sigma upper limit to 1.7e-3 count/s. The X-ray data suggest the source faded with a decay slope of at least ~0.8.
This circular is an official product of the Swift-XRT team.
GCN Circular #8938
S. T. Holland (CRESST/GSFC/USRA) and A. P. Beardmore (U Leicester) report on the behalf of the Swift UVOT team:
The Swift/UVOT observed the field of GRB 090305 starting 78 s after the BAT trigger (Beardmore, et al. 2009, GCN Circ. 8932). Settled exposures started at T+96 s. We do not find any new source, relative to the DSS, USNO-B1.0, or 2MASS, or any variable source at the position of the GMOS-S afterglow (Cenko, et al. 2009, GCN Circ. 8933). Preliminary 3-sigma upper limits for detecting a source in the white finding chart, and the co-added images, using a 2.5 arcsecond radius circular aperture, are
```
Filter   T_start   T_stop   Exp(s)     Mag
------------------------------------------
white        96      198      100   >20.6


v        3503   11,765     1034   >20.6
b        4323   15,980     1278   >21.8
u        4118     5755      393   >20.6
uvw1       3913     5550      393   >20.6
uvm2       3708     5345      393   >20.3
uvw2       4734   17,549     1723   >21.6
white      4528   16,892     1982   >22.7
------------------------------------------
```
The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight corresponding to a reddening of E_{B-V} = 0.21 mag (Schlegel, et al., 1998, ApJS, 500, 525). All photometry is on the UVOT photometry system described in Poole et al. (2008, MNRAS, 383, 627).
The GMOS-S afterglow is located in the wings of the B = 13.72 mag USNO-B1.0 star 0584-0391760. UVOT photometry at this location is contaminated by this star.
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Jochen Greiner, last update: 06-Mar-2009 [Disclaimer]