- GCN/BACODINE POSITION NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Thu 08 Sep 05 05:43:00 UT
NOTICE_TYPE: Swift-BAT GRB Position
TRIGGER_NUM: 154112, Seg_Num: 0
GRB_RA: 20.464d {+01h 21m 51s} (J2000),
20.534d {+01h 22m 08s} (current),
19.845d {+01h 19m 23s} (1950)
GRB_DEC: -12.971d {-12d 58' 16"} (J2000),
-12.942d {-12d 56' 29"} (current),
-13.233d {-13d 13' 57"} (1950)
GRB_ERROR: 4.00 [arcmin radius, statistical only]
GRB_INTEN: 8621 [cnts] Image_Peak=311 [image_cnts]
TRIGGER_DUR: 2.048 [sec]
TRIGGER_INDEX: 262 E_range: 25-100 keV
BKG_INTEN: 88454 [cnts]
BKG_TIME: 20520.00 SOD {05:42:00.00} UT
BKG_DUR: 24 [sec]
GRB_DATE: 13621 TJD; 251 DOY; 05/09/08
GRB_TIME: 20551.38 SOD {05:42:31.38} UT
GRB_PHI: 20.79 [deg]
GRB_THETA: 27.80 [deg]
SOLN_STATUS: 0x3
RATE_SIGNIF: 9.38 [sigma]
IMAGE_SIGNIF: 9.29 [sigma]
MERIT_PARAMS: +1 +0 +0 +2 +2 +2 +0 +0 +83 +1
SUN_POSTN: 166.82d {+11h 07m 16s} +5.65d {+05d 38' 45"}
SUN_DIST: 145.97 [deg]
MOON_POSTN: 213.19d {+14h 12m 46s} -15.49d {-15d 29' 19"}
MOON_DIST: 148.93 [deg]
MOON_ILLUM: 18 [%]
GAL_COORDS: 151.11,-74.15 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 13.74,-19.97 [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.
- red DSS finding chart
ps-file
- GCN/SWIFT NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Thu 08 Sep 05 05:44:24 UT
NOTICE_TYPE: Swift-XRT Nack-Position
TRIGGER_NUM: 154112, Seg_Num: 0
POINT_RA: 20.463d {+01h 21m 51s} (J2000)
POINT_DEC: -13.015d {-13d 00' 52"} (J2000)
GRB_DATE: 13621 TJD; 251 DOY; 05/09/08
GRB_TIME: 20657.59 SOD {05:44:17.59} UT
COUNTS: 40 Min_needed= 20
STD_DEV: 50.04 Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER: 2 Max_iter_allowed= 4
ERROR_CODE: 3
COMMENTS: SWIFT-XRT Nack Position.
COMMENTS: Standard deviation too large.
- GCN/SWIFT NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Thu 08 Sep 05 05:45:57 UT
NOTICE_TYPE: Swift-BAT GRB Lightcurve
TRIGGER_NUM: 154112, Seg_Num: 0
GRB_RA: 20.464d {+01h 21m 51s} (J2000),
20.534d {+01h 22m 08s} (current),
19.845d {+01h 19m 23s} (1950)
GRB_DEC: -12.971d {-12d 58' 16"} (J2000),
-12.942d {-12d 56' 29"} (current),
-13.233d {-13d 13' 57"} (1950)
GRB_DATE: 13621 TJD; 251 DOY; 05/09/08
GRB_TIME: 20551.38 SOD {05:42:31.38} UT
TRIGGER_INDEX: 262
GRB_PHI: 20.79 [deg]
GRB_THETA: 27.80 [deg]
DELTA_TIME: 65465.00 [sec]
TRIGGER_DUR: 2.048 [sec]
LC_URL: sw00154112000msb.lc
SUN_POSTN: 166.82d {+11h 07m 16s} +5.65d {+05d 38' 45"}
SUN_DIST: 145.97 [deg]
MOON_POSTN: 213.19d {+14h 12m 46s} -15.49d {-15d 29' 19"}
MOON_DIST: 148.93 [deg]
MOON_ILLUM: 18 [%]
GAL_COORDS: 151.11,-74.15 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 13.74,-19.97 [deg] ecliptic lon,lat of the pointing direction
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.
- GCN/SWIFT NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Thu 08 Sep 05 05:46:18 UT
NOTICE_TYPE: Swift-UVOT Source List
TRIGGER_NUM: 154112, Seg_Num: 0
POINT_RA: 20.463d {+01h 21m 51s} (J2000)
POINT_DEC: -13.015d {-13d 00' 52"} (J2000)
POINT_ROLL: 99.270d
GRB_DATE: 13621 TJD; 251 DOY; 05/09/08
GRB_TIME: 20655.88 SOD {05:44:15.88} UT
FILTER: 3, V
BKG_MEAN: 1053193505
N_STARS: 1435
X_OFFSET: 1514 [pixels]
Y_OFFSET: 12 [pixels]
X_MAX: 476 [pixels]
Y_MAX: 555 [pixels]
DET_THRESH: 6
PHOTO_THRESH: 2
SL_URL: sw00154112000msufc.fits
SUN_POSTN: 166.82d {+11h 07m 16s} +5.65d {+05d 38' 43"}
SUN_DIST: 145.97 [deg]
MOON_POSTN: 213.20d {+14h 12m 49s} -15.50d {-15d 29' 42"}
MOON_DIST: 148.88 [deg]
MOON_ILLUM: 18 [%]
GAL_COORDS: 151.18,-74.19 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 13.72,-20.01 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Source List.
- GCN/SWIFT NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Thu 08 Sep 05 05:47:12 UT
NOTICE_TYPE: Swift-UVOT Processed Source List
TRIGGER_NUM: 154112, Seg_Num: 0
POINT_RA: 20.463d {+01h 21m 51s} (J2000)
POINT_DEC: -13.015d {-13d 00' 52"} (J2000)
POINT_ROLL: 99.270d
GRB_DATE: 13621 TJD; 251 DOY; 05/09/08
GRB_TIME: 20655.88 SOD {05:44:15.88} UT
FILTER: 3, V
BKG_MEAN: 1053193505
N_STARS: 1435
X_OFFSET: 1514 [pixels]
Y_OFFSET: 12 [pixels]
X_MAX: 476 [pixels]
Y_MAX: 555 [pixels]
DET_THRESH: 6
PHOTO_THRESH: 2
SL_URL: sw00154112000msufc.fits
SUN_POSTN: 166.82d {+11h 07m 16s} +5.65d {+05d 38' 43"}
SUN_DIST: 145.97 [deg]
MOON_POSTN: 213.20d {+14h 12m 49s} -15.50d {-15d 29' 42"}
MOON_DIST: 148.88 [deg]
MOON_ILLUM: 18 [%]
GAL_COORDS: 151.18,-74.19 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 13.72,-20.01 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Processed Source List.
- GCN/SWIFT NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Thu 08 Sep 05 05:47:22 UT
NOTICE_TYPE: Swift-UVOT Image
TRIGGER_NUM: 154112, Seg_Num: 0
POINT_RA: 20.463d {+01h 21m 51s} (J2000)
POINT_DEC: -13.015d {-13d 00' 52"} (J2000)
ROLL: 99.270d
GRB_DATE: 13621 TJD; 251 DOY; 05/09/08
GRB_TIME: 20655.88 SOD {05:44:15.88} UT
FILTER: 3, V
EXPOSURE_ID: 2256
X_OFFSET: 1564 [pixels]
Y_OFFSET: 875 [pixels]
WIDTH: 0 [pixels]
HEIGHT: 0 [pixels]
X_GRB_POS: 0
Y_GRB_POS: 0
BINNING_INDEX: 0
IM_URL: sw00154112000msuni.fits
SUN_POSTN: 166.82d {+11h 07m 16s} +5.65d {+05d 38' 43"}
SUN_DIST: 145.97 [deg]
MOON_POSTN: 213.20d {+14h 12m 49s} -15.50d {-15d 29' 42"}
MOON_DIST: 148.88 [deg]
MOON_ILLUM: 18 [%]
GAL_COORDS: 151.18,-74.19 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 13.72,-20.01 [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 1x1 binning (ie no compression).
- GCN/SWIFT NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Thu 08 Sep 05 05:47:44 UT
NOTICE_TYPE: Swift-UVOT Processed Image
TRIGGER_NUM: 154112, Seg_Num: 0
POINT_RA: 20.463d {+01h 21m 51s} (J2000)
POINT_DEC: -13.015d {-13d 00' 52"} (J2000)
ROLL: 99.270d
GRB_DATE: 13621 TJD; 251 DOY; 05/09/08
GRB_TIME: 20655.88 SOD {05:44:15.88} UT
FILTER: 3, V
EXPOSURE_ID: 2256
X_OFFSET: 1564 [pixels]
Y_OFFSET: 875 [pixels]
WIDTH: 0 [pixels]
HEIGHT: 0 [pixels]
X_GRB_POS: 0
Y_GRB_POS: 0
BINNING_INDEX: 0
IM_URL: sw00154112000msuni.fits
SUN_POSTN: 166.82d {+11h 07m 16s} +5.65d {+05d 38' 43"}
SUN_DIST: 145.97 [deg]
MOON_POSTN: 213.20d {+14h 12m 49s} -15.50d {-15d 29' 42"}
MOON_DIST: 148.88 [deg]
MOON_ILLUM: 18 [%]
GAL_COORDS: 151.18,-74.19 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 13.72,-20.01 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Processed Image.
COMMENTS: If you have elected to receive attachments:
COMMENTS: The uvot_catalog_image.fits file does not exist; skipping the attachment.
- GCN notice #3942
M. Goad (U. Leicester), H. Krimm (GSFC/USRA), D. Burrows (PSU),
M. Chester (PSU), N. Gehrels (GSFC), C. Markwardt (GSFC/UMD),
J. Osborne (U. Leicester), C. Pagani (PSU), K. Page (U. Leicester),
D. Palmer (LANL), A. Parsons (GSFC) on behalf of the Swift team:
At 05:42:31 UT, Swift-BAT triggered and located GRB050908
(trigger=154112). The BAT on-board calculated location is RA,Dec 20.464,
-12.971 {01h 21m 51s, -12d 58' 16"} (J2000), with an uncertainty of
3 arcmin (radius, 90% containment, stat+sys). The BAT light curve shows
a roughly triangular shape with a possible two peaks and total duration
of ~25 seconds. The peak count rate is ~1000 cts/sec.
The S/C slewed immediately and the XRT began observations at
05:44:18 UT, T+106.2 seconds. The instrument was not able to calculate
an on-board centroid. No bright source was initially apparent, but the initial
lightcurve suggests that a source in the field of view may have brightened
and then decayed in the first few minutes of the observation. Further
analysis will require processing of the full telemetry data following the
next ground station contact.
The UVOT began observations at 05:44:15.6. Further analysis will require
processing of the full telemetry data following the next ground
station contact.
- GCN notice #3943
K. Torii (Osaka U.) reports:
"The error region of GRB 050908 (Goad et al. GCN 3942)
was observed by the 0.30 m telescope in the New Mexico Sky
Observatory. Several 120 s exposures were obtained in V, Rc, and Ic
bands starting at 05:56:25 UT (14 minutes after the burst).
We identify a low significance optical counterpart candidate at
R.A. 01:21:50.7
Dec. -12:57:16
(J2000, 1".5 uncertainty)
with an USNO-A2.0R magnitude of about 18.8."
- GCN notice #3944
S. Bradley Cenko (Caltech), Derek B. Fox (Penn State), and Edo Berger
(Carnegie Observatories) report on behalf of a larger collaboration:
We have imaged the error circle of GRB 050908 (Swift 154112, GCN 3942,
Goad et al.) with the automated Palomar 60-inch Telescope. The optical
candidate identified by Torii (GCN 3943) is detected in our images, and
shows clear signs of fading. Approximately 22 minutes after the burst,
the afterglow has faded to a magnitude of R ~ 19.4 +/- 0.3 (based on a
comparison with the Guide Star Catalog). We therefore confirm this object
is the afterglow of GRB 050908.
Further observations are planned.
- GCN notice #3945
W. Li, University of California, Berkeley, on behalf of the
KAIT GRB team, report:
"We remotely observed GRB 050908 (Swift Trigger #154112;
Goad et al. GCN GCN 3942) with the 0.76-m Katzman Automatic
Imaging Telescope (KAIT) at Lick Observatory, and identified
a fading object at the position
R. A. = 01:21:50.75
DEC. = -12:57:17.2 (J2000, 0.3" uncertainty)
which is probably the same object as reported by Torii (GCN 3943).
The object is at magnitude about 20.1 (unfiltered; calibrated
via the USNO-B1.0 catalog) in a 600 s unfiltered image started at
06:36:24 UT, 3233s after the bust.
This message may be cited.
- GCN notice #3946
M. Goad (UL), C. Pagani (PSU), K. Page (UL) and D. Burrows (PSU)
report on behalf of the Swift XRT team:
We have analysed the ground data from GRB 050908 (BAT Trigger #154112).
We find a previously uncatalogued, X-ray source at the following
coordinates:
RA(J2000): 01 21 50.3
Dec(J2000): -12 57 20.3
with an uncertainty of 6 arcseconds radius (90% containment). This
position is 56.6 arcseconds from the BAT position reported in GCN 3942
(Goad et al.) and 7.3 arseconds from the optical counterpart reported in
GCN 3943 (Torii).
- GCN notice #3947
J. Kirschbrown, C. MacLeod, D. Reichart, M. Nysewander, A. Crain, A.
Foster, A. LaCluyze report on behalf of the UNC team of the FUN GRB
Collaboration.
Under the control of Skynet, PROMPT automatically observed the localization
of GRB 050908 (Goad et al., GCN 3942) beginning 50 sec after the burst in
repeating blocks of BVRcIc (two filters simultaneously).
We detect the afterglow (Torii, GCN 3943) and measure its brightness to be
Rc ~ 19 mag at 20 min after the burst.
PROMPT is still being built and commissioned.
- GCN notice #3948
D. Fugazza (INAF/OABr), F. Fiore (INAF/OARm), N. Patat, C. Ledoux (ESO),
P. D'Avanzo (INAF/OABr), L.A. Antonelli (INAF/OARm), G. Chincarini
(INAF/OABr & Univ. Milano-Bicocca), D. Malesani (SISSA/ISAS), S. Covino,
G. Tagliaferri (INAF/OABr), S. Piranomonte and L. Stella (INAF/OArm),
report on behalf of the MISTICI collaboration:
We observed the optical afterglow (Torii, GCN 3943; Cenko, Fox & Berger,
GCN 3944) of GRB 050908 (Goad et al., GCNs 3942, 3946) with the ESO-VLT
UT2, equipped with the FORS1 instrument. Spectroscopy was performed with
the grism 300V, covering the wavelength range 4500-8500 AA. Twenty
minutes of exposure were acquired starting on 2005 Sep 8, 07:19 UT. Data
reduction was performed using archivial calibration files, so that small
systematic uncertainties may be present in our analysis.
Based on the detection of Lyalpha, SiIV1309,1402, CIV1548,1550,
SiII1206, and the Lyman limit, we measure a redshift z = 3.350 +- 0.005.
Further analysis is in progress and results will be communicated later.
We acknowledge the outstanding support received from the ESO staff.
This message can be cited.
- GCN notice #3949
R. J. Foley (UCB), H.-W. Chen (UChicago), J. S. Bloom (UCB), and Jason X.
Prochaska (UCO/Lick Observatory) report:
"We obtained 2x1200 sec dithered exposures of the optical candidate (GCN
3943) of GRB 050908 using GMOS on the Gemini-North telescope with the B600
grating. The observations started at 20050908.39 UT (~ 4 hrs after the
initial Swift trigger). We measure a redshift of z = 3.3437 +/- 0.0002
based on a series of absorption features due to HI 1215, SiIII 1206, SiII
1260, SiIV 1393, 1402, and CIV 1548, 1550. We also observe a flux
discontinuity at 5285.9 Ang at the onset of the Lya forest absorption from
the intergalactic medium. Our redshift measurement is somewhat lower than
but still consistent with the redshift of 3.350 +/- 0.005 reported by
Fugazza et al. (GCN 3948). Using the HI 1215 absorption line, we estimate
a neutral hydrogen column density of log N(HI) ~ 19.2.
In addition to this system, which we contend is the redshift of the host
galaxy, we see several other, intervening systems at z = 2.81 and 3.039.
The system at z = 2.81 is particularly interesting. It shows CIII 1909 and
CIV 1549 emission."
- GCN notice #3950
D. T. Durig, N. P. McLarty and J. R. Manning (Cordell-Lorenz
Observatory) report on behalf of the AAVSO International High Energy
Network on optical observations of GRB050908 (GCN #3942; Goad et al.):
The optical afterglow reported by K. Torii (GCN #3943) was detected and
its fading behaviour was confirmed with observations starting 14 minutes
after the Swift trigger. Full details and URL to the FITS image are below.
The AAVSO thanks the Curry Foundation for support of the AAVSO
International High Energy Network.
Report filed on Thu Sep 8 06:22:58 2005:
Name: Dr. Douglas T. Durig
email: ddurig@sewanee.edu
Observer: D. T. Durig, N. P. McLarty, J. R. Manning
Site: Cordell-Lorenz Observatory
Location: Sewanee, Tenn., USA
LatitudeLongitude: 35 12 N 85 55 W
Elevation: 600 m
Scope: SCT 0.30 m
ScopeFocalRatio: 1770 mm f/5.9
CCDVendor: SBIG ST-8E
CCDDetector: KAF 1600
CCDSize: 1530x1020, binned 3x3
CCDPixelScale: 3.15 arc sec
CCDFOV: 26.7 x 17.8 arc min/13.35x8.9 shown
Object: GRB050908
ObsDate: 2005 09 08
ObsMidPointTime: 07:59:09
TimePerFrame: 300 sec
NumberOfFrames: 48
Filters: CR
Processing: dark, flat, register, add, 1/2 frame crop
Seeing: ~5 arc sec
LimitingMag: ~21.5-22 ???
Sky: mostly clear, occasional high clouds, no wind
afterglowmag: 19th fading to 21st
afterglowerr: 0.3 mag
compstars: 310 USNO B1.0 stars in field
Report: I had to use my backup CCD because my primary is in for repair.
I started imaging at 05:56:39 ( 2453621.7477 JD ) and did 30 x 300 sec
exposures followed by an additional 18. I was analysing the first 10 and
had identified the potential candidate on my own. I was checking the
fading behaviour when GCN 3943 from Torii announced the same candidate.
I then used my first 20 frames added in sets of 5 to confirm clear
fading
behaviour:
8.25483 01 21 50.72 -12 57 17.4 19.3 R
8.27272 01 21 50.73 -12 57 17.0 19.8 R
8.29063 01 21 50.69 -12 57 17.1 20.4 R
8.30853 01 21 50.79 -12 57 17.0 21.0 R
I then used sets of 10 and 20 to get later data points for the full set
of images.
Full data set:
08.25483 01 21 50.72 -12 57 17.4 19.3 R 850
08.26378 01 21 50.72 -12 57 17.2 19.6 R 850
08.27272 01 21 50.73 -12 57 17.0 19.8 R 850
08.28168 01 21 50.71 -12 57 17.2 19.9 R 850
08.29063 01 21 50.69 -12 57 17.1 20.4 R 850
08.29958 01 21 50.67 -12 57 17.8 20.7 R 850
08.33539 01 21 50.73 -12 57 15.8 20.2 R 850
08.35454 01 21 50.69 -12 57 16.9 21.0 R 850
08.37369 01 21 50.64 -12 57 18.1 21.4 R 850
A FITS image has been uploaded to:
ftp://ftp.aavso.org/grb/Dr.DouglasT.Durig_GRB050908_2453621.93262_.fits
- GCN notice #3951
G. Sato (ISAS), L. Barbier (GSFC), S. Barthelmy (GSFC),
P. Boyd (GSFC/UMBC), J. Cummings (GSFC/NRC), D. Hullinger (GSFC/UMD),
E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC),
T. Sakamoto (GSFC/NRC), J. Tueller (GSFC), W. Voges (MPE),
on behalf of the Swift-BAT team:
Using the data set from T-60 to T+120 sec from the recent telemetry
downlink, we report further analysis of Swift-BAT GRB 050908
(trigger #154112) (Goad, et al., GCN 3942). The refined BAT ground position
is (RA,Dec) = 20.451,-12.962 {01h 21m 48s, -12d 57' 45"} [deg; J2000]
+- 1.6 arcmin, (radius, 90% containment, statistical plus systematic).
This is 35 arcsec from the optical position reported by the KAIT GRB team
in Li et al. 2005, GCN 3945. The partial coding was 80%.
The mask-weighted BAT light curve shows a roughly triangular shape with a
single peak rising from T-8 sec to peak at T+2 sec and return to background
levels at T+15 sec. The duration T90 (15-350 keV) is 20 +/- 2 sec.
(estimated error including systematics). There is an indication of hard to
soft spectral evolution. The soft emission decays more slowly and in fact
the duration in the 50-300 keV band is T90 = 7 +/- 1 seconds.
The power law index of the time-averaged spectrum fit over T-10.3 to
T+15.4 sec is 1.93 +- 0.17. The fluence in the 15-150 keV band is
(5.1 +/- 0.5) x 10^-7 erg/cm2. The 1-s peak photon flux measured from
T+1.66 sec to T+2.66 sec in the 15-150 keV band is (0.7 +/- 0.1) ph/cm2/s.
All the quoted errors are at the 90% confidence level.
Given the measured redshift for this burst, z=3.35 (Fugazza et al., GCN 3948;
Foley et al., GCN 3949) and assuming a cosmology with Omega_M = 0.3,
Omega_lamda = 0.7, H0 = 65, we derive Eiso for this burst of 1.36 x 10^52 ergs
in 65.25 - 652.50 keV at the GRB rest frame.
- GCN notice #3952
M. Goad (UL), K. Page (UL), D. Burrows (PSU)
report on behalf of the Swift XRT team:
We have analysed the XRT data for GRB050908 (BAT trigger 154112),
between 118s and 24000 s after the trigger. As previously reported
by Goad et al. (GCN3946), there is an uncatalogued fading X-ray source
in the field of view. The refined coordinates for this burst are
RA(J2000) : 01 21 50.38
Dec(J2000): -12 57 19.89
with an uncertainty of 6 arcseconds (90% containment). This is
43 arcseconds from the refined BAT position (GCN3951) and 6 arcseconds
from the position of the candidate optical counterpart (GCN3943).
The initial lightcurve displays 2 large flares with approximately equal
amplitude peaking at T0+145 s and T0+397 s.
The spectrum of the burst in the first orbit of data is well fit by a single
powerlaw with photon index 3.9 +1.1/-0.5 (0.3-10 keV), with evidence for
excess column above the Galactic value of 2.1e20 cm^-2 of NH~3e20 cm^-2.
The spectrum of the burst from T0+4200 to T0+24000 s appears to be harder
with a powerlaw slope of 2.0 +/-0.6.
After the flares the light-curve declines with a slope of -1.33.
If the light-curve continues to decline at this rate the predicted count-rate
at 24 hours after the burst is 5.3e-4 ct s^-1, corresponding to a 0.3-10 keV
unabsorbed flux of 3.3e-14 erg cm^-2 s^-1.
- GCN notice #3953
S. Piranomonte, L. Calzoletti (INAF/OAR), P. D'Avanzo (INAF/OABr),
L.A. Antonelli (INAF/OAR), N. Patat, C. Ledoux (ESO), D. Malesani
(SISSA/ISAS), G. Chincarini (INAF/OABr & Univ. Milano-Bicocca), S.
Covino, D. Fugazza, G. Tagliaferri(INAF/OABr), F. Fiore and L. Stella
(INAF/OAR), report on behalf of the MISTICI collaboration:
"We observed the optical afterglow (Torii, GCN 3943; Cenko, Fox &
Berger, GCN 3944) of GRB 050908 (Goad et al., GCNs 3942, 3946) with the
ESO-VLT UT2, equipped with the FORS1 instrument. R-band observations
were performed in Rapid Response Mode (RRM) on Sep 8.268 UT and as a
ToO on Sept 8.415 UT (42 and 255 minutes after the GRB respectively).
During the two epoch observations the afterglow decays as a power law
having decay index of -0.93+/-0.05.
This message may be cited"
- GCN notice #3954
M. De Pasquale (MSSL), M. Goad (U. Leicester),
F. Marshall (GSFC), J. Norris(GSFC), K. Hurley
(Berkeley), N. Gehrels, on behalf of the Swift/UVOT team
The Swift/UVOT began observing the field of
GRB050908 at 05:44:15 UT, 104 seconds after the
BAT trigger (Goad et al., GCN 3942). No new
source with respect to the DSS was detected in
the initial 100 s V-band UVOT image with a
significance of 3 sigma at the position of the
optical afterglow found by Torii et al.
(GCN 3943). The corresponding 3 sigma upper
limit is 18.8.
There was also no optical/UV counterpart detected
in the summed images from all filters, down to the
following 3 sigma magnitude upper limits:
Filter T_range(s) Exp (s) 3sig UL
V 104-6922 942 19.9
B 250-5254 1020 21.1
U 236-1098 190 19.5
UVW1 223-993 100 19.1
UVM2 208-11040 987 20.9
UVW2 265-6163 997 20.6
Where T_range is the time post-trigger over which
the summed images were accumulated and Exp is the
total exposure time. The magnitudes upper limits
are not corrected for extinction.
These magnitudes are based on preliminary zero-
points, measured in orbit, and will require
refinements with further calibrations.
- GCN notice #3957
D. Dale, R. Barlow, C. Paul, C. Rodgers, D. Allen, R. Canterna, M. Pierce
report on behalf of the Wyoming Infrared Observatory GRB Team as part of
the FUN GRB Collaboration. We responded to GRB 050908 (GCN 3942) at
07:40:25 UT with a 2 minute I exposure and at 10:25:35 UT with a 4 minute
I exposure centered on the position of the original Swift-BAT GRB Position
under 1.5 arcsecond photometric conditions. The source was detected in
the 2 minute I exposure in the same position reported by GCN 3943 (Torii
et al.). Zero points were calculated using the USNO B1.0 catalogue.
UT Time Since Filter Magnitude
07:40:25 1:57:54 I 18.410 +/- 0.128
The source was no longer detected in the 4 minute I exposure.
UT Time Since Filter Limiting Magnitude
10:25:35 4:43:04 I 18.620
10 sigma limiting magnitude were derived from the USNO-B1.0 catalogue.
This message may be cited.
- GCN notice #3958
D. Allen, C. Rodgers, R. Canterna (U. of Wyoming) report on behalf of the
Red Buttes Observatory (0.6m) GRB Team as part of the FUN GRB
Collaboration.
We responded to GRB 050908 (GCN 3942) at 08:01:52 UT with a 10 minute I
exposure centered on the position of the original Swift-BAT GRB Position
under 3.9 arcsecond differential conditions. The source was not detected
in
the 10 minute I exposure in the same position reported by GCN 3943 (Torii
et al.) due to our detection limits.
UT Time Since Filter Limiting Magnitude
08:01:52 2:19:21 I 16.056
10 sigma limiting magnitude were derived from the USNO-B1.0 catalogue.
This message may be cited.
- GCN notice #3960
M. De Pasquale (UCL-MSSL), M. Goad (U. Leicester), A. J. Blustin
(UCL-MSSL), M. Chester (PSU), L. Angelini (GSFC-JHU),
N. Gehrels (GSFC) on behalf of the Swift/UVOT team
Further analysis of the early Swift/UVOT data for GRB050908
(Goad et al., GCN 3942) reveals a faint, decaying source at the
position of the optical counterpart reported by Torii (GCN 3943).
In summed V-band images taken between 104-650 s after the trigger,
a source is visible at 19.3 +/0.1 mag in a total exposure time of
149 s. It is not detected in data taken later than this; in summed
V-band images from 700-40650 s post-trigger a 3-sigma upper limit of
20.5 mag is obtained at the same position in 2296 s of co-added
exposure time. The source is only detected in the V band.
These magnitudes are uncorrected for extinction and are based on
preliminary zero-points, measured in orbit, and will require
refinement with further calibration.
- GCN notice #3971
J. X. Prochaska (UCO-Lick/UCSC), R. J. Foley (UCB), H.-W. Chen
(U Chichago), J. S. Bloom (UCB), K. Hurley (SSL/UCB), M. Cooper (UCB),
R. Guhathakurta (UCO-Lick/UCSC), W. Li (UCB) report on behalf of the
GRAASP collaboration:
"We have obtained Keck/DEIMOS spectra of the afterglow of 050908
starting
at 20050908.56 UT. The 1200/7500 grating data has a resolution of ~0.33
Ang and S/N~10 per resolution element covering wavelengths 6300-9000
Ang.
We refine the GRB host redshift to be z=3.3440 +/- 0.0001 based on the
strongest component of the CIV profile.
The DEIMOS spectrum overlaps with GMOS spectrum between 6330 and 7950 A,
and does not confirm the emission feature originally detected in the
GMOS
data at 7273 A. We therefore conclude that the intervening system at
z=2.81 reported in GCN 3949 is not likely to be real.
Adopting log N(HI)=19 and ignoring ionization corrections, the
non-detections of CII 1334, OI 1302 and AlII 1670 imply a metallicity of
less than 1/100 solar. Ionization corrections could imply even 10x
lower values.
In contrast to the low-ion transitions, the host shows very strong SiIV
and CIV absorption spanning ~500 km/s."
This message may be cited.
- GCN notice #4049
D. Sharapov, G. Abdullaeva, M. Ibrahimov (MAO), A.Pozanenko (IKI) on behalf
of larger GRB follow up collaboration report:
We observed the error box of GRB050908 (Goad et al, GCN 3942) with 1.5m
telescope of Maidanak Astronomical Observatory. Set of R images were taken
between Sep.8 (UT) 21:28 - 22:04. The OT found by Torii (GCN 3943) is
clearly visible in a stacked image. Preliminary photometry of the stacked
image against of USNO A2.0 is following:
Mid time, Exposure, Filter, Mag.
(UT) (s)
Sep.08 21:46 6x300 R 21.88 +/- 0.25
The stacked image can be found in
http://grb.rssi.ru/GRB050908/
The message may be cited.
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