GRB 050827
GCN Circular 3906
Subject
GRB 050827: Swift XRT preliminary analysis results
Date
2005-09-01T08:29:17Z (21 years ago)
From
Milvia Capalbi at ISAC/ASDC <capalbi@asdc.asi.it>
M. Capalbi (ASDC), G. Tagliaferri (INAF-OAB), P. Romano (INAF-OAB),
P. Boyd (GSFC-UMBC), W. Voges (MPE), D. N. Burrows (PSU)
and N. Gehrels (GSFC) report on behalf of the Swift XRT team:
We have analyzed 62 ks of Swift XRT data of GRB 050827 (Capalbi et al.,
GCN 3893) collected up to August 30, 2005 at 21:16:58 UT.
The XRT 0.3-10 keV light curve shows a temporal decay with a power
law index of -1.2 +/- 0.2 (90% confidence level), thus confirming
that the source suggested in the previous circular (Capalbi et al.,
GCN 3899) is the X-ray afterglow of GRB 050827.
A spectral fit to the data in the 0.3-10 keV band, gives a power law
photon index of 1.9 +/- 0.2 (90% confidence level) with an absorption
column density of 4.0 (-1.0, +1.5)E21 cm^-2 (90% confidence
level), slightly in excess of the Galactic value(1.95E21cm^-2).
GCN Circular 3903
Subject
GRB 050827 : OSN 1.5m optical observations
Date
2005-08-29T17:52:41Z (21 years ago)
From
Sergei Guziy at IAA <gss@iaa.es>
S. Guziy, J. Gorosabel, A.J. Castro-Tirado, V. Casanova,
A. de Ugarte Postigo, M. Jelinek, (IAA-CSIC) report:
"We have acquired R and I-band images of the GRB 050827
XRT error box (Capalbi et al. GCN Circ. 3899) with the OSN
1.5m telescope. We detect two objects consistent with the
8" radius XRT error circle. The coordinates of the two
objects are:
Source 1:
RA(J2000) = 04:17:08.9
DEC(J2000)= +18:11:57.0
Source 2:
RA(J2000) = 04:17:09.6
DEC(J2000)= +18:12:02.0
with a conservative astrometric error of 1.5".
Based on the USNO catalog we estimate magnitudes of
R=23.7 � 0.37 and R=23.4 � 0.26 for S1 and S2,
respectively. A finding chart can be found at:
http://www.dsri.dk/~jgu/grb050827/FCs/osn.R.gif
Further observations are encouraged to check the
reliability/variability of the two optical sources.
We thank Julius Halpern for making us available his
1.3m MDM telescope images."
This message can be cited.
GCN Circular 3902
Subject
GRB 050827: P200 NIR Observations
Date
2005-08-29T07:06:07Z (21 years ago)
From
S. Bradley Cenko at Caltech <cenko@srl.caltech.edu>
Dae-Sik Moon and S. Bradley Cenko (Caltech) report on behalf of a larger
collaboration:
We have imaged the error circle of GRB 050827 (Capalbi et al., GCN 3893)
with the Wide-Field Infrared Camera mounted on the Palomar 200-inch Hale
Telescope. We find no sources within the possible XRT error circle
(Capalbi et al., GCN 3899) at the following limits:
Mean Epoch (UT) Time Since Burst Filter Limit
--------------------------------------------------------------------------
28 August 09:40 14.7 hours J > 21
28 Auguts 10:50 15.9 hours Ks > 20
GCN Circular 3901
Subject
GRB050827: Swift/UVOT upper limits
Date
2005-08-29T02:25:11Z (21 years ago)
From
Alexander Blustin at MSSL-UCL <ajb@mssl.ucl.ac.uk>
A. J. Blustin (UCL-MSSL), M. Capalbi (ASDC), F. Marshall (GSFC),
J. Nousek (PSU), N. Gehrels (GSFC) on behalf of the Swift UVOT team
Swift/UVOT began observing the field of GRB050827 17.8 hours after
the BAT trigger (Capalbi, et al., GCN 3893); previous to that, the
target was unobservable due to a moon constraint. No new source with
respect to the DSS image is detected in the XRT error circle
(Capalbi, et al., GCN 3899) down to the following upper limits in
the six filters:
Filter T-range (hrs) Exp (s) 3sig_limit
V 20.9-24.3 1800 20.1
B 19.5-26.2 2444 21.0
U 19.3-25.9 2699 21.1
UVW1 18.1-25.7 2939 20.6
UVM2 17.8-24.6 2531 20.7
UVW2 20.6-24.1 1800 20.8
Where T_range is the time range in hours post-trigger over which the
summed images were accumulated and Exp is the total exposure time
(in seconds) of the summed image. The magnitude upper limits are not
corrected for extinction.
These magnitudes are based on preliminary zero-points, measured
in orbit, and will require refinement with further calibration.
GCN Circular 3900
Subject
GRB 050827: Optical Limit
Date
2005-08-28T20:04:21Z (21 years ago)
From
Jules Halpern at Columbia U. <jules@astro.columbia.edu>
J. P. Halpern (Columbia U.) reports on behalf of the MDM Observatory
GRB follow-up team:
"I observed the error box of GRB 050827 (Swift trigger #152325, GCN #3893)
in the R band with the MDM 1.3m telescope for 50 minutes starting on
Aug. 28 09:32 UT, or 14.6 hours after the burst. There is no optical
object to a limiting magnitude R=23.5 within 16", or twice the error circle
radius, of the XRT candidate afterglow reported by Capalbi et al. (GCN #3899).
Even after correcting this limit for Galactic absorption A(R)=1.47 mag at its
location (Schlegel et al. 1988), it would be unusual for a persistent X-ray
source of flux 1.0E-12 erg cm^-2 s^-1 to have no optical counterpart. So
this supports the identification of the X-ray source as the GRB afterglow."
GCN Circular 3899
Subject
GRB 050827: XRT possible afterglow detection
Date
2005-08-28T18:04:29Z (21 years ago)
From
Milvia Capalbi at ISAC/ASDC <capalbi@asdc.asi.it>
M. Capalbi (ASDC), V. Mangano (INAF-IASF), G. Tagliaferri (INAF-OAB),
J. Kennea (PSU), N. Gehrels (GSFC), D. Hinshaw (GSFC-SPSYS),
F. Marshall (GSFC) report on behalf of the Swift XRT team:
We have analyzed the Swift XRT data from the first
observation (2 orbits) of GRB 050827 (Capalbi, et al., GCN 3893).
The spacecraft slewed to this burst after 17.8 hrs due to the Moon
constraint.
An uncatalogued, X-ray source was detected at the following position:
RA(J2000) = 04h 17m 09.4s
Dec(J2000) = +18 11 57.9
with an uncertainty of 8 arcseconds radius (90% containment).
No other source is detected within the BAT error circle.
This position is 69 arcsec from the refined BAT position given
in GCN 3894 (Sakamoto et al.).
This source has a count rate of (2.0+/-0.3)E-02 cts s^-1
that approximately corresponds to a flux of 1.0E-12 erg cm^-2 s^-1
(there are not enough counts for a spectral fit).
The light curve however does not seem to decay, thus we need
more data to confirm this source as the afterglow of GRB 050827.
GCN Circular 3895
Subject
GRB050827: RTT150 optical observations
Date
2005-08-28T02:47:40Z (21 years ago)
From
Irek Khamitov at TUG <irekk@tug.tug.tubitak.gov.tr>
Z. Aslan, I. Khamitov (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.),
I. Bikmaev, A. Galeev, N. Sakhibullin (KSU/AST),
R. Burenin, M. Pavlinsky, R. Sunyaev (IKI),
report:
We have observed the error box of Swift-BAT GRB 050827
(trigger #152325) (Capalbi, et al., GCN 3893; T. Sakamoto, et al., GCN
3894) with the Russian-Turkish 1.5-m telescope (Bakirlitepe, TUBITAK
National Observatory, Turkey) using TFOSC in R band.
We made 2*300s exposures at UT 23:27, August 27 (midtime),
and 2*300s at UT 01:39, August 28, 2005.
We found no fading source brighter than ~21.4.
This message may be cited.
GCN Circular 3894
Subject
GRB 050827: Swift-BAT refined analysis
Date
2005-08-27T23:39:07Z (21 years ago)
From
Hans Krimm at NASA-GSFC <krimm@milkyway.gsfc.nasa.gov>
T. Sakamoto (GSFC/NRC), L. Barbier (GSFC), S. Barthelmy (GSFC),
J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hinshaw (GSFC-SPSYS), D. Hullinger (UMD), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), K. McLean (LANL), D. Palmer (LANL),
A. Parsons (GSFC), G. Sato (ISAS), J. Tueller (GSFC),
on behalf of the Swift-BAT team:
Using the full data set from T-300 to T+300 sec from the recent telemetry
downlink, we report further analysis of Swift-BAT GRB 050827
(trigger #152325) (Capalbi, et al., GCN 3893). The refined BAT ground
position is (RA,Dec) = 64.297,+18.217 {04h 17m 11s, +18d 13' 01"}
[deg; J2000] +-1.3 arcmin, (90% containment). The partial coding was 61%.
The mask-weighted light curve shows two peaks, with the first peak
significantly larger than the second. The first peak is triangular in
shape beginning at T-15 sec, rising to a maximum at T+0 and returning
to background at T+9 sec. This peak shows a hint of spectral hardening
as it progresses. There is a smaller second peak of duration ~3 sec,
beginning at T+25 sec and a hint of a ~4-sec peak at T+31 sec.
T90 (15-350 keV) is (49 +- 2) seconds (estimated error including
systematics).
The power law index of the time-averaged spectrum is 1.37 +- 0.10.
The fluence in the 15-150 keV band is (2.11 +- 0.12) x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+2.5 sec in the 15-150 keV
band is (1.78 +- 0.19) ph/cm2/sec. All the quoted errors are at the 90%
confidence level.
[GCN OPS NOTE(28aug05): The "05027: in the subject-line was changed to "050827".]
GCN Circular 3893
Subject
GRB050827: Swift-BAT detection of a burst
Date
2005-08-27T19:26:32Z (21 years ago)
From
Scott Barthelmy at NASA/GSFC <Scott@lheamail.gsfc.nasa.gov>
M. Capalbi (ASDC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC),
N. Gehrels (GSFC), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
on behalf of the Swift-BAT team:
At 18:57:15 UT, Swift-BAT triggered and located GRB050827 (trigger=152325).
The spacecraft did not slew because of Moon constraint, and it will not be
observable until ~13:00 UT 28/Aug/05 (T+18 hrs). The BAT on-board
calculated location is RA,Dec 64.279d,+18.218d {04h 17m 07s,+18d 13' 03"}
(J2000), with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys).
The BAT light curve shows multi-peaks with some pre-trigger emission
starting at T-10 sec with a total duration of ~45 sec. The peak count rate
was ~2500 counts/sec (15-350 keV), at ~2 seconds after the trigger.