GRB 050915A, GRB 050915
GCN Circular 4001
Subject
GRB 050915a: Radio Observations
Date
2005-09-19T12:14:54Z (21 years ago)
From
Dale A. Frail at NRAO <dfrail@nrao.edu>
P. B. Cameron (Caltech) and D. A. Frail (NRAO) report on behalf of a
larger collaboration:
"VLA observations were made toward the XRT position (GCN 3983) of
GRB 050915a at a frequency of 8.46 GHz on September 18.58 UT. No radio
sources are seen in the error circle above a 3-sigma level of 93 uJy.
The flux density at the position of the IR transient reported by
Bloom (GCN 3990) is 43 +/- 31 uJy.
No further observations are planned.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc."
GCN Circular 3990
Subject
GRB 050915a: IR Transient
Date
2005-09-16T14:52:12Z (21 years ago)
From
Josh Bloom at UC Berleley <jbloom@astron.berkeley.edu>
J. S. Bloom (UC Berkeley) reports:
"Further imaging of the field of GRB 050915a (GCNs 3977, 3979, 3983)
with the PAIRITEL 1.3m began at 2005-09-16 10:58:38 UTC. We confirm
that the source present in the first epoch (GCN 3984) has faded and
is thus the likely IR afterglow of GRB 050915a. In particular, the
mean H-band magnitude of the source during the first epoch was
H=18.25 +/- 0.16. The source was undetected in the second epoch, with
an approximate 3-sigma detection threshold of H(upper limit)=18.55 mag.
An improved astrometric solution was obtained for the imaging on
2005-09-15 UTC, yielding a J2000 position of the IRT of:
RA = 05:26:44.804
DEC = -28:00:59.27
The 1 sigma uncertainties relative to the 2MASS catalog are 0.18" and
0.09" in RA and DEC, respectively. This position is 3.2" from the
revised XRT position reported by Grupe et al. (GCN 3983).
We encourage deep z band and NIR imaging."
This message may be cited.
GCN Circular 3986
Subject
GRB050915: Swift/UVOT upper limits
Date
2005-09-15T20:42:37Z (21 years ago)
From
Alexander Blustin at MSSL-UCL <ajb@mssl.ucl.ac.uk>
A. J. Blustin (UCL-MSSL), D. Grupe (PSU), T. Poole (UCL-MSSL),
P. Roming (PSU), N. White (GSFC), D. Hinshaw (GSFC-SPSYS),
N. Gehrels (GSFC) report on behalf of the Swift-UVOT team:
The Swift/UVOT began observing the field of GRB050915 85 s
after the BAT trigger (Grupe et al. GCN 3977). No new source is
detected at the position of the refined XRT error circle (Grupe
et al. GCN 3983) in the initial 100 s V-band image down to a
3-sigma upper limit of 19.0, or in summed exposures with any of
the filters down to the following 3-sigma magnitude upper limits:
Filter T_range (s) Exp (s) 3sig UL
V 85-6154 1049 20.3
B 230-17031 324 20.6
U 216-12846 958 20.9
W1 203-11939 958 20.5
M2 188-6743 640 20.2
W2 246-677 59 19.6
The magnitudes are uncorrected for extinction.
GCN Circular 3985
Subject
GRB 050915: KAIT optical limit
Date
2005-09-15T20:10:25Z (21 years ago)
From
Weidong Li at UC Berkeley KAIT/LOSS <weidong@astron.berkeley.edu>
W. Li, University of California, Berkeley, on behalf of the
KAIT GRB team, report:
"The robotic 0.76-m Katzman Automatic Imaging Telescope (KAIT)
at Lick Observatory observed GRB 050915 (Swift trigger 155242;
Grupe et al. GCN 3977). A series of images was automatically
obtained from 11:27:32 UT (290s after the burst) to 12:21:36 UT
(3534s after the burst). The sequence includes a combination of
images taken with the V and I filters, as well as some that are
unfiltered. We did not detect a new object in our images when
compared to the DSS II images. In particular, no new object was
found within the error circle of the revised XRT position
(Grupe et al. GCN 3983). Our first 15s unfiltered image started
at 290s after the burst has a 3-sigma limiting magnitude of about
18.2 when compared to the USNO-B1.0 catalog."
GCN Circular 3984
Subject
GRB 050915: IR Observations
Date
2005-09-15T18:34:05Z (21 years ago)
From
Josh Bloom at UC Berleley <jbloom@astron.berkeley.edu>
J. S. Bloom and K. Alatalo (UC Berkeley), on behalf of a larger
collaboration, reports:
"Starting at 2005-09-15 11:33:18 UTC, the 1.3m PAIRITEL on Mt.
Hopkins began imaging the field of GRB 050915 (Swift trigger 155242;
GCN 3977). In a stack of exposures amounting to 1130 sec of
integration time we detect a red source at (J2000):
RA 05:26:44.83
DEC -28:00:59.5
The position is uncertain to about 400 ms but may be improved with
further analysis.
This source appears to be consistent with the revised XRT position
(Grupe et al. GCN 3983).
Since the source is significantly more faint than the 2MASS detection
level, we make no claims about variability at this time. Further
analysis is in progress."
An image will be posted to:
http://astro.berkeley.edu/~jbloom/grb050915_jhk.gif
This message may be cited.
GCN Circular 3983
Subject
GRB 050915: Swift XRT refined analysis
Date
2005-09-15T18:14:14Z (21 years ago)
From
Dirk Grupe at PSU/Swift-XRT <grupe@astro.psu.edu>
D. Grupe, J. Kennea, D. Burrows (PSU), and N. Gehrels GSFC) on report
behalf of the Swift XRT team:
We have analyzed the Swift XRT data of the first three orbits of GRB050915
(Grupe et al. GCN 3977, BAT trigger 155242). The new refined position
based
on the SDC quicklook data is:
RA (J2000) = 05h26m44.6s
DEC(J2000) = -28d01m01.0s
This position is 5.8 arcsec away from the XRT position reported by
Kennea et al.
(GCN 3979) based on the preliminary data analysis and 29 arcsec from the
refined BAT position (Barthelmy et al., GCN 3982).
The WT data show a spectrum that can be fitted by a single power law
with excess
absorption above the Galactic value. The X-ray energy spectral slope is
beta-x =
1.33+/-0.23. The integrated 0.3-10.0 keV Flux during the WT observation
was
4.6e-10 ergs/s/cm2 (corrected for absorption).
The XRT light curve started 87s after the burst and shows a rapidly
decaying
source after a light increased in flux at the beginning. The decay
slope is
alpha-1 = 3.00+/-0.14. The light curves shows a clear break in the PC
mode data
at 210s after the burst and flattens to a decay slope alpha-2=0.75 �0.04.
Extrapolating this light curve we estimate the 0.3-10.0 flux to be in
the order
of 5e-13 ergs/s/cm2 24 hours after the burst. However, this estimate
does not
take any late time break, which are usually observed in GRBs several
hours after
the burst, into consideration.
GCN Circular 3982
Subject
GRB 050915: Swift-BAT refined analysis
Date
2005-09-15T15:53:42Z (21 years ago)
From
Jay R. Cummings at NASA/GSFC/Swift <jayc@milkyway.gsfc.nasa.gov>
S. Barthelmy (GSFC), L. Barbier (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),
P. Meszaros (PSU), D. Palmer (LANL), A. Parsons (GSFC),
T. Sakamoto (GSFC/NRC), G. Sato (ISAS), J. Tueller (GSFC),
on behalf of the Swift-BAT team:
Using the data set from T-100 to T+300 sec from the recent telemetry
downlink, we report further analysis of Swift-BAT GRB 050915 (trigger
#155242) (Grupe, et al., GCN 3977). The refined BAT ground position is
RA,Dec = 81.682d,-28.010d {5h26m43.7s,-28d0'36"} [J2000] +/- 1.4 arcmin,
(radius, sys+stat, 90% containment). This position is 25 arcsec from
the XRT afterglow position reported in Kennea, et al. (GCN circ. 3979).
The partial coding was 75%.
The light curve shows about seven 2-second long peaks from T-10 to
T+20 sec and one more peak at about T+43 sec. T90 (15-350 keV) is
53 +- 3 sec (estimated error including systematics).
The time-averaged spectrum from T-8 to T+56 sec is well fit by a
simple power law. The power law index is 1.36 +- 0.16. The fluence
in the 15-150 keV band is 8.8 +- 0.9 x 10^-7 erg/cm2. The 1-sec peak
photon flux measured from T+13.7 sec in the 15-150 keV band is
0.8 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
GCN Circular 3981
Subject
GRB050915: P60 Optical Observations
Date
2005-09-15T13:54:17Z (21 years ago)
From
S. Bradley Cenko at Caltech <cenko@srl.caltech.edu>
S. Bradley Cenko (Caltech) and Derek B. Fox (Penn State) report on behalf
of a larger collaboration:
We have imaged the error circle of GRB 050915 (Grupe et al., GCN 3977)
with the automated Palomar 60-inch telescope. Observations began
approximately 4 minutes after the burst in the Kron R and Gunn i filters.
Inside the XRT error circle (Kennea et al., GCN 3979), we find no source
present.
Using the USNO-B object located at 05:26:48.6, -28:00:48.9 (J2000.0, R2 =
17.90, I2 = 17.88) as a reference, we find the following 3-sigma upper
limits for any point-source in the XRT error circle:
Filter Int Time (s) Mean UT Tb (min) Mag
---------------------------------------------------------------------------
R 540 11:41 18 > 21.0
i 540 11:43 20 > 20.5
GCN Circular 3980
Subject
GRB050915, optical observations
Date
2005-09-15T13:38:42Z (21 years ago)
From
Arne A. Henden at AAVSO <arne@aavso.org>
P. Kilmartin and A. Gilmore (Canterbury) report on behalf
of the AAVSO International High Energy Network:
We observed the localization of the Swift burst GRB050915
(Grupe et al. GCN 3977) with the 60cm OCS telescope of Mount John
Observatory. 600 seconds of stacked unfiltered observations
with mipoint at 050915.542 (1.6hrs after the burst) reached
a limiting magnitude of CR=18.0 estimated from USNO-A2.0 stars.
No new object is present by comparison with DSS2-R. Observations
are continuing.
The AAVSO thanks the Curry Foundation for their continued support of the
AAVSO International High Energy Network.
GCN Circular 3979
Subject
GRB050915: XRT position
Date
2005-09-15T13:10:48Z (21 years ago)
From
Jamie A. Kennea at PSU/Swift-XRT <kennea@astro.psu.edu>
J.A. Kennea, D.N. Burrows, D. Grupe and C. Pagani (PSU) report on
behalf of the
Swift/XRT team:
We have analysed ground processed data from the burst GRB050915 (BAT
trigger 155242). We find a bright fading uncatalogued X-ray source at the
following coordinates:
RA(J2000): 05 26 44.8
Dec(J2000): -28 00 55.8
with an estimated uncertainty of 8 arcseconds (90% containment). This
position lies 100 arcseconds from the BAT position reported in GCN 3977.
GCN Circular 3978
Subject
GRB 050915: ROTSE-III optical limits
Date
2005-09-15T12:09:48Z (21 years ago)
From
Sarah Yost at U.Michigan <sayost@umich.edu>
S.A. Yost, E.S. Rykoff (U Mich), B. Schaefer (Louisiana State), D.A.
Smith (Guilford), T. Guver (U. Istanbul) report on behalf of the ROTSE
collaboration:
ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB
050915 (Swift trigger 155242), producing images beginning 7.5 s after
the GCN notice time. An automated response took the first image at
11:23:10.5 UT, 28.2 s after the burst, under fair conditions. We took
10 5-sec, 10 20-sec and 20 60-sec eposures. These unfiltered images are
calibrated relative to USNO A2.0 (R). With the arrival of morning
twilight, few further images are expected.
Comparison to the DSS (second epoch) reveals no new sources within the
3-sigma error circle, for both single images and coadding into sets of
10. Individual images have limiting magnitudes ranging from 16.0-17.4;
we set the following specific limits.
start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd?
--------------------------------------------------------------------
11:23:10.5 11:24:32.5 82 17.4 28.2 Y
11:24:33.4 11:29:34.4 301 18.0 111.1 Y
GCN Circular 3977
Subject
GRB 050915: Swift detection of a GRB
Date
2005-09-15T12:07:39Z (21 years ago)
From
David Palmer at LANL <dmpalmer@mac.com>
D. Grupe (PSU), A. Beardmore (U. Leicester), D. Burrows (PSU),
J. Cummings (GSFC/NRC), K. Page (U. Leicester), D. Palmer (LANL),
P. Roming (PSU), E. Rol (U. Leicester) N. Gehrels (GSFC)
on behalf of the Swift Team
At 11:22:42 UT, Swift-BAT triggered and located GRB050915
(trigger=155242). The BAT on-board calculated location is
RA,Dec 81.714d, -28.030d {05h 26m 51s, -28d 01' 48"} (J2000),
with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys).
The BAT light curve showed a multi-peak structure with at least
4 well-separated peaks and a total duration of 25 sec. The peak
count rate was ~1500 counts/sec (15-350 keV), at ~14 seconds after
the trigger.
The spacecraft slewed immediately and the XRT began
observing the BAT position at 11:24:09 UT (T+87 s). The
count rate was too low for an on-board centroid, but the
spectrum and lightcurve strongly suggest that XRT observed a
rapidly-fading X-ray source in the field. The XRT position
will be available following the next ground station data
dump.
UVOT finds no obvious new sources in the BAT error circle in
a 100 sec image starting at T+85 s. Further analysis will
follow.