- GCN Circular #15128
G.Vianello (Stanford), E.Sonbas (NASA/GSFC/Adiyaman Univ.) report on
behalf of the Fermi-LAT team:
At 07:20:00.15 on 2013-08-28 Fermi LAT detected high energy emission
from GRB 130828A, which was also detected by Fermi-GBM (trigger
399367203).
The best LAT on-ground location is found to be RA, DEC 259.83, +28.00
(J2000) with an error radius of 0.3 deg (68% containment, statistical
error only), this was 40 deg from the LAT boresight at the time of the
trigger, and triggered an autonomous repoint of the spacecraft.
The data from the Fermi LAT show a significant increase (>> 5 sigma)
in the event rate within 2.3 degree of the best HITL GBM location
after the GBM trigger that is spatially and temporally correlated with
the GBM emission with high significance. More than 30 photons above
100 MeV and 2 photons above 1 GeV are observed within 1000 seconds.
The highest energy photon is a 1.5 GeV event which is observed 225
seconds after the GBM trigger.
The Fermi LAT point of contact for this burst is Eda Sonbas
(esonbas@slac.stanford.edu).
The Fermi LAT is a pair conversion telescope designed to cover the
energy band from 20 MeV to greater than 300 GeV. It is the product of
an international collaboration between NASA and DOE in the U.S. and
many scientific institutions across France, Italy, Japan and Sweden.
- GCN Circular #15129
Andrew C. Collazzi (NASA/ORAU) reports on behalf of the
Fermi GBM Team:
"At 07:20:00.15 UT on 28 August 2013, the Fermi Gamma-ray Burst
Monitor (GBM) triggered and located GRB 130828A (trigger 399367203 /
130828.306). The on-ground calculated location, using the Fermi GBM
trigger data, is RA = 258.14, Dec = +29.76 (J2000 degrees, equivalent
to J2000 17h 12m, +29d 45' ), with a statistical uncertainty of 1.0
degrees (radius, 1-sigma containment, statistical only; there is
additionally a systematic error which is currently estimated to be 2
to 3 degrees). The angle from the Fermi LAT boresight is 46 degrees.
The burst was strong enough to trigger an Automatic Repointing
Request (ARR) on the Fermi spacecraft. The GRB position was
placed in the center of the LAT Field-of-view for 2.5 hours (subject
to Earth angle constraints).
The GBM light curve shows consists of several pulses, and is
possibly on top of a particle event. We find a duration (T90)
of about 159 +/- 23 s (50-300 keV). We find the 1.024s peak flux
during this time to be (7.39 +/- 0.37) ph/s/cm^2. The time-averaged
spectrum from T0-4.10 to T0+159.75 s is best fit by a Band function
with Epeak = 320.7 +/- 21.0 keV, alpha = -0.90 +/- 0.03, and
beta = -2.22 +/- 0.03. The fluence (10-1000 keV) in this time
interval is (6.05 +/- 0.09)E-05 erg/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
- GCN Circular #15130
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a series of observations, tiled on the sky, of the
Fermi/LAT GRB 130828A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00018
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the Fermi/LAT event is high: any X-ray source
considered to be a probable afterglow candidate will be reported via a GCN Circular
after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; and 2009, MNRAS, 397, 1177).
This circular is an official product of the Swift-XRT team.
- GCN Circular #15132
K. Hurley and J. Goldsten, on behalf of the MESSENGER NS GRB team,
S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks,
D. Svinkin, and T. Cline, on behalf of the Konus-Wind team,
A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C.
Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
K. Yamaoka, M. Ohno, Y. Hanabata, Y. Fukazawa, T. Takahashi, M. Tashiro,
Y. Terada, T. Murakami, and K. Makishima on behalf of the Suzaku WAM team,
S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer, on behalf of
the Swift-BAT team, and
V. Connaughton, M. S. Briggs, C. Meegan, and V. Pelassa, on behalf of the Fermi
GBM team, report:
GRB 130828A (GCN 15128, 15129, 15130) has been observed by Fermi,
INTEGRAL (SPI-ACS), Konus-Wind, MESSENGER GRNS, Suzaku, and Swift
(outside the coded field of view), so far. We have triangulated it to
an annulus centered at RA(2000)=340.597 deg (22 h 42 m 23 s),
Dec(2000)=-9.971 deg (-9 d 58 m 17 s), whose radius is 86.782 +/- 0.092
degrees (3 sigma). This annulus intersects the Fermi-LAT 1 sigma error
circle (GCN 15128) to form an error box whose area (280 sq. arcmin.) is
about 3.6 times smaller than that of the LAT error circle , and whose
corners are
RA(2000) Dec(2000)
259.541=17 h 18 m 09 s 27.843= 27 d 50 ' 34 "
259.649=17 h 18 m 35 s 28.254= 28 d 15 ' 13 "
259.722=17 h 18 m 53 s 27.716= 27 d 42 ' 56 "
259.875=17 h 19 m 30 s 28.297= 28 d 17 ' 50 "
A map has been posted at ssl.berkeley.edu/ipn3/130828A.
Some improvement in this triangulation is possible.
- GCN Circular #15133
K. Hurley reports:
The title of GCN 15132 should have been "IPN triangulation of GRB 130828A",
rather than 130821A. I apologize for the confusion and thank Kim Page for
catching this quickly.
- GCN Circular #15135
Dirk Grupe (PSU), Craig Swenson, and Mike Siegel
report on behalf of the Swift team:
Swift-XRT has observed the error circle of the Fermi/LAT GRB
130828A (Vianello & Sonbas, GCN Circ 15128)
in a series of observations tiled on the sky. In 2.5 ks of data,
beginning 105 ks after the Fermi/LAT trigger, we detect an
uncatalogued X-ray source at RA, Dec = 259.73234, 27.99570 which
is equivalent to:
RA (J2000.0) = 17h 18m 55.76s
Dec (J2000.0) = +27d 59' 44.5"
with an uncertainty of 4.1 arcsec (radius, 90% confidence).
This source is within the LAT error circle given in GCN circular
15128).
At the present time we cannot determine whether the source is
fading, therefore we cannot be certain whether this is the
afterglow of GRB 130828A or a serendipitous source.
The source was detected in observations with target ID 00020292.
The results of the automated XRT processing of this source are
available at
http://www.swift.ac.uk/xrt_products/TILED_GRB00018/20292/index_1.php
The Swift UVOT observed this field for 2.5 ks in the u filter.
There are two sources at the edge of the XRT error circle, one is a
Seyfert 1.9 galaxy, SDSS J171855.44+275947.4, which may be the
counter part of the X-ray source. However, the origin of the X-ray
source is unclear at this point.
This circular is an official product of the Swift team.
- GCN Circular #15138
K. Hurley and J. Goldsten, on behalf of the MESSENGER NS GRB team,
S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks,
D. Svinkin, and T. Cline, on behalf of the Konus-Wind team,
I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin,
on behalf of the HEND-Odyssey GRB team,
W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr, on
behalf of the GRS-Odyssey GRB team,
A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C.
Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
K. Yamaoka, M. Ohno, Y. Hanabata, Y. Fukazawa, T. Takahashi, M. Tashiro,
Y. Terada, T. Murakami, and K. Makishima on behalf of the Suzaku WAM team,
S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer, on behalf of
the Swift-BAT team, and
V. Connaughton, M. S. Briggs, C. Meegan, and V. Pelassa, on behalf of the Fermi
GBM team, report:
GRB 130828A (GCN 15128, 15129, 15130, 15132, 15133) was also observed
by Mars Odyssey-HEND. We have triangulated this burst to the following
3 sigma error box, whose area is 28 square arcminutes:
RA(2000) Dec(2000)
259.728=17 h 18 m 54 s 28.196= 28 o 11 ' 46 "
259.867=17 h 19 m 28 s 28.316= 28 o 18 ' 58 "
259.707=17 h 18 m 49 s 28.115= 28 o 06 ' 54 "
259.846=17 h 19 m 23 s 28.235= 28 o 14 ' 06 "
The Swift XRT source (GCN 15135) lies outside this error box.
A map has been posted at ssl.berkeley.edu/ipn3/130828A.
- GCN Circular #15206
Dirk Grupe (PSU) reports on behalf of the Swift team:
We report on two follow-up observations of the field of GRB 130828A
which was discovered by the FERMI LAT as reported by Vianello &
Sonbas (GCN circ 15128). The first Swift observation was performed
on 2013-09-04 (obsID 20293) for 2.6ks and was centered on the
X-ray source reported in Grupe et al. (GCN circ. 15135). This X-ray
source is still present in the new observation suggesting that
these X-rays are emitted from the Seyfert 1.9 galaxy
SDSS J171855.44+275947.4 as suggested by Grupe et al. Support
for this assumption comes from new IPN measurements by
Hurley et al. (GCN circ. 15138) who published a new IPN error box.
The X-ray source associated with SDSS J171855.44+275947.4 is
significantly outside this error box.
We re-examined the Swift observation of the field which contains
the IPN error box (obsID 20289) and found enhanced X-ray emission
within the IPN error box reported by Hurley et al. Applying the
Bayesian statistics as described by Kraft et al. (1991, ApJ, 374,
344) suggesting a source detection at the 3sigma level of
(2.4+4.2-2.1)e-3 counts/s. The position of this marginally
detected source is:
RA(hh mm ss.s) = 17h19m09.24s
Dec(dd mm ss.s) = +28:13:14.05
with an uncertainty of 8".
We re-observed the position of this source with Swift on 2013-09-07
for a total of 5157s (obsID 20295). No source was detected in this
observation. The 3sigma upper limit at the position of the
previously detected X-ray source within the IPN error box is
1.3e-3 counts/s. This may suggest that the X-ray source found
within the IPN error box during observation 20289 is the X-ray
afterglow of GRB 130828A. Note, however, that considering the
3sigma errors given above, this upper limit is non-conclusive.
No further Swift observations are planned of this GRB.
This circular is an official product of the Swift team.
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