GRB 090418B
GCN Circular 9159
Subject
GRB 090418B: Detection of a bright burst from Swift-BAT slew data
Date
2009-04-18T22:19:33Z (16 years ago)
From
Antonio Copete at Harvard U <acopete@head.cfa.harvard.edu>
A. Copete, J. Grindlay (Harvard)
S. Barthelmy, C. Markwardt, N. Gehrels (NASA/GSFC)
We report the detection of a bright GRB by the BAT Slew Survey (BATSS)
in the slew that started at 08:59:02 and lasted 151 sec. The ground-
calculated position is RA, Dec = 225.910, +17.224 deg, which is
RA (J2000) = 15h 03m 38s
Dec(J2000) = +17d 13' 26"
with an uncertainty of 1.91 arcmin (90% confidence, including
systematics). The detection was triggered by simultaneous independent
detections of 86.0 sigma and 41.8 sigma from imaging in the 15-50 keV
and 50-150 keV energy bands, respectively. The burst mask-tagged
lightcurve lightcurve in the 15-150 keV band shows a strong and broad
multi-peaked emission structure starting at T+25sec as the burst
enters the BAT field-of-view, lasting 48 sec, and peaking 6 times at T
+29, T+35, T+38, T+47, T+58 and T+62sec. This is followed by a weaker
broad peak starting at T+87sec, lasting 28sec and peaking at T+100sec.
T90 = 65.0sec and T50 = 17.0sec.
The time-averaged spectrum over the 120 sec exposure time of the
source is best fit by a power law with an exponential cutoff, with
photon index 1.42 and high-energy cut at 319 keV. The fluence in the
15-150 keV band is 1.6 x 10^-5 erg/cm^2, and the peak 1-sec flux is
6.5 x 10^-7 erg/cm^2/sec at T+38sec. A follow-up Swift ToO observation
for this burst has been scheduled.
GCN Circular 9171
Subject
Konus-Wind observation of GRB 090418B
Date
2009-04-20T13:30:41Z (16 years ago)
From
Valentin Pal'shin at Ioffe Inst <val@mail.ioffe.ru>
S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, P.
Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind
team report:
The long Swift-BATSS GRB 090418B (Copete et al., GCN 9159)
triggered Konus-Wind at T0=32366.325 s UT (08:59:26.325).
The burst light curve shows a soft weak precursor at ~T0-20 s, the main
multipeaked pulse at T0 with a duration of ~45 s, and a weak soft pulse
at ~T0+70 with a duration of ~30 s (the same lc structure was seen by
BAT: Copete et al., GCN 9159).
As observed by Konus-Wind the burst
had a fluence of (2.31 +/- 0.09)x10^-5 erg/cm2,
and a 256-ms peak flux measured from T0+15.840 s
of (1.54 +/- 0.20)x10^-6 erg/cm2/s
(both in the 20 keV - 1 MeV energy range).
The time-integrated spectrum of the burst
(from T0 to T0+40.704 s) can be fitted (in the 20 keV-1 MeV range)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -1.23(-0.09, +0.010),
and Ep = 117(-7, +8) keV (chi2 = 62.0/56 dof).
Fitting by GRB (Band) model yields the same alpha and Ep,
and only an upper limit on the high energy
photon index: beta < -3.18 (chi2 = 62.0/55 dof).
All the quoted errors are at the 90% confidence level.
The Konus-Wind light curve of this GRB is available
at http://www.ioffe.ru/LEA/GRBs/GRB090418_T32366/
GCN Circular 9176
Subject
GRB 090418B: Faulkes Telescope North observations
Date
2009-04-20T20:29:19Z (16 years ago)
From
Cristiano Guidorzi at Ferrara U,Italy <guidorzi@fe.infn.it>
C. Guidorzi (U. Ferrara), R.J. Smith, I.A. Steele, C.G. Mundell,
D. Bersier (Liverpool JMU), A. Gomboc (U. Ljubljana), P. O'Brien,
N. Tanvir (U. Leicester) on behalf of a large collaboration report:
On 2009 April 19 at 12:53:50 UT we observed the Swift-BAT Slew Survey
GRB 090418B (Copete et al., GCN Circ. 9159) with the 2-m Faulkes
Telescope North using the i' and R filters.
From a set of 6x300 s frames in each filter, we could not find any
uncatalogued object inside the BAT error circle with respect to the SDSS
field stars, down to the following limiting magnitudes:
Mid Time Exposure Filter Limit
(days) (s) (mag)
-------------------------------------
1.17 6x300 i' > 21
1.20 6x300 R > 21.5
-------------------------------------
GCN Circular 9178
Subject
GRB 090418B: GROND observations
Date
2009-04-20T22:22:31Z (16 years ago)
From
Jochen Greiner at MPI <jcg@mpe.mpg.de>
P. Afonso (MPE), S. Klose (Tautenburg), T. Kruehler and J. Greiner (both
MPE Garching), report on behalf of the GROND team:
GROND (Greiner et al. 2008, PASP 120, 405), mounted at the 2.2m ESO/MPI
telescope at La Silla Observatory (Chile) started follow-up observations of
GRB 090418B (Copete et al., GCN #9150) on April 19, at 03:00 UTC (18.0 h
after the burst). In addition, a second epoch of imaging was obtained,
which started on April 20, 04:05 UTC.
Similar to Guidorzi et al. (2009, GCN #9176) we do not detect any new object
with respect to SDSS/2MASS inside the BAT error circle. Image subtraction
between the two epochs does not reveal any obvious variable source. Upper
limits from the first observation are as follows (all in the AB system):
g' > 23.8 mag
r' > 24.0 mag
i' > 23.2 mag
z' > 23.0 mag
J > 22.0 mag
H > 21.4 mag
K > 20.8 mag
Quoted upper limits have been derived using SDSS and 2MASS field stars as
reference.
GCN Circular 9181
Subject
GRB 090418B: GRAS002 observatios
Date
2009-04-21T06:27:00Z (16 years ago)
From
Veli-Pekka Hentunen at Taurus Hill Obs,A95 <veli-pekka.hentunen@kassiopeia.net>
Markku Nissinen (Taurus Hill Observatory) and Veli-Pekka Hentunen (Taurus
Hill Observatory) report:
Global-rent-a-scope GRAS002 Tak Mewlon 0.30m telescope with SBIG ST-8E
CCD at Mayhill (New Mexico, USA) was used for follow-up observations of
GRB090418B. The observations were started on April 19, at 03:55 UTC (19 hours
after the burst) and stopped at 05:35 UTC. Four unfiltered 600 seconds images
were taken. We do not detect any new object with respect to POSSII F/USNO-B1.0
inside the BAT error circle. Upper limit for the observations is > 20.5 mag (3UL). Quoted
upper limit has been derived using POSSII F and USNO-B1.0 field stars as reference.
Quoted upper limit has been derived using POSSII F and USNO-B1.0 field stars
as reference.
GCN Circular 9186
Subject
GRB 090418B: Suzaku WAM observation of the prompt emission
Date
2009-04-22T09:12:55Z (16 years ago)
From
Kenta Kono at Miyazaki U <kenta0514@astro.miyazaki-u.ac.jp>
K. Kono, E. Sonoda, M. Yamauchi, N. Ohmori, H. Hayashi,
K. Noda, A. Daikyuji, Y. Nishioka (Univ. of Miyazaki),
M. Ohno, M. Suzuki, M. Kokubun, T. Takahashi (ISAS/JAXA),
W. Iwakiri, M. Tashiro, Y. Terada, A. Endo, K. Onda,
T. Sugasahara (Saitama U.), Y. Urata (NCU),
T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo),
K. Yamaoka, S. Sugita (Aoyama Gakuin U.), Y. E. Nakagawa, T. Tamagawa
(RIKEN),
T. Uehara, T. Takahashi, Y. Fukazawa, Y. Hanabata (Hiroshima U.),
S. Hong (Nihon U.), N. Vasquez (Tokyo Tech.),
on behalf of the Suzaku WAM team, report:
The long GRB 090418B
was detected by the Suzaku Wide-band All-sky Monitor (WAM)
which covers an energy range of 50 keV - 5 MeV at 08:54:21.299 UT (=T0).
The observed light curve shows a multi-peaked structure
starting at T0-3 s, ending at T0+35 s,
with a duration (T90) of about 29 seconds.
The fluence in 100 - 1000 keV was 1.22 (-0.14, +0.06) x10-5 erg/cm2.
The 1-s peak flux measured from T0+32 s was 2.13 (-0.58, +0.35) photons/cm2/s
in the same energy range.
Preliminary result shows that the time-averaged spectrum from T0+14 s to
T0+52 s is well fitted by a single power-law with a photon index
of 2.09 (-0.20, +0.22) (chi2/d.o.f = 13/17).
All the quoted errors are at statistical 90% confidence level,
in which the systematic uncertainties are not included.
The light curves for this burst will be available at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/untrig/grb_table.html
GCN Circular 9191
Subject
GRB 090418B: RTT150 optical observations
Date
2009-04-22T13:44:41Z (16 years ago)
From
Rodion Burenin at IKI, Moscow <rodion@hea.iki.rssi.ru>
I. Bikmaev, R.Zhuchkov, N. Sakhibullin (KSU/AST),
I. Khamitov, Z. Eker (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.),
R. Burenin, M. Pavlinsky, R. Sunyaev (IKI)
report:
The field of GRB 090418B (Copete et al., GCN 9159) was observed with
Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National
Observatory, Turkey). We obtained series of 3x300s exposures in Rc filter,
centered on April 19, 01:04 UT, i.e. 16 hours after the burst. In addition,
a second epoch of 4x300 sec exposures was obtained in Rc filter on April 20,
0:17 UT.
Similarly to Guidorzi et al. (GCN 9176), Afonso et al. (GCN 9178), Nissinen
et al. (GCN 9181) we do not detect any obvious fading optical source inside
the BAT error circle. The upper limit for the first epoch of our
observations is Rc > 22.7 mag.