GRB 090904B
GCN Circular 9881
Subject
GRB 090904B: Swift detection of a burst
Date
2009-09-04T01:50:16Z (16 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
V. D'Elia (ASDC), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),
J. R. Cummings (NASA/UMBC), S. T. Holland (CRESST/USRA/GSFC),
J. A. Kennea (PSU), C. B. Markwardt (CRESST/GSFC/UMD),
F. E. Marshall (NASA/GSFC), C. Pagani (PSU), M. Perri (ASDC),
M. H. Siegel (PSU), M. Stamatikos (OSU/NASA/GSFC), M. A. Stark (PSU)
and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:
At 01:24:18 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 090904B (trigger=361831). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 264.191, -25.212 which is
RA(J2000) = 17h 36m 46s
Dec(J2000) = -25d 12' 43"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows multiple overlapping peaks
starting at T-5 sec with a duration of about 60 sec. The peak count rate
was ~1800 counts/sec (15-350 keV), at ~3 sec after the trigger.
The XRT began observing the field at 01:26:32.3 UT, 134.2 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 264.1854, -25.2138
which is equivalent to:
RA(J2000) = 17h 36m 44.50s
Dec(J2000) = -25d 12' 49.7"
with an uncertainty of 2.4 arcseconds (radius, 90% containment). This
location is 19 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (3.28e+21
cm^-2, Kalberla et al. 2005), with an excess column of 4.8
(+5.33/-4.01) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White
filter starting 137 seconds after the BAT trigger. No credible
afterglow candidate has been found in the initial data products. The
2.7'x2.7' sub-image covers 100% of the XRT error circle. The 8'x8'
region for the list of sources generated on-board covers 100% of the
XRT error circle. Because of the density of catalogued stars,further
analysis is required to report an upper limit for any afterglow in the
region.
We note that this is a separate burst from the "A" burst.
But there may be some confusion resulting from overlapping GCN Notices.
Burst Advocate for this burst is V. D'Elia (delia AT asdc.asi.it).
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
GCN Circular 9882
Subject
GRB090904B: REM observations
Date
2009-09-04T03:03:22Z (16 years ago)
From
Angelo Antonelli at Obs. Astro. di Roma <a.antonelli@oa-roma.inaf.it>
S. Covino, L.A. Antonelli, P. D'Avanzo, D. Fugazza, S. Campana, G. Chincarini,
V. D'Elia, F. D'Alessio, F. Fiore, P. Goldoni, C. Guidorzi, E. Maiorano, L.
Nicastro, E. Palazzi, E. Pian, S. Piranomonte, L. Stella, G. Tagliaferri, G.
Tosti, V. Testa, S.D. Vergani, F. Vitali report on behalf of the REM team:
The REM 60-cm robotic telescope located at ESO-La Silla reacted promptly after
the Swift alert for GRB09094B. Observations began 108 seconds after the GRB time
(40 s after the trigger) with the R and H bands and continued with all the
available filters (VRIJHK). No transient was singled out in the images, although
a not varying 2MASS star with H=11.95 seems to be coincident with the XRT position.
The field is located very close to the Galactic Center (LII = 2.12 deg, BII =
3.64 deg) and is heavily reddened and crowded, requiring further analyses to
evaluate the chance for this positional coincidence.
Further observations are in progress.
-------------------------------------------------
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GCN Circular 9887
Subject
GRB 090904B: Enhanced Swift-XRT position
Date
2009-09-04T12:55:48Z (16 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester)
report on behalf of the Swift-XRT team.
Using 1190 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 090904B, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 264.18534, -25.21305 which is equivalent
to:
RA (J2000): 17h 36m 44.48s
Dec (J2000): -25d 12' 47.0"
with an uncertainty of 1.8 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the
Swift-XRT team.
GCN Circular 9890
Subject
GRB 090904B: Swift-BAT refined analysis
Date
2009-09-04T13:27:29Z (16 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), V. D'Elia (ASDC), E. E. Fenimore (LANL),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD),
D. M. Palmer (LANL), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC),
T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-119 to T+303 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 090904B (trigger #361831)
(D'Elia, et al., GCN Circ. 9881). The BAT ground-calculated position is
RA, Dec = 264.194, -25.219 deg, which is
RA(J2000) = 17h 36m 46.5s
Dec(J2000) = -25d 13' 09.0"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 8%.
The mask-weighted light curve shows the burst starting at ~T-30 sec, with
several overlapping peaks between T-5 to T+20 sec and another series
from T+30 to T+50 sec. The burst is over by ~T+70 sec T90 (15-350 keV)
is 47.0 +- 1.7 sec (estimated error including systematics).
The time-averaged spectrum from T-2.5 to T+49.7 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.59 +- 0.07. The fluence in the 15-150 keV band is 1.1 +- 0.0 x 10^-5 erg/cm2.
The 1-sec peak photon flux measured from T+12.42 sec in the 15-150 keV band
is 5.3 +- 0.9 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/361831/BA/
GCN Circular 9892
Subject
GRB 090904B: MOA-II Optical observation
Date
2009-09-04T15:29:08Z (16 years ago)
From
Kenta Nishimoto at Nagoya U/MOA-II <nishimo@stelab.nagoya-u.ac.jp>
K. Nishimoto, T. Sako, and D. Suzuki (STE Lab, Nagoya Univ.)
on behalf of the MOA Collaboration report:
We searched for an optical afterglow of GRB090904B (GCN9881, V. D'Elia
et al.) starting from 07:34:56.9 UT on 2009 Sep 4 (6 hours after the
burst) with the MOA-II 1.8m telescope at Mt.John observatory in New Zealand.
In a single image of a 60 sec exposure with a wideband Red filter
(center wavelength ~ 750nm and FWHM ~ 250nm), we did not find any object
within the error circle of the Swift XRT source position (GCN 9887),
except a USNO-B1.0 catalog star, 0647-0516939, which has I mag=15.10 and
the separation of 1.8 arcsec from the center of the position.
Quick estimation of the limiting magnitude is >20.5 calibrated by using
USNO-B1.0 catalog.
GCN Circular 9893
Subject
GRB 090904B: Swift XRT Refined Analysis
Date
2009-09-04T16:49:07Z (16 years ago)
From
Valerio D'Elia at INAF-OAR <delia@mporzio.astro.it>
V. D'Elia, G. Stratta, M. Perri (ASDC) report on behalf of
the Swift-XRT team:
We have analysed 6.2 ks of XRT data for GRB 090904B (D'Elia et al. GCN
Circ. 9881), from 159 s to 37.1 ks after the BAT trigger. The data are
entirely in Photon Counting (PC) mode. The enhanced XRT position for
this burst was given by Osborne et al. (GCN. Circ 9987).
The light curve, after an initial rise, peaks at T+260 s, while the
following
decay can be modelled with a power-law with a decay
index of alpha=1.20+-0.05 (90% confidence level).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.67 (+0.26, -0.24, 90%
confidence level). The best-fitting absorption column is 6.3
(+2.5, -1.1) x 1021 cm-2, in excess with respect to the Galactic value of
3.3 x 1021 cm-2 (Kalberla et al. 2005). The counts to observed
(unabsorbed) 0.3-10 keV flux conversion factor deduced from this
spectrum is 6.8 x 10-11 (1.1 x 10-10) erg cm-2 count-1.
If the light curve continues to decay with a power-law decay index of
1.20, the count rate at T+24 hours will be 0.0040 count s-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.7 x
10-13 (4.4 x 10-13) erg cm-2 s-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00361831.
This circular is an official product of the Swift-XRT team.
GCN Circular 9895
Subject
GRB 090904B: Fermi GBM detection
Date
2009-09-04T22:01:47Z (16 years ago)
From
Adam Goldstein at Fermi-GBM/UAH <adam.m.goldstein@msfc.nasa.gov>
A. Goldstein (UAH) reports on behalf of the Fermi GBM Team:
"At 01:24:13.93 UT on 04 September 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090904B (trigger 273720255 / 090904058),
which was also detected by the SWIFT-BAT (D'Elia et al. 2009, GCN 9881).
The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight is 113 degrees.
The GBM light curve consists of three bright peaks
with a duration (T90) of about 71 s (8-1000 keV).
The time-averaged spectrum from T0-9.2 s to T0+65.5 s is
well fit by a power law function with an exponential
high energy cutoff. The power law index is 1.41 +/- 0.08 and
the cutoff energy, parameterized as Epeak, is 149.30 +/- 22.10 keV
(chi squared 243.6 for 238 d.o.f.).
The event fluence (8-1000 keV) in this time interval is
(2.44 +/- 0.15)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+21.5 s in the 8-1000 keV band
is 9.8 +/- 0.7 ph/s/cm^2.
A Band function fits the spectrum equally well
(chi squared 239.0 for 237 d.o.f.) with Epeak= 106.30 +/- 24.60 keV,
alpha = -1.26 +/- 0.15 and beta = -2.18 +/- 0.18.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 9898
Subject
GRB 090904B: Swift/UVOT Refined Analysis
Date
2009-09-05T05:45:47Z (16 years ago)
From
Tyler Pritchard at PSU <tapritchard@astro.psu.edu>
T. A. Pritchard (PSU) and D'Elia (ASDC) report on behalf of the
Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 090904B,
138 seconds
after the BAT trigger (D'Elia et al., GCN Circ. 9881). We do not detect
any source
at the UVOT-enhanced XRT position (J.P. Osbourne et al., GCN Circ.9887).
The 3-sigma upper limits for the exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag (3-sigma upper limit)
-------------------------------------------------------------
white 138 1357 369 > 22.17
v 625 1237 78 > 19.08
b 551 1335 78 > 20.08
u 295 545 246 > 20.41
-------------------------------------------------------------
The quoted upper limits have not been corrected for the highly uncertain
extinction
corresponding to a reddening along the line of sight of of E_(B-V) =
1.76 mag
Schlegel et al., (1998, ApJS, 500, 525). All photometry is on the UVOT
photometric
system described in Poole et al. (2008, MNRAS, 383, 627).
GCN Circular 9901
Subject
GRB 090904B: GROND detection of the optical afterglow
Date
2009-09-07T12:54:08Z (16 years ago)
From
Thomas Kruehler at MPE/MPI <kruehler@mpe.mpg.de>
F. Olivares, P. Afonso, T. Kruehler, J. Greiner (all MPE Garching), report
on behalf of the GROND team:
The field of GRB 090904B (Swift trigger 361831, D'Elia et al., GCN #9881,
also GBM trigger 273720255/090904058, Goldstein, GCN #9895) was observed
simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120,
405) mounted at the 2.2 m ESO/MPI telescope at La Silla Observatory
(Chile). Observations started at 01:28 UT, on September 4, 2009, 4 minutes
after the GRB trigger. The field was observed during a second epoch,
starting at 01:28 UT, on September 5, 2009, 24.07 hours after the GRB
trigger. Image subtraction between the two epochs reveals a fading source
on the edge of the enhanced Swift/XRT error circle (Osborne et al., GCN
#9887). The position of the afterglow is
RA (J2000.0) = 17h 36m 44.59s
DEC (J2000.0) = -25d 12' 46.5"
with an uncertainty of 0.5" in each coordinate.
The afterglow is located roughly 1.1" South/East of the 2MASS/USNO star
reported by REM (Covino et al., GCN #9882) and MOA-II (Nishimoto et al.,
GCN #9892), and both sources are strongly blended in the GROND images of
1.0" seeing.
At a midtime of 6.5 minutes after the burst, we measure rough preliminary
AB magnitudes of the optical afterglow of r' ~ 22.2, i ~ 20.6 and z' ~ 19.7.
Calibrations were done against GROND zero points, and given magnitudes are
not corrected for the significant Galactic extinction corresponding to a
reddening of E(B-V) = 1.76 mag (Schlegel et al. 1998). The object is
detected in all bands except g', which, given the large Galactic foreground
extinction, does not constrain the redshift.
GCN Circular 9931
Subject
GRB090904B : IRSF NIR upper limit
Date
2009-09-25T02:00:32Z (16 years ago)
From
Kenta Nishimoto at Nagoya U/MOA-II <nishimo@stelab.nagoya-u.ac.jp>
K. Nishimoto, T. Sako(Nagoya Univ.) on behalf of the MOA Collaboration,
M. Kurita on behalf of the IRSF Collabration, T. Yosikawa(Kyoto Univ.),
T. Suenaga(Soken Univ.) report:
We searched for a NIR afterglow of GRB090904B (GCN9881, V. D'Elia et
al.) starting from 17:6:57.7 UT on 2009 Sep 4 (15.71 hours after the burst)
with the SIRIUS on the IRSF 1.4m telescope at SAAO in South Africa.
In images of a 300sec exposure with J, H and Ks filter, we did not find
any object except the reported star (GCN9882, Covino et al and GCN9892,
Nishimoto et al.) within the error circle of the Swift XRT source
position (GCN9887, J.P. Osborne et al.).
Quick estimation of the limiting magnitude calibrated by using 2MASS
catalog:
J > 17.14
H > 16.57
K > 15.79