GRB 090807
GCN Circular 9746
Subject
GRB 090807: Swift detection of a burst
Date
2009-08-07T15:18:32Z (16 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
J. K. Cannizzo (NASA/UMBC), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),
P.A. Curran (MSSL-UCL), A. de Ugarte Postigo (INAF-OAB),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC),
C. Guidorzi (U Ferrara), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), N. P. M. Kuin (MSSL),
J. Mao (INAF-OAB), R. Margutti (Univ Bicocca&OAB),
K. L. Page (U Leicester), T. Sakamoto (NASA/UMBC),
M. H. Siegel (PSU), M. Stamatikos (NASA/ORAU),
T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the
Swift Team:
At 15:00:27 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 090807 (trigger=359378). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 273.744, +10.281 which is
RA(J2000) = 18h 14m 59s
Dec(J2000) = +10d 16' 51"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT TDRSS light curve does not show anything
as is typical for image triggers.
The XRT began observing the field at 15:03:00.5 UT, 153.5 seconds after
the BAT trigger. Using promptly downlinked data we find a bright, fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 273.7438,
10.2665 which is equivalent to:
RA(J2000) = 18h 14m 58.51s
Dec(J2000) = +10d 15' 59.3"
with an uncertainty of 2.4 arcseconds (radius, 90% containment). This
location is 52 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 (8.6e+20
cm^-2, Kalberla et al. 2005), with an excess column of 2 (+1.68/-1.50)
x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 8.55e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of nominal 150 seconds with the
White filter starting 163 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
3-sigma upper limit is about 19.2 mag. The 8'x8' region for the list
of sources generated on-board covers 100% of the XRT error circle.
The list of sources is typically complete to about 18.0 mag. No
correction has been made for the expected extinction corresponding
to E(B-V) of 0.18.
Burst Advocate for this burst is J. K. Cannizzo (cannizzo AT milkyway.gsfc.nasa.gov).
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 9747
Subject
GRB 090807, RIMOTS optical upper limits
Date
2009-08-07T16:43:17Z (16 years ago)
From
Kenta Kono at Miyazaki U <kenta0514@astro.miyazaki-u.ac.jp>
K.Kono, K.Noda, E.Sonoda, N.Ohmori, H.hayasi,
A.Daikyuji, Y.Nisioka, M.Yamauchi
(University of Miyazaki)
We have observed the field covering the error circle of
GRB 090807 (Swift trigger 359378, GCN 9746, J. K. Cannizzo et al.)
with the unfiltered CCD camera on the 30-cm telescope
at University of Miyazaki.
The observation was started 15:04:25 UT, about 2.2 min
after the Swift trigger time.
We have compared our data of 30 sec exposures
with the USNO-A2.0 catalog,
There is no new source at the reported position.
(GCN 9746, J. K. Cannizzo et al.)
the upper limits are as follows:
--------------------------------------------------------------
Start(UT) End(UT) $B!!!!(BNum. of frames $B!!(BLimit (mag.)
--------------------------------------------------------------
15:04:25 15:04:55 1 12.6
15:04:25 15:30:26 19 18.5
---------------------------------------------------------------
GCN Circular 9748
Subject
GRB 090807: Enhanced Swift-XRT position
Date
2009-08-07T19:10:10Z (16 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester)
report on behalf of the Swift-XRT team.
Using 1531 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 090807, 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 = 273.74377, +10.26583 which is equivalent
to:
RA (J2000): 18h 14m 58.50s
Dec (J2000): +10d 15' 57.0"
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, arXiv:0812.3662).
This circular was automatically generated, and is an official product of the
Swift-XRT team.
GCN Circular 9749
Subject
GRB 090807, Swift-BAT refined analysis
Date
2009-08-07T20:06:11Z (16 years ago)
From
Hans Krimm at NASA-GSFC <hans.krimm@nasa.gov>
T. N. Ukwatta (GWU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. K. Cannizzo (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD),
D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC),
G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC),
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+423 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 090807 (trigger #359378)
(Cannizzo, et al., GCN Circ. 9746). The BAT ground-calculated position is
RA, Dec = 273.741, 10.279 deg which is
RA(J2000) = 18h 14m 57.8s
Dec(J2000) = +10d 16' 45.9"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 64%.
The mask-weighted light curve shows a complex structure lasting from
T-5 to T+150 seconds with at least five peaks superimposed on a broad,
soft and slowly varying background. There is an additional peak at
T+185 sec which corresponds to a large flare seen in the Swift/XRT.
There is also possible precursor activity from T-200 to T-80 sec.
T90 (15-350 keV) is 140.8 +- 13.1 sec (estimated error including
systematics).
The time-averaged spectrum from T-9.5 to T+151.5 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
2.25 +- 0.14. The fluence in the 15-150 keV band is 2.2 +- 0.2 x 10-6 erg/cm2.
The 1-sec peak photon flux measured from T+41.96 sec in the 15-150 keV band
is 0.7 +- 0.2 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/359378/BA/
GCN Circular 9750
Subject
GRB 090807: Swift-XRT refined analysis
Date
2009-08-07T22:37:04Z (16 years ago)
From
Raffaella Margutti at U. di Milano Bicocca <raffaella.margutti@brera.inaf.it>
R. Margutti (Univ. Bicocca & INAF-OAB), J. Mao (INAF-OAB),
A. de Ugarte Postigo (INAF-OAB) and J. K. Cannizzo (NASA/UMBC)
report on behalf of the Swift-XRT team:
We have analysed the first orbit of Swift-XRT data obtained for
GRB 090807 (Cannizzo et al. GCN Circ. 9746), covering 149 s of
Windowed Timing (WT) and 1.5 ks of Photon Counting (PC) mode data,
respectively, between 154 s and 1.9 ks after the trigger.
The UVOT-enhanced XRT position was given by Beardmore et al. in
GCN Circ. 9748.
The light curve shows a large flare peaking around 185 s which was
also detected in the 15-150 keV energy range by Swift/BAT (Ukwatta et
al. GCN Circ. 9749). The underlying light curve decays
with a power-law index of 5.0 +/- 0.5. Around T+580 s the decay flattens,
to a slope of 0.87 +/- 0.42.
The spectrum extracted from WT data can be modelled with an absorbed simple
power-law, with Gamma = 2.2 +/- 0.1 and NH = (3.0+/-0.2)x10^21 cm^-2 in
excess of the Galactic column in this direction which is 8.6x10^20 cm^-2
(Kalberla et al. 2005).
A spectrum extracted from PC data in the time interval T+310 s - T+1840 s
has a best-fitting photon index of 2.6 +/- 0.4 and a best-fitting
absorption
column of NH = (3.3+/-0.1)x10^21 cm^-2 in excess of the Galactic value.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 3.1 x 10^-11 (8.4 x 10^-11) erg cm^-2
count^-1.
If the light curve continues to decay with a power-law decay index
of 0.9, the count rate at T+24 hours will be 0.002 count s^-1,
corresponding
to an observed (unabsorbed) 0.3-10 keV flux of 6.2 x 10^-14 (1.7 x 10^-13)
erg cm^-2 s^-1. However, the light-curve is possible to break before
this time,
making this prediction unreliable.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00359378.
This circular is an official product of the Swift-XRT team.
GCN Circular 9751
Subject
GRB 090807: Swift/UVOT Upper Limits
Date
2009-08-07T23:57:25Z (16 years ago)
From
Craig Swenson at PSU/Swift <cswenson@astro.psu.edu>
C. A. Swenson (PSU) and Cannizzo (NASA/UMBC)report on behalf of the
Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 090807
164 s after the BAT trigger (Cannizzo et al., GCN Circ. 9746).
No optical afterglow consistent with the XRT position (Beardmore et al.,
GCN Circ. 9748) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC)
exposure and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 164 313 147 >21.2
u_FC 322 571 246 >20.1
white 164 1026 295 >21.1
u 322 571 246 >20.1
The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.18 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 9752
Subject
GRB 090807: MITSuME optical upper limit
Date
2009-08-08T07:58:00Z (16 years ago)
From
Michitoshi Yoshida at Okayama Astrophysical Obs <yoshida@oao.nao.ac.jp>
M. Yoshida, D. Kuroda, K. Yanagisawa, Y. Shimizu, S. Nagayama,
H. Toda (OAO, NAOJ) and N. Kawai (Tokyo Tech) report on behalf
of the MITSuME collaboration:
We observed the field of GRB 090807 (Cannizzo et al. GCN 9746)
with optical three color (g', Rc and Ic) CCD camera attached to
the MITSuME 50cm telescope of Okayama Astrophysical Observatory.
The observation started on 2009-08-07 15:03:35 UT (3m 8s after
the burst). We did not find any point source in the error circle
of the XRT position reported by Beardmore et al. (GCN 9748) in
all the three bands.
Three sigma upper limits of the OT are listed below. We used USNO
B1 catalog for flux calibration.
PDAY MID-UT T-EXP g' Rc Ic
---------------------------------------------------
0.00589 15:08:56 540.0 >18.3 >18.5 >18.2
0.04169 16:00:30 4860.0 >18.9 >19.1 >18.7
---------------------------------------------------
GCN Circular 9753
Subject
GRB 090807: Liverpool Telescope observations
Date
2009-08-08T11:31:45Z (16 years ago)
From
Cristiano Guidorzi at Ferrara U,Italy <guidorzi@fe.infn.it>
C. Guidorzi (U. Ferrara), A. Gomboc (U. Ljubljana), R.J. Smith, C.G.
Mundell,
I.A. Steele, A. Melandri, S. Kobayashi, C.J. Mottram, D.F. Bersier, Z.
Cano (Liverpool JMU),
N.R. Tanvir, P. O'Brien (U. Leicester) report on behalf of a large
collaboration:
On 2009 August 07 at 23:45:24 UT we observed the Swift GRB 090807
(Cannizzo et al., GCN Circ. 9746) with the 2-m Liverpool Telescope.
Observations started 8.75 hours after the BAT trigger time and were
performed using the r' and i' filters. We could not find any
uncatalogued object inside the UVOT-enhanced XRT error circle (Beardmore
et al.
GCN Circ. 9748) down to the following limiting magnitudes:
Time Interval Total Exp Filter Limit
(hours from GRB) (s) (mag)
----------------------------------------------
8.75-9.27 6x300 R > 22.1
9.29-9.90 6x300 I > 22.0
----------------------------------------------
Magnitudes have been calibrated against the nearby USNOB-1 star
RA=18:15:00.349, Dec=+10:15:45.21, using R2=16.19, I=15.82.
We note the presence of an uncatalogued source lying outside the XRT error
circle at 4.2" from the XRT centroid, at RA=18:14:58.24, Dec=+10:15:58.4
with
estimated magnitudes R=22.4 +/- 0.2, I=21.6 +/- 0.2:
http://www.fe.infn.it/u/guidorzi/090807_LT_ri.png
At the moment we cannot assess whether this source is fading.
GCN Circular 9924
Subject
GRB 090807: Skynet/DSO Observations
Date
2009-09-18T06:01:13Z (16 years ago)
From
Josh Haislip at U.North Carolina <haislip@physics.unc.edu>
J. Haislip, D. Reichart, A. Smith, D. Caton, L. Hawkins, K. Ivarsen, M.
Schubel, A. LaCluyze, A. Foster, J. Moore, A. Oza, M. Schubel, J. Styblova,
A. Trotter, J. A. Crain, and M. Nysewander report:
Skynet observed the Swift/BAT localization of GRB 090807 (Cannizzo et al.,
GCN 9746) with the 14" Dark Sky Observatory telescope in North Carolina
beginning 10.4 hours after the trigger in I.
We do not detect the afterglow (Cannizzo et al., GCN 9746). Stacking only
images that increase the limiting magnitude yields:
mean 1-sig. 1-sig.
time 3-sig. sys. stat.
since lim. cal. cal. cal.
trig. tel. exp. fil. mag. stars unc. unc.
(h) (# x s) (mag) (mag)
10.7 DSO-14 10 x 160 I 18.9 807 USNO B1 0.489 0.000