GRB 090621
GCN Circular 9540
Subject
GRB 090621: Swift detection of a burst
Date
2009-06-21T04:53:59Z (16 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
P.A. Curran (MSSL-UCL), W. H. Baumgartner (GSFC/UMBC),
A. P. Beardmore (U Leicester), N. Gehrels (NASA/GSFC),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
C. B. Markwardt (CRESST/GSFC/UMD), K. L. Page (U Leicester),
D. M. Palmer (LANL), M. Stamatikos (NASA/ORAU), M. C. Stroh (PSU),
T. N. Ukwatta (GSFC/GWU) and H. Ziaeepour (UCL-MSSL) report on behalf
of the Swift Team:
At 04:22:43 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 090621 (trigger=355303). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 10.986, +61.968 which is
RA(J2000) = 00h 43m 57s
Dec(J2000) = +61d 58' 04"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed weak emission during
the 8 seconds of the trigger interval. The peak count rate
was ~1000 counts/sec (15-350 keV), at ~4 sec after the trigger.
There was a second BAT trigger (trigger=355304) at 04:27:05, about
4 minutes after the initial trigger from the same location. This
portion of the BAT light curve is not immediately available from
TDRSS, but the retrigger could indicate an extended prompt phase.
The XRT began observing the field at 04:24:40.46 UT, 117.3 seconds after
the BAT trigger. XRT found an uncatalogued, variable X-ray source located
at RA, Dec 11.0191, 61.9417 which is equivalent to:
RA(J2000) = 00h 44m 04.58s
Dec(J2000) = +61d 56' 30.2"
with an uncertainty of 5.0 arcseconds (radius, 90% containment). This
location is 110 arcseconds from the BAT onboard position, within the BAT
error circle. There is a bright peak at about 250s after the initial trigger
which could be X-ray emission during prolonged prompt emission.
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 122 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 25% of
the BAT error circle. The typical 3-sigma upper limit has been about 19.6 mag.
The 8'x8' region for the list of sources generated on-board covers 100% of the
BAT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the large, but uncertain extinction expected.
Burst Advocate for this burst is P.A. Curran (pac AT mssl.ucl.ac.uk).
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 9543
Subject
GRB 090621: Swift-XRT Team refined analysis
Date
2009-06-21T12:18:05Z (16 years ago)
From
Kim Page at U.of Leicester <kpa@star.le.ac.uk>
K.L. Page (U. Leicester) & P.A. Curran (UCL-MSSL) report on behalf of the
Swift-XRT team:
We have analysed the first four orbits of XRT data obtained for GRB
090621 (Curran et al., GCN Circ. 9540), comprising 192 s of Windowed
Timing (WT) mode and 6.4 ks of Photon Counting (PC) mode. The refined XRT
position is RA, Dec = 11.01982, 61.94115, which is equivalent to
RA (J2000) = 00 44 04.76
Dec(J2000) = +61 56 28.1
with an uncertainty of 3.6 arcsec (radius, 90% containment).
The X-ray light-curve shows a large increase in emission peaking at 264 s
after the initial trigger, corresponding to the time of the second BAT
trigger (Curran et al., GCN Circ. 9540). The underlying decay, however,
can be parameterised as a single power-law with alpha = 0.81 +/- 0.04.
As is common, there is clear spectral evolution during the flare. A
spectrum extracted from the PC mode data after the flare subsides (500 s
after the trigger) can be modelled with a power-law of Gamma = 2.07
+0.37/-0.35 and a total absorbing column of (1.5 +/- 0.4)x10^22 cm^-2; the
Galactic column in this direction is 5.6x10^21 cm^-2 (Kalberla et al.
2005). Using this spectrum, the counts to observed (unabsorbed) flux
conversion factor is 6.3x10^-11 (1.5x10^-10) erg cm^-2 count^-1.
If the light-curve continues to decay with alpha ~ 0.81, the predicted
count rate at 24 hours is 0.015 count s^-1, corresponding to an observed
(unabsorbed) flux of 9.5x10^-13 (2.2x10^-12) erg cm^-2 s^-1.
This circular is an official product of the Swift-XRT team.
GCN Circular 9544
Subject
GRB 090621: Swift/UVOT Upper Limits
Date
2009-06-21T12:29:18Z (16 years ago)
From
Peter Curran at MSSL <pac@mssl.ucl.ac.uk>
P.A. Curran (UCL-MSSL) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 090621
123 s after the BAT trigger (Curran et al., GCN 9540). No optical
afterglow consistent with the refined XRT position (Page et al., GCN
9543) 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 exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
wh 123 7115 805 >21.5
v 613 6089 333 >19.4
b 538 6910 310 >20.5
u 282 6705 736 >20.5
uw1 662 6500 320 >19.8
um2 637 6295 333 >19.7
uw2 588 5884 333 >19.9
The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 9556
Subject
GRB 090621: Fermi GBM observation
Date
2009-06-22T17:28:10Z (16 years ago)
From
Arne Rau at MPE <arau@mpe.mpg.de>
Arne Rau (MPE) reports on behalf of the Fermi GBM Team:
"At 04:26:34.49 UT on 21 June 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090621 (trigger 267251196 / 090621185) which was
also detected by the Swift/BAT (Curan et al. 2009, GCN 9540). The GBM
triggered on the second BAT trigger (355304) and at approx. 4 min after the
initial BAT trigger (355303) for this event. The GBM on-ground location is
consistent with the Swift position.
The angle from the Fermi LAT boresight is 12 degrees.
The GBM light curve shows a faint peak coinciding with the initial Swift
trigger (355303) and two brighter peaks starting at the GBM trigger time.
The burst duration (T90) including the first faint peak is about 294 s
(8-1000 keV).
The time-averaged spectrum of the two brighter peaks starting from the GBM
trigger time T0-6.10 s to T0+45.06 s is best fit by a Band function with
Epeak = 56.0 +/- 10.7 keV, alpha = -1.1 +/- 0.2, and beta = -2.12 +/- 0.09
(chi squared 377 for 366 d.o.f.).
The event fluence (8-1000 keV) in the above time interval is
(4.4 +/- 1.0)E-06 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0+35.840 s in the 8-1000 keV band is 1.92 +/- 0.06
ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 10001
Subject
Short-Duration GRB 090621: Skynet/Dolomiti Observations
Date
2009-10-08T15:11:31Z (16 years ago)
From
Josh Haislip at U.North Carolina <haislip@physics.unc.edu>
J. Haislip, D. Reichart, M. Maturi, K. Ivarsen, 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 short-duration GRB 090621
(Curran et al., GCN 9545) with the 16" telescope at the Dolomiti
Astronomical Observatory in Italy beginning 26.2 minutes after the trigger
in Red, which we have calibrated to R.
We do not detect the afterglow (Curran et al., GCN 9545). 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.
(m) (# x s) (mag) (mag)
35.3 DAO-16 4 x 160 R 19.9 1518 USNO B1 0.277 0.000
+ 3 x 80