GRB 050820A
GCN Circular 4045
Subject
GRB 050820A: NIR photometry at the TNG
Date
2005-09-28T17:08:00Z (20 years ago)
From
Stefano Covino at Brera Astronomical Observatory <covino@merate.mi.astro.it>
F. Mannucci, S. Covino, D. Malesani, on behalf of the CIBO collaboration
report:
We observed the field of GRB 050820A (Page et al., GCN 3830) in the NIR
at the TNG equipped with NICS on the 21st of August at 05:00 UT, about
22.4 hours after the high-energy event. The OT identified by Fox et al.
(GCN 3829) is clearly visible with J magnitude:
J = 18.48 +/- 0.08
Calibration has been derived by comparison with a suitable number of
2MASS stars in the field.
This message can be cited.
GCN Circular 3896
Subject
GRB050820A: RTT150 optical observations
Date
2005-08-28T04:19:16Z (20 years ago)
From
Irek Khamitov at TUG <irekk@tug.tug.tubitak.gov.tr>
Z. Aslan, I. Khamitov (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.),
I. Bikmaev, A. Galeev, N. Sakhibullin (KSU/AST),
R. Burenin, M. Pavlinsky, R. Sunyaev (IKI),
report:
We have continued observing the OT of GRB 050820A (GCN 3829) with
the Russian-Turkish 1.5-m telescope (Bakirlitepe, TUBITAK National
Observatory, Turkey) using TFOSC in R band.
We made 5*300s exposures between UT 22:40 - 23:05, August 27. Using
Henden's stars (GCN 3845) present in the frames, we estimated the
magnitude of the co-added image as R=22.14+/-0.1 (184.25h after the
trigger).
The OT is fading with the same power-law decay. Using all the data
obtained at the RTT150 (GCN3864, GCN3853) we estimated an alpha index of
power-law decay of -1.06+/-0.03.
The JPG-image is available at:
http://www.tug.tubitak.gov.tr/~irekk/grb/grb050820a/grb050820A_050827r.JPG
This message may be cited.
GCN Circular 3864
Subject
GRB050820A: RTT150 optical observations
Date
2005-08-24T12:26:30Z (20 years ago)
From
Irek Khamitov at TUG <irekk@tug.tug.tubitak.gov.tr>
I. Khamitov, Z. Aslan (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.),
I. Bikmaev, A. Galeev, N. Sakhibullin (KSU/AST),
R. Burenin, M. Pavlinsky, R. Sunyaev (IKI),
report:
We have continued observing the OT of GRB 050820A (GCN 3829) with
the Russian-Turkish 1.5-m telescope (Bakirlitepe, TUBITAK National
Observatory, Turkey) on the nights of August 22 and 23 in B,Rc,Ic bands.
We made a series of exposures between UT 20:23 - 01:33, August 22/23,
and between UT 20:09-00:34, August 23/24, 2005. The afterglow is still
clearly detected in all bands. Using Henden's stars (GCN 3845) present
in the frames, we estimated the magnitudes as follow:
t-t0 Band mag merr exptime
(hours) (sec,total)
64.39 B 22.24 -/+ 0.06 7860
64.43 Rc 21.02 -/+ 0.03 3900
64.53 Ic 20.46 -/+ 0.05 3900
87.57 B 22.57 +/- 0.08 5400
87.72 Rc 21.30 +/- 0.04 2700
87.82 Ic 20.87 +/- 0.09 2700
We note that, on re-examining the co-added image for 21 Aug in B-band
(GCN 3853), we noticed that it included a cosmic ray event close to OT.
More careful calculation has resulted in a fainter value of B magnitude:
21.47 +/- 0.06 (40.93h after the trigger).
This message may be cited.
GCN Circular 3863
Subject
GRB050820a: PROMPT RcIc Observations
Date
2005-08-23T21:22:02Z (20 years ago)
From
Chelsea Louise MacLeod at UNC-Chapel Hill/PROMPT <chelseam@physics.unc.edu>
C. MacLeod, M. Nysewander report on behalf of the UNC team of the FUN GRB
Collaboration:
We have observed the position of the GRB 050820a afterglow reported by Fox
et al. (GCN 3829). We detect the afterglow in RcIc:
Mean Time Integration Filter Magnitude Telescope
Since GRB Time
2.2 hr 39 x 40 sec Ic 17.40 +/- .08 PROMPT-3
2.2 hr 22 x 30 sec Rc 17.64 +/- .09 PROMPT-5
21.5 hr 136 x 40 sec Ic 18.42 +/- .11 PROMPT-3
21.7 hr 179 x 30 sec Rc 20.06 +/- .31 PROMPT-5
Rc and Ic calibrations were made relative to 7 calibration stars posted by
Henden (GCN 3845).
PROMPT is still being built and commissioned.
GCN Circular 3858
Subject
GRB 050820A BAT observations of second, larger episode of emission
Date
2005-08-22T19:55:41Z (20 years ago)
From
Jay R. Cummings at NASA/GSFC/Swift <jayc@milkyway.gsfc.nasa.gov>
J. Cummings (GSFC/NRC), L. Barbier (GSFC), S. Barthelmy (GSFC),
D. Hullinger (GSFC/UMD), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS),
J. Tueller (GSFC)
on behalf of the Swift-BAT team:
A second, larger, harder episode of gamma rays from T+217 to T+270
sec was detected from GRB 050820A, as noted by Golenetskii et al.
in GCN circ. 3846, 3852. We confirm that this larger episode of
emission was from the same source as the first episode (from T-17
to T+22 sec), using BAT mask-weighting on a partial data set.
Swift was entering the SAA as the first episode of emission was
ending. We reported BAT refined analysis for the period covering
the first episode of emission in GCN circ. 3835, 3848. The BAT
entered SAA mode at T+241 sec. At this time data collection became
very limited. We use mask-weighted data prior to this time, and a
non-directional residual rate with a background model subtraction
after this time, for the following information on the second
episode:
There were two peaks at T+228 and T+259 sec. T90 was 50 +/- 5 sec
(for the second episode alone). In a simple power law fit, the
photon index for the first part of the second episode from T+217
to T+241 was 1.06 +/- 0.03. The 1-sec peak flux is estimated to
be 6 +/- 1 ph/cm^2/sec (15-350 keV) at T+259 sec. For reference,
the previously reported photon index for the first episode of
emission from T-17 to T+22 sec was 1.7 +/- 0.1 and the 1-sec peak
flux was 1.3 +/- 0.2 ph/cm^2/sec (15-350 keV).
We estimate the total fluence for the entire event including both
episodes to be 8.4 +/- 0.3 x 10^-6 erg/cm^2 in the 15-150 keV band.
The quoted uncertainty is statistical. Roughly 60% of the fluence
is in the period lacking mask-weighted data and having a very high
background rate, thus systematic errors may be large and we
estimate them to be +/- 0.6 x 10^-6 erg/cm^2. The fluence estimate
includes the assumption that the part of the second episode after
T+241 sec had the same spectrum as it did from T+217 to T+241 sec.
For the entire burst then, using the measured redshift of 2.612
(Prochaska, et al. GCN 3833), we calculate the isotropic-equivalent
energy in the 54-542 keV band in the GRB rest frame (15-150 keV
band in the observer's frame) as ~1.5 x 10^53 ergs.
--
Jay Cummings
GCN Circular 3853
Subject
GRB050820A: RTT150 optical observations
Date
2005-08-22T12:40:21Z (20 years ago)
From
Irek Khamitov at TUG <irekk@tug.tug.tubitak.gov.tr>
I. Bikmaev, A. Galeev, N. Sakhibullin (KSU/AST),
R. Burenin, M. Pavlinsky, R. Sunyaev (IKI),
I. Khamitov, Z. Aslan (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.),
report:
We have observed the OT of GRB 050820A (GCN 3829) with the
Russian-Turkish 1.5-m telescope (Bakirlitepe, TUBITAK National
Observatory, Turkey) in two consequative nights .
We made a series of exposures in Rc between UT 18:35 - 22:15, August
20, 2005, and in BRcIc between UT 22:46-01:15, August 21/22, 2005.
Moonlight produced variable background in all images for both nights. The
afterglow is clearly detected in all bands. Using Henden's stars (GCN 3845)
present in the frames, we estimated the magnitudes as follow:
t-t0 Band mag merr exptime
(hours, midtime) (sec,total)
18.05 Rc 19.48 +/- 0.01 900
41.42 Rc 20.38 +/- 0.05 1800
40.93 B 21.00 +/- 0.06 1800
41.55 Ic 19.83 +/- 0.07 1800
On the basis of our Rc data, we estimeted an alpha index of power-law
decay for the observed period as ~ -1.0.
The JPG-images of BRcIc and color combined image are available at:
http://www.tug.tubitak.gov.tr/~irekk/grb/grb050820a/grb050820A_b.JPG
http://www.tug.tubitak.gov.tr/~irekk/grb/grb050820a/grb050820A_r.JPG
http://www.tug.tubitak.gov.tr/~irekk/grb/grb050820a/grb050820A_i.JPG
http://www.tug.tubitak.gov.tr/~irekk/grb/grb050820a/grb050820_bri.JPG
This message may be cited.
GCN Circular 3852
Subject
GRB 050820a - corrections to GCN 3846
Date
2005-08-22T11:36:41Z (20 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
V. Pal'shin and D.Frederiks on behalf of the Konus-Wind team:
There were several misprints in our GCN 3846.
The subject line should have read:
------------------------------------
"GRB 050820a - a long GRB like GRB041219a? (Konus-Wind observation)"
------------------------------------
The correct circular text should be:
------------------------------------
"S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks
and T. Cline on behalf of the Konus-Wind team,
and A. Rau, A. von Kienlin, G. Lichti on behalf of the INTEGRAL SPI-ACS
GRB team report:
A long soft GRB triggered Konus-Wind at T0=23954.512s UT (06:39:14.512)
on August 20. It was also detected by INTEGRAL SPI-ACS. Because the
burst was soft, the SPI-ACS response was weak, and precise triangulation
of this burst is not possible. But the estimated time delay is
consistent with the
position of GRB 050820a, detected by Swift-BAT ~260 sec before
Konus-Wind trigger (Page, et al., GCN 3830; Cummings, et al., GCN 3835).
The Konus-Wind GRB consists of two parts:
from ~T0-35s to ~T0+29s and from ~T0+135s to ~T0+235s
and is much more intense than the Swift burst (precursor?),
which was weakly seen by Konus-Wind in background data.
The total burst duration is ~270 s.
The Konus-Wind light curve recorded in the background mode
is very similar to the light curve of the famous GRB 041219a
(Vestrand et al., Nature, 435, 178 (2005)):
weak precursor, main pulse at ~250 sec after it,
second pulse at ~150 s after main and then - weaker pulse(s).
The Konus-Wind light curve of this GRB can be seen
at http://www.ioffe.rssi.ru/LEA/GRBs/GRB050820_T23954/
Based on these facts, we strongly suggest that this GRB is the main part
of the GRB 050820a.
In this case the optical transient reported by Fox and Cenko (GCN 3829)
and by Wren et al. (GCN 3836) is in fact the prompt optical emission of
very long GRB 050820a (the total burst duration including Swift
precursor is ~500 sec).
We hope, that the further analysis of this event will clarify this
issue."
---------------------------------
We apologize for these misprints.
GCN Circular 3848
Subject
Correction to Eiso calculation in GCN 3835 on GRB 050820A
Date
2005-08-21T22:35:20Z (20 years ago)
From
Takanori Sakamoto at NASA/GSFC <takanori@milkyway.gsfc.nasa.gov>
T. Sakamoto (GSFC/NRC) on behalf of the Swift-BAT team:
The isotropic-equivalent energy of GRB050820A reported in GCN 3835
is not correctly represented. We want to correct the last paragraph
of GCN 3835 to the following.
"The isotropic-equivalent energy using the redshift of 2.612
(Prochaska, et al. GCN 3833) is (2.2 +- 0.13) x 10^52 ergs
in the 54-542 keV band in the GRB rest frame (15-150 keV band
in the observer's frame) using a simple power-law model."
We would like to thank Dr. Arnon Dar for reporting about this mistake.
GCN Circular 3847
Subject
GRB050820A: Radio Observation
Date
2005-08-21T19:51:46Z (20 years ago)
From
Dale A. Frail at NRAO <dfrail@nrao.edu>
P. B. Cameron (Caltech) and D. A. Frail (NRAO) report on behalf of a
larger collaboration:
"We have undertaken VLA observations at a frequency of 8.46 GHz toward
GRB 050820A (GCN 3830) on August 20.39 UT and 21.20 UT, about 2.9 hrs
and 22.3 hrs after the burst, respectively. On the first epoch no
significant radio emission was detected at the position of the optical
afterglow (GCN 3829), but on the second epoch a new radio source has
appeared with a flux density of 690+/- 41 microJy.
Further observations are planned.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc."
GCN Circular 3845
Subject
GRB050820a BVRcIc field photometry
Date
2005-08-21T16:44:01Z (20 years ago)
From
Arne A. Henden at AAVSO <arne@aavso.org>
A. Henden (AAVSO/USNO) reports on behalf of the USNO GRB Team:
We have acquired BVRcIc all-sky photometry for a 23x23arcmin
field centered on the coordinates of the optical afterglow
(Fox and Cenko, GCN 3829) for the Swift burst GRB050820a
(Page et al., GCN 3830) with the USNOFS 1.0-m telescope
on one photometric night but with bright moonlight. Stars
brighter than V=12.0 are saturated and should be used with
care. We have placed the photometric data on our anonymous
ftp site:
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb050820.dat
The astrometry in this file is based on linear plate solutions
with respect to UCAC2. The external errors are about 100mas.
The estimated external photometric error is about 0.03mag.
As always, you should check the dates on the .dat file prior to
final publication to get the latest photometry. There is
a README file on the ftp directory to give you information
about the procedures used to calibrate these fields.
GCN Circular 3843
Subject
GRB 050820a: NIR Observations by WIRO
Date
2005-08-21T05:51:50Z (20 years ago)
From
Daryl Macomb at Boise STate U <dmacomb@boisestate.edu>
Daryl Macomb, Jessica Elias (Boise State U.),
Jerry Bonnell, Alexander Kutyrev, Jay Norris (NASA/GSFC),
and Ron Canterna, Mike Pierce (U. Wyoming) report:
We observed the position reported by Fox and Cenko (GCN 3829)
of the afterglow for GRB 050820a (Swift trigger #151207, Page et al.,
GCN 3830) with the 2.3-meter WIRO telescope. Starting at 08:10 UT
(96 minutes after the GRB trigger) and continuing until 11:30 UT,
we detected the fading afterglow in the J band in each of 120 40-s
integrations. J magnitudes determined at the following times were
(relative to burst trigger):
Epoch T-Ttrig J mag
1 6240 s 16.0
2 9600 s 16.7
3 16020 s 16.9
Between epochs 1 and 2, the inferred average power-law decay index
is -1.5, steeper than the -0.9 index reported by Cenko and Fox
(GCN 3834) for the initial decay during the interval ~ 7 - 93 minutes
after the burst. Between epoches 2 and 3, the average decay index
flattens to -0.44, after which our observations ended due to twilight.
The times of the three reported epochs are arbitrary. Detailed
analysis to yield accurate break times and indices is in progress.