GRB 060728
GCN Circular 5393
Subject
GRB 060728: Upper limits of the X-ray emission
Date
2006-08-03T20:52:00Z (19 years ago)
From
Claudio Pagani at PSU/Swift-XRT <pagani@astro.psu.edu>
C. Pagani (PSU), D. Morris (PSU) and D.N. Burrows (PSU) report on behalf of
the Swift-XRT team:
The XRT performed 2 observations of the field of GRB 060728 (GCN 5360),
starting at 2006-07-28-22:26:35 UT (124 seconds after the BAT trigger) to
2006-07-29-19:06:56 UT and from 2006-08-02-01:41:22 to 2006-08-02-22:57:56
UT, collecting 17.8 and 13.2ks of data in PC mode respectively.
No new source is detected within the BAT refined error circle (GCN 5363) in
either of the two exposures. The 3 sigma upper limit on the count-rate is
1.0e-3 counts/sec for the first observation, which corresponds to an
unabsorbed flux of 4.0e-14 erg cm-2 s-1 in the energy range 0.3-10 keV,
assuming a Crab-like spectrum, and 1.2e-3 counts/sec for the second
observation (unabsorbed flux of 4.8e-14 erg cm-2 s-1).
Combining the two observations the 3 sigma upper limit is 9.2e-4 counts/sec,
corresponding to an unabsorbed flux of 3.7e-14 erg cm-2 s-1.
This is the first case of a long GRB for which Swift performed a prompt slew
without a decection of the afterglow by the XRT. The only previously
undetected X-ray afterglow of a long GRB discovered by Swift is GRB 050911
(Page et al. 2006), for which the XRT observations started 4.6 hours after
the BAT trigger.
GCN Circular 5364
Subject
GRB 060728: Swift/UVOT Upper Limits
Date
2006-07-29T16:22:11Z (19 years ago)
From
Adam Morgan at PSU/Swift-UVOT <qmorgan@gmail.com>
A. N. Morgan, M. M. Chester, and C. Pagani (PSU) report on
behalf of the Swift/UVOT team:
The Swift UVOT began taking data on the field of GRB 060728
121s after the BAT trigger (Pagani et al., GCN Circ 5360).
No new source, relative to the DSS, is seen inside the
refined BAT error circle (Palmer et al., GCN Circ 5363).
Images were not taken in all filters due to a bright source
in the field-of-view. The 3-sigma limiting magnitudes for
the first finding chart and the coadded images are listed
below.
Finding chart:
Filter Midpoint (s) Exposure (s) 3-sigma LM
V 319 393 19.3
Coadded images:
Filter T_range(s) EXPOSURE (s) 3-sigma LM
V 121-6586 1113 19.9
UVW1 551-10828 1553 21.2
UVM2 527-6690 765 20.9
UVW2 578-11225 1029 21.2
T_range is calculated from the time of the burst. These
upper limits have not been corrected for the estimated
Galactic reddening of E(B-V) = 0.012 mag (Schlegel et
al. 1998).
GCN Circular 5363
Subject
GRB 060728: Refined analysis of the Swift-BAT burst
Date
2006-07-29T16:09:28Z (19 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
D. Palmer (LANL), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/ORAU), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), M. Koss (GSFC/UMD),
C. Markwardt (GSFC/UMD), C. Pagani (PSU), A. Parsons (GSFC),
T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC)
on behalf of the Swift-BAT team:
Using the data set from T-239 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 060728 (trigger #221627)
(Pagani, et al., GCN Circ. 5360). The BAT ground-calculated position is
RA,Dec = 16.646,-41.390 deg {1h 6m 35.1s, -41d 23' 23.1"} (J2000)
+- 3.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%.
The mask-weighted lightcurve shows a smooth (at 10-sec binning) single peak
starting at T_zero and ending at ~T+70 sec. T90 (15-350 keV) is 60 +- 10 sec
(estimated error including systematics).
The time-averaged spectrum from T+0.0 to T+64.0 is best fit by a
simple power-law model. The power law index of the time-averaged spectrum
is 1.40 +- 0.45. The fluence in the 15-150 keV band is
2.4 +- 0.7 x 10^-07 erg/cm2. All the quoted errors are at the 90%
confidence level.
Given (a) the weakness of this event and (b) the lack of an x-ray counterpart
(Pagani et al., GCN Circ 5361) and optical counterpart (Pagani et al., 5360),
we can not rule out the possibility that this is a hard x-ray transient,
but is most likely a burst. We note that Swift has not had a long GRB
with no XRT detection when a prompt slew occurred.
GCN Circular 5362
Subject
GRB 060728, SMARTS optical/IR observations
Date
2006-07-29T07:48:35Z (19 years ago)
From
Bethany Cobb at Yale U <cobb@astro.yale.edu>
B. E. Cobb, part of the larger SMARTS consortium, reports:
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we
obtained optical/IR imaging of the error region of GRB 060728
(Pagani et al. GCN 5360) with a mid-exposure time of ~6.8 hours
post-burst (2006-07-29 05:13 UT). Optical imaging in V and I has a
field of view of 6'x6' and, therefore, covers the entire GRB
error circle. IR imaging in J and K has a smaller field
of view (2.4'x2.4') and covers a region totaling 5.8 square arcminutes in
the middle of the quoted BAT error region. Total summed exposure
times amounted to 15 minutes in I and V and 12 minutes in J and K.
Preliminary visual comparison of the optical and IR images to the DSS
does not reveal any new sources. Our I-band limiting magnitude
is I ~ 22 (in comparison with several USNO-B1.0 stars). Our J-band
images does not contain any 2MASS stars, but the few sources detected in
the J-band image are all consistent with sources found in the DSS.
GCN Circular 5360
Subject
GRB 060728: Swift detection of a burst
Date
2006-07-28T23:07:24Z (19 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
C. Pagani (PSU), L. M. Barbier (NASA/GSFC), S. D. Barthelmy (GSFC),
M. M. Chester (PSU), J. R. Cummings (NASA/UMD),
C. B. Markwardt (GSFC/UMD), K. M. McLean (LANL/UTD),
A. N. Morgan (PSU), D. M. Palmer (LANL) and M. Stamatikos (NASA/ORAU)
report on behalf of the Swift Team:
At 22:24:30 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 060728 (trigger=221627). Swift slewed immediately
to the burst. The BAT on-board calculated location is RA,Dec
16.694, -41.386 {01h 06m 46s, -41d 23' 10"} (J2000) with an
uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). This is an 64-sec image trigger
so there is very little information in the TDRSS lightcuve.
The XRT began taking data at 22:26:35 UT, 124 seconds after the BAT
trigger. The XRT on-board centroid algorithm did not find a source in the
image and no prompt position is available. We are waiting for down-linked
data to detect and determine a position for the source.
The UVOT began observing at 22:26:31.7 UT, 121.1 seconds after the BAT trigger.
Images have been taken in V only, not in white, due to a bright source
in the field-of-view. Ground processing indicates an uncataloged, non-fading
source, V=16.93, 58 arcsecs from the BAT position.
We are currently in the Malindi gap in data downlinks, so it will
be about 6 hours until we get the full data set.