GRB 170728A
GCN Circular 21465
Subject
GRB 170728A: 15 GHz upper limits from AMI
Date
2017-08-11T18:11:16Z (8 years ago)
From
Kunal Mooley at Oxford U <kunal.mooley@physics.ox.ac.uk>
K. P. Mooley (Hintze Fellow, Oxford), T. D. Staley, R. P. Fender
(Oxford), G. E. Anderson (Curtin), T. Cantwell (Manchester), D.
Titterington, S. H. Carey, J. Hickish, Y. C. Perrott, N. Razavi-Ghods,
P. Scott (Cambridge), K. Grainge, A. Scaife (Manchester)
The AMI Large Array robotically triggered on the Swift alert for GRB
170728A (Cannizzo et al., GCN 21367) as part of the 4pisky program, and
subsequent follow up observations were obtained up to 10 days
post-burst. Our observations at 15 GHz on 2017 Jul 28.32, Jul 30.25, Aug
01.27 and Aug 05.23 (UT) do not reveal any radio source at the XRT
location (Goad et al., GCN 21368), with 3sigma upper limits of 141 uJy,
131 uJy, 129 uJy and 133 uJy respectively.
We thank the AMI staff for scheduling these observations. The AMI-GRB
database is a log of all GRB follow up observations with the AMI, and is
available at http://4pisky.org/ami-grb/.
GCN Circular 21386
Subject
GRB 170728A: Swift/UVOT Detection
Date
2017-07-29T21:09:59Z (8 years ago)
From
Sam LaPorte at PSU <sjl5346@psu.edu>
GRB 170728A: Swift/UVOT Detection
S. J. Laporte (PSU) and J. K. Cannizzo (NASA/UMBC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 170728A
74 s after the BAT trigger (Cannizzo et al., GCN Circ. 21367).
A fading source consistent with the XRT position
(Goad et al. GCN Circ. 21368)
is detected in the initial UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 03:55:33.17 = 58.88819 (deg.)
Dec (J2000) = +12:10:54.7 = 12.18187 (deg.)
with an estimated uncertainty of 0.56 arc sec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limits using the UVOT photometric
system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 70 219 147 19.20+-0.17
white 70 4048 342 19.93+-0.18
v 4264 5808 267 >19.1
b 3655 11916 345 >19.7
u 287 22167 1283 >20.0
w1 6020 21852 1105 >20.1
m2 5814 16112 1082 >20.6
w2 4059 4259 197 >19.6
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.24 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 21382
Subject
GRB 170728A: LCO observations
Date
2017-07-29T14:47:33Z (8 years ago)
From
Antonino Cucchiara at UVI <antonino.cucchiara@uvi.edu>
A. Cucchiara, D. Morris (U. of Virgin Islands), and
C. Guidorzi (U. Ferrara), reports on behalf of a larger
collaboration:
"On July 28.38 UT (T_0 +2.1h) we began observing the center
of the field of GRB 170728A (Cannizzo et al. GCN 21367,
Evans et al. GCN 21368) using the Las Cumbres Observatory
1m telescope in Cerro Tololo.
We performed a series of 4x240s observations in R and Ic band
for a total of 16 minutes on sky in each filter at average
airmass of 1.8. Further observations were requested in Sloane
i' filter for a total of 360s.
In the full combined R and I+i' stacks we identified no optical
counterpart within the center of Swift-XRT refined position
(Evans et al. GCN 21368) at the following 3-sigma limits:
R > 18.9 mag
I > 18.4 mag
These magnitudes are calibrated against nearby USNO-B1 sources,
and are not corrected for Galactic extinction."
GCN Circular 21378
Subject
GRB 170728A: Swift-XRT refined Analysis
Date
2017-07-29T07:03:35Z (8 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU),
S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo
(INAF-OAB) and J.K. Cannizzo report on behalf of the Swift-XRT team:
We have analysed 4.8 ks of XRT data for GRB 170728A (Cannizzo et al.
GCN Circ. 21367), from 84 s to 22.2 ks after the BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position
for this burst was given by Goad et al. (GCN Circ. 21368).
The light curve can be modelled with a power-law decay with a decay
index of alpha=0.89 (+/-0.07).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.22 (+0.32, -0.25). The
best-fitting absorption column is 2.7 (+1.1, -0.4) x 10^21 cm^-2,
consistent with the Galactic value of 2.3 x 10^21 cm^-2 (Willingale et
al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum is 3.3 x 10^-11 (5.3 x
10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 2.7 (+1.1, -0.4) x 10^21 cm^-2
Galactic foreground: 2.3 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index: 2.22 (+0.32, -0.25)
If the light curve continues to decay with a power-law decay index of
0.89, the count rate at T+24 hours will be 2.8 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.1 x
10^-14 (1.5 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/00765008.
This circular is an official product of the Swift-XRT team.
GCN Circular 21370
Subject
GRB 170728A: Swift-BAT refined analysis
Date
2017-07-28T22:55:07Z (8 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
M. Stamatikos (OSU), S. D. Barthelmy (GSFC),
J. K. Cannizzo (NASA/UMBC), J. R. Cummings (CPI),
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 170728A (trigger #765008)
(Cannizzo et al., GCN Circ. 21367