GRB 171004A
GCN Circular 21974
Subject
GRB 171004A: Swift/UVOT Upper Limits
Date
2017-10-05T14:03:40Z (8 years ago)
From
Jeffrey Gropp at PSU <jdg44@psu.edu>
J. D. Gropp (PSU) and S. B. Cenko (GSFC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 171004A
184 s after the BAT trigger (Cenko et al., GCN Circ. 21966).
No optical afterglow consistent with the refined XRT position
(Osborne et al. GCN Circ. 21970)
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 184 4143 233 >20.3
b 3903 4103 197 >19.8
u 3698 3898 197 >19.7
The magnitudes in the table 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 21973
Subject
GRB 171004A: Swift-BAT refined analysis
Date
2017-10-04T21:13:14Z (8 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC),
S. B. Cenko (GSFC), 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), M. Stamatikos (OSU)
(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 171004A (trigger #776347)
(Cenko et al., GCN Circ. 21966). The BAT ground-calculated position is
RA, Dec = 139.150, 52.684 deg which is
RA(J2000) = 09h 16m 35.9s
Dec(J2000) = +52d 41' 01.5"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 42%.
The mask-weighted light curve shows several overlapping peaks that starts
at ~ T+9 and ends at ~ T+160 s. The burst location went out of the BAT FOV
at ~ T+580 s, and thus we only have information of the burst emission before
then. T90 (15-350 keV) is 107.1 +- 14.5 sec (estimated error including
systematics).
The time-averaged spectrum from T+9.08 to T+138.31 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.67 +- 0.12. The fluence in the 15-150 keV band is 3.0 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+48.34 sec in the 15-150 keV band
is 0.9 +- 0.3 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/776347/BA/
GCN Circular 21972
Subject
GRB 171004A: Correction to RATIR Astrometry and Photometry
Date
2017-10-04T20:04:21Z (8 years ago)
From
Alan M. Watson at Instituto de Astronomia UNAM <alan@astro.unam.mx>
Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC),
William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J.
Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI),
Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz
(UCSC), Jes��s Gonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM), Harvey
Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki
Toy (UMD) report:
The position and magnitudes of the uncataloged source reported by Watson
et al. (GCN Circ. 21968) are incorrect. We thank David Alexander Kann
for drawing our attention to this error.
The correct position is RA, Dec = 139.169462 52.693080 (J2000) or
09:16:40.67 +52:41:35.1. This position lies 0.4 arcsec from the enhanced
XRT position (Osborne et al., GCN Circ. 21970).
The correct magnitudes are
r = 21.17 +/- 0.06
i = 20.87 +/- 0.05
Z = 20.72 +/- 0.10
Y = 20.59 +/- 0.13
J = 20.36 +/- 0.14
H = 20.17 +/- 0.17
A fit to the i-band light curve of the source shows that the flux
behaves as t^(-0.9+/-0.4). That is, it is fading at the 2-sigma level.
The positional coincidence combined with the weak evidence for fading
suggest that this source might well be the afterglow of the GRB.
GCN Circular 21971
Subject
GRB 171004A: Swift-XRT refined Analysis
Date
2017-10-04T18:21:58Z (8 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
A.P. Beardmore (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia
(ASDC), A. D'Ai (INAF-IASFPA), S. J. LaPorte (PSU), J.A. Kennea (PSU),
B. Sbarufatti (INAF-OAB/PSU), P.A. Evans (U. Leicester), S.L. Gibson
(U. Leicester) and S.B. Cenko report on behalf of the Swift-XRT team:
We have analysed 7.5 ks of XRT data for GRB 171004A (Cenko et al. GCN
Circ. 21966), from 164 s to 17.4 ks after the BAT trigger. The data
comprise 296 s in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Osborne et
al. (GCN Circ. 21970).
The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=1.1 (+/-0.4). At T+205 s the decay
steepens to an alpha of 4.1 (+0.9, -0.8). The light curve breaks again
at T+524 s to a decay with alpha=0.3 (+0.5, -1.3), before a final
break at T+5520 s s after which the decay index is 2.25 (+0.26, -0.16).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.25 (+/-0.08). The
best-fitting absorption column is 2.41 (+0.28, -0.27) x 10^21 cm^-2,
in excess of the Galactic value of 1.5 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.98 (+/-0.11) and a
best-fitting absorption column of 8.8 (+2.8, -2.7) x 10^20 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 3.3 x 10^-11 (4.0 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 8.8 (+2.8, -2.7) x 10^20 cm^-2
Galactic foreground: 1.5 x 10^20 cm^-2
Excess significance: 4.5 sigma
Photon index: 1.98 (+/-0.11)
If the light curve continues to decay with a power-law decay index of
2.25, the count rate at T+24 hours will be 2.1 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.9 x
10^-14 (8.3 x 10^-14) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00776347.
This circular is an official product of the Swift-XRT team.
GCN Circular 21970
Subject
GRB 171004A: Enhanced Swift-XRT position
Date
2017-10-04T17:32:21Z (8 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester)
report on behalf of the Swift-XRT team.
Using 2218 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 171004A, 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 = 139.16941, +52.69319 which is equivalent
to:
RA (J2000): 09h 16m 40.66s
Dec (J2000): +52d 41' 35.5"
with an uncertainty of 1.4 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, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the
Swift-XRT team.
GCN Circular 21968
Subject
GRB 171004A: RATIR Optical and NIR Observations
Date
2017-10-04T13:26:20Z (8 years ago)
From
Alan M. Watson at Instituto de Astronomia UNAM <alan@astro.unam.mx>
Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC),
William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J.
Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI),
Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz
(UCSC), Jes��s Gonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM), Harvey
Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki
Toy (UMD) report:
We observed the field of GRB 171004A (Cenko et al., GCN Circ. 21966)
with the Reionization and Transients Infrared Camera (RATIR;
www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio
Astron��mico Nacional on Sierra San Pedro M��rtir from 2017/10 4.45 to
2017/10 4.45 to 2017/10 4.52 UTC (2.97 to 4.45 hours after the BAT
trigger), obtaining a total of 1.07 hours exposure in the r and i bands
and 0.45 hours exposure in the Z, Y, J, and H bands.
We detect two sources within the Swift-XRT error circle. One is a
cataloged SDSS source. The other is at 09:16:40.66 +52:41:30.4 (J2000
+/- 0.5 arcsec) and, in comparison with the SDSS DR9 and 2MASS catalogs,
has
r = 21.91 +/- 0.11
i = 21.32 +/- 0.07
Z = 21.13 +/- 0.15
Y = 20.43 +/- 0.12
J = 20.45 +/- 0.15
H = 19.88 +/- 0.13
These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.
We thank the staff of the Observatorio Astron��mico Nacional in San Pedro
M��rtir.
GCN Circular 21966
Subject
GRB 171004A: Swift detection of a burst
Date
2017-10-04T08:20:31Z (8 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
S. B. Cenko (GSFC), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), A. A. Breeveld (UCL-MSSL),
P. A. Evans (U Leicester), J.D. Gropp (PSU), K. L. Page (U Leicester)
and M. H. Siegel (PSU) report on behalf of the Swift Team:
At 07:55:32 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 171004A (trigger=776347). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 139.162, +52.680, which is
RA(J2000) = 09h 16m 39s
Dec(J2000) = +52d 40' 48"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). As is typical for image triggers, there is nothing
significant in the real-time light curve.
The XRT began observing the field at 07:58:26.9 UT, 174.7 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 139.1713, 52.6937 which is equivalent to:
RA(J2000) = +09h 16m 41.11s
Dec(J2000) = +52d 41' 37.3"
with an uncertainty of 4.9 arcseconds (radius, 90% containment). This
location is 53 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy.
The initial flux in the 2.5 s image was 3.22e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 52 seconds with the White filter
starting 184 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 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
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.02.
Burst Advocate for this burst is S. B. Cenko (brad.cenko AT 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.)