GRB 170710A
GCN Circular 21308
Subject
GRB 170710A: Swift detection of a burst
Date
2017-07-10T00:57:28Z (8 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
P. A. Evans (U Leicester), D. N. Burrows (PSU),
A. Cholden-Brown (PSU), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester) and
D. M. Palmer (LANL) report on behalf of the Swift Team:
At 00:45:44 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 170710A (trigger=761119). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 231.812, -38.547 which is
RA(J2000) = 15h 27m 15s
Dec(J2000) = -38d 32' 48"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a single-peaked
structure with a duration of about 10 sec. The peak count rate
was ~800 counts/sec (15-350 keV), at ~2 sec after the trigger.
The XRT began observing the field at 00:47:48.3 UT, 123.7 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 231.82076, -38.48434 which
is equivalent to:
RA(J2000) = 15h 27m 16.98s
Dec(J2000) = -38d 29' 03.6"
with an uncertainty of 4.4 arcseconds (radius, 90% containment). This
location is 226 arcseconds from the BAT onboard position. This position
may be improved as more data are received; the latest position is
available at http://www.swift.ac.uk/sper. We cannot determine whether
the source is fading at the present time. No spectrum from the promptly
downlinked event data is yet available to determine the column density.
The initial flux in the 2.5 s image was 4.07e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 131 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
0.17.
Burst Advocate for this burst is P. A. Evans (pae9 AT star.le.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 21309
Subject
GRB 170710A: Prompt enhanced Swift-XRT position
Date
2017-07-10T01:33:45Z (8 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Using promptly downlinked XRT event data for GRB 170710A, we find an
enhanced XRT position of the afterglow: RA, Dec: 231.8199, -38.4852
which is equivalent to:
RA (J2000) = 15 27 16.77
Dec (J2000) = -38 29 06.6
with an uncertainty of 2.3 arcseconds (radius, 90% confidence).
Analysis of the promptly available data is online at
http://www.swift.ac.uk/sper/761119.
Position enhancement is is described by Goad et al. (2007, A&A, 476,
1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular is an official product of the Swift-XRT team.
GCN Circular 21310
Subject
GRB 170710A: Enhanced Swift-XRT position
Date
2017-07-10T06:58:48Z (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 3131 s of XRT Photon Counting mode data and 4 UVOT
images for GRB 170710A, 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 = 231.82030, -38.48496 which is equivalent
to:
RA (J2000): 15h 27m 16.87s
Dec (J2000): -38d 29' 05.8"
with an uncertainty of 1.9 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 21311
Subject
GRB 170710A: Gemini-S candidate counterpart
Date
2017-07-10T11:04:40Z (8 years ago)
From
Antonino Cucchiara at UVI <antonino.cucchiara@uvi.edu>
A. Cucchiara (U. of the Virgin Islands) reports on
behalf of a larger collaboration:
"On July 10.17UT we imaged the field of GRB 170710A
(Evans et al. GCN 21308, 21309, Osborne et al. GCN 21310)
with the Gemini-South Telescope equipped with the GMOS camera.
We obtained 4x900s spectra covering the 5660-10300 Angstrom
wavelength range.
In our single 180 seconds acquisition image in i' band centered
on the Swift-XRT position we identified an uncatalogued
point-like sources at the edge of the refined position:
RA= +15:27:16.87
Dec= -38:29:06.0
Using nearby USNO-B1 stars for calibration, we measure a
magnitude of i' = 21.13 +/- 0.05.
At this point it is not possible to assess the variability
of this possible counterpart.
Preliminary analysis of the spectra reveals a faint trace
clearly visible down to the blue end of the spectrum.
No clear absorption or emission features are evident,
but more detailed analysis of the data is in progress.
We thank the Gemini staff for the prompt response, in particular
Veronica Firpo."
GCN Circular 21312
Subject
GRB 170710A: Swift-XRT refined Analysis
Date
2017-07-10T12:13:53Z (8 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), V. D'Elia
(ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), J.A. Kennea
(PSU), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), B. Mingo (U.
Leicester) and P. A. Evans (U Leicester) report on behalf of the
Swift-XRT team:
We have analysed 9.8 ks of XRT data for the Swift/BAT-detected burst
GRB 170710A (Evans et al. GCN Circ. 21308), from 114 s to 30.4 ks after
the Swift/BAT trigger. The data comprise 102 s in Windowed Timing (WT)
mode (the first 8 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. 21309).
The light curve can be modelled with an initial power-law decay with an
index of alpha=4.43 (+0.26, -0.23), followed by a break at T+446 s to
an alpha of 0.49 (+0.07, -0.08).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.81 (+/-0.10). The
best-fitting absorption column is 3.6 (+/-0.3) x 10^21 cm^-2, in
excess of the Galactic value of 1.8 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.96 (+0.28, -0.26)
and a best-fitting absorption column of 2.5 (+1.2, -0.7) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 3.7 x 10^-11 (5.1 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 2.5 (+1.2, -0.7) x 10^21 cm^-2
Galactic foreground: 1.8 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.96 (+0.28, -0.26)
If the light curve continues to decay with a power-law decay index of
0.49, the count rate at T+24 hours will be 0.011 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.1 x
10^-13 (5.7 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/00761119.
This circular is an official product of the Swift-XRT team.
GCN Circular 21313
Subject
GRB 170710A: Swift-BAT refined analysis
Date
2017-07-10T17:03:52Z (8 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), P. A. Evans (U Leicester),
H. A. Krimm (NSF/USRA), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+607 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 170710A (trigger #761119)
(Evans et al., GCN Circ. 21308). The BAT ground-calculated position is
RA, Dec = 231.851, -38.523 deg which is
RA(J2000) = 15h 27m 24.2s
Dec(J2000) = -38d 31' 22.2"
with an uncertainty of 3.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 22%.
The mask-weighted light curve shows a single-peaked structure that starts
and peaks at ~T0, and ends at ~T+37 s. T90 (15-350 keV) is 32.6 +- 10.5 sec
(estimated error including systematics).
The time-averaged spectrum from T+0.16 to T+36.91 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.91 +- 0.37. The fluence in the 15-150 keV band is 7.4 +- 1.7 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.48 sec in the 15-150 keV band
is 1.0 +- 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/761119/BA/
GCN Circular 21315
Subject
GRB170710A: Swift/UVOT detection
Date
2017-07-10T19:37:22Z (8 years ago)
From
Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>
A. A. Breeveld (UCL-MSSL), F. E. Marshall (NASA/GSFC) and P. A. Evans
(U. Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 170710A
132 s after the BAT trigger (Evans et al., GCN Circ. 21308).
An optical afterglow consistent with the enhanced XRT position (Osborne
et al., GCN Circ. 21310) and Gemini position (Cuchhiara, GCN Circ.
21311) is detected in the initial UVOT white finding chart.
Preliminary detection and 3-sigma upper limits using the UVOT
photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for
the first finding chart (FC) exposure and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 132 281 147 20.95 +/- 0.3
white 5808 6007 197 >21.0
v 2122 2141 19 >17.9
b 546 565 19 >18.9
u 290 539 246 >20.2
w1 2171 2166 20 >17.1
w2 2098 2117 20 >17.6
The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.172 in the direction of
the burst (Schlegel et al. 1998).
GCN Circular 21967
Subject
GRB 170710A: LCO Observations
Date
2017-10-04T12:24:38Z (8 years ago)
From
Antonino Cucchiara at UVI <antonino.cucchiara@uvi.edu>
A. Cucchiara (U. Virgin Islands) report on behalf of a larger
collaboration:
"On July 10.05 UT (T_0 +30 min) we began observing the
center of the field of GRB 170710A (Evans et al.
GCN 21308, Osborne et al. GCN 21310) using the Las Cumbres
Observatory 1m telescope located in Cerro Tololo.
We performed a series of 10x60s observations in SDSS I band
for a total of 10 minutes on sky.
In the full median stacked images we identified no optical
counterpart at the location of the optical counterpart
(Cucchiara et al. GCN 21311, Breeveld et al. GCN 21315).
Nevertheless, at the OT location we identified a
2-sigma excess corresponding to I=21.28 +- 0.24 mag, consistent
with other observations at similar time post-burst.
These magnitudes are calibrated against nearby USNO-B1 sources,
and not corrected for Galactic extinction."