GRB 171020A
GCN Circular 22028
Subject
GRB 171020A: Swift detection of a burst
Date
2017-10-20T23:28:53Z (8 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
K. L. Page (U Leicester), A. P. Beardmore (U Leicester),
J.D. Gropp (PSU), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL),
A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC),
B. Sbarufatti (PSU) and M. H. Siegel (PSU) report on behalf of the
Swift Team:
At 23:07:10 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 171020A (trigger=780845). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 39.262, +15.186 which is
RA(J2000) = 02h 37m 03s
Dec(J2000) = +15d 11' 10"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a multi-peaked
structure with a duration of about 50 sec. The peak count rate
was ~2000 counts/sec (15-350 keV), at ~2 sec after the trigger.
Note that the BAT light curve might be contaminated by Swift J0243.6+6124,
which has a period of 9.86 s (ATel #10809).
The XRT began observing the field at 23:09:35.2 UT, 144.4 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 39.2482,
15.2038 which is equivalent to:
RA(J2000) = 02h 36m 59.57s
Dec(J2000) = +15d 12' 13.5"
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This
location is 80 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 1.55
x 10^21 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 147 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
0.19.
Burst Advocate for this burst is K. L. Page (klp5 AT leicester.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 22029
Subject
GRB 171020A: NOT optical afterglow detection
Date
2017-10-21T00:19:15Z (8 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
D. Malesani (DARK/NBI), M. Stone (Turku Univ.), K. Karhunen (Turku
Univ.), A. de Ugarte Postigo (IAA/CSIC and DARK/NBI), and D. Xu
(NAOC/CAS), report on behalf of a larger collaboration:
We observed the field of GRB 171020A (Page et al., GCN 22028) with the
Nordic Optical Telescope equipped with the AlFOSC imager and
spectrograph. Observations were carried out in the r and z filters,
starting on 2017 Oct 20.979 UT (22.9 min after the trigger).
Within the XRT error circle, we detect an uncatalogued source at
coordinates (J2000):
RA = 02:36:59.62
Dec = +15:12:16.0
By comparison with nearby stars from the Pan-STARRS catalog, we measure
r = 20.98 +- 0.03 AB. As this object is not visible in the deeper,
archival Pan-STARRS images, and given the coincidence with the X-ray
counterpart, we suggest this object to be the optical afterglow of GRB
171020A.
GCN Circular 22030
Subject
GRB 171020A: Mini-MegaTORTORA upper limits on simultaneous optical emission
Date
2017-10-21T00:31:17Z (8 years ago)
From
Sergey Karpov at SAO RAS <karpov@sao.ru>
S.Karpov, G.Beskin (SAO RAS and Kazan Federal University, Russia), S.Bondar,
E.Ivanov, E.Katkova, N.Orekhova, A.Perkov (OJS RPC PSI, Russia), A.Biryukov
(SAI MSU and Kazan Federal University, Russia), V.Sasyuk (Kazan Federal
University, Russia)
Mini-MegaTORTORA nine-channel wide-field monitoring system with high
temporal resolution has been observing the Swift field of view before,
during and after the time of Swift BAT trigger corresponding to GRB171020A
(Page et al, GCN 22028). The whole burst localization region has been
covered since 2017-10-20 23:00:07.90 UT (T0-422 s) and until 2017-10-20
23:10:17.68 UT (T0+187 s, thus including the whole gamma-ray activity
interval) with temporal resolution of 0.1 s in white light. Dedicated
real-time transient detection pipeline did not detect any events longer
than 0.3 s and brighter than approximately V=10.5 mag during this interval.
Visual inspection of co-added images with 10 s effective exposure
(summation of 100 consecutive frames each) has not revealed any variable
source down to V=12.0 mag during that interval. Also, the multi-regime
follow-up (when all channels except for the one containing the trigger are
repointed towards it and observe it with various exposures with and without
photometric and polarimetric filters installed) has been initiated at
2017-10-20 23:08:12.0 UT (T0+61.25 s). The inspection of 10 s exposure
frames acquired in white light between 2017-10-20 23:08:12.0 UT (T0+61.25
s) and 2017-10-20 23:09:43 UT (T0+152.25 s) did not reveal any source
brighter than V=13.5 mag at the position of the burst.
Mini-MegaTORTORA belongs to Kazan Federal University and is located at
Special Astrophysical Observatory near Russian 6-m telescope.
The message may be cited.
GCN Circular 22031
Subject
GRB 171020A: Confirmation of OT fading
Date
2017-10-21T03:32:12Z (8 years ago)
From
Moskvitin Alexander at SAO RAS <mosk@sao.ru>
A. Moskvitin (SAO RAS), O. Spiridonova (SAO RAS), A. Volnova (IKI RAS)
We observed the field of GRB 171020A (Page et al., GCN 22028)
with the 1-m telescope of SAO RAS, Zeiss-1000 on 2017.10.20,
starting at 23:18 UT, i.e. ~11 minutes after the trigger.
The OT (Malesani et al., GCN 22029) is clearly detected
in the individual 300 sec. frames. The coordinates of OT:
R. A. = 02:36:59.62; Dec. = +15:12:15.6 (J2000).
Date UT start t - T0 Filter Exp. OT Err. UL
(mid, days) (s)
2017.10.20 23:18:05 0.02016 Rc 6*300 20.9 +/- 0.1 22.3
23:55:27 0.04827 Rc 7*300 21.5 +/- 0.1 22.5
The temporal decay slope is about -0.3, F ~ (t-T0)^alpha.
The calibration were made against the nearby USNO-B1.0 stars
(R2 magnitudes):
1051-0026883 02:37:00.38 +15:11:09.6 18.59
1052-0027787 02:36:57.49 +15:12:36.8 16.62
1052-0027776 02:36:50.26 +15:12:39.8 18.15
GCN Circular 22032
Subject
GRB 171020A: Correction of alpha in GCN 22031
Date
2017-10-21T03:49:17Z (8 years ago)
From
Moskvitin Alexander at SAO RAS <mosk@sao.ru>
A. Moskvitin (SAO RAS), O. Spiridonova (SAO RAS), A. Volnova (IKI RAS)
In our previous GCN 22031 we reported incorrect slope.
The correct decay slope is about -0.6 +/- 0.2.
We apologize for any confusion caused by the earlier report.
GCN Circular 22033
Subject
GRB 171020A: LT observations
Date
2017-10-21T06:30:48Z (8 years ago)
From
Cristiano Guidorzi at Ferrara U,Italy <guidorzi@fe.infn.it>
C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell (U. Bath),
A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU) on behalf of a large
collaboration report:
The 2-m Liverpool Telescope automatically began observing Swift GRB
171020A (Page et al. GCN 22028) on October 20, 23:10:12 UT (3.0 minutes
from the GRB trigger time) with the RINGO3 polarimeter and the IO:O
camera in the SDSS-R filter. We clearly detect the optical afterglow
(Malesani et al, GCN 22029; Moskvitin et al., GCN 22031) with the
following magnitude:
Mid Time���������� Exposure������������ Filter������������ Magnitude (AB)
(min)�������������������� (s)
-------------------------------------------------------
35.8���������������������� 6x10 ���������������� SDSS-R������������ 21.12 +- 0.14
-------------------------------------------------------
as calibrated against nearby Pan-STARRS objects.
GCN Circular 22034
Subject
GRB 171020A: Enhanced Swift-XRT position
Date
2017-10-21T08:10:11Z (8 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester)
report on behalf of the Swift-XRT team.
Using 5393 s of XRT Photon Counting mode data and 8 UVOT
images for GRB 171020A, 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 = 39.24837, +15.20413 which is equivalent
to:
RA (J2000): 02h 36m 59.61s
Dec (J2000): +15d 12' 14.9"
with an uncertainty of 1.6 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 22035
Subject
GRB 171020A: Swift-XRT refined Analysis
Date
2017-10-21T10:34:06Z (8 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
A. Tohuvavohu (PSU), S. J. LaPorte (PSU), J.A. Kennea (PSU), A.P.
Beardmore (U. Leicester), P.A. Evans (U. Leicester), P. D'Avanzo
(INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA) and K.L. Page
report on behalf of the Swift-XRT team:
We have analysed 7.5 ks of XRT data for GRB 171020A (Page et al. GCN
Circ. 22028), from 128 s to 35.4 ks after the BAT trigger. The data
comprise 10 s in Windowed Timing (WT) mode (taken while Swift was
slewing), with the remainder in Photon Counting (PC) mode. The enhanced
XRT position for this burst was given by Evans et al. (GCN Circ.
22034).
The light curve can be modelled with an initial power-law decay with an
index of alpha=2.23 (+0.45, -0.21), followed by a break at T+563 s to
an alpha of 0.88 (+0.08, -0.07).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.58 (+0.17, -0.15). The
best-fitting absorption column is 1.84 (+0.70, -0.28) x 10^21 cm^-2,
consistent with the Galactic value of 1.6 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 4.5 x 10^-11 (5.3 x
10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 1.84 (+0.70, -0.28) x 10^21 cm^-2
Galactic foreground: 1.6 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.58 (+0.17, -0.15)
If the light curve continues to decay with a power-law decay index of
0.88, the count rate at T+24 hours will be 5.4 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.4 x
10^-13 (2.9 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/00780845.
This circular is an official product of the Swift-XRT team.
GCN Circular 22037
Subject
GRB 171020A: RATIR Optical and NIR Observations
Date
2017-10-21T15:28:40Z (8 years ago)
From
Nat Butler at Az State U <natbutler@asu.edu>
Nat Butler (ASU), Alan M. Watson (UNAM), 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 171020A (Page, et al., GCN 22028) 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 21.16 to 2017/10 21.50 UTC (4.60 to
12.98 hours after the BAT trigger), obtaining a total of 5.30 hours
exposure in the r and i bands and 2.20 hours exposure in the Z, Y, J, and H
bands.
We detect the NOT optical transient (Malesani, et al., GCN 22029), which
continues to fade (see also, Moskvitin, et al., GCN 22031). In comparison
with the USNO-B1 and 2MASS catalogs, we obtain the following detections and
upper limit (3-sigma):
r = 22.91 +/- 0.12
i = 22.76 +/- 0.11
Z > 21.44
Y = 21.72 +/- 0.35
J = 21.54 +/- 0.23
H = 21.69 +/- 0.35
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 22038
Subject
GRB 171020A: Swift-BAT refined analysis
Date
2017-10-21T15:54:40Z (8 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
H. A. Krimm (NSF/USRA), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), K. L. Page (U Leicester)
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+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 171020A (trigger #780845)
(Page et al., GCN Circ. 22028). The BAT ground-calculated position is
RA, Dec = 39.260, 15.199 deg which is
RA(J2000) = 02h 37m 02.3s
Dec(J2000) = +15d 11' 57.0"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 48%.
The mask-weighted light curve shows a weak pulse that starts at ~T0 and
ends at ~ T+45 s. T90 (15-350 keV) is 41.9 +- 9.2 sec (estimated error
including systematics).
The time-averaged spectrum from T-0.97 to T+46.68 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.04 +- 0.20. The fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+19.92 sec in the 15-150 keV band
is 0.7 +- 0.2 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/780845/BA/
GCN Circular 22039
Subject
GRB 171020A: NOT spectroscopic redshift
Date
2017-10-21T16:43:25Z (8 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
D. Malesani (DARK/NBI), J. P. U. Fynbo (NBI), K. E. Heintz (Univ.
Iceland and DARK/NBI), M. Stone (Turku Univ.), K. Karhunen (Turku
Univ.), report on behalf of a larger collaboration:
Following our imaging sequence (Malesani et al., GCN 22029), we secured
spectra of the optical afterglow of GRB 171020A (Page et al., GCN
22028), using the AlFOSC spectrograph at the Nordic Optical Telescope. A
total of 4x1200 s exposure was secured using grism #4, covering the
wavelength range ~3600-9400 AA. Spectroscopy started on 2017 Oct 21.005
UT (1 hr after the trigger).
A faint trace is detected down to at least ~4000 A. Several weak
absorption features are detected, which we interpret as due to Mg II, Fe
II, and C IV all at a common redshift z = 1.87.
We thank the NOT staff for support, in particular Amanda Djupvik and
Sergio Armas.
GCN Circular 22040
Subject
GRB 171020A: Swift/UVOT Upper Limits
Date
2017-10-22T06:43:09Z (8 years ago)
From
Sam LaPorte at PSU <sjl5346@psu.edu>
GRB 171020A: Swift/UVOT Upper Limits
S. J. LaPorte (PSU) and K. L. Page (U. Leicester)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 171020A
147 s after the BAT trigger (Page et al., GCN Circ. 22028).
No optical afterglow consistent with the XRT position
(Page et al. GCN Circ. 22028)
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 first
finding chart (FC) exposure and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 147 297 147 >20.6
u_FC 306 556 246 >20.2
white 147 7652 811 >21.4
v 636 6640 338 >19.4
b 562 7460 529 >20.8
u 306 7254 756 >20.2
w1 686 7050 491 >20.7
m2 6645 6845 197 >20.3
w2 1016 6435 216 >20.3
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.19 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 22041
Subject
GRB 171020A: TAROT Calern observatory optical observations
Date
2017-10-22T13:08:21Z (8 years ago)
From
Alain Klotz at IRAP-CNRS-OMP <Alain.Klotz@free.fr>
Klotz A., Noysena.K., Atteia J.L. (CNRS-OMP-IRAP),
Boer, M., Eymar, L. (CNRS-ARTEMIS),
Gendre B. (UVI - Etelman Obs.) report:
We imaged the field of GRB 171020A detected by SWIFT
(trigger 780845) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.
The observations started 68s after the GRB trigger
(13s after the notice). The elevation of the field
increased from 58 degrees above horizon and weather
conditions were good.
The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We do not detect any OT with a limiting magnitude of:
t0+68s to t0+128s : Rlim = 17.5
The OT (Malesani et al., GCN 22029) is detected
in the median of three individual frames:
t0+141s to t0+251s : R = 18.7 +/- 0.35
We co-added a series of exposures. The OT is no
longer detected:
t0+262s to t0+533s : Rlim = 18.9
Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.
GCN Circular 22042
Subject
GRB 171020A: Continued RATIR Optical and NIR Observation
Date
2017-10-22T21:19:00Z (8 years ago)
From
Nat Butler at Az State U <natbutler@asu.edu>
Nat Butler (ASU), Alan M. Watson (UNAM), 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 171020A (Page, et al., GCN 22028) 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 22.13 to 2017/10 22.47 UTC (27.94 to
36.23 hours after the BAT trigger), obtaining a total of 5.27 hours
exposure in the r and i bands and 2.21 hours exposure in the Z and Y bands.
We contine to detect the optical transient (Malesani, et al., GCN 22029;
also, Moskvitin, et al., GCN 22031; Butler, et al., GCN 22037). In
comparison with the USNO-B1 and 2MASS catalogs, we obtain the following
detections and upper limits (3-sigma):
r = 23.25 +/- 0.14
i = 23.01 +/- 0.11
Z > 21.75
Y > 22.05
These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB. Compared to our observations last
night, these data suggest either a slow afterglow fade (~t^-0.2) or that
our measured flux contains flux from the GRB host galaxy.
We thank the staff of the Observatorio Astron��mico Nacional in San Pedro
M��rtir.