GRB 170921A
GCN Circular 21951
Subject
GRB 170921A: 15 GHz upper limits from AMI
Date
2017-10-01T20:13:58Z (9 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
170921A (D'Ai et al., GCN 21901) 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 Sep 21.89, Sep 27.04 and
Sep 28.97 (UT) do not reveal any radio source at the XRT location
(Beardmore et al., GCN 21906), with 3sigma upper limits of 186 uJy, 117
uJy and 159 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 21915
Subject
GRB 170921A: RATIR Optical Afterglow Detection and NIR Observations
Date
2017-09-22T23:22:09Z (9 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 (ASU), and Vicki Toy (UMD) report:
We observed the field of GRB 170921A (D'Ai, et al., GCN 21901) 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 2017/09 22.18 to 2017/09 22.51 UTC (13.82 to
21.76 hours after the BAT trigger), obtaining a total of 5.29 hours
exposure in the r and i bands and 2.22 hours exposure in the Z, Y, J, and H
bands.
For a source within the Swift-XRT error circle (Beardmore, et al., GCN
21906), in comparison with the SDSS DR9 and 2MASS catalogs, we obtain the
following weak detections and upper limits (3-sigma):
r = 24.45 +/- 0.34
i = 24.38 +/- 0.34
Z > 23.05
Y > 22.83
J > 22.47
H > 22.19
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 21913
Subject
GRB 170921A: Swift/UVOT Upper Limits
Date
2017-09-22T14:56:56Z (9 years ago)
From
Sam LaPorte at PSU <sjl5346@psu.edu>
GRB 170921A: Swift/UVOT Upper Limits
S. J. LaPorte (PSU) and A. D'Ai (INAF-IASFPA)
report on behalf of the Swift/UVOT team:
(Beardmore et al. GCN Circ. 21906)
The Swift/UVOT began settled observations of the field of GRB 170921A
101 s after the BAT trigger (D'Ai et al., GCN Circ. 21901).
No optical afterglow consistent with the XRT position
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 101 251 147 >20.7
u_FC 259 509 246 >20.4
white 101 6816 766 >21.4
v 590 7186 451 >19.9
b 516 6611 471 >20.6
u 259 12926 1346 >21.1
w1 639 12273 1171 >20.6
m2 1412 11366 1102 >21.0
w2 566 16512 687 >21.0
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.05 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 21912
Subject
GRB 170921A: Swift-BAT refined analysis
Date
2017-09-22T14:27:15Z (9 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
T. Sakamoto (AGU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), A. D'Ai (INAF-IASFPA)
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
M. Stamatikos (OSU), 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 170921A (trigger #773509)
(D'Ai et al., GCN Circ. 21901). The BAT ground-calculated position is
RA, Dec = 26.840, 30.880 deg which is
RA(J2000) = 01h 47m 21.6s
Dec(J2000) = +30d 52' 47.1"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 86%.
The mask-weighted light curve shows a single-peaked structure that starts at
~T-22 s, peaks at ~T+3 s, and ends at ~T+13 s. T90 (15-350 keV) is
28.9 +- 6.0 sec (estimated error including systematics).
The time-averaged spectrum from T-21.82 to T+13.00 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.76 +- 0.17. The fluence in the 15-150 keV band is 6.7 +- 0.8 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+2.74 sec in the 15-150 keV band
is 0.8 +- 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/773509/BA/
GCN Circular 21910
Subject
GRB 170921A: LCO 2m telescope observations
Date
2017-09-22T12:07:33Z (9 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), A. Cucchiara, D. Morris,
and B. Gendre (U. Virgin Islands) on behalf of a large collaboration report:
We began observing Swift GRB 170921A (D'Ai et al. GCN 21901) on
September 21, from 14:52 to 15:05 UT (from 24 to 37 minutes since the
GRB trigger time) with the LCO 2-m telescope in Hawaii in the SDSS R and
I filters. Within the enhanced Swift-XRT circle (Beardmore et al. GCN
21906) we do not detect any optical counterpart down to the following
limits, in agreement with previous reports (Klotz et al. GCN 21903;
Kuroda et al. GCN 21905; Feng et al. GCN 21907; Malesani et al. GCN 21909):
Mid Time����� Exposure������ Filter������ Magnitude (AB)
(min)���������� (s)
-------------------------------------------------------
26.8���������� 5x60��������� SDSS-R������� > 20.7
34.0���������� 3x60��������� SDSS-I������� > 19.8
-------------------------------------------------------
as calibrated against nearby SDSS objects.
GCN Circular 21909
Subject
GRB 170921A: NOT optical observations
Date
2017-09-22T07:23:28Z (9 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
D. Malesani (DARK/NBI), K. E. Heintz (Univ. Iceland and DARK/NBI), N. R.
Tanvir (Univ. Leicester), D. A. Kann (IAA/CSIC), T. Pursimo (NOT), and
S. Dyrbye (NOT) report on behalf of a larger collaboration:
We observed the field of GRB 170921A (D'Ai et al., GCN 21901) with the
Nordic Optical Telescope equipped with the AlFOSC imager. Observations
were carried out with the SDSS r' and z' filters, for a total exposure
of 900 and 1800 s, respectively.
We did not detect any new object inside or in the proximity of the
enhanced X-ray error circle (Beardmore et al., GCN 21906). At mean
epochs 2017 Sep 21.941 and Sep 21.958 UT (8.1 and 8.5 hr after the GRB),
we report 3-sigma limiting magnitudes r' > 24.3 and z' > 23.3,
respectively (both AB, calibrated against the Pan-STARRS catalog).
Our non-detections are consistent with the reports by TAROT (Klotz et
al., GCN 21903), MITSuME (Kuroda et al., GCN 21905), and Nanshan (Feng
et al., GCN 21907).
GCN Circular 21907
Subject
GRB 170921A: Nanshan optical upper limit
Date
2017-09-22T00:33:24Z (9 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
H.X. Feng (NAOC), Y.D. Hu (IAA-CSIC), D. Xu, Z.P. Zhu (NAOC), X. Zhang, T.Z. Yang, J.Z. Liu, A. Esamdin, L. Ma (XAO), Y. Qin (Geneva Obs.) report:�� We observed the field of long GRB 170921A (D'Ai et al., GCN 21901)��using the 1m telescope located at Nanshan, Xinjiang, China. We obtained��3*180s R-band frames, starting at 15:52:35.04 UT on 2017-09-21 (i.e., 1.39 hr after the BATtrigger).�� No optical source is detected at the XRT position (Beardmore et al., GCN 21906) in the stacked image, down to a limiting magnitude of m(R)~20.3,��calibrated with the USNO-B1 catalog.��
GCN Circular 21906
Subject
GRB 170921A: Enhanced Swift-XRT position
Date
2017-09-21T23:19:36Z (9 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester)
report on behalf of the Swift-XRT team.
Using 2671 s of XRT Photon Counting mode data and 5 UVOT
images for GRB 170921A, 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 = 26.84906, +30.90673 which is equivalent
to:
RA (J2000): 01h 47m 23.77s
Dec (J2000): +30d 54' 24.2"
with an uncertainty of 1.5 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 21905
Subject
GRB 170921A: MITSuME Okayama upper limits
Date
2017-09-21T22:40:42Z (9 years ago)
From
Daisuke Kuroda at OAO/NAOJ <dikuroda@oao.nao.ac.jp>
D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ),
S. Nagayama (NAOJ), M. Yoshida (Subaru, NAOJ), K. Ohta (Kyoto)
and N. Kawai(Tokyo Tech) report on behalf of MITSuME collaboration:
We observed the field of GRB 170921A (D'Ai et al., GCNC 21901)
with the optical three color (g', Rc and Ic) CCD camera attached
to the MITSuME 50cm telescope of Okayama Astrophysical Observatory.
The observation started on 2017-09-21 14:39:14 UT (~10 min after
the burst). We did not find any new point source within the XRT
error circle (D'Ai et al., GCNC 21901) in all the three bands.
Three sigma upper limits of the OT are listed below.
We used SDSS-DR8 catalog for flux calibration.
#T0+[day] MID-UT T-EXP[sec] g' Rc Ic
-----------------------------------------------------
0.04269 15:30:16 5760.0 >20.1 >19.8 >18.8
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
GCN Circular 21904
Subject
GRB 170921A: Swift-XRT refined Analysis
Date
2017-09-21T22:29:22Z (9 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
B. Sbarufatti (INAF-OAB/PSU), S.L. Gibson (U. Leicester), J.P. Osborne
(U. Leicester), K.L. Page (U. Leicester), V. D'Elia (ASDC), A. Melandri
(INAF-OAB), D.N. Burrows (PSU), A. Tohuvavohu (PSU) and A. D'Ai report
on behalf of the Swift-XRT team:
We have analysed 6.5 ks of XRT data for GRB 170921A (D'Ai et al. GCN
Circ. 21901), from 82 s to 16.5 ks after the BAT trigger. The data
comprise 8 s in Windowed Timing (WT) mode (taken while Swift was
slewing), with the remainder in Photon Counting (PC) mode. The best
available XRT position (using the promptly downlinked event data, the
XRT-UVOT alignment and matching UVOT field sources to the USNO-B1
catalogue) is RA, Dec = 26.8487, 30.9067 which is equivalent to:
RA (J2000): 01 47 23.70
Dec(J2000): +30 54 24.3
with an uncertainty of 2.1 arcsec (radius, 90% confidence).
The light curve can be modelled with an initial power-law decay with an
index of alpha=3.3 (+0.5, -0.4), followed by a break at T+238 s to an
alpha of 0.85 (+0.10, -0.09).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.7 (+0.4, -0.3). The
best-fitting absorption column is 1.00 (+0.27, -0.23) x 10^22 cm^-2,
in excess of the Galactic value of 5.5 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 3.5 x 10^-11 (1.2 x 10^-10) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 1.00 (+0.27, -0.23) x 10^22 cm^-2
Galactic foreground: 5.5 x 10^20 cm^-2
Excess significance: 6.7 sigma
Photon index: 2.7 (+0.4, -0.3)
If the light curve continues to decay with a power-law decay index of
0.85, 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 7.3 x
10^-14 (2.5 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/00773509.
This circular is an official product of the Swift-XRT team.
GCN Circular 21903
Subject
GRB 170921A: TAROT Calern observatory optical observations
Date
2017-09-21T19:35:55Z (9 years ago)
From
Alain Klotz at IRAP-CNRS-OMP <Alain.Klotz@free.fr>
Klotz A., Atteia J.L. (CNRS-OMP-IRAP),
Boer, M., Laugier, R. (CNRS-ARTEMIS),
Gendre B. (UVI - Etelman Obs.) report:
We imaged the field of GRB 170921A detected by SWIFT
(trigger 773509) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.
The observations started 3.86h after the GRB trigger.
The elevation of the field increased from
12 degrees above horizon and weather conditions
were good.
We co-added a series of exposures.
No OT is detected with a limiting magnitude of:
t0+3.86h to t0+4.23h : Rlim = 19.5
Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.
GCN Circular 21901
Subject
GRB 170921A: Swift detection of a burst
Date
2017-09-21T14:44:31Z (9 years ago)
From
Boris Sbarufatti at PSU <bxs60@psu.edu>
A. D'Ai (INAF-IASFPA), V. D'Elia (ASDC), P. A. Evans (U Leicester),
J.D. Gropp (PSU), J. A. Kennea (PSU), H. A. Krimm (NSF/USRA),
S. J. LaPorte (PSU), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), B. Sbarufatti (PSU) and M. H. Siegel (PSU)
report on behalf of the Swift Team:
At 14:28:48 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 170921A (trigger=773509). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 26.849, +30.874 which is
RA(J2000) = 01h 47m 24s
Dec(J2000) = +30d 52' 27"
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 20 sec. The peak count rate
was ~1000 counts/sec (15-350 keV), at ~5 sec after the trigger.
The XRT began observing the field at 14:30:25.8 UT, 97.3 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 26.8484,
30.9069 which is equivalent to:
RA(J2000) = 01h 47m 23.63s
Dec(J2000) = +30d 54' 24.8"
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This
location is 118 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 in excess of the Galactic value (5.49 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 1.4
(+0.67/-0.55) x 10^22 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 100 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 none of
the XRT error circle. 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 0.05.
Burst Advocate for this burst is A. D'Ai (antonino.dai AT ifc.inaf.it).
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.)