GRB 190926A
GCN Circular 25848
Subject
GRB 190926A: Swift detection of a burst
Date
2019-09-26T10:06:20Z (6 years ago)
From
Hans Krimm at NSF/NASA-GSFC <hkrimm@nsf.gov>
A. Melandri (INAF-OAB), M. G. Bernardini (INAF-OAB),
P. D'Avanzo (INAF-OAB), P. A. Evans (U Leicester), J.D. Gropp (PSU),
H. A. Krimm (NSF), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC)
and K. L. Page (U Leicester) report on behalf of the Neil Gehrels
Swift Observatory Team:
At 09:52:16 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 190926A (trigger=926515). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 100.599, +59.511 which is
RA(J2000) = 06h 42m 24s
Dec(J2000) = +59d 30' 40"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). Since this is an image trigger, the BAT
light curve showed no significant structure.
The XRT began observing the field at 09:54:30.4 UT, 134.0 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 100.5699, 59.5292 which is equivalent to:
RA(J2000) = 06h 42m 16.78s
Dec(J2000) = +59d 31' 45.1"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This
location is 84 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 5.87e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 144 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 0.06.
Burst Advocate for this burst is A. Melandri (andrea.melandri AT brera.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/)
GCN Circular 25850
Subject
GRB 190926A: Enhanced Swift-XRT position
Date
2019-09-26T19:43:25Z (6 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester)
report on behalf of the Swift-XRT team.
Using 3630 s of XRT Photon Counting mode data and 3 UVOT
images for GRB 190926A, 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 = 100.57044, +59.52920 which is equivalent
to:
RA (J2000): 06h 42m 16.90s
Dec (J2000): +59d 31' 45.1"
with an uncertainty of 2.0 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 25851
Subject
GRB 190926A: Swift-XRT refined Analysis
Date
2019-09-26T19:45:30Z (6 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
B. Sbarufatti (PSU), D.N. Burrows (PSU), J. D. Gropp (PSU), J.P.
Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U.
Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB) and A.
Melandri report on behalf of the Swift-XRT team:
We have analysed 10 ks of XRT data for GRB 190926A (Melandri et al. GCN
Circ. 25848), from 140 s to 23.8 ks after the BAT trigger. The data
comprise 685 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Goad et al. (GCN Circ. 25850).
The late-time light curve (from T0+4.1 ks) can be modelled with an
initial power-law decay with an index of alpha=0.661 (+0.053, -0.030),
followed by a break at T+677 s to an alpha of 3.34 (+0.30, -0.12).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.804 (+/-0.023). The
best-fitting absorption column is 3.00 (+/-0.11) x 10^21 cm^-2, in
excess of the Galactic value of 7.5 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 4.1 x 10^-11 (5.5 x 10^-11) erg
cm^-2 count^-1.
A summary of the WT-mode spectrum is thus:
Total column: 3.00 (+/-0.11) x 10^21 cm^-2
Galactic foreground: 7.5 x 10^20 cm^-2
Excess significance: 33.3 sigma
Photon index: 1.804 (+/-0.023)
If the light curve continues to decay with a power-law decay index of
3.34, the count rate at T+24 hours will be 3.2 x 10^-6 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.3 x
10^-16 (1.7 x 10^-16) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00926515.
This circular is an official product of the Swift-XRT team.
GCN Circular 25852
Subject
GRB 190926A: KAIT Optical Upper Limit
Date
2019-09-26T20:22:19Z (6 years ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on
behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to Swift GRB 190926A (Melandri et al.,
GCN 25848) starting at ~59 minutes after the burst. Observations
were performed in the clear (roughly R) filters, a total of 102
images were obtained and the exposure time was 60 s per image.
We do not detect any optical afterglow candidate within the Enhanced
XRT position error circle (Goad et al., GCN 25850), neither in single
image, nor in the co-add images. The typical limiting magnitude
of our single clear image is about 19.0 mag.
GCN Circular 25853
Subject
GRB 190926A: Swift/UVOT Upper Limits
Date
2019-09-26T20:47:53Z (6 years ago)
From
Samantha Oates at MSSL <sro@mssl.ucl.ac.uk>
S. R. Oates (U.Warwick) and A. Melandri (INAF-OAB)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 190926A
144 s after the BAT trigger (Melandri et al., GCN Circ. 25848).
No optical afterglow consistent with the enhanced XRT position
(Goad et al. GCN Circ. 25850)
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 144 294 147 >20.2
u_FC 303 553 246 >19.3
white 144 6525 580 >20.9
v 634 11670 1116 >20.0
b 559 6321 432 >20.2
u 303 6115 659 >20.0
w1 685 5910 413 >19.8
m2 659 12294 1022 >20.3
w2 610 10756 1148 >20.6
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.06 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 25854
Subject
GRB 190926A: MITSuME Akeno optical upper limits
Date
2019-09-27T03:33:15Z (6 years ago)
From
Adachi Ryo at Tokyo Institute of Tech <adachi@hp.phys.titech.ac.jp>
R. Adachi, K. L. Murata, M. Oeda, K.Shiraishi, K. Iida, M. Niwano,
F. Ogawa, R. Hosokawa, S. Toma, Y. Yatsu, and N. Kawai (TokyoTech)
report on behalf of the MITSuME collaboration:
We searched for the optical counterpart of GRB 190926A (A. Melandri et
al., GCN Circular #25848) with the optical three color (g', Rc, and
Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno
Observatory, Yamanashi, Japan.
The observation started on 16:16:33 UT. We did not find any new point
sources within the XRT circle (M.R. Goad et al., GCN Circular #25850)
in all three bands.
We obtained the following 5-sigma limits for the magnitudes.
T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
~7.0 18:13:34 6960 g'>19.8, Rc>19.5, Ic>19.2
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used UCAC4 catalog for flux calibration.
The magnitudes are expressed in the AB system.
GCN Circular 25856
Subject
GRB 190926A: Upper Limit from OSN T150 Observation
Date
2019-09-27T19:44:40Z (6 years ago)
From
Alexander Kann at IAA-CSIC <kann@iaa.es>
D. A. Kann, M. Blazek (both HETH/IAA-CSIC), A. de Ugarte Postigo
(HETH/IAA-CSIC, DARK/NBI), C. C. Thoene, K. Bensch, J. F. Agui (all
HETH/IAA-CSIC), and A. Sota (IAA-CSIC) report:
We observed the field of GRB 190926A (Melandri et al. GCN #25848) with
the 1.5m OSN telescope, at Sierra Nevada Observatory (Granada, Spain).
The observation is centered 0.7321 days after the GRB and consisted of
41 x 180 s exposures in the Ic band for a total exposure time of 7380 s.
No new object is detected within the refined XRT error circle (Goad et
al. GCN #25850) down to a 3-sigma limit of Ic(AB) = 23.6 mag, as
compared to stars of the PanSTARRS catalog. This is in agreement with
other non-detections (Lipunov et al., GCN #25849, Zheng & Filippenko,
GCN # 25852, Oates & Melandri, GCN #25853, Adachi et al., GCN #25854);
and the very high-significance detection of excess hydrogen column
density in the XRT observations (Sbarufatti et al., GCN #25851)
indicates this is a dark GRB, and less likely a high-redshift one.
GCN Circular 25860
Subject
GRB 190926A: Swift-BAT refined analysis
Date
2019-09-28T20:05:29Z (6 years ago)
From
Hans Krimm at NSF/NASA-GSFC <hkrimm@nsf.gov>
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
H. A. Krimm (NSF), A. Y. Lien (GSFC/UMBC), A. Melandri (INAF-OAB),
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-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 190926*A (trigger #926515)
(Melandri, et al., GCN Circ. 25848). The BAT ground-calculated position is
RA, Dec = 100.616, 59.531 deg which is
RA(J2000) = 06h 42m 27.9s
Dec(J2000) = +59d 31' 51.2"
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 50%.
The BAT mask-weighted light curve shows a complex structure with multiple
peaks extending from roughly T-120 sec to T+450 sec. T90 (15-350 keV) is
368.9 +- 20.9 sec (estimated error including systematics).
The time-averaged spectrum from T-0.00 to T+395.46 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
2.14 +- 0.18. The fluence in the 15-150 keV band is 2.5 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+52.95 sec in the 15-150 keV band
is 0.6 +- 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/926515/BA/
GCN Circular 25862
Subject
GRB 190926A: AbAO upper optical limit
Date
2019-09-29T10:55:59Z (6 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI), A. Pozanenko (IKI), R. Ya. Inasaridze (AbAO,
Samtskhe-Javakheti State University), E. Mazaeva (IKI), A. Volnova
(IKI), V. R. Ayvazian (AbAO, Samtskhe-Javakheti State University),
G.V. Kapanadze (AbAO, Samtskhe-Javakheti State University), I. Molotov
(KIAM) report on behalf of larger IKI GRB follow-up collaboration:
We observed GRB 190926A (Melandri et al., GCN 25848) with AS-32 (0.7m)
telescope of Abastumani Observatory starting on Sep. 27 (UT) 01:16:46.
We obtained several 60 s exposures in R-filter. We do not detect any
source within enhanced Swift-XRT position (Goad et al., GCN 25850) in
the stacked image. Photometry of the field is following
Date UT start t-T0 Filter Exp. OT Err. UL
(mid, days) (s)
2019-09-27 01:16:46 0.6493 R 21*60 n/d n/d 20.8
Photometry is based on nearby USNO-B1.0 star (R2 magnitude):
USNO-B1.0_id R2
1496-0169403 18.52
The non detection in an agreement with previously reported results
(Lipunov et al., GCN #25849, Zheng & Filippenko, GCN # 25852, Oates &
Melandri, GCN #25853, Adachi et al., GCN #25854; Kann et al., GCN #25856).
GCN Circular 25937
Subject
GRB 190926A: Upper limit from CAHA 2.2m observation
Date
2019-10-03T14:31:18Z (6 years ago)
From
Alexander Kann at IAA-CSIC <kann@iaa.es>
M. Blazek, D. A. Kann (both HETH/IAA-CSIC), A. de Ugarte Postigo
(HETH/IAA-CSIC, DARK/NBI), C. C. Thoene, K. Bensch, J. F. Agui (all
HETH/IAA-CSIC), I. Hermelo, and S. Pedraz (both CAHA) report:
We observed the field of GRB 190926A (Melandri et al. GCN #25848) with
the 2.2m telescope at Calar Alto Observatory, Spain. The observation is
centered 0.6523 days after the GRB and consisted of 3 x 360 s exposures
in the V band for a total exposure time of 1080 s, obtained before
technical problems shut down the observation sequence.
No new object is detected within the refined XRT error circle (Goad et
al. GCN #25850) down to a 3-sigma limit of V(AB) = 21.9 mag, as compared
to stars of the GSC 2.3 catalog. This is in agreement with the deep
non-detection by OSN (Kann et al., GCN #25856).