GRB 180809B
GCN Circular 23105
Subject
GRB 180809B: Swift detection of a burst with an optical afterglow
Date
2018-08-09T20:40:30Z (7 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
M. J. Moss (George Washington University), S. D. Barthelmy (GSFC),
V. D'Elia (ASDC), C. Gronwall (PSU), J.D. Gropp (PSU),
J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL) and
A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 20:28:48 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 180809B (trigger=852553). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 299.712, -15.302, which is
RA(J2000) = 19h 58m 51s
Dec(J2000) = -15d 18' 06"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows multiple bright peaks
structure with a total duration of about 80 sec. The peak count rate
was ~35,000 counts/sec (15-350 keV), at ~35 sec after the trigger.
XRT found a bright, uncatalogued X-ray source located at RA, Dec
299.6998, -15.2988 which is equivalent to:
RA(J2000) = +19h 58m 47.95s
Dec(J2000) = -15d 17' 55.7"
with an uncertainty of 6.1 arcseconds (radius, 90% containment). No
event data are yet available to determine the column density using
X-ray spectroscopy.
The initial flux in the 0.1 s image was 1.51e-08 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 81 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 19:58:47.96 = 299.69983
DEC(J2000) = -15:17:56.9 = -15.29915
with a 90%-confidence error radius of about 0.64 arc sec. This position is 1.3
arc sec. from the center of the XRT error circle. The estimated magnitude is
18.91 with a 1-sigma error of about 0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.16.
Burst Advocate for this burst is M. J. Moss (mikejmoss3 AT gmail.com).
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 23109
Subject
GRB180809B: MASTER OT observation
Date
2018-08-10T00:26:43Z (7 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
V. Lipunov, N.Tiurina, E. Gorbovskoy,
V.Kornilov, A.Kuznetsov, V.Chazov, I. Gorbunov,
D.Zimnukhov, D.Kuvshinov, P.Balanutsa, V.Vladimirov, D. Vlasenko
Lomonosov Moscow State University,SAI
R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias (IAC)
D. Buckley,
South African Astronomical Observatory (SAAO)
A. Tlatov, V.Senik, D. Dormidontov
Kislovodsk Solar Station of the Pulkovo Observatory
R. Podesta, F. Podesta, C. Lopez, C.Francile
Observatorio Astronomico Felix Aguilar (OAFA)
H.Levato,
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)
O. Gres, N.M.Budnev , Yu.Ishmuhametova
Irkutsk State University (ISU)
A. Gabovich, V. Yurkov, Yu. Sergienko
Blagoveschensk Educational State University (BSPU)
MASTER-SAAO robotic telescope (MASTER-Net: http://observ.pereplet.ru,
Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in
South Africa (South African Astronomical Observatory)
was pointed to the GRB180809B(Moss et al. GCN 23105) 16 sec after notice
time and 42 sec after trigger time at 2018-08-09 20:30:40 UT.
On our 3-th (20s exposure) set , obtained 101 sec after tigger time at 2018-08-09 20:31:39 UT,
we found 1 optical transient within SWIFT error-box
T-Tmid Date Time Expt. Ra Dec mag
---------|---------------------|-------|-----------------|-----------------|-------
111 2018-08-09 20:31:39 20 (19h 58m 48.0s , -15d 17m 57.1s) 16.87
also detected by Swift UVOT (Moss et al. GCN 23105)
The 5-sigma upper limit has been about 17.4mag
The message may be cited.
GCN Circular 23110
Subject
GRB 180809B: RATIR Optical Observations and Confirmation of Rapid Fading
Date
2018-08-10T07:17:19Z (7 years ago)
From
Alan M. Watson at Instituto de Astronomia UNAM <alan@astro.unam.mx>
Alan M. Watson (UNAM), Eleonora Troja (GSFC), 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), 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 180809B (Moss et al., GCN Circ. 23105) 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 2018/08 10.19 to 2018/08 10.29
UTC (8.2 to 10.6 hours after the BAT trigger), obtaining a total of 1.42
hours exposure in the r and i bands.
We do not detect the UVOT and MASTER optical counterpart (Moss et al.,
GCN Circ. 23105; Lipunov et al., GCN Circ. 23109) to the following
3-sigma limits:
r > 23.6
i > 23.5
These magnitudes are in comparison with the USNO-B1, are in the AB
system and are not corrected for Galactic extinction in the direction of
the GRB.
The optical counterpart has faded by more than 6 magnitudes between the
MASTER and RATIR observations.
We thank the staff of the Observatorio Astron��mico Nacional in San Pedro
M��rtir.
GCN Circular 23111
Subject
GRB 180809B: GROND Detection of the NIR Afterglow
Date
2018-08-10T07:19:10Z (7 years ago)
From
Patricia Schady at Swift <p.schady@bath.ac.uk>
Tassilo Schweyer (MPE Garching) and Patricia Schady (University of Bath) report:
We observed the field of GRB 180809B (Swift trigger 852553; Moss et al., GCN #23105) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile).
Observations started at 23:00UT on 2018-08-09, 2.5 hrs after the GRB trigger. They were performed at an average seeing of 1.3" and at an average airmass of 2.
We detect a source in the JHK bands consistent with the position of the X-ray and optical afterglow (Mass et al., GCN #23105; Lipunov et al., GCN #23109). Based on a total exposure of time of 19 minutes in g'r'i'z' and 29 minutes in JHK we estimate the following AB magnitudes and upper limits at the position of the UVOT detection:
g' > 23.9 mag
r' > 23.9 mag
i' > 22.9 mag
z' > 22.4 mag
J = 21.0 +/- 0.3 mag
H = 19.9 +/- 0.2 mag
K = 18.7 +/- 0.1 mag
Given magnitudes are calibrated against PanSTARRS and 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.14 in the direction of the burst (Schlafly & Finkbeiner 2011).
We thank Markus Rabus for the excellent support from La Silla.
GCN Circular 23112
Subject
GRB 180809B: LCO Sutherland observations
Date
2018-08-10T08:59:56Z (7 years ago)
From
Cristiano Guidorzi at Ferrara U,Italy <guidorzi@fe.infn.it>
C. Guidorzi, R. Martone (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell
(U. Bath), A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU), A. Cucchiara,
D. Morris (U. of Virgin Islands) on behalf of a large collaboration report:
We observed Swift GRB 180809B (Moss et al. GCN 23105) with the LCO 1-m
units at Sutherland Observatory (South Africa) on August 09, from 20:58
to 22:29 UT (corresponding to 0.5 to 2.0 hours from the GRB trigger
time) with the SDSS r' and i' filters. We clearly detect the optical
afterglow (Moss et al; Lipunov et al. GCN 23109; Watson et al. GCN
23110; Schweyer et al. GCN 23111) in both filters with the following
magnitudes:
Mid time from GRB���������� Exposure���������������� Filter Magnitude
trigger time (hrs)�������� (s)
---------------------------------------------------------------------
0.55������������������������������������ 5x60������������������������ SDSS r'���������������� 19.54 +- 0.08
0.70������������������������������������ 5x60������������������������ SDSS i'���������������� 19.24 +- 0.07
---------------------------------------------------------------------
as calibrated against nearby Pan-STARRS objects.
GCN Circular 23113
Subject
GRB180809B: MASTER Triple Independent Automatic OT Detection
Date
2018-08-10T09:07:16Z (7 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
N.Tiurina, V. Lipunov, E. Gorbovskoy,
V.Kornilov, A.Kuznetsov, V.Chazov, I. Gorbunov,
D.Zimnukhov, D.Kuvshinov, P.Balanutsa, V.Vladimirov, D. Vlasenko
Lomonosov Moscow State University,SAI
R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias (IAC)
D. Buckley,
South African Astronomical Observatory (SAAO)
A. Tlatov, V.Senik, D. Dormidontov
Kislovodsk Solar Station of the Pulkovo Observatory
R. Podesta, F. Podesta, C. Lopez, C.Francile
Observatorio Astronomico Felix Aguilar (OAFA)
H.Levato,
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)
O. Gres, N.M.Budnev , Yu.Ishmuhametova
Irkutsk State University (ISU)
A. Gabovich, V. Yurkov, Yu. Sergienko
Blagoveschensk Educational State University (BSPU)
We have already reported the observation of the optical transient GRB
180809B (Moss et al., GCN # 23105) by one of the telescopes of the MASTER
Global Network (Lipunov et al., GCN 23109).
Here we report on the triple independent, automatic detection of the
optical transient (also found by Swift UVOT (Moss et al., GCN 23105)). The
relatively later guidance of the three MASTER robotic telescopes is due to
the fact that the first socket message did not indicate the time of the
trigger. As a result, everyone went to the CALET Alert (trig
number 1217881726) with poor defined coordinates.
Nevertheless, we were able to obtain detailed light curves
with a maximum in 4 polarizations.
MASTER-SAAO robotic telescope (MASTER-Net: http://observ.pereplet.ru,
Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in
South Africa (South African Astronomical Observatory) was pointed to the
GRB180809.85 16 sec after notice time and 111 sec after trigger time at
2018-08-09 20:30:39 UT. On our 1-th (10s exposure) set in two
polarizations (/\), obtained 111
sec after tigger time at 2018-08-09 20:30:39 UT, we found 1 optical transient
within SWIFT error-box (ra=299.7 dec=-15.2989 r=0.05) brighter then 17.4.
T-Tmid Date Time Expt. Ra Dec Mag
s UT s
-------|--------------------|-------|-----------------|---------------|-------
116 2018-08-09 20:30:39 10 (19h 58m 48.0s , -15d 17m 57.1s) 16.5
The 5-sigma upper limit has been about 17.9 mag
The observations started on zenit distance = 21 deg., galactic latitude b
= -22 deg. The moon ( 4 % bright part) was below the horizon (The altitude
of the Moon = -75 deg ). The sun altitude = -56.3 degree. The object
can be observed till 2018-08-10 04:03:58 UT.
MASTER-Tavrida robotic telescope (MASTER-Net: http://observ.pereplet.ru,
Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in
Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the
GRB180809.85 35 sec after notice time and 133 sec after trigger time at
2018-08-09 20:31:01 UT. On our first (10s
exposure) set we found 1 optical transient within SWIFT error-box
(ra=299.7 dec=-15.2989 r=0.05) brighter then 17.9:
T-Tmid Date Time Expt. Ra Dec Mag
s UT s
------|--------------------|-------|-----------------|-----------------|-------
138 2018-08-09 20:31:01 10 ( 19h 58m 48.0s , -15d 17m 56.5s) 16.8
The 5-sigma upper limit has been about 17.9 mag
The observations made on zenit distance = 60 degrees, galaxy latitude b = -22 degree.
The moon ( 4 % bright part) below the horizon (The altitude of the Moon is
-25 degree ). The sun altitude is -27.0 degree.
The object can be observed till 2018-08-10 01:29:20.
MASTER-IAC robotic telescope (MASTER-Net: http://observ.pereplet.ru,
Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in
Spain (IAC Teide Observatory) was pointed to the GRB180809.85 120 sec
after notice time and 147 sec after trigger time at 2018-08-09 20:31:15
UT in two polarizations (|-).
On our first set, obtained we found 1 optical transient within SWIFT
error-box (ra=299.7 dec=-15.2989 r=0.05):
T-Tmid Date Time Expt. Ra Dec Mag
---------|---------------------|-------|-----------------|-----------------|-------
152 2018-08-10 20 31 15 20 ( 19h 58m 43.3s , -15d 20m 37.9s) 15.5
The 5-sigma upper limit has been about 16.0 magThe message may be cited.
The observations made on zenit distance = 44 degrees, galaxy latitude b =
-22 degree. The moon ( 3 % bright part) below the horizon (The altitude of
the Moon is -41 degree ). The sun altitude is -9.1 deg.
The object can be observed till 2018-08-10 05:19:05 UT.
The message may be cited.
GCN Circular 23114
Subject
GRB 180809B: VLT optical upper limits
Date
2018-08-10T10:18:56Z (7 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
J. Japelj (U. Amsterdam), D. B. Malesani (DAWN/NBI and DARK/NBI), J.
Selsing (DAWN/NBI), N. R. Tanvir (U. Leicester), D. A. Kann
(HETH/IAA-CSIC), V. D'Elia (ASI-SSDC), G. Pugliese (U. Amsterdam), K. E.
Heintz (Univ. Iceland and DAWN/NBI), J. P. U. Fynbo (DAWN/NBI), A. J.
Levan (Univ. Warwick), P. Schady (University of Bath), report on behalf
of the Stargate collaboration:
We observed the field of GRB 180809B with the ESO VLT UT2 (Kueyen),
using the X-shooter acquisition camera. In a single 120-s r-band
exposure, with a mean epoch Aug 10.055 UT (4.84 hr after the GRB), we
detect no object at the position of the optical afterglow (e.g., Moss et
al., GCN 23105; Lipunov et al., GCN 23109; Schweyer et al. GCN 23111;
Guidorzi et al., GCN 23112, Tiurina et al., GCN 23113), down to a
limiting magnitude r > 24.7 AB (calibrated against nearby Pan-STARRS
sources).
Compared to the r-band measurement by Guidorzi et al. (GCN 23112), and
assuming an unbroken power-law decay F(t) propto t^-alpha, the
corresponding decay index is alpha > 2.2 between 0.55 and 4.84 hr after
the GRB.
We acknowledge excellent support from the observing team in Paranal,
including Steffen Mieske and Boris Haeussler.
GCN Circular 23116
Subject
GRB 180809B: CALET Gamma-Ray Burst Monitor detection
Date
2018-08-10T12:21:10Z (7 years ago)
From
Takanori Sakamoto at AGU <tsakamoto@phys.aoyama.ac.jp>
M. L. Cherry (LSU), A. Yoshida, T. Sakamoto, V. Pal'shin,
S. Sugita, Y. Kawakubo, A. Tezuka, S. Matsukawa, H. Onozawa,
T. Ito, H. Morita, Y. Sone (AGU), K. Yamaoka (Nagoya U),
S. Nakahira (RIKEN), I. Takahashi (IPMU),
Y. Asaoka, S. Ozawa, S. Torii (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR),
S. Ricciarini (U of Florence),
A. V. Penacchioni, P. S. Marrocchesi (U of Siena)
and the CALET collaboration:
The long, bright GRB 180809B (Swift-BAT trigger #852553: Moss et al.,
GCN Circ. 23105) triggered the CALET Gamma-ray Burst Monitor (CGBM)
at 20:28:41.478 UTC on 9 August 2018 while exiting the radiation belts.
The burst signal was seen by all CGBM detectors.
The burst light curve shows the main multi-peaked emission episode which
starts at T-5 sec, peaks at T+41.4 sec, and ends at T+79.9 sec, followed by
a weaker pulse which starts at T+210.0 sec and ends at T+254.6 sec.
The T90 and the T50 durations measured by the SGM data are
227.6 +- 5.4 sec and 28.3 +- 5.7 sec (40-1000 keV), respectively.
Since the CGBM HV was set to its nominal value at T-21 sec for
the HXM1 and HXM2 detectors and at T-5 sec for the SGM detector,
CGBM was blind to a possible earlier emission.
The ground processed light curve is available at
http://cgbm.calet.jp/cgbm_trigger/ground/1217881726/
The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at the Waseda University.
GCN Circular 23120
Subject
GRB 180809B: Swift/UVOT Detection
Date
2018-08-10T16:29:24Z (7 years ago)
From
Sam LaPorte at PSU <sjl5346@psu.edu>
GRB 180809B: Swift/UVOT Detection
S. Sebzda (PSU) and M. Moss (George Washington University)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180809B
82 s after the BAT trigger (Moss et al., GCN Circ. 23105).
A fading source consistent with the XRT position
(Moss et al. GCN Circ. 23105)
is detected in the initial UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 19:58:47.96 = 299.69984 (deg.)
Dec (J2000) = -15:17:57.1 = -15.29920 (deg.)
with an estimated uncertainty of 0.48 arc sec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limits using the UVOT photometric
system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 81 231 293 18.99+-0.07
white 573 6926 441 >21.55
v 623 7289 444 >19.8
b 549 6721 294 >20.9
u 294 6516 520 >21.0
w1 672 13027 915 >20.7
m2 648 11053 906 >20.9
w2 599 16967 1262 >21.3
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.16 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 23123
Subject
GRB 180809B, Swift-BAT refined analysis
Date
2018-08-10T18:20:37Z (7 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
M. Stamatikos (OSU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
M. J. Moss (GWU), D. M. Palmer (LANL),
T. Sakamoto (AGU), 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 180809B (trigger #852553)
(Moss et al., GCN Circ. 23105). The BAT ground-calculated position is
RA, Dec = 299.712, -15.293 deg which is
RA(J2000) = 19h 58m 50.8s
Dec(J2000) = -15d 17' 34.0"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 63%.
The mask-weighted light curve shows a multi-peaked structure that starts
at ~T-36 s and ends at ~T+80 s, followed by another pulse that starts
at ~T+200 s and ends at ~T+250 s. The total burst emission ends at ~T+300 s.
T90 (15-350 keV) is 233.2 +- 1.1 sec (estimated error including systematics).
We note that the later pulse overlaps with the XRT flare and some ground-based
optical observations (e.g. Tiurina et al.; GCN #23113), which indicates an increase
in the optical magnitude from Mag 16.5 to 15.5 at the pulse time.
The time-averaged spectrum from T-36.1 to T+302.3 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.26 +- 0.02. The fluence in the 15-150 keV band is 7.3 +- 0.1 x 10^-5 erg/cm2.
The 1-sec peak photon flux measured from T+35.10 sec in the 15-150 keV band
is 26.3 +- 0.6 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/852553/BA/
GCN Circular 23124
Subject
GRB 180809B: CrAO optical observations
Date
2018-08-10T19:50:36Z (7 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
E. Mazaeva (IKI), V. Rumyantsev (CrAO), A. Pozanenko (IKI), A.
Volnova (IKI), report on behalf of larger GRB follow-up collaboration:
We observed the field of the GRB 180809B (Moss et al., GCN 23105)
with ZTSH 2.6m telescope of CrAO observatory starting on Aug. 9 (UT)
21:14:58. We took several images in BVRI filters with exposures of 120
s. We detect the afterglow (e.g., Moss et al., GCN 23105; Lipunov et
al., GCN 23109; Schweyer et al. GCN 23111; Guidorzi et al., GCN 23112,
Tiurina et al., GCN 23113).
Preliminary photometry of the afterglow in R- filter is following
UT start t-T0 Filter Exp. OT err
(mid, days) (s)
21:14:58.579 0.03276 R 1*120 19.80 0.05
21:17:05.489 0.03423 R 1*120 19.86 0.04
21:19:12.801 0.03570 R 1*120 19.93 0.05
21:25:54.597 0.04035 R 1*120 20.35 0.05
21:34:27.347 0.04629 R 1*120 20.86 0.08
21:43:00.178 0.05519 R 2*120 21.51 0.11
The photometry is based on nearby USNO-B1.0 stars:
Ref.stars
USNO-B1.0_id R2
0747-0765959 19.65
0746-0776364 18.76
0746-0776499 19.18
GCN Circular 23125
Subject
GRB 180809B: Swift-XRT refined Analysis
Date
2018-08-10T20:40:03Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
Z. Liu (NAOC / U. Leicester), A. Melandri (INAF-OAB), P. D'Avanzo
(INAF-OAB), V. D'Elia (ASDC), A. Tohuvavohu (PSU), S. J. LaPorte (PSU),
J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester) and M.J. Moss report on behalf of the Swift-XRT team:
We have analysed 3.9 ks of XRT data for GRB 180809B (Moss et al. GCN
Circ. 23105), from 74 s to 12.6 ks after the BAT trigger. The data
comprise 1.7 ks in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. Using 1724 s of PC mode data and 4 UVOT
images, we find an enhanced XRT position (using the XRT-UVOT alignment
and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec =
299.69997, -15.29893 which is equivalent to:
RA (J2000): 19h 58m 47.99s
Dec(J2000): -15d 17' 56.1"
with an uncertainty of 1.4 arcsec (radius, 90% confidence).
The late-time light curve (from T0+4.7 ks) can be modelled with a
power-law decay with a decay index of alpha=1.37 (+/-0.12).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.609 (+/-0.017). The
best-fitting absorption column is 2.29 (+0.09, -0.08) x 10^21 cm^-2,
in excess of the Galactic value of 1.2 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.63 (+/-0.11) and a
best-fitting absorption column of 2.4 (+/-0.5) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 4.6 x 10^-11 (5.6 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 2.4 (+/-0.5) x 10^21 cm^-2
Galactic foreground: 1.2 x 10^21 cm^-2
Excess significance: 4.0 sigma
Photon index: 1.63 (+/-0.11)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00852553.
This circular is an official product of the Swift-XRT team.
GCN Circular 23127
Subject
GRB180809B TUG T60 observations
Date
2018-08-11T11:25:53Z (7 years ago)
From
Yucel Kilic at TUBITAK,TUG <yucel.kilic@tubitak.gov.tr>
Y. Kilic, M. Dindar, T. Ozisik, M. T. Ozkan, S. Ozdemir
TUBITAK National Observatory (TUG)
TUG T60 robotic telescope (http://tug.tubitak.gov.tr/en/teleskoplar/t60-0,
Dindar, M. et al. Exp Astron (2015)) located in TUBITAK National Observatory
in Antalya was pointed to GRB180809B (Moss et al. GCN 23105) field 54 seconds
after receiving the alert and began to take the exposure. In total, 8 R filter
images and 4 B filter images were taken with the FLI PL 3041 CCD camera.
No source could be detected on B filter. The GRB180809B is detected in the all
the images observed in the R filter within the SWIFT error-box. Astrometry was
made with the astrometry.net and magnitudes were estimated using the NOMAD catalog.
T-Tmid Date Time Expt. Ra Dec Mag.
s UT s R
---------|---------------------|-------|-----------------|---------------|----
64 2018-08-09 20:31:13 20 19h 58m 48.0s -15d 17m 56.7s 16.07
91 2018-08-09 20:31:39 20 19h 58m 48.0s -15d 17m 56.7s 16.24
117 2018-08-09 20:32:05 20 19h 58m 48.0s -15d 17m 56.7s 16.52
183 2018-08-09 20:33:12 60 19h 58m 48.0s -15d 17m 56.7s 16.29
249 2018-08-09 20:34:18 60 19h 58m 48.0s -15d 17m 56.7s 16.59
316 2018-08-09 20:35:25 60 19h 58m 48.0s -15d 17m 56.7s 16.90
382 2018-08-09 20:36:31 60 19h 58m 48.0s -15d 17m 56.7s 17.20
449 2018-08-09 20:37:38 60 19h 58m 48.0s -15d 17m 56.7s 17.37
GCN Circular 23128
Subject
Konus-Wind observation of GRB 180809B
Date
2018-08-11T16:06:36Z (7 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks,
M. Ulanov, A. Tsvetkova, A. Lysenko, A.Kozlova, and T. Cline
on behalf of the Konus-Wind team, report:
The long-duration GRB 180809B
(Swift-BAT detection: Moss et al., GCN Circ. 23105;
CALET-GBM detection: Cherry, et al., GCN Circ. 23116)
triggered Konus-Wind at T0=73730.033 s UT (20:28:50.033).
The burst light curve shows a bright multi-peaked emission episode
which starts at ~T0-4 s and has a duration of ~80 s, followed by a
weaker episode at ~T0-205 s. The total burst duration is ~300 s.
The emission is seen up to ~10 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180809_T73730/
As observed by Konus-Wind, the burst
had a fluence of 3.07(-0.30,+0.36)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+37.952 s,
of 2.66(-0.41,+0.42)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst
(measured from T0 to T0+252.672 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.87(-0.10,+0.12),
the high energy photon index beta = -2.44(-0.24,+0.19),
the peak energy Ep = 275(-30,+25) keV
(chi2 = 123/97 dof).
The spectrum near the maximum count rate
(measured from T0+36.608 to T0+38.144 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.77(-0.12,+0.15),
the high energy photon index beta = -2.20(-0.21,+0.15),
the peak energy Ep = 525(-95,+103) keV
(chi2 = 66/68 dof).
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
GCN Circular 23133
Subject
GRB 180809B: ePESSTO NTT NIR observations
Date
2018-08-12T14:02:05Z (7 years ago)
From
Paolo D'Avanzo at INAF-OAB <paolo.davanzo@brera.inaf.it>
Z. Kostrzewa-Rutkowska (SRON/RU), E. Callis (UCD), R. Stein (HU Berlin/DESY), P. D'Avanzo (INAF-OAB), M. Fraser (UCD), J. Lyman (Warwick), D. B. Malesani (DAWN/NBI and DARK/NBI), C. Inserra (Southampton), E. Kankare (QUB), K. Maguire (QUB), S. J. Smartt (QUB), O. Yaron (Weizmann), D. R. Young (QUB), I. Manulis (Weizmann) report:
We observed the field of GRB 180809B (Moss et al., GCN Circ. 23105) under the extended Public ESO Spectroscopic Survey for Transient Objects (ePESSTO; see Smartt et al. 2015, A&A, 579, 40 http://www.pessto.org <http://www.pessto.org/> ). The observations were performed on the ESO New Technology Telescope at La Silla with the SofI instrument in imaging mode starting on 2018-08-12 between 03:38 and 04:27 UT (i.e. about 2.298 and 2.332 days from the burst) with the H filter.
The NIR counterpart (Schweyer et al. GCN Circ. 23111) is clearly detected. From preliminary photometry, we estimate a magnitude of H ~ 20.3 (Vega, calibrated against the 2MASS catalogue). Compared to earlier reports (Schweyer et al. GCN Circ. 23111), our measure indicates significan fading. However, we cannot assess if we already reached the host galaxy level.
GCN Circular 23144
Subject
GRB 180809B: AstroSat CZTI detection
Date
2018-08-17T11:29:28Z (7 years ago)
From
Vidushi Sharma at IUCAA <vidushi@iucaa.in>
V. Sharma (IUCAA), V. Bhalerao (IIT-B), D. Bhattacharya (IUCAA), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the Astrosat CZTI collaboration:
Analysis of AstroSat CZTI data showed the detection of a long GRB 180809B, which was also detected by Swift (Moss M. J. et al., GCN 23105), CALET (Cherry M. L. et al., GCN 23116) and Konus-Wind (Svinkin D. et al., GCN 23128).
The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with strongest peak at 20:29:23.500 UT. The measured peak count rate is 2562 cts/s above the background in combined data of four quadrants, with a total of 38208 cts. The local mean background count rate was 501 cts/s. Using cumulative rates, we measure a T90 of 44.1 s. In preliminary analysis, we find that 3257 compton events are associated with this event.
It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range.
CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.