GRB 180620A
GCN Circular 25671
Subject
GRB 180620A: SEDM Observations
Date
2019-09-05T22:46:33Z (6 years ago)
From
Virginia Cunningham at U of MD <vcunning@astro.umd.edu>
V. Cunningham (U of Maryland), J. D. Neill (Caltech), S. B. Cenko
(NASA GSFC), and R. Walters (Caltech) report on behalf of the
SEDM team:
We observed the optical counterpart to GRB 180620A (Evans, et al.,
GCN 22798) with the Spectral Energy Distribution Machine (SEDM)
on the 60 inch telescope at Palomar Observatory. The SEDM is a
low resolution (R ~ 100) integral field unit spectrometer with a multi-
band (ugri) rainbow camera imager (see Blagorodnova et al. 2018,
PASP, 130, 035003, and Rigault et al. 2019, A&A, 627, A115).
The SEDM began observing the optical counterpart at 9:37:37 UTC
(63 minutes after the burst trigger time). We performed 2 x 1200 s
exposures over the wavelength range 3800-9200 A. The continuum
emission is well-fit by a power law spectrum with index alpha = 1.4
(f_nu ~ nu^-alpha). We do not confidently identify any obvious
emission or absorption features in the spectrum.
GCN Circular 22843
Subject
GRB 180620A: AstroSat CZTI detection
Date
2018-06-25T15:56:07Z (7 years ago)
From
Vidushi Sharma at IUCAA <vidushi@iucaa.in>
V. Sharma and D. Bhattacharya (IUCAA), V. Bhalerao (IIT-B), 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 180620A, which was also detected by Swift (Evans P. A. et al., GCN 22798) and Konus-Wind (D. Svinkin D. et al., GCN 22824).
The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with strongest peak at 08:35:08.5 UT. The measured peak count rate is 287.9 cts/s above the background in combined data of four quadrants, with a total of 2046 cts. The local mean background count rate was 503 cts/s. Using cumulative rates, we measure a T90 of 14.8 s.
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.
GCN Circular 22826
Subject
GRB 180620A iTelescope observation
Date
2018-06-23T09:36:13Z (7 years ago)
From
Takanori Sakamoto at AGU <tsakamoto@phys.aoyama.ac.jp>
M. Nakamura, T. Sakamoto (AGU)
We observed the field of GRB 180620A detected by Swift
(Evans et al., GCN Circ. 22798) with the iTelescope.Net
(http://www.itelescope.net) T11 (Planewave 20") telescope
located at the New Mexico Skies Observatory (NM, USA).
20 images of 60 sec exposures were taken in the R filter
starting from June 20 on 10:11:01 (UT) about 1.6 hours after
the trigger and stopped on 10:44:55 (UT). Due to the tracking
issue of the telescope, we only obtained nine good quality images.
We do not detect the optical afterglow both in the individual
images and the stacked image at the UVOT position
(Evans et al., GCN Circ. 22798). The estimated five sigma
upper limit of the combined image (total exposure of 540 sec)
is ~18.1 using the USNO-B1 catalog.
GCN Circular 22824
Subject
Konus-Wind observation of GRB 180620A
Date
2018-06-22T15:25:50Z (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 180620A
(Swift-BAT detection: Evans et al., GCN Cric. 22798)
triggered Konus-Wind at T0=30906.173 s UT (08:35:06.173).
The burst light curve shows a multi-peaked structure
which starts at ~T0-6.6 s and has a total duration of ~16 s.
The emission is seen up to ~2 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180620_T30906/
As observed by Konus-Wind, the burst
had a fluence of 9.80(-1.02,+1.74)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0+7.504 s,
of 2.69(-0.82,+0.94)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 4 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.19(-0.14,+0.16),
the high energy photon index beta = -3.09(-6.91,+0.63),
the peak energy Ep = 164(-24,+29) keV
(chi2 = 70/75 dof).
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
GCN Circular 22818
Subject
GROND observations of GRB 180620A
Date
2018-06-21T11:16:12Z (7 years ago)
From
Patricia Schady at MPE/Swift <pschady@mpe.mpg.de>
Tassilo Schweyer and Patricia Schady (MPE Garching) report:
We observed the field of GRB 180620A (Swift trigger 843211; Evans et al.,
GCN #22807) 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 04:35 UT on 2018-06-21, 20 hours after the GRB
trigger. They were performed at an average seeing of 1.4" and at an
average airmass of 1.7.
We detect a faint point source consistent with the position of the
reported X-ray and optical afterglow (Elenin et al., GCN #22800; Osborne
et al., GCN #22802; Breeveld et al., GCN #22805). Based on a total
exposures time of around 30mins we estimate the following AB magnitudes:
g' = 23.9 +/- 0.1 mag
r' = 23.4 +/- 0.1 mag
i' = 23.1 +/- 0.1 mag
z' > 23.2 mag
J > 21.2 mag
H > 20.5 mag
K > 19.3 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)=0.11 in the direction of the burst
(Schlafly & Finkbeiner 2011).
We thank Markus Rabus for the excellent support from La Silla.
GCN Circular 22815
Subject
GRB 180620A: Swift-BAT refined analysis
Date
2018-06-21T02:37:49Z (7 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
M. Stamatikos (OSU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), P. A. Evans (U Leicester),
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), 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 180620A (trigger #843122)
(Evans et al., GCN Circ. 22798). The BAT ground-calculated position is
RA, Dec = 279.890, 23.239 deg which is
RA(J2000) = 18h 39m 33.5s
Dec(J2000) = +23d 14' 18.6"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 42%.
The mask-weighted light curve shows a multi-peaked structure that starts
at ~T-7 s and ends at ~T+37 s. The two main peaks occur at ~T+5 s and ~T+12 s,
respectively. T90 (15-350 keV) is 23.16 +- 4.82 sec (estimated error including
systematics).
The time-averaged spectrum from T-6.92 to T+37.07 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.72 +- 0.05. The fluence in the 15-150 keV band is 5.8 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+4.47 sec in the 15-150 keV band
is 7.7 +- 0.4 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/843122/BA/
GCN Circular 22812
Subject
GRB 180620A: KAIT Optical Observations
Date
2018-06-20T20:13:48Z (7 years ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
WeiKang Zheng and Alex Filippenko (UC Berkeley) report on
behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT) at
Lick Observatory responded to Swift GRB 180620A (Evans et al.,
GCN 22798) starting at 08:37:19 UT, 141s after the burst.
Observations were performed with an automatic sequence in the
V, I, and clear (roughly R) filters, and the exposure time was
20 s per image, observations lasted about 3 hours.
The optical afterglow (Evans et al., GCN 22790; Butler et al.,
GCN 22799; Elenin et al., GCN 22800; Tyurina et al., GCN 22801;
Guidorzi et al., GCN 22803; Breeveld et al., GCN 22805;
Watson et al., GCN 22806; Zhu et al., GCN 22811) was well
detected in our V, I and clear filter images. A preliminary
analysis shows that the afterglow rises at early time and peaked
around 300s (also seen by Butler et al. GCN 22799; Watson et al.,
GCN 22806). After that the light curve shows monotonic decay,
followed by a flat phase between ~1ks to ~3ks.
A preliminary light curve is posted at:
http://astro.berkeley.edu/~zwk/grb/GRB180620A/GRB180620A_kait.png
GCN Circular 22811
Subject
GRB 180620A: Xinglong-2.16m optical observations
Date
2018-06-20T19:20:31Z (7 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
Z.P. Zhu, D. Xu, J.B. Zhang (NAOC), X. Zhang, J.H. Liu (XAO) report
We observed the field of GRB 180620A (Evans et al., GCN 22790) using the
2.16-m telescope located at Xinglong, Hebei, China, equipped with the
BFOSC camera. We obtained 3x600s R-band frames, starting at 12:39:01 UT
on 2018-06-20, i.e., 4.068 hrs after the BAT trigger.
The GRB's optical afterglow (Evans et al., GCN 22790; Butler et al., GCN
22799; Elenin et al., GCN 22800; Tyurina et al., GCN 22801; Guidorzi et
al., GCN 22803) is clearly detected in each frame. Preliminary
photometry shows the afterglow has decayed to m(R)~20.0, calibrated with
nearby USNO B1 stars.
We acknowledge the excellent support from the Xinglong staff,
particularly Xiao Feng and Huijuan Wang, in obtaining these observations.
GCN Circular 22808
Subject
GRB 180620A: Swift-XRT refined Analysis
Date
2018-06-20T17:03:02Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), A. Tohuvavohu (PSU), S.
J. LaPorte (PSU), J.A. Kennea (PSU), S.L. Gibson (U. Leicester), Z. Liu
(NAOC / U. Leicester), J.P. Osborne (U. Leicester), P. D'Avanzo
(INAF-OAB) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 9.6 ks of XRT data for GRB 180620A (Evans et al. GCN
Circ. 22798), from 274 s to 23.4 ks after the BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position
for this burst was given by Osborne et al. (GCN Circ. 22802).
The late-time light curve (from T0+6.1 ks) can be modelled with a
power-law decay with a decay index of alpha=2.16 (+/-0.13).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.46 (+0.10, -0.08). The
best-fitting absorption column is 1.76 (+0.43, -0.16) 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 4.9 x 10^-11 (5.6 x
10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 1.76 (+0.43, -0.16) x 10^21 cm^-2
Galactic foreground: 1.6 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.46 (+0.10, -0.08)
If the light curve continues to decay with a power-law decay index of
2.16, the count rate at T+24 hours will be 2.3 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x
10^-13 (1.3 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/00843122.
This circular is an official product of the Swift-XRT team.
GCN Circular 22806
Subject
GRB 180620A: COATLI Detection and Light Curve
Date
2018-06-20T15:16:55Z (7 years ago)
From
Alan M. Watson at Instituto de Astronomia UNAM <alan@astro.unam.mx>
Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), William
H. Lee (UNAM), Carlos Rom��n-Z����iga (UNAM), Alexander Kutyrev (GSFC), and
Eleonora Troja (GSFC) report:
We observed the field of GRB 180620A (Evans et al., GCN 22798) with the
COATLI 50-cm telescope and interim imager at the Observatorio
Astron��mico Nacional on the Sierra de San Pedro M��rtir
(http://coatli.astroscu.unam.mx) from 2018-06-20 08:35:37 to 11:17:31
(from 39.2 seconds after the trigger or 21.1 seconds after the alert to
2.7 hours after the trigger), obtaining a total of 6250 seconds of
exposure in the w filter.
We detect the source reported by Butler et al. (GCN Circ. 22799) with
w = 18.00 +/- 0.02
This magnitude is in the USNO system and is not corrected for Galactic
extinction in the direction of the GRB.
Our light curve shows a sharp initial fall from 16.5 mag to 17.3 mag,
followed by a slower rise to 16.7 mag (also seen by Butler et al.),
followed by a monotonic fall to 19.0 mag.
We thank the COATLI technical team (Fernando ��ngeles, Oscar Chapa,
Salvador Cuevas, Alejandro Farah, Jorge Fuentes, Rosal��a Langarica,
Fernando Quir��s, and Carlos Tejada) and the staff of the Observatorio
Astron��mico Nacional.
GCN Circular 22805
Subject
GRB 180620A: Swift/UVOT Detection
Date
2018-06-20T14:19:58Z (7 years ago)
From
Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>
A. A. Breeveld (UCL-MSSL) 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 180620A
270 s after the BAT trigger (Evans et al., GCN Circ. 22798).
A fading source consistent with the XRT position (Osborne et al. GCN
Circ. 22802), and also detected by Butler et al. (GCN Circ. 22799),
Elenin et al. (GCN Circ. 22800), Tyurina et al. (GCN Circ. 22801) and
Guidorzi et al. (GCN Circ. 22803), is detected in the initial UVOT
exposures. The detection in the UVOT uvw2 filter implies a redshift
limit of 1.2.
The preliminary UVOT position is:
RA (J2000) = 18:39:35.09 = 279.89619 (deg.)
Dec (J2000) = +23:14:39.1 = 23.24419 (deg.)
with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence).
Preliminary detections 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 270 420 147 17.68 �� 0.04
v 427 1420 117 18.43 �� 0.19
b 525 717 39 18.77 �� 0.20
u 500 692 39 17.92 �� 0.17
w1 476 2158 194 18.86 �� 0.20
m2 623 7111 391 19.65 �� 0.27
w2 574 8136 588 20.00 �� 0.23
The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.13 in the direction of the
burst (Schlegel et al. 1998).
GCN Circular 22803
Subject
GRB 180620A: LCO McDonald observations
Date
2018-06-20T12:01:56Z (7 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 (U. of
Virgin Islands) on behalf of a large collaboration report:
The LCO 1-m unit at McDonald Observatory began observing Swift GRB
180620A (Evans et al. GCN 22798) on June 20, 08:55 UT (20 min since the
GRB trigger time) with the SDSS griz filters. The optical counterpart
(Evans et al.; Butler et al. GCN 22799; Elenin et al. GCN 22800; Tyurina
et al. GCN 22801) is clearly detected in each individual frame with the
following magnitudes:
Mid Time since GRB��� Exposure�������� Filter������� Magnitude
(hrs)����������������� (s)
------------------------------------------------------------------
0.349���������������� 1x120����������� SDSS-R������� 18.63 +- 0.04
0.583���������������� 1x120����������� SDSS-I������� 18.27 +- 0.04
------------------------------------------------------------------
as calibrated against nearby PanSTARRS objects.
GCN Circular 22802
Subject
GRB 180620A: Enhanced Swift-XRT position
Date
2018-06-20T10:42:13Z (7 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 1128 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 180620A, 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 = 279.89648, +23.24418 which is equivalent
to:
RA (J2000): 18h 39m 35.15s
Dec (J2000): +23d 14' 39.0"
with an uncertainty of 1.8 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 22801
Subject
GRB 180620A: MASTER OT observation
Date
2018-06-20T09:27:40Z (7 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
N.Tyurina, V. Lipunov, E. Gorbovskoy, V.Kornilov, A.Kuznetsov,
I. Gorbunov, D. Vlasenko, D.Zimnukhov, D.Kuvshinov, P.Balanutsa, V.Vladimirov
Lomonosov Moscow State University,
Sternberg Astronomical Institute, Moscow State University
R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias
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, C. Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)
D. Buckley
South African Astronomical Observatory
O. Gres, N.M.Budnev , Yu.Ishmuhametova
Irkutsk State University
A. Gabovich, V. Yurkov, Yu. Sergienko
Blagoveschensk Educational State University, Blagoveschensk
MASTER-OAFA robotic telescope (MASTER-Net: http://observ.pereplet.ru
Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) ,
located in Argentina (OAFA observatory of San Juan National University),
was pointed to the Swift GRB180620A ( Evans et al. GCN #22798)
20 sec after Notice and 41 sec after trigger time at 2018-06-20 08:35:39
UT.
We see OT at Swift UVOT coordinates ~17 mag (Evans et al. GCN #22798).
====================================================================
The observations made on zenit distance = 72 degrees, galaxy latitude b =
12 degree.
The moon (49 % bright part) below the horizon (The altitude of the Moon is
-50 degree ).
The sun altitude is -37.3 degree.
The object can be observed till 2018-06-20 10:23:39.
GCN Circular 22800
Subject
GRB 180620A: ISON-MN afterglow confirmation
Date
2018-06-20T09:21:07Z (7 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
L. Elenin (KIAM), A. Pozanenko (IKI), A. Volnova (IKI), E. Mazaeva, I.
Molotov (KIAM) report on behalf of larger GRB follow-up collaboration:
We observed the field of the Swift GRB 180620A (Evans et al., GCN 22798)
with ISON-NM observatory. Observation started 84 s after burst trigger. We
find fading object in coordinates (J2000) 18:39:35.09 +23:14:39.0 which
correspond to the OT candidate (Evans et al., GCN 22798). Preliminary
photometry of the OT in the first image started on 2018-06-20T08:36:21.666
is 17.1m in clear filter. Observation is ongoing.
GCN Circular 22799
Subject
GRB 180620A: RATIR Optical Afterglow Detection
Date
2018-06-20T09:16:28Z (7 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 180620A (Evans, et al., GCN 22798) 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 2018/06 20.36 to 2018/06 20.38 UTC (0.03
to 0.47 hours after the BAT trigger), obtaining a total of 0.36 hours
exposure in the r and i bands.
For a source within the Swift-XRT error circle, in comparison with the
USNO-B1 and 2MASS catalogs, we
obtain the following detections:
r = 18.01 +/- 0.01
i = 17.71 +/- 0.01
These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB. We observe the rise and
initial decline of the afterglow.
We thank the staff of the Observatorio Astron��mico Nacional in San Pedro
M��rtir. Further observations are planned.
GCN Circular 22798
Subject
GRB 180620A: Swift detection of a burst with an optical counterpart
Date
2018-06-20T08:50:56Z (7 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
P. A. Evans (U Leicester), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), A. A. Breeveld (UCL-MSSL),
S. W. K Emery (UCL-MSSL), A. Y. Lien (GSFC/UMBC),
K. L. Page (U Leicester), D. M. Palmer (LANL),
R. L. C. Starling (U Leicester) and A. Tohuvavohu (PSU) report on
behalf of the Neil Gehrels Swift Observatory Team:
At 08:34:58 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 180620A (trigger=843122). Swift slewed to the burst with a 3 min delay.
The BAT on-board calculated location is
RA, Dec 279.883, +23.265, which is
RA(J2000) = 18h 39m 32s
Dec(J2000) = +23d 15' 55"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows several overlapping peaks
with a total duration of about 25 sec. The peak count rate
was ~8000 counts/sec (15-350 keV), at ~12 sec after the trigger.
The XRT began observing the field at 08:39:25.1 UT, 267.1 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 279.89575, 23.24373 which is equivalent
to:
RA(J2000) = 18h 39m 34.98s
Dec(J2000) = +23d 14' 37.4"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 87 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 1.60
x 10^21 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of nominal 150.000 seconds with the White
filter starting 270 seconds after the BAT trigger. There is a candidate
afterglow in the list of sources generated on-board at
RA(J2000) = 18:39:35.08 = 279.89618
DEC(J2000) = +23:14:39.7 = 23.24437
with a 90%-confidence error radius of about 1.10 arc sec. This position is 1.7
arc sec. from the center of the XRT error circle. The estimated magnitude is
18.24. No correction has been made for the expected extinction corresponding to
E(B-V) of 0.13.
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.)