GRB 180618A
GCN Circular 22790
Subject
GRB 180618A: Swift detection of a burst with an optical counterpart
Date
2018-06-18T00:53:53Z (7 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
S. J. LaPorte (PSU), S. D. Barthelmy (GSFC), J. A. Kennea (PSU),
A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL), M. H. Siegel (PSU) and A. Tohuvavohu (PSU) report
on behalf of the Neil Gehrels Swift Observatory Team:
At 00:43:13 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 180618A (trigger=842475). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 169.937, +73.848 which is
RA(J2000) = 11h 19m 45s
Dec(J2000) = +73d 50' 52"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a single FRED
structure with a duration of about 20 sec. The peak count rate
was ~10000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 00:44:30.5 UT, 77.6 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 169.9415, 73.8358 which is equivalent to:
RA(J2000) = +11h 19m 45.96s
Dec(J2000) = +73d 50' 08.9"
with an uncertainty of 5.4 arcseconds (radius, 90% containment). This
location is 44 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 1.27e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 86 seconds after the BAT trigger. There is a candidate afterglow in
the list of sources generated on-board at
RA(J2000) = 11:19:45.78 = 169.94074
DEC(J2000) = +73:50:13.3 = 73.83704
with a 90%-confidence error radius of about 1.10 arc sec. This position is 4.5
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.81. No correction has been made for the expected extinction corresponding to
E(B-V) of 0.07.
Burst Advocate for this burst is S. J. LaPorte (extragsam 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 22791
Subject
GRB 180618A: Enhanced Swift-XRT position
Date
2018-06-18T03:26:07Z (7 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 1241 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 180618A, 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 = 169.94141, +73.83731 which is equivalent
to:
RA (J2000): 11h 19m 45.94s
Dec (J2000): +73d 50' 14.3"
with an uncertainty of 1.7 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 22792
Subject
GRB 180618A: LT prompt observations
Date
2018-06-18T08:18:45Z (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) on behalf of a large
collaboration report:
The 2-m Liverpool Telescope automatically began observing Swift GRB
180618A (LaPorte et al. GCN 22790) on June 18, 00:46:30 UT (197 s since
the GRB trigger time) with the RINGO3 polarimeter and the IO:O camera in
the SDSS-R filter. The optical counterpart identified by Swift-UVOT is
clearly detected with r'=19.36 +- 0.05 mag in a 6x10s exposure at a mid
time of 36.3 minutes post GRB, as calibrated against nearby SDSS objects.
GCN Circular 22793
Subject
GRB 180618A: Swift-XRT refined Analysis
Date
2018-06-18T10:23:59Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), D.N.
Burrows (PSU), A. Tohuvavohu (PSU), S. J. LaPorte (PSU), P.A. Evans (U.
Leicester), S.L. Gibson (U. Leicester), Z. Liu (NAOC / U. Leicester)
and S.J. LaPorte report on behalf of the Swift-XRT team:
We have analysed 7.8 ks of XRT data for GRB 180618A (LaPorte et al. GCN
Circ. 22790), from 83 s to 24.6 ks after the BAT trigger. The data
comprise 293 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. 22791).
The light curve can be modelled with an initial power-law decay with an
index of alpha=0.66 (+0.19, -0.31), followed by a break at T+158 s to
an alpha of 1.80 (+/-0.05).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.91 (+/-0.09). The
best-fitting absorption column is 2.0 (+0.4, -0.3) x 10^21 cm^-2, in
excess of the Galactic value of 4.4 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.23 (+0.22, -0.21)
and a best-fitting absorption column of 2.9 (+0.8, -0.7) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 3.3 x 10^-11 (5.4 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 2.9 (+0.8, -0.7) x 10^21 cm^-2
Galactic foreground: 4.4 x 10^20 cm^-2
Excess significance: 5.3 sigma
Photon index: 2.23 (+0.22, -0.21)
If the light curve continues to decay with a power-law decay index of
1.80, the count rate at T+24 hours will be 1.9 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.4 x
10^-15 (1.1 x 10^-14) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00842475.
This circular is an official product of the Swift-XRT team.
GCN Circular 22794
Subject
GRB 180618A: Fermi GBM detection
Date
2018-06-18T15:47:53Z (7 years ago)
From
Rachel Hamburg at UAH <rkh0007@uah.edu>
R. Hamburg (UAH) and E. Bissaldi (Politecnico & INFN Bari)
report on behalf of the Fermi GBM Team:
"At 00:43:13.11 UT on 18 June 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180618A (trigger 550975398 / 180618030),
which was also detected by the Swift/BAT (LaPorte et al. 2018, GCN 22790).
The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 103
degrees.
The GBM light curve shows one main peak
with a duration (T90) of about 3.7 s (50-300 keV).
LaPorte et al. 2018 report a longer duration of
~20 s in the Swift/BAT. Given the soft tail following
the initial hard spike, we suggest the discrepancy
may be due to extended emission of this short GRB.
The time-averaged spectrum from T0 to T0+1.8 s
is adequately fit a power law function with an exponential
high-energy cutoff. The power law index is 1.08 +/- 0.06 and
the cutoff energy, parameterized as Epeak, is 2.8 +/- 0.8 MeV.
The event fluence (10-1000 keV) in this time interval is
(2.12 +/- 0.12)E-06 erg/cm^2. The 64-ms peak photon flux measured
starting from T0 in the 10-1000 keV band is 14.6 +/- 1.9 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 22796
Subject
GRB 180618A: Swift-BAT refined analysis (a short GRB with extended emission)
Date
2018-06-18T18:27:23Z (7 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
T. Sakamoto (AGU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF/USRA),
S. J. LaPorte (PSU), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), J. P. Norris (BSU),
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 180618A (trigger #842475)
(LaPorte et al., GCN Circ. 22790). The BAT ground-calculated position is
RA, Dec = 169.948, 73.825 deg which is
RA(J2000) = 11h 19m 47.6s
Dec(J2000) = +73d 49' 29.3"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 70%.
The mask-weighted light curve shows a short multi-peaked structure from ~ T0
to ~T+0.3, followed by some extended emission that lasts till ~T+50 s.
T90 (15-350 keV) is 47.4 +- 11.1 sec (estimated error including systematics).
The time-averaged spectrum from T-0.06 to T+56.33 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.39 +- 0.27. The fluence in the 15-150 keV band is 6.7 +- 1.0 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.08 sec in the 15-150 keV band
is 2.2 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
The structure of the burst shows similarity to those of short GRBs with
extended emission, as mentioned in Hamburg et al., GCN Circ. 22794.
We thus perform further analysis on the short spike and the extended emission.
The spectrum of the short multi-peaked structure from T-0.056 to T+0.264 sec
is best fit by a simple power-law model, with power-law index of 0.60 +- 0.24
and fluence (15-150 keV) of 1.3 +- 0.2 x 10^-7 erg/cm2. The spectrum of the
extended emission from T+0.264 to T+56.328 sec is best fit by a simple power-law
model, with power-law index of 1.53 +- 0.31 and fluence (15-150 keV) of
5.5 +- 1.0 x 10^-7 erg/cm2. These values are consistent with those of short GRBs
with extended emission (Lien & Sakamoto et al. 2016).
Using a 4-ms binned light curve, the lag analysis of the first two tallest pulses
(from ~T0 to ~T+0.1 s) finds a lag of 0.7 +/- 0.9 ms for the 100-350 keV to 25-50 keV
band, and 1.5 (+1.8, -1.2) ms for the 50-100 keV to 15-25 keV band. Therefore, the
lag values of these short pulses are consistent with those of short GRBs.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/842475/BA/
GCN Circular 22797
Subject
GRB 180618A: MASTER OT observation (a short GRB with extended emission)
Date
2018-06-19T12:00:58Z (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-Kislovodsk robotic telescope (MASTER-Net: http://observ.pereplet.ru
Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) ,
located in Kislovodsk Solar Station of Pulkovo observatory,
was pointed to the Swift GRB180618A (LaPorte et al. GCN #22790; Sakamoto
et al., GCN #22796)
25 sec after notice time and 41 sec after trigger time at 2018-06-18
00:43:53 UT.
On our first (10s exposure) polarization set we haven`t found optical
transient within SWIFT error-box (ra=169.933 dec=73.8478 r=0.05).
The 5-sigma upper limit has been about 15.2 mag
The observations made on zenit distance = 61 degrees, galaxy latitude b =
42 degree.
The moon (24 % bright part) below the horizon (The altitude of the Moon is
-31 degree ).
Observations started at twilight and bad transparency. The sun altitude
is -6.8 degree.
MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru)
located in IAC was pointed to the GRB180618A 1734 sec after trigger time
at 2018-06-18 01:12:07 UT.
On our first (180s exposure) set we found ~19 mag optical transient
within SWIFT UVOT error-box (LaPorte et al. GCN #22790; Guidorzi et al.,
GCN #22792;).
The 5-sigma upper limit has been about 19.0 mag on single (180 s) and
20.5 on coadd (1800 s) exposures.
====================================================================
The observations made on zenit distance = 64 degrees, galaxy latitude b =
42 degree.
The moon (24 % bright part) below the horizon (The altitude of the Moon is
-15 degree ).
The sun altitude is -38.3 degree.
The object can be observed till sunrise at 2018-06-18 06:08:21
The message may be cited.
GCN Circular 22804
Subject
GRB 180618A: Xinglong-2.16m optical upper limit
Date
2018-06-20T13:02:02Z (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), Z.B. Dai
(YNAO) report:
We observed the field of GRB 180618A (LaPorte et al., GCN 22790) using
the 2.16-m telescope located at Xinglong, Hebei, China, equipped with
the BFOSC camera. We obtained 6x600s R-band frames, starting at 12:43:22
UT on 2018-06-19, i.e., 1.50 days after the BAT trigger.
The previously detected optical afterglow of the GRB (e.g., LaPorte et
al., GCN 22790; Guidorzi et al., GCN 22792; Tyurina et al., GCN 22797)
was not present in our stacked image, down to a limiting magnitude of
R~21.4 mag, calibrated with the SDSS field.
GCN Circular 22809
Subject
GRB 180618A: TSHAO optical upper limit
Date
2018-06-20T17:57:39Z (7 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
E. Mazaeva (IKI), A. Kusakin (FAPHI), A. Pozanenko (IKI), I. Reva
(FAPHI), A. Volnova (IKI), M. Krugov (FAPHI) report on behalf of
larger GRB follow-up collaboration:
We observed the field of GRB GRB 180618A (LaPorte et al., GCN 22790)
with Zeiss-1000 1-m telescope of Tien Shan Astronomical Observatory
starting on June 18 (UT) 15:39:19. We obtained several images in
R-filter. The optical afterglow (LaPorte et al., GCN 22790; Guidorzi et
al., GCN 22792; Tyurina et al., GCN 22797) is not detected in a stacked
image. Preliminary photometry of the field is following.
Date UT start t-T0 Filter Exp. OT Err. UL
(mid, days) (s)
2018-06-18 15:39:19 0.65209 R 36*120 n/d n/d 22.2
The photometry is based on several nearby SDSS-DR10 stars.
Ref.stars
SDSS_id R(Lupton)
J112037.79+735136.8 17.37
J111905.28+734733.2 17.54
J111907.19+734657.8 17.04
GCN Circular 22810
Subject
GRB 180618A: Swift/UVOT Detection
Date
2018-06-20T18:15:17Z (7 years ago)
From
Mike Siegel at PSU/Swift MOC <siegel@swift.psu.edu>
M. H. Siegel (PSU) and S. J. LaPorte (PSU)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180618A
86 s after the BAT trigger (LaPorte et al., GCN Circ. 22790). We confirm
the previously reported fading optical afterglow, also detected by LT (Guidorzi
et al., GCN Circ. 22792) and MASTER (Tyurina et al., GCN Circ. 22797). We find
that the source had faded away completely by the second orbit. The detection of the
afterglow in six of UVOT's filters places an upper limit on the redshift of z < 1.2.
The preliminary UVOT position is:
RA (J2000) = 11:19:45.84 = 169.94102 (deg.)
Dec (J2000) = +73:50:13.5 = 73.83707 (deg.)
with an estimated uncertainty of 0.43 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 (fc) 86 236 147 17.46 +/- 0.04
white 86 1544 390 17.95 +/- 0.03
white 5680 7315 393 >21.09
v 628 1596 117 18.71 +/- 0.22
v 6090 6290 196 >19.25
b 553 1175 58 18.84 +/- 0.16
b 5475 7110 393 >20.39
u (fc) 298 548 246 17.50 +/- 0.06
u 298 1497 313 17.62 +/- 0.06
u 5270 6905 393 >19.94
w1 676 1472 97 18.59 +/- 0.24
w1 5065 6700 393 >19.63
m2 1254 1621 58 >17.6
w2 604 1398 97 18.85 +/- 0.28
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.07 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 22822
Subject
Konus-Wind observation of GRB 180618A (a short GRB with extended emission)
Date
2018-06-22T10:32:51Z (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 bright, short-duration, hard GRB 180618A
(Swift-BAT detection: LaPorte et al., GCN Circ 22790;
Fermi-GBM detection: Hamburg et al., GCN Circ 22794)
triggered Konus-Wind at T0=2591.201 s UT (00:43:11.201).
The burst light curve shows a bright multi-peaked initial pulse
with a total duration of ~0.250 s, followed by
an extended emission seen up to ~T0+10 s.
The emission of the initial pulse is seen up to ~10 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180618_T02591/
As observed by Konus-Wind, the burst
had a fluence of 6.24(-1.13,+1.20)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0-0.010 s,
of 5.60(-1.83,+1.88)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the initial pulse
(measured from T0 to T0+0.192 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.36(-0.24,+0.30)
and Ep = 2461(-565,+788) keV (chi2 = 47/38 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.4
(chi2 = 47/37 dof).
The time-averaged spectrum of the extended emission
(measured from T0+0.256 to T0+8.448 s)
is best fit in the 20 keV - 2 MeV range
by the CPL model with alpha = -0.68(-0.79,+1.59),
Ep = 170(-66,+203) keV (chi2 = 102/98 dof).
Among ~300 bursts from the Konus catalog of short GRBs
(Svinkin et al., 2016, ApJS 224, 10), GRB 180618A is within top 1%
in the terms of 16-ms peak energy flux and within top 15% in the terms
of the total energy fluence, both in the 20 keV - 10 MeV range.
In the terms of Epeak, the burst is within 1% hardest
GRBs in the sample.
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
GCN Circular 22842
Subject
GRB 180618A: AstroSat CZTI detection
Date
2018-06-25T13:49:11Z (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 short GRB 180618A, which was also detected by Swift (LaPorte S. J. et al., GCN 22790), Fermi-GBM (Hamburg R. et al., GCN 22794), Konus-Wind (Svinkin D. et al., GCN 22822).
The source was clearly detected in the 40-200 keV energy range. The light curve shows a single peak of emission with peak at 00:43:13.5 UT. The measured peak count rate is 217.1 cts/s above the background in combined data of four quadrants, with a total of 140.9 cts. The local mean background count rate was 456.9 cts/s. Using cumulative rates, we measure a T90 of 2.1 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.