GRB 180706A
GCN Circular 22989
Subject
GRB 180706A: OSN detection
Date
2018-07-21T05:26:20Z (8 years ago)
From
Alexander Kann at IAA-CSIC <kann@iaa.es>
D. A. Kann, L. Izzo (both HETH/IAA-CSIC) and A. Sota (IAA-CSIC) report
on behalf of HETH:
We observed the position of the Swift GRB 180706A (Stamatikos et al.,
GCN #22909) with the T150 telescope of the Observatorio Sierra Nevada
(OSN) near Granada, Spain.
We obtained 6 x 300 s Ic images (mean time after trigger 0.546615 days)
and further 5 x 300 s Ic images a night later (mean time after trigger
1.57231 days).
The afterglow (Stamatikos et al., GCN #22909; Watson et al., GCN #22910;
Oates et al., GCN #22922; Volnova et al., GCN #22923) is clearly
detected in the first night, and we derive Ic = 20.56 +/- 0.06 mag. It
is not detected anymore in the second night to a limit of Ic > 22.5. The
detection magnitude is in good agreement with the earlier measurement of
Volnova et al. when typical Rc-Ic colors of GRBs are taken into account.
The lead author is sorry for the long vacation this data took.
GCN Circular 22924
Subject
GRB 180706A: GOTO optical limits
Date
2018-07-06T23:16:00Z (8 years ago)
From
Danny Steeghs at U.of Warwick/GOTO <D.T.H.Steeghs@warwick.ac.uk>
K.Ulaczyk, D.Steeghs (U. Warwick), G.Ramsay (Armagh O.), M.Dyer
(U. Sheffield), B.Gompertz, J.Lyman, A.Levan, R.Cutter (U. Warwick)
K. Ackley, D.Galloway, E.Rol (Monash U.), V.Dhillon (U. Sheffield),
P.O'Brien, N.Tanvir (U. Leicester), S.Poshyachinda (NARIT),
D.Pollacco (U. Warwick), E.Thrane (Monash U.)
report on behalf of the GOTO collaboration:
In response to GRB 180706A (GCN 22909, 22910, 22916, 22917, 22919,
22921), the Gravitational-wave Optical Transient Observer (GOTO)
observed the field near the XRT position as reported by Osborne
et al. (GCN 22916).
Observations started at 2018-07-06T21:26:42 UT (13 hours after the
burst) and ended at 2018-07-06T23:49:54 and consisted of a set of
12x120s exposures in our wide L filter(400-700nm). We did not detect
a significant source corresponding to the reported optical counterpart.
A stacked image was used to derive a 5-sigma upper limit of V>21.6,
after astrometric and photometric (APASS V) calibrations.
This is consistent with the photometric evolution between the early
optical detections (GCN 22910, 22922) and the TSHAO magnitude reported
in Volnova et al. (GCN 22923).
GOTO is operated at the La Palma observing facilities of the University
of Warwick on behalf of a consortium including the University of
Warwick, Monash University, Armagh Observatory, the University of
Leicester, the University of Sheffield, the National Astronomical
Research Institute of Thailand (NARIT) and the Instituto de Astrofisica
de Canarias (IAC)
https://goto-observatory.org/
GCN Circular 22923
Subject
GRB 180706A: TSHAO optical observations
Date
2018-07-06T21:15:30Z (8 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
A. Volnova (IKI), I. Reva (FAPHI), E. Mazaeva (IKI), A. Pozanenko (IKI),
A. Kusakin (FAPHI), M. Krugov (FAPHI) report on behalf of larger GRB
follow-up collaboration:
We observed the field of GRB 180706A (Stamatikos et al., GCN 22909)
with Zeiss-1000 telescope of Tien Shan Astronomical Observatory starting
on July 06 (UT) 16:18:35. We obtained several images in R-filter. The
optical afterglow (Stamatikos et al., GCN 22909; Watson et al., GCN
22910) is clearly detected in a combined image. Preliminary photometry
of the afterglow is following.
Date UT start t-T0 Filter Exp. OT Err. UL
(mid, days) (s)
2018-07-06 16:18:35 0.35345 R 29*120 20.65 0.09 22.2
The photometry is based on several SDSS-DR12 stars.
Ref.stars
SDSS-DR12_id R(Lupton)
J120642.39+660133.6 18.5600.025
J120649.22+660218.2 17.5190.018
J120653.24+660249.5 17.9870.017
GCN Circular 22922
Subject
GRB 180706A: Swift/UVOT Detection
Date
2018-07-06T18:42:37Z (8 years ago)
From
Samantha Oates at MSSL <sro@mssl.ucl.ac.uk>
S. R. Oates (U.Warwick) and M. Stamatikos (OSU/NASA/GSFC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180706A
95 s after the BAT trigger (Stamatikos et al., GCN Circ. 22909).
A source consistent with the XRT position
(Osborne et al. GCN Circ. 22916) and the COATLI optical detection
(Watson et al. GCN Circ. 22910) is detected in the initial UVOT exposures.
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) 95 245 147 19.88 +/- 0.34
white 587 607 20 18.11 +/- 0.21
v 637 1582 117 >18.5
b 563 756 39 18.34 +/- 0.30
u 308 557 246 17.90 +/- 0.12
w1 686 1459 78 18.44 +/- 0.33
m2 661 1606 117 >18.8
w2 613 1558 117 >19.1
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 22921
Subject
GRB 180706A: Swift-BAT refined analysis
Date
2018-07-06T18:11:57Z (8 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),
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-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 180706A (trigger #846395)
(Stamatikos et al., GCN Circ. 22909). The BAT ground-calculated position is
RA, Dec = 181.687, 66.044 deg which is
RA(J2000) = 12h 06m 45.0s
Dec(J2000) = +66d 02' 40.1"
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 86%.
The mask-weighted light curve shows a double-peaked structure that starts
at ~T-20 s and ends at ~T+50 s. The smaller peak occurs at ~T+2 s, and
the larger peak happens at ~T+28 s. T90 (15-350 keV) is 42.7 +- 8.7 sec
(estimated error including systematics).
The time-averaged spectrum from T-18.77 to T+50.99 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.90 +- 0.08. The fluence in the 15-150 keV band is 2.4 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+27.82 sec in the 15-150 keV band
is 3.2 +- 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/846395/BA/
GCN Circular 22919
Subject
GRB 180706A: Fermi GBM observation
Date
2018-07-06T17:06:31Z (8 years ago)
From
Elisabetta Bissaldi at INFN,Bari <elisabetta.bissaldi@ba.infn.it>
E. Bissaldi (Politecnico & INFN Bari)
reports on behalf of the Fermi GBM Team:
"At 08:25:09.03 UT on 06 July 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180706A (trigger 552558314 / 180706351),
which was also detected by the Swift/BAT (Stamatikos et al. 2018, GCN 22909).
The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 60 degrees.
The GBM light curve consists of multiple peaks
with a duration (T90) of about 38 s (50-300 keV).
The time-averaged spectrum from T0-30 s to T0+10 s is
adequately fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.98 +/- 0.13 and
the cutoff energy, parameterized as Epeak, is 53 +/- 4 keV.
The event fluence (10-1000 keV) in this time interval is
(3.3 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-2 s in the 10-1000 keV band is 4.9 +/- 0.3 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 22917
Subject
GRB 180706A: Swift-XRT refined Analysis
Date
2018-07-06T15:38:54Z (8 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB),
B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), A. Tohuvavohu (PSU),
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore
(U. Leicester) and M. Stamatikos report on behalf of the Swift-XRT
team:
We have analysed 6.1 ks of XRT data for GRB 180706A (Stamatikos et al.
GCN Circ. 22909), from 77 s to 17.9 ks after the BAT trigger. The data
comprise 169 s in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Osborne et
al. (GCN Circ. 22916).
The late-time light curve (from T0+5.5 ks) can be modelled with a
power-law decay with a decay index of alpha=0.58 (+0.21, -0.22).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 3.11 (+/-0.09). The
best-fitting absorption column is 1.65 (+/-0.18) x 10^21 cm^-2, in
excess of the Galactic value of 1.4 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.16 (+0.17, -0.16)
and a best-fitting absorption column of 6.7 (+3.7, -3.3) x 10^20 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 3.0 x 10^-11 (3.6 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 6.7 (+3.7, -3.3) x 10^20 cm^-2
Galactic foreground: 1.4 x 10^20 cm^-2
Excess significance: 2.6 sigma
Photon index: 2.16 (+0.17, -0.16)
If the light curve continues to decay with a power-law decay index of
0.58, the count rate at T+24 hours will be 0.026 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.7 x
10^-13 (9.3 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/00846395.
This circular is an official product of the Swift-XRT team.
GCN Circular 22916
Subject
GRB 180706A: Enhanced Swift-XRT position
Date
2018-07-06T14:46:59Z (8 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 1356 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 180706A, 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 = 181.64259, +66.03714 which is equivalent
to:
RA (J2000): 12h 06m 34.22s
Dec (J2000): +66d 02' 13.7"
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 22910
Subject
GRB 180706A: COATLI Optical Detection
Date
2018-07-06T09:02:57Z (8 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), Carlos
Rom��n-Z����iga (UNAM), and William H. Lee (UNAM) report:
We observed the field of the GRB 180706A (Stamatikos et al., GCN Circ.
22909) with the COATLI 50-cm telescope and interim imager (Watson et al.
2016, Proc. SPIE, 9908, 50) at the Observatorio Astron��mico Nacional on
the Sierra de San Pedro M��rtir from 2018-07-06 08:25:26.83 (29.5 seconds
after alert and 46.4 seconds after trigger) to 08:50:34, obtaining 795
seconds of exposure in the w filter.
We detect an uncatalogued source in the XRT error region with a
preliminary magnitude of
w = 18.73 +/- 0.08
This magnitude is calibrated against the USNO-B1 catalog (adjusted to an
approximate AB system) and is not corrected for Galactic extinction in
the direction of the GRB.
At the moment we have no information on fading. Further observations are
planned.
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 22909
Subject
GRB 180706A: Swift detection of a burst with optical counterpart
Date
2018-07-06T08:43:15Z (8 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
M. Stamatikos (OSU/NASA/GSFC), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), A. D'Ai (INAF-IASFPA),
V. D'Elia (ASDC), P. A. Evans (U Leicester), J.D. Gropp (PSU),
J. A. Kennea (PSU) and K. L. Page (U Leicester) report on behalf of
the Neil Gehrels Swift Observatory Team:
At 08:24:40 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 180706A (trigger=846395). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 181.665, +66.035, which is
RA(J2000) = 12h 06m 40s
Dec(J2000) = +66d 02' 05"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows two main peaks
with a total duration of about 40 sec. The peak count rate
was ~4000 counts/sec (15-350 keV), at ~28 sec after the trigger.
The XRT began observing the field at 08:26:08.0 UT, 87.7 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source with an enhanced position: RA, Dec 181.6428,
66.0366 which is equivalent to:
RA(J2000) = 12h 06m 34.28s
Dec(J2000) = +66d 02' 11.6"
with an uncertainty of 2.4 arcseconds (radius, 90% containment). This
location is 32 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. We
cannot determine whether the source is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 1.44
x 10^20 cm^-2 (Willingale et al. 2013).
The initial flux in the 2.5 s image was 7.91e-10 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 250 seconds with the U filter starting
307 seconds after the BAT trigger. There is a candidate afterglow in the
rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 12:06:34.34 = 181.64308
DEC(J2000) = +66:02:13.6 = 66.03712
with a 90%-confidence error radius of about 0.77 arc sec. This position is 2.9
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.74 with a 1-sigma error of about 0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.02.
Burst Advocate for this burst is M. Stamatikos (Michael.Stamatikos-1 AT nasa.gov).
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.)