GRB 180602A
GCN Circular 22760
Subject
GRB 180602A: MITSuME Ishigakijima optical upper limits
Date
2018-06-04T16:41:32Z (8 years ago)
From
Yutaro Tachibana at Tokyo Tech <tachibana@hp.phys.titech.ac.jp>
T. Horiuchi, H. Hanayama, M. Honma (IAO, NAOJ),
Y. Tachibana, R. Itoh, K. L. Murata, S. Harita, K. Morita, T. Ozawa, H. Mamiya,
K. Shiraishi, Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:
We searched for the optical counterpart of GRB 180602A
(Cenko et al., GCN Circular #22752, Osborne et al., GCN Circular #22753, Gropp and Cenko, GCN Circular #22758)
with the optical three color (g', Rc, and Ic) CCD cameras attached to
the Murikabushi 1m telescope of Ishigakijima Astronomical Observatory.
The observation started on 2018-06-02 12:38:23 UT.
We did not find any point source at the position of the XRT error
circle in all three bands. We obtained following 3-sigma upper limits:
T0+[hour] MID-UT T-EXP[sec] g' Rc Ic
-------------------------------------------------------------------------------------------------------
~4.5 12:51:13.3 1,560 >19.4 >19.1 >18.7
-------------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used UCAC-4 catalog for flux calibration.
GCN Circular 22758
Subject
GRB 180602A: Swift/UVOT Upper Limits
Date
2018-06-03T17:11:58Z (8 years ago)
From
Jeffrey Gropp at PSU <jdg44@psu.edu>
J. Gropp (PSU) and S. B. Cenko (GSFC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180602A
133 s after the BAT trigger (Cenko et al., GCN Circ. 22752).
No optical afterglow consistent with the enhanced XRT position
(Osborne et al. GCN Circ. 22753)
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 133 283 147 >19.9
u_FC 291 541 246 >19.8
white 133 1715 411 >20.8
v 621 2283 194 >19.0
b 547 2208 175 >20.0
u 291 2183 401 >20.3
w1 670 2159 175 >20.0
m2 645 665 19 >18.7
w2 597 2086 136 >20.4
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 22757
Subject
GRB 180602A: MITSuME Akeno optical upper limits
Date
2018-06-03T09:29:22Z (8 years ago)
From
Katsuhiro L. Murata at Nagoya U <murata@u.phys.nagoya-u.ac.jp>
K. L. Murata, Y. Tachibana, R. Itoh, T. Yoshii, S. Harita, K. Morita, T.
Ozawa, H. Mamiya, K. Shiraishi, K. Iida, M. Oeda, R. Adachi, S. Niwano, Y.
Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:
We searched for the field of GRB 180602A (Cenko et al., GCN Circular
#22752) 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 2018-06-02 11:12:09 UT (~3 hours after the
burst). We did not find any new point source within the enhanced XRT error
circle (Osborne et al., GCN Circular #22753) in all the three bands.
T0+[hour] MID-UT T-EXP[sec] g' Rc Ic
------------------------------------------------------------
-------------------------------------------
~3.1 ~12:24 1200 >18.9 >18.3 >18.0
------------------------------------------------------------
-------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used GSC2.3 catalog for flux calibration.
GCN Circular 22756
Subject
GRB 180602A: Swift-XRT refined Analysis
Date
2018-06-03T02:52:27Z (8 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore
(U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), P.
D'Avanzo (INAF-OAB), S. J. LaPorte (PSU), J.A. Kennea (PSU), B.
Sbarufatti (INAF-OAB/PSU) and S.B. Cenko report on behalf of the
Swift-XRT team:
We have analysed 8.4 ks of XRT data for GRB 180602A (Cenko et al. GCN
Circ. 22752), from 130 s to 59.7 ks after the BAT trigger. The data
comprise 85 s in Windowed Timing (WT) mode with the remainder in Photon
Counting (PC) mode. The enhanced XRT position for this burst was given
by Osborne et al. (GCN Circ. 22753).
The late-time light curve (from T0+5.6 ks) can be modelled with a
power-law decay with a decay index of alpha=1.38 (+0.16, -0.13).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.36 (+0.28, -0.25). The
best-fitting absorption column is 4.0 (+1.3, -1.1) x 10^21 cm^-2, in
excess of the Galactic value of 1.6 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.04 (+0.16, -0.15)
and a best-fitting absorption column of 4.2 (+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 3.8 x 10^-11 (6.2 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 4.2 (+0.8, -0.7) x 10^21 cm^-2
Galactic foreground: 1.6 x 10^20 cm^-2
Excess significance: 9.1 sigma
Photon index: 2.04 (+0.16, -0.15)
If the light curve continues to decay with a power-law decay index of
1.38, the count rate at T+24 hours will be 7.3 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.8 x
10^-13 (4.5 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/00835200.
This circular is an official product of the Swift-XRT team.
GCN Circular 22755
Subject
GRB 180602A: Swift-BAT refined analysis
Date
2018-06-02T17:18:13Z (8 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC),
S. B. Cenko (GSFC), J. R. Cummings (CPI),
H. A. Krimm (NSF/USRA), C. B. Markwardt (GSFC),
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 180602A (trigger #835200)
(Cenko et al., GCN Circ. 22752). The BAT ground-calculated position is
RA, Dec = 142.343, 32.080 deg which is
RA(J2000) = 09h 29m 22.4s
Dec(J2000) = +32d 04' 48.1"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 78%.
The mask-weighted light curve shows a single-peaked structure that starts
at ~T-30 s, peaks at ~T-20 s, and ends at ~T+25 s. We note that the burst
emission indeed started and peaked during a pre-planned spacecraft slew,
and the trigger occurred near the end of the pulse when the slew settled.
T90 (15-350 keV) is 45.4 +- 7.1 sec (estimated error including systematics).
The time-averaged spectrum from T-29.32 to T+25.73 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.72 +- 0.11. The fluence in the 15-150 keV band is 1.6 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-20.12 sec in the 15-150 keV band
is 0.9 +- 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/835200/BA/
GCN Circular 22754
Subject
GRB 180602A: MITSuME Okayama optical upper limits
Date
2018-06-02T12:30:27Z (8 years ago)
From
Yutaro Tachibana at Tokyo Tech <tachibana@hp.phys.titech.ac.jp>
Y. Tachibana, R. Itoh, K. L. Murata, S. Harita, K. Morita,
T. Ozawa, H. Mamita, K. Shiraishi, Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:
We observed the field of GRB 180602A (Cenko et al., GCN Circular #22752)
with the optical three color (g', Rc and Ic) CCD camera attached
to the MITSuME 50cm telescope of Okayama Astrophysical Observatory.
The observation started on 2018-06-02 11:14:03.47 UT (~3 hours after
the burst). We did not find any new point source within the
enhanced XRT error circle (Osborne et al., GCN Circular #22753) in all
the three bands.
We obtained following limits for the magnitudes.
T0+[hour] MID-UT T-EXP[sec] g' Rc Ic
-------------------------------------------------------------------------------------------------------
~3.07 ~11:18:47 420 >17.8 >17.7 >17.1
-------------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used GSC2.3 catalog for flux calibration.
GCN Circular 22753
Subject
GRB 180602A: Enhanced Swift-XRT position
Date
2018-06-02T10:38:54Z (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 2068 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 180602A, 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 = 142.33181, +32.06710 which is equivalent
to:
RA (J2000): 09h 29m 19.63s
Dec (J2000): +32d 04' 01.6"
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 22752
Subject
GRB 180602A: Swift detection of a burst
Date
2018-06-02T08:35:07Z (8 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
S. B. Cenko (GSFC), J.D. Gropp (PSU), A. Y. Lien (GSFC/UMBC),
A. Melandri (INAF-OAB), K. L. Page (U Leicester), D. M. Palmer (LANL)
and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 08:14:50 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 180602A (trigger=835200). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 142.339, +32.093 which is
RA(J2000) = 09h 29m 21s
Dec(J2000) = +32d 05' 34"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The burst appears to have been in progress
as Swift was slewing to the pre-planned pointing target before the
nominal trigger time. The BAT light curve showed a single peak
structure with a duration of about 50 seconds, however the start
of the peak may be due to the GRB entering the FOV during the slew.
The peak count rate was ~1300 counts/sec (15-350 keV), at ~20 sec
before the trigger.
The XRT began observing the field at 08:16:55.2 UT, 124.3 seconds after
the BAT trigger. The position determined from promptly downlinked data
differs significantly from the on-board position, suggesting that the
XRT may have centroided on a cosmic ray; the initial XRT position
notice should be treated with caution. Using promptly downlinked data
we find an uncatalogued X-ray source with an enhanced position: RA, Dec
142.3319, 32.0661 which is equivalent to:
RA(J2000) = 09h 29m 19.65s
Dec(J2000) = +32d 03' 58.1"
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This
location is 99 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 in excess of the Galactic value (1.56 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 6.1
(+2.76/-2.42) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 133 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 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag.
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
0.02.
Burst Advocate for this burst is S. B. Cenko (brad.cenko 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.)