GRB 230618A
GCN Circular 34085
Subject
GRB 230618A: Swift-BAT refined analysis
Date
2023-06-27T00:39:58Z (2 years ago)
From
Sibasish Laha at GSFC <sibasish.laha@nasa.gov>
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa), D. M. Palmer (LANL),
T. Parsotan (GSFC/UMBC), T. Sakamoto (AGU),
M. Stamatikos (OSU) (i.e. the Swift-BAT team):
Using the data set from T-275 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 230618A (trigger #1175438)
(Page et al., GCN Circ. 33989). The BAT ground-calculated position is
RA, Dec = 196.642, 3.278 deg which is
RA(J2000) = 13h 06m 34.1s
Dec(J2000) = +03d 16' 39.6"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
The BAT light curve showed a complex structure with a duration of about 200 sec.
T90 (15-350 keV) is 104.05 +- 22.86 sec (estimated error including systematics).
The time-averaged spectrum from T-27.78 to T+107.00 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.35 +- 0.15. The fluence in the 15-150 keV band is 1.5 +- 0.2 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+9.04 sec in the 15-150 keV band
is 0.5 +- 0.1 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/1175438/BA/
GCN Circular 34024
Subject
GRB 230618A: Osservatorio Astronomico Nastro verde upper limit
Date
2023-06-19T20:14:40Z (2 years ago)
From
Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy - MPC Code C82 <osservatorionastroverde@gmail.com>
Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy
in a large collaboration with:
M.G. Dainotti (National Astronomical Observatory of Japan),
Y. Niino (Tokyo University, Institute of Astronomy),
K. Kalinowski (Aarhus University, Department of Physics and Astronomy),
B. De Simone (Universita' degli Studi Di Salerno)
report:
We image the field of GRB 230618A detected by SWIFT (Page et al., GCN 33989)
with telescope of Nastro Verde Observatory - Sorrento (Naples), Italy. Member of:
AAVSO - American Association of Variable Star Observers.
UAI/SSV - Unione Astrofili Italiani/sezione stelle variabili.
AstroCampania Associazione
Observations began at 21:02 UT on 2023/06/18, 19 hours after GRB's detection,
with principal telescope SC 0.35 f/10 with focal reduced + CCD Sbig ST10 XME
I took 24 image of 60 sec each. All images are unfiltered, calibrated with masterdark and masterflat,stacked with Tycho Tracker software
We have not detected any clearly visible sources, up to 20.3th magnitude with clear sky at
RA(J2000) = 13h 06m 24.75s
Dec(J2000) = +03d 18' 09.3"
on a field of view 23.3 x 15.7 arcmin
Start End Rlim
21:02:25 UT 21:29:28 UT 20.3
Magnitudes were estimated with the Gaia DR2 cat. and
are not corrected for galactic dust extinction.
The message may be cited.
GCN Circular 34009
Subject
GRB 230618A: Enhanced Swift-XRT position
Date
2023-06-18T21:36:36Z (2 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.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 3710 s of XRT Photon Counting mode data and 5 UVOT
images for GRB 230618A, 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 = 196.60314, +3.30351 which is equivalent
to:
RA (J2000): 13h 06m 24.75s
Dec (J2000): +03d 18' 12.6"
with an uncertainty of 2.0 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 34008
Subject
GRB 230618A: Swift/UVOT Upper Limits
Date
2023-06-18T17:05:34Z (2 years ago)
From
Paul Kuin at MSSL <npkuin@gmail.com>
N.P.M. Kuin (MSSL/UCL) and K. L. Page (U. Leicester)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 230618A
137 s after the BAT trigger (Page et al., GCN Circ. 33989).
No optical afterglow consistent with the XRT position (Evans GCN
Circ. 33990) is detected in the initial UVOT exposures. The source
was however detected in r and i (Strausbaugh et al, GCN Circ. 33992 and KAIT
(Zhang and Filipenko, GCN Cric. 34001) in clear (R).
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 137 287 147 >20.4
u_FC 296 546 246 >19.9
white 137 1022 295 >20.7
u 296 546 246 >19.9
w1 5114 5178 63 >18.9
m2 4909 5108 197 >19.7
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.025 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 34007
Subject
GRB 230618A: Swift-XRT refined Analysis
Date
2023-06-18T15:56:45Z (2 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
M.G. Bernardini (INAF-OAB), J. D. Gropp (PSU), S. Dichiara (PSU), J.A.
Kennea (PSU), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester),
K.L. Page (U. Leicester), E. Ambrosi (INAF-IASFPA) , M. Capalbi
(INAF-IASFPA) report on behalf of the Swift-XRT team:
We have analysed 6.3 ks of XRT data for GRB 230618A, from 118 s to 30.0
ks after the BAT trigger. The data comprise 157 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 best available XRT position
(using the promptly downlinked event data, the XRT-UVOT alignment and
matching UVOT field sources to the USNO-B1 catalogue) is RA, Dec =
196.60531, 3.30238 which is equivalent to:
RA (J2000): 13 06 25.27
Dec(J2000): +03 18 08.6
with an uncertainty of 1.9 arcsec (radius, 90% confidence).
The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=1.10 (+0.13, -0.10). At T+594 s the decay
steepens to an alpha of 2.90 (+0.40, -0.23) before breaking again at
T+3047 s to a final decay with index alpha=0.29 (+0.68, -0.29).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.55 (+0.13, -0.12). The
best-fitting absorption column is 1.4 (+0.5, -0.4) x 10^21 cm^-2, in
excess of the Galactic value of 2.1 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.73 (+/-0.17) and a
best-fitting absorption column of 2.1 (+0.7, -0.6) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 4.1 x 10^-11 (5.2 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 2.1 (+0.7, -0.6) x 10^21 cm^-2
Galactic foreground: 2.1 x 10^20 cm^-2
Excess significance: 5.0 sigma
Photon index: 1.73 (+/-0.17)
If the light curve continues to decay with a power-law decay index of
0.29, the count rate at T+24 hours will be 8.8 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.6 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/01175438.
This circular is an official product of the Swift-XRT team.
GCN Circular 34001
Subject
GRB 230618A: KAIT Optical Observations
Date
2023-06-18T09:20:07Z (2 years ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on
behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to GRB 230618A detected by Swift
(Page et al., GCN 33989) starting at 04:31:35 UT, about 0.69 hours
after the bust. Observations were performed in the clear (roughly R)
filter, and the exposure time was 60s per image, with a total of 31
images were obtained. We marginally detected the optical afterglow
reported by Strausbaugh et al. (GCN 33992) in our coadd image
in clear band, which we measured its brightness of 20.8 +/- 0.3 mag
at a mid time of ~0.79 hours after the burst, calibrated to the
Pan-STARRS1 catalog.
GCN Circular 33994
Subject
Swift GRB 230618A: Global MASTER-Net observations report
Date
2023-06-18T06:40:49Z (2 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
V. Lipunov, V.Kornilov, E.Gorbovskoy, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko,
G.Antipov, D.Zimnukhov, V.Senik, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D.Cheryasov, Ya.Kechin
(Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile
(Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra
(The Instituto de Astrofisica de Canarias),
D. Buckley
(South African Astronomical Observatory),
O.A. Gres, N.M. Budnev
(Irkutsk State University, API),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),
A. Tlatov, D. Dormidontov
(Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov
(Blagoveschensk Educational State University)
MASTER-OAFA robotic telescope (Global 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 GRB 230618A ( K. L. Page (U Leicester) and S. Laha (GSFC/UMBC) report on behalf of et al., GCN 33989) errorbox 10 sec after notice time and 42 sec after trigger time at 2023-06-18 03:54:03 UT, with upper limit up to 19.5 mag. The observations began at zenith distance = 67 deg. The sun altitude is -78.0 deg.
The galactic latitude b = 66 deg., longitude l = 314 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2224051
We obtain a following upper limits.
Tmid-T0 | Site |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________
48 | MASTER-OAFA | C | 10 | 16.9 |
79 | MASTER- | C | 10 | 15.6 |
89 | MASTER-OAFA | C | 10 | 16.9 |
113 | MASTER- | C | 20 | 16.1 |
135 | MASTER-OAFA | C | 20 | 17.3 |
158 | MASTER- | C | 30 | 16.5 |
191 | MASTER-OAFA | C | 30 | 17.7 |
241 | MASTER-OAFA | C | 130 | 18.7 | Coadd
213 | MASTER- | C | 40 | 16.6 |
258 | MASTER-OAFA | C | 40 | 17.9 |
278 | MASTER- | C | 50 | 16.7 |
339 | MASTER-OAFA | C | 60 | 18.2 |
353 | MASTER- | C | 60 | 17.1 |
440 | MASTER-OAFA | C | 80 | 18.5 |
555 | MASTER-OAFA | C | 310 | 19.3 | Coadd
443 | MASTER- | C | 80 | 17.1 |
553 | MASTER- | C | 100 | 17.1 |
561 | MASTER-OAFA | C | 100 | 18.6 |
683 | MASTER- | C | 120 | 17.1 |
708 | MASTER-OAFA | C | 130 | 18.7 |
838 | MASTER- | C | 150 | 17.2 |
884 | MASTER-OAFA | C | 160 | 18.7 |
1064 | MASTER-OAFA | C | 520 | 19.5 | Coadd
1023 | MASTER- | C | 180 | 17.5 |
1085 | MASTER-OAFA | C | 180 | 18.6 |
1222 | MASTER- | C | 180 | 17.1 |
1297 | MASTER-OAFA | C | 180 | 18.8 |
1422 | MASTER- | C | 180 | 17.1 |
1508 | MASTER-OAFA | C | 180 | 18.6 |
1688 | MASTER-OAFA | C | 540 | 19.3 | Coadd
1622 | MASTER- | C | 180 | 17.1 |
1822 | MASTER- | C | 180 | 17.1 |
1902 | MASTER-OAFA | C | 180 | 18.5 |
2097 | MASTER- | C | 180 | 17.0 |
2114 | MASTER-OAFA | C | 180 | 18.5 |
2325 | MASTER-OAFA | C | 180 | 18.3 |
2505 | MASTER-OAFA | C | 540 | 19.0 | Coadd
2438 | MASTER- | C | 180 | 17.5 |
2536 | MASTER-OAFA | C | 180 | 18.5 |
2747 | MASTER-OAFA | C | 180 | 18.3 |
2778 | MASTER- | C | 180 | 17.4 |
2958 | MASTER-OAFA | C | 180 | 18.1 |
3118 | MASTER- | C | 180 | 17.4 |
3170 | MASTER-OAFA | C | 180 | 17.9 |
3381 | MASTER-OAFA | C | 180 | 17.9 |
3458 | MASTER- | C | 180 | 17.4 |
3799 | MASTER- | C | 180 | 17.5 |
3947 | MASTER-OAFA | C | 180 | 17.7 |
4138 | MASTER- | C | 180 | 17.5 |
4158 | MASTER-OAFA | C | 180 | 17.7 |
4477 | MASTER- | C | 180 | 17.5 |
4551 | MASTER-OAFA | C | 180 | 17.4 |
4763 | MASTER-OAFA | C | 180 | 17.3 |
4817 | MASTER- | C | 180 | 17.4 |
5011 | MASTER-OAFA | C | 180 | 17.0 |
5158 | MASTER- | C | 180 | 17.5 |
5222 | MASTER-OAFA | C | 180 | 16.9 |
5499 | MASTER- | C | 180 | 17.4 |
5795 | MASTER-OAFA | C | 180 | 16.5 |
5837 | MASTER- | C | 180 | 17.5 |
6177 | MASTER- | C | 180 | 17.5 |
6516 | MASTER- | C | 180 | 17.5 |
6856 | MASTER- | C | 180 | 17.5 |
7197 | MASTER- | C | 180 | 17.5 |
7537 | MASTER- | C | 180 | 17.5 |
7877 | MASTER- | C | 180 | 17.5 |
8218 | MASTER- | C | 180 | 17.5 |
8558 | MASTER- | C | 180 | 17.5 |
8899 | MASTER- | C | 180 | 17.5 |
9240 | MASTER- | C | 180 | 17.5 |
9581 | MASTER- | C | 180 | 17.5 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 33992
Subject
GRB230618A: LCOGT Optical Observations
Date
2023-06-18T06:19:09Z (2 years ago)
From
Robert Strausbaugh at University of Minnesota <rstrausb@umn.edu>
R. Strausbaugh (University of Minnesota), A. Cucchiara (NASA) report on
behalf of a larger collaboration:
We observed the GRB 230618A (Page et al., GCN 33989) field with the LCOGT
1-meter Sinistro instrument at the McDonald Observatory, Texas, USA site,
on June 18, from 04:31 to 05:03 UT (corresponding to 0.33 to 1.20 hours
from the GRB trigger time) with the SDSS r and i filters.
We performed a series of 3x300s exposures in each band. We detect an
uncatalouged source within the Swift-XRT enhanced error region (P.A. Evans
et al., GCN 33990).
The following magnitudes are calculated using the PanSTARRS catalog as
reference:
r = 20.62 +/- 0.02
i = 19.16 +/- 0.02
These magnitudes are not corrected for galactic extinction.
GCN Circular 33990
Subject
GRB 230618A: Prompt enhanced Swift-XRT position
Date
2023-06-18T04:31:34Z (2 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Using promptly downlinked XRT event data for GRB 230618A, we find an
enhanced XRT position of the afterglow: RA, Dec: 196.60310, 3.30343
which is equivalent to:
RA (J2000) = 13 06 24.74
Dec (J2000) = +03 18 12.3
with an uncertainty of 1.9 arcseconds (radius, 90% confidence).
Analysis of the promptly available data is online at
http://www.swift.ac.uk/sper/1175438.
Position enhancement is is described by Goad et al. (2007, A&A, 476,
1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular is an official product of the Swift-XRT team.
GCN Circular 33989
Subject
GRB 230618A: Swift detection of a burst
Date
2023-06-18T04:09:22Z (2 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
K. L. Page (U Leicester) and S. Laha (GSFC/UMBC) report on behalf of
the Neil Gehrels Swift Observatory Team:
At 03:51:12 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 230618A (trigger=1175438). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 196.588, +3.306 which is
RA(J2000) = 13h 06m 21s
Dec(J2000) = +03d 18' 20"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). Due to a telemetry outage caused by
a recent storm in Guam, no further BAT data will be available
until a ground station pass.
Using promptly downlinked data we find a bright, uncatalogued X-ray
source located at RA, Dec 196.60313, 3.30257 which is equivalent to:
RA(J2000) = 13h 06m 24.75s
Dec(J2000) = +03d 18' 09.3"
with an uncertainty of 5.8 arcseconds (radius, 90% containment). This
position may be improved as more data are received; the latest position
is available at https://www.swift.ac.uk/sper. No spectrum from the
promptly downlinked event data is yet available to determine the column
density.
The initial flux in the 2.5 s image was 6.46e-10 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of nominal 150.000 seconds with the White
filter starting 137 seconds after the BAT trigger. No credible afterglow
candidate has been found in the initial data products. Data from the 2.7'x2.7'
sub-image are not available at this time. 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 0.025.
Burst Advocate for this burst is K. L. Page (klp5 AT leicester.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/)