GRB 230628E
GCN Circular 34110
Subject
GRB 230628E: Swift detection of a burst
Date
2023-06-28T23:00:04Z (2 years ago)
From
N. Klingler at NASA-GSFC/UMBC/CRESST II <noelklingler@gmail.com>
CRESSTII), C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB), M. H. Siegel (PSU) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 22:26:10 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 230628E (trigger=1177054). Swift slewed immediately to the burst. The BAT on-board calculated location is
RA, Dec 171.841, -11.447 which is
RA(J2000) = 11h 27m 22s
Dec(J2000) = -11d 26' 47"
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peaked structure with a duration of about 5 sec. The peak count rate was ~600 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 22:29:48.3 UT, 217.7 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 171.8499, -11.4641 which is equivalent to:
RA(J2000) = +11h 27m 23.77s
Dec(J2000) = -11d 27' 50.2”
with an uncertainty of 1.9 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.
UVOT took a finding chart exposure of 150 seconds with the White filter starting 221 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 none of the XRT error circle. 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 0.040.
Burst Advocate for this burst is N. J. Klingler (noelklin AT umbc.edu). 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/)
GCN Circular 34112
Subject
GRB 230628E: LCOGT Optical Upper Limit
Date
2023-06-29T00:32:59Z (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 230628E (Klingler et al., GCN 34110) field with the LCOGT
1-meter Sinistro instrument at the Cerro Tololo Interamerican Observatory,
Chile site, on June 28, from 23:08 to 23:40 UT (corresponding to 0.70 to
1.23 hours from the GRB trigger time) with the SDSS r and i filters.
We performed a series of 3x300s exposures in each band. We do not detect a
source within the Swift-XRT error region (Klingler et al., GCN 34110) in
either band.
The following upper limits are calculated using the PanSTARRS catalog as
reference:
r > 19.2
i > 19.0
These magnitudes are not corrected for galactic extinction.
GCN Circular 34116
Subject
GRB 230628E: Enhanced Swift-XRT position (Correction to name in GCN 34115)
Date
2023-06-29T04:37:07Z (2 years ago)
From
K.L. Page at U Leicester <klp5@leicester.ac.uk>
K.L. Page and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT
team:
GCN 34115 incorrectly referred to GRB 230628A; the enhanced position given
was instead for GRB 230628E. We repeat the details here, with the correct
name:
Using 3999 s of XRT Photon Counting mode data and 9 UVOT images for GRB
230628E, 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 = 171.84876, -11.46370 which is equivalent to:
RA (J2000): 11h 27m 23.70s
Dec (J2000): -11d 27' 49.3"
with an uncertainty of 2.1 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest
position can be viewed at https://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 is an official product of the Swift-XRT team.
GCN Circular 34117
Subject
GRB 230628E: Swift-XRT refined Analysis
Date
2023-06-29T06:42:28Z (2 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), K.L. Page (U.
Leicester), A.P. Beardmore (U. Leicester), M. Capalbi (INAF-IASFPA), M.
Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), D.N. Burrows
(PSU) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 6.3 ks of XRT data for GRB 230628E, from 226 s to 22.6
ks after the BAT trigger. The data are entirely in Photon Counting
(PC) mode.
The light curve can be modelled with a power-law decay with a decay
index of alpha=0.85 (+/-0.05).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.94 (+/-0.18). The
best-fitting absorption column is 9.5 (+4.9, -4.3) x 10^20 cm^-2, in
excess of the Galactic value of 4.3 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 3.4 x 10^-11 (4.1 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 9.5 (+4.9, -4.3) x 10^20 cm^-2
Galactic foreground: 4.3 x 10^20 cm^-2
Excess significance: 2.0 sigma
Photon index: 1.94 (+/-0.18)
If the light curve continues to decay with a power-law decay index of
0.85, the count rate at T+24 hours will be 8.1 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.8 x
10^-13 (3.3 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/01177054.
This circular is an official product of the Swift-XRT team.
GCN Circular 34118
Subject
GRB230628E: VLT optical identification of afterglow candidate
Date
2023-06-29T07:14:44Z (2 years ago)
From
J. T. Palmerio at Observatoire de Paris - GEPI <jesse.palmerio@obspm.fr>
D. B. Malesani (Radboud Univ. and DAWN/NBI) and J. Palmerio (GEPI / Paris Obs.) report on behalf of the STARGATE collaboration:
We observed the field of GRB 230628E (Salvaggio et al., GCN 34110) with the ESO VLT UT3 (Melipal) equipped with the X-shooter acquisition camera.
In a single 30 s exposure acquired in the r band, with mid time June 29.0252 UT (2.17 hr after the GRB), we see a new object, very close to the Swift/XRT position, which is not visible in the Pan-STARRS images of this field. Its coordinates (J2000, calibrated against the Gaia catalog, 0.5" error) are:
RA = 11:27:23.60
Dec = -11:27:49.21
Preliminary photometry (against the Pan-STARRS catalog) yields a magnitude r = 21.2
We consider this object a strong candidate as the afterglow of GRB 230628E, due to its consistency with the X-ray position and lack of detection in the Pan-STARRS archival images.
Further observations are in progress. We acknowledge expert support from the observing staff in Paranal, in particular Eleonora Sani (to whom we wish a happy birthday), Thomas Romain (on his last observing night in Paranal), Ditte Slumstrup (who actually discovered the afterglow), and Thomas Rivinius.
GCN Circular 34122
Subject
GRB 230628E - VLT spectroscopic observations
Date
2023-06-29T13:05:51Z (2 years ago)
From
J. T. Palmerio at Observatoire de Paris - GEPI <jesse.palmerio@obspm.fr>
J. T. Palmerio (GEPI / Paris Obs. and IAP), D. B. Malesani (Radboud Univ. and DAWN/NBI), A. Saccardi (GEPI / Paris Obs.), L. Izzo (INAF/OACn & DARK/NBI), P. Schady (Univ. Bath), A. de Ugarte Postigo (OCA) report on behalf of the STARGATE collaboration:
We observed the optical afterglow candidate of GRB 230628E (Malesani et al. GCN 34118) with the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph.
Spectroscopy was carried out, covering the wavelength range 3000-21000 AA, and consisting of 4 exposures of 600 s each. The observation mid time was 2023 June 29 at 01:05 UT (~2.7 hours after the GRB).
Only a faint continuum is detected from this source down to ~3700 Angstrom, which allows us to set a redshift upper limit z <~ 2.
We note a possible, very faint emission feature at ~15550 Angstrom but in the absence of other associated emission features, we do not derive a redshift from this.
We acknowledge expert support from the observing staff in Paranal, in particular Eleonora Sani, Thomas Romain, Ditte Slumstrup, and Thomas Rivinius.
GCN Circular 34132
Subject
GRB 230628E: ATCA rapid radio follow-up
Date
2023-07-02T04:53:29Z (2 years ago)
From
Gemma Anderson at Curtin U <gemma.anderson@curtin.edu.au>
G. E. Anderson (Curtin), J. K. Leung (USyd), A. J. van der Horst (GWU), A. Gulati (USyd), L. Rhodes (Oxford), S. Chastain (UNM) on behalf of the PanRadio GRB collaboration
The Australia Telescope Compact Array (ATCA) rapidly performed observations of the long GRB 230628E (Klingler et al. GCN 34110) at 5.5, 9, 16.7 and 21.2 GHz as part of the Large ATCA “PanRadio GRB” follow-up programme C3542 (PI. Anderson). ATCA was on target observing at 2023-06-29 02:11 UT when the source had risen above the horizon, just 3.75 hrs post-burst and observed for 10.5 hrs. There is no radio source coincident with the enhanced XRT position (Page et al. GCN 34116) with 3 sigma upper limits of 44, 39, 54 and 78 microJy/beam at 5.5, 9.0, 16.7 and 21.2 GHz, respectively. Further observations are planned.
We thank the CSIRO Space and Astronomy staff for supporting these observations and maintaining the ATCA rapid-response observing mode.
We acknowledge the Gomeroi people as the traditional owners of the Observatory site. The Australia Telescope Compact Array is part of the Australia Telescope National Facility (https://ror.org/05qajvd42) which is funded by the Australian Government for operation as a National Facility managed by CSIRO.
GCN Circular 34134
Subject
GRB 230628E: Swift-BAT refined analysis
Date
2023-07-02T13:03:50Z (2 years ago)
From
Sibasish Laha at GSFC <sibasish.laha@nasa.gov>
T. Parsotan (GSFC/UMBC), S. D. Barthelmy (GSFC),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU) (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 230628E (trigger #1177054)
(Salvaggio et al., GCN Circ. 34110). The BAT ground-calculated position is
RA, Dec = 171.851, -11.430 deg which is
RA(J2000) = 11h 27m 24.3s
Dec(J2000) = -11d 25' 46.5"
with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 41%.
The BAT light curve shows a complex structure with a duration of ~ 15 sec.
T90 (15-350 keV) is 4.72 +- 1.08 sec (estimated error including systematics).
The time-averaged spectrum from T-0.50 to T+4.81 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.45 +- 0.30. The fluence in the 15-150 keV band is 3.3 +- 0.6 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T+0.33 sec in the 15-150 keV band
is 1.1 +- 0.3 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/1177054/BA/
GCN Circular 34135
Subject
GRB 230628E: Swift/UVOT Detection
Date
2023-07-02T18:36:09Z (2 years ago)
From
Samantha Oates at University of Birmingham <samantha.oates@alumni.ucl.ac.uk>
S. R. Oates (U. Birmingham) and N. Klingler (NASA-GSFC/UMBC/CRESST II)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 230628E
221 s after the BAT trigger (Klingler et al., GCN Circ. 34110).
A source consistent with the XRT position (Page et al., GCN Circ. 34116)
and the optical position (Malesani et al., GCN Circ. 34118)
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) 221 371 167 20.10 +/- 0.20
wh 501 1194 223 20.69 +/- 0.34
v 379 1243 68 >19.1
b 477 1170 78 >19.9
u 452 1145 78 >19.6
w1 428 1120 78 >19.4
m2 1249 1269 19 >18.2
w2 700 720 19 >18.5
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.040 in the direction of the burst
(Schlegel et al. 1998).