GRB 230506C
GCN Circular 33731
Subject
GRB 230506C: Swift detection of a burst
Date
2023-05-06T17:21:56Z (2 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
A. Tohuvavohu (U Toronto), J. A. Kennea (PSU),
K. L. Page (U Leicester), D. M. Palmer (LANL), M. H. Siegel (PSU) and
M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 17:09:19 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 230506C (trigger=1167288). Swift did not immediately slew
due to an observing constraint. The BAT on-board calculated location is
RA, Dec 134.373, +45.126 which is
RA(J2000) = 08h 57m 30s
Dec(J2000) = +45d 07' 32"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a complex
structure with a duration of about 30 sec. The peak count rate
was ~1200 counts/sec (15-350 keV), at ~0 sec after the trigger.
Due to an observing constraint, Swift will not slew until T0+55.3
minutes. There will be no XRT or UVOT data until this time.
Burst Advocate for this burst is A. Tohuvavohu (aaron.tohu 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/)
GCN Circular 33734
Subject
GRB 230506C: TSHAO possible afterglow candidate
Date
2023-05-06T23:13:08Z (2 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
N. Pankov (HSE), I. Reva (FAI), A. Pozanenko (IKI), S. Belkin (IKI) report on behalf of GRB-IKI-FuN:
We observed the field of GRB 230506C detected by Swift (Tohuvavohu et al., GCN 33731) with Zeiss-1000 telescope of Tien Shan Astronomical Observatory stating on May, 06 (UT) 17:24:54 in R-filter.
Within Swift-BAT error circle (Tohuvavohu et al., GCN 33731) we detected uncatalogued object in coordinates of (J2000) 08:57:28.13 +45:07:59.48 with uncertainties of 0.3 arcsec in each coordinate. The object is absent in SDSS images. A distance of the object from the center of BAT error circle is ~30 arces. Preliminary photometry of a stacked images is following
Date UT start t-T0 Filter Exp. OT Err. UL(3 sigma)
(mid, days) (s)
2023-05-06 17:24:54 0.02914 R 23*120 20.1 0.1 21.5
The photometry is based on nearby USNO-B1.0 stars.
We suggest that the object is a candidate for the afterglow of GRB 230506C.
GCN Circular 33735
Subject
GRB 230506C: Candidate afterglow observation by D50
Date
2023-05-06T23:44:46Z (2 years ago)
From
Martin Jelinek at Astro.Inst-AVCR,Ondrejov <martin.jelinek@asu.cas.cz>
M. Jelinek, J. Strobl, R. Hudec, C. Polasek (ASU CAS Ondrejov) report:
We observed the position of the Swift-detected GRB 220506C (Tohuvavohu et
al.
GCNC 33731) with the D50 telescope of the Astronomical Institute Ondrejov,
near
Prague, Czech Republic. Our observation started at 19:58 UT, i.e. 2.8 h
after
the initial trigger and was performed with an SDSS i' filter.
We confirm the presence of an object not present in the SDSS survey
reported by
Pankov et al. (GCNC 33734) in a combined image with exp. mean time ~4.0 h
after
trigger (exposed 19:58--22:35UT). The AB magnitude of the object in this
frame
is i' = 20.54 +/- 0.11.
GCN Circular 33736
Subject
GRB 230506C: Swift-XRT analysis
Date
2023-05-07T00:20:13Z (2 years ago)
From
Jamie Kennea at Penn State U <jak51@psu.edu>
J. A. Kennea (PSU), A. Tohuvavohu (Toronto), P.A. Evans and
M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team:
We have analysed 1.6 ks of XRT data for GRB 230506C, from 4.6 ks to
11.0 ks after the BAT trigger. The data are entirely in Photon
Counting (PC) mode. Using 1145 s of PC mode data and 2 UVOT images, we
find an enhanced XRT position (using the XRT-UVOT alignment and
matching UVOT field sources to the USNO-B1 catalogue): RA, Dec =
134.36766, +45.13302 which is equivalent to:
RA (J2000): 08h 57m 28.24s
Dec(J2000): +45d 07' 58.9"
with an uncertainty of 2.4 arcsec (radius, 90% confidence).
This circular is an official product of the Swift-XRT team.
The light curve can be modelled with a power-law decay with a decay
index of alpha=1.0 (+0.5, -0.4).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.2 (+0.4, -0.3). The
best-fitting absorption column is 1.2 (+0.9, -0.8) x 10^21 cm^-2, in
excess of the Galactic value of 2.2 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 3.0 x 10^-11 (4.1 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 1.2 (+0.9, -0.8) x 10^21 cm^-2
Galactic foreground: 2.2 x 10^20 cm^-2
Excess significance: 2.2 sigma
Photon index: 2.2 (+0.4, -0.3)
If the light curve continues to decay with a power-law decay index of
1.0, the count rate at T+24 hours will be 0.012 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.8 x
10^-13 (5.1 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/01167288.
This circular is an official product of the Swift-XRT team.
GCN Circular 33738
Subject
GRB 230506C: NUTTelA-TAO / BSTI Early Optical Limits
Date
2023-05-07T10:19:24Z (2 years ago)
From
Toktarkhan Komesh at Nazarbayev University <toktarkhan.komesh@nu.edu.kz>
T. Komesh (NU), B. Grossan (UCB, NU), Zh. Maksut (NU), Zh. Abdullayev (NU), N. Shaimoldin (NU), M. Krugov (FAI), report on behalf of the Energetic Cosmos Laboratory:
The Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) observed the field of GRB 230506C, 8 s after receipt an automated GCN / BAT position alert, observing in Sloan i' band, with the Burst Simultaneous Three-Channel Imager (BSTI; Grossan, Kumar & Smoot 2019, JHEA, 32, 14).
We started observations at 17:09:56 UT on 2023-05-06, 37 s after the BAT trigger. Observations were made in cloudy conditions. No source consistent with the XRT (J. A. Kennea et al., GCN Circ. 33736) was detected. We report the following results:
start time t-t0(s) end time ULi' exposure_time (s)
------------ ----- ----------- ----- ------
17:09:56 37 17:10:48 17.4 52.5
17:11:03 104 17:13:33 18.0 150
start time is in UT. t-t0(s) gives the time since trigger, in seconds. UL i', gives the 5 sigma upper limit sensitivity in magnitudes, for images co-added to the given exposure time. The first row in the table corresponds to co-adds of an initial short exposure image sequence of 7.5 s. The second row corresponds to co-adds from a continuing series of 15 s exposures. Calibration was done with the 3 bright Pan-STARRS catalog stars on our images.
----------------------------------
NU = Nazarbayev University, Nur-Sultan, Kazakhstan
UCB = University of California, Berkeley, USA
FAI = Fesenkov Astrophysical Institute, Kazakhstan
This research has been funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP14870504). The NUTTelA-TAO Team acknowledges the support of the staff of the Assy-Turgen Astrophysical Observatory, Almaty, Kazakhstan, and the Fesenkov Astrophysical Institute, Almaty, Kazkhstan.
GCN Circular 33739
Subject
GRB 230506C: Swift/UVOT Upper Limits
Date
2023-05-07T11:27:27Z (2 years ago)
From
Paul Kuin at MSSL <npkuin@gmail.com>
Paul Kuin (MSSL/UCL) and A Tohuvavohu (U Toronto) report on behalf
of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 230506C
4.6 ks after the BAT trigger (Tohuvavohu et al., GCN Circ. 33731).
No optical afterglow consistent with the enhanced XRT position 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 4625 4825 197 >18.5
v 5036 5236 197 >19.2
u 5614 5814 197 >19.6
uvw1 5446 5646 197 >20.6
uvm2 5241 5441 197 >21.5
uvw2 4831 5031 197 >20.3
GCN Circular 33741
Subject
GRB 230506C: spectro-imaging observations of the optical afterglow with T193-OHP
Date
2023-05-07T18:22:12Z (2 years ago)
From
Emeric Le Floc'h at CEA-Saclay <emeric.lefloch@cea.fr>
C. Adami, S. Basa (LAM), E. Le Floc’h, D. Götz, D.Turpin (CEA Paris-Saclay), B. Schneider (MIT), S. D. Vergani (GEPI, Obs. de Paris), report on behalf of a larger collaboration:
We observed the field of GRB 230506C (Tohuvavohu et al., GCN 22731) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. 5 exposures were obtained in the imaging mode with the r-band filter (4x300s + 1x600s) from 2023 6 May 20:46:12 UT to 2023 6 May 21:16:27 UT (mid time ~3.8h after trigger). In the combined frame, we detect a source consistent with the position of the X-ray counterpart reported by Kennea et al. (GCN 33736) and with the location of the optical afterglow reported by Pankov et al. (GCN 33734) and Jelinek et al. (GCN 33735). The r’ AB magnitude of this source is 20.9 +/- 0.06 mag. The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitude is not corrected for Galactic extinction.
In addition, we exposed for 30min (2x15min) with the MISTRAL spectroscopic blue setting, covering from 4200A to 8000A, at R~750. We detect a faint continuum at the GRB position, clearly visible at wavelength redder than ~5100A, but the absence of continuum at Lambda bluer than 5100A may be due to the lack of efficiency of the instrument. The S/N is also too low to provide any significant emission or absorption line detection.
We acknowledge the excellent support from Observatoire de Haute-Provence, in particular Jean-Pierre Troncin.
GCN Circular 33743
Subject
GRB 230506C: Swift-BAT refined analysis
Date
2023-05-07T18:42:20Z (2 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
H. A. Krimm (NSF), S. D. Barthelmy (GSFC),
S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Parsotan (GSFC/UMBC), T. Sakamoto (AGU),
M. Stamatikos (OSU), A. Tohuvavohu (U Toronto)
(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 230506C (trigger #1167288)
(Tohuvavohu et al., GCN Circ. 33731). The BAT ground-calculated position is
RA, Dec = 134.371, 45.131 deg which is
RA(J2000) = 08h 57m 29.1s
Dec(J2000) = +45d 07' 50.7"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 46%.
The mask-weighted light curve shows a multi-peaked structure that starts
at ~T-9 s and ends at ~T+28 s. The main peak occurs at ~T+1 s.
T90 (15-350 keV) is 31.00 +- 6.32 sec (estimated error
including systematics).
The time-averaged spectrum from T-8.59 to T+28.41 sec is best fit by
a simple power-law model. The power law index of the time-averaged
spectrum is 1.89 +- 0.17. The fluence in the 15-150 keV band
is 1.7 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured
from T+0.41 sec in the 15-150 keV band is 2.4 +- 0.5 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/1167288/BA/
GCN Circular 33744
Subject
GRB 230506C: Swift-XRT refined Analysis
Date
2023-05-07T22:44:46Z (2 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), J.P. Osborne
(U. Leicester), B. Sbarufatti (INAF-OAB), A. D'Ai (INAF-IASFPA), A.
Melandri (INAF-OAR), J. D. Gropp (PSU), S. Dichiara (PSU), J.A. Kennea
(PSU) report on behalf of the Swift-XRT team:
We have analysed 6.2 ks of XRT data for GRB 230506C, from 4.6 ks to
97.1 ks after the BAT trigger. The data are entirely in Photon
Counting (PC) mode. Using 1929 s of PC mode data and 5 UVOT images, we
find an enhanced XRT position (using the XRT-UVOT alignment and
matching UVOT field sources to the USNO-B1 catalogue): RA, Dec =
134.36764, +45.13295 which is equivalent to:
RA (J2000): 08h 57m 28.23s
Dec(J2000): +45d 07' 58.6"
with an uncertainty of 2.1 arcsec (radius, 90% confidence).
The light curve can be modelled with a power-law decay with a decay
index of alpha=0.81 (+0.11, -0.10).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.09 (+0.25, -0.23). The
best-fitting absorption column is 9.1 (+6.2, -5.3) x 10^20 cm^-2, in
excess of the Galactic value of 2.2 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 3.1 x 10^-11 (3.9 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 9.1 (+6.2, -5.3) x 10^20 cm^-2
Galactic foreground: 2.2 x 10^20 cm^-2
Excess significance: 2.2 sigma
Photon index: 2.09 (+0.25, -0.23)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01167288.
This circular is an official product of the Swift-XRT team.
GCN Circular 33748
Subject
GRB 230506C: SAO RAS optical observations
Date
2023-05-09T16:04:41Z (2 years ago)
From
Moskvitin Alexander at SAO RAS <mosk@sao.ru>
A. Moskvitin, O. Maslennikova (SAO), N. Pankov (HSE, IKI)
and A. Pozanenko (IKI), report on behalf of GRB follow-up team.
We observed the field of GRB 230506C (Tohuvavohu et al., GCN 22731)
with the SAO RAS 1-m telescope Zeiss-1000 + CCD photometer.
The observations started since 1.3528 hours after the trigger
under mediocre weather conditions. We obtained 3 x 300 sec. exposures
in Rc band (May 6, 18:30:29 -- 18:48:26 UT, T_mid - T_0 = 1.5024 h).
The OT (Kuin & Dichiara, GCN 33733; Pankov et al., GCN 33734;
Jelinek et al., GCN 33735; Adami et al., GCN 33741) is marginally
detected in the stacked image with the brightness of R = 20.5 +/- 0.3.
Preliminary photometry is based on R2 magnitudes of nearby USNO-B1
stars. The OT magnitude is not corrected for the Galactic extinction.
GCN Circular 33749
Subject
GRB 230506C: T193-OHP MISTRAL tentative redshift
Date
2023-05-10T06:47:00Z (2 years ago)
From
Damien Turpin at CEA-Saclay <dturpin-astro@hotmail.com>
C. Adami (LAM), J. Palmerio, S. D. Vergani (GEPI, Obs. de Paris), B. Schneider (MIT), E. Le Floc’h, D. Götz, D.Turpin (CEA Paris-Saclay), S. Basa (LAM) report on behalf of a larger collaboration:
We performed a refined analysis of our spectrum (Adami et al. GCN33741) of GRB 230506C (Tohuvavohu et al., GCN 33731, Jelinek et al. GCN 33735, Moskvitin et al. GCN 33748) taken at OHP/T193 with the MISTRAL spectroscopic blue setting, covering from 4200A to 8000A, at R~750 (midtime = T0+4.4h) .
Despite the very low quality of the spectrum, due to the faintness of the object, we can identify a break that we tentatively interpret as a Lyman-alpha break, and for which we find a corresponding Lyman-limit flux drop, indicating 3.7<z<~4.0.
We acknowledge the excellent support from Observatoire de Haute-Provence, in particular Jean Pierre Troncin, the SOPHIE observer Daniel Sebastian and the LAM AMAZED team.
GCN Circular 33755
Subject
GRB 230506C: Fermi GBM detection
Date
2023-05-10T17:37:35Z (2 years ago)
From
Suraj Poolakkil at UAH <sp0076@uah.edu>
S. Poolakkil (UAH) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:
"At 17:09:16.97 UT on 6 May 2023, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 230506C (trigger 705085761 / 230506715)
which was also detected by the Swift/BAT (Tohuvavohu et al. 2023, GCN 33731).
The angle from the Fermi LAT boresight at the GBM trigger time is 15 degrees.
The GBM light curve consists of a single peak followed
by some extended emission with a duration (T90) of about 23 s (50-300 keV).
The time-averaged spectrum from T0-6.1 s to T0+11.3 s
is best fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.19 +/- 0.11 and
the cutoff energy, parameterized as Epeak, is 163 +/- 30 keV.
The event fluence (10-1000 keV) in this time interval is
(3.1 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+3.0 s in the 10-1000 keV band
is 3.3 +/- 0.2 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular 35181
Subject
GRB230506C: VIRT optical upper limit
Date
2023-11-24T20:35:39Z (2 years ago)
From
Priya Gokuldass at ERAU <gokuldap@my.erau.edu>
Via
Web form
Kiwanee’ Smith (UVI), P. Gokuldass (ERAU), N. Orange (OrangeWave Innovative Science, LLC), D. Morris (NASA), Ki’Vante’ Smith (UVI), K. Noonan (UVI), R. Querrard (UVI), T. Lombardi (Eckerd College)
We observed the field of GRB230506C (Tohuvavohu et al. GCN 33731) with the 0.5m Virgin Island Robotic Telescope (VIRT) at the University of the Virgin Islands' Etelman Observatory on 05-07-2023 starting at 00:17:36.395 (T+7.07 hrs). We performed a series of exposures in R filter with a total exposure of 3810 s. The weather conditions were clear during the hours of observation with an average airmass of ~1.55.
We do not detect the source identified by others (Pankov et al., GCN 33734; Jelinek et al., GCN 33735; Adami et al., GCN 33741; Moskvitin et al., GCN 33748) and report the following 3-sigma upper limit:
T_mid ||Exposure ||Filter ||Limit
T+7.3 hrs ||3810s ||R ||>20.5
The limit is estimated from comparison to nearby USNO B1 stars and is not corrected for Galactic extinction. The VIRT is still in the commissioning phase.
We acknowledge financial support from NASA MUREP MIRO award 80NSSC21M0001, NASA EPSCoR award 80NSSC22M0063, and NSF EiR award 1901296. R.Q. and N.B.O. also acknowledge financial support from South Carolina Space Grant award 80NSSC20M0054. This message can be cited.