GRB 230307A
GCN Circular 33747
Subject
GRB 230307A: JWST second-epoch observations
Date
2023-05-08T21:30:32Z (2 years ago)
From
Andrew Levan at Radboud University <a.levan@astro.ru.nl>
A.J. Levan (Radboud), N. R. Tanvir (U. Leicester), E. Burns (LSU), G.P. Lamb (LJMU), J. P. U. Fynbo (DAWN/NBI), A.S. Fruchter (STScI), K. Bhirombhakdi (STScI), P O’Brien (U. Leicester), P. Jakobsson (U. Iceland), D. B. Malesani (Radboud and DAWN/NBI), B. P. Gompertz (U. Birmingham), A. Martin-Carrillo (UCD), D. Watson (DAWN/NBI), S. Smartt (Oxford) , J. Hjorth (DARK/NBI) report for a larger collaboration:
We obtained a second epoch of JWST observations of the exceptionally bright GRB 230307A (Fermi GBM team, GCN 33405; Xiong et al., GCN 33406; Xiao & Krucker, GCN 33410; Cosentini et al., GCN 33412; Navaneeth et al., GCN 33415) on 8 May 2023 (about 62 days post-burst). Imaging was obtained with NIRCam in the F115W, F150W, F277W and F444W filters and spectroscopy with the NIRSpec prism.
The source at the location of the optical/IR afterglow (Levan et al., GCNs 33439, 33569) is still detected but has faded significantly, particularly in the redder bands. In the F444W filter, it faded by 2.7 mag.
This result confirms that the very red continuum noted in the first epoch by Levan et al. (GCN 33569) is due to a variable source and does not contain a significant contribution from any underlying host. However, we do note the presence of a faint galaxy, approximately 0.3” from the burst position, which is plausibly the source of the emission lines seen in previous NIRSpec spectroscopy (Levan et al., GCN 33580). Although further analysis is required, the rapid IR fading is consistent with the expectations of kilonova emission. If that interpretation is correct, the higher redshift source has to be an unrelated background galaxy, aligned by chance with the GRB. Alternatively, if associated with the galaxy at z = 3.87, the counterpart would have exhibited unprecedented temporal and chromatic behaviour.
GCN Circular 33635
Subject
GRB 230307A: iTelescope optical upper limit (likely)
Date
2023-04-16T15:31:19Z (2 years ago)
From
Filipp Dmitrievich Romanov at Amateur astronomer <filipp.romanov.27.04.1997@gmail.com>
On 2023-03-09 I observed the field of GRB 230307A (Fermi GBM team, GCN
Circ. 33405) remotely using the telescope T17 (0.43-m f/6.8 reflector
+ CCD) of iTelescope.Net in Siding Spring Observatory (Australia). Ten
images with exposures of 300 seconds and Ic filter (Astrodon
Johnson-Cousins Ic) were obtained, the midtime of the stacked image is
10:52:40.7 UT (1.8 d. after the trigger). I did not detect a clear
optical afterglow near the Swift-XRT position (Burrows et al., GCN
Circ. 33465), but in this area in the stacked image there is what I
can consider a noise (SNR <2), but I do not exclude that it may be
faint afterglow near the upper limit of about 20 magnitudes in this
band.
GCN Circular 33580
Subject
GRB 230307A: JWST NIRSpec observations, possible higher redshift
Date
2023-04-06T17:00:47Z (2 years ago)
Edited On
2024-11-18T09:45:29Z (10 months ago)
From
Andrew Levan at U.of Leicester <a.levan@astro.ru.nl>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Leo P. Singer at NASA/GSFC <leo.p.singer@nasa.gov>
A.J. Levan (Radboud), D. Watson (DAWN/NBI), J. Hjorth (DARK/NBI), N. R. Tanvir (Leicester), D. B. Malesani (Radboud, DAWN/NBI), E. Burns (LSU), B. P. Schneider (MIT), J. P. U. Fynbo (DAWN/NBI), S. D. Vergani (CNRS-Paris Observatory), W. Fong (Northwestern), A. Fruchter (STScI), G. Pugliese (API/UvA), S. Smartt (Oxford) report for a larger collaboration:
"In addition to the JWST/NIRCam observations of GRB 230307A (Fermi GBM team, GCN 33405) reported in GCN 33569, we also obtained observations with NIRSpec on 5 April 2023. The observations were obtained for a total integration time of approximately 1 hour, using the prism to obtain a spectrum in the range 0.5-5.5 um. The trace confirms the spectral shape measured from NIRCam observations. Blueward of 2 um, the source has a flat spectrum, but low signal to noise, and a strong upturn redward of 2 um.
We note the presence of two weak, narrow emission features in the spectrum, both of which are offset from the trace by approximately 0.1-0.2". These are consistent with the H-alpha and [O III] (5007 AA) emission lines at z = 3.87. Excess flux in the spectrum is also visible at the location of H-beta at this redshift. If the GRB is from a low redshift merger, as suggested by GCN 33569, then this could only be explained by a chance alignment with an unrelated background galaxy. It is hard to quantify this possibility, given that we could be seeing both transient and galaxy light, however the chances are clearly low.
Alternatively, the lines could be from the host galaxy, implying that GRB 230307A lies at z = 3.87. The very red colours of the continuum source would not naturally match the expectations of any afterglow models at z = 3.87, but in fact could be consistent with those of a dusty, red galaxy. Given only one epoch in the mid-IR is available, we cannot rule out this possibility, although such a galaxy would be extremely compact, and the transient would have to decay very steeply since the last ground-based observations. We note that, at this redshift, GRB 230307A would be by far the most energetic burst ever detected, with E_iso ~ 10^56 erg. This would be an order of magnitude more energetic than any of the ~500 GRBs with available isotropic energy releases. This may require a unique progenitor system."
GCN Circular 33579
Subject
GRB 230307A: further analysis of the Konus-Wind detection and rest-frame energetics
Date
2023-04-06T16:11:37Z (2 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
D. Svinkin, D. Frederiks, A. Ridnaia, A. Tsvetkova,
and A. Lysenko on behalf of the Konus-Wind team, report:
Following the probable host galaxy identification
(Gillanders et al. GCN Circ. 33485; Levan at al., GCN Circ. 33569),
we present a further analysis of the KW detection
(Svinkin et al., GCN Circ. 33427)
of the extremely bright, long-duration GRB 230307A
(GCNs 33405, 33406, 33407, 33410, 33411, 33412,
33413, 33414, 33415, 33416, 33418, 33424, 33425, 33461).
As measured by KW the burst durations are
T50=9.17+/-0.04 s and T90 = 31.2 +/-0.4 s,
both in the 100-1700 keV energy band.
The refined burst fluence is 4.05(-0.03,+0.03)x10^-3 erg/cm2,
and a 64-ms peak flux, measured from T0+6.224 s,
is 6.85(-0.27,+0.27)x10^-4 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
Assuming the redshift of the host galaxy z=0.065 (GCN 33485)
and a standard cosmology model with H_0 = 67.3 km/s/Mpc,
Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is (4.21+/-0.03)x10^52 erg,
the peak luminosity L_iso is (7.58 +/-0.33)x10^51 erg/s,
the rest-frame peak energy of the time-integrated spectrum,
Ep,i,z is (933+/-12) keV, and the rest-frame peak energy at the peak
luminosity Ep,p,z is (1388+/-52) keV.
With these values, GRB 230307A is outside the 90% prediction band of
both 'Amati' and 'Yonetoku' relations built for the sample of >300 long
KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al.,
2021).
In both Eiso-Ep,i,z and Liso-Ep,p,z planes, GRB 230307A is shifted
towards the short-hard (Type I, merger-origin) GRB population,
see http://www.ioffe.ru/LEA/GRBs/GRB230307_T56645/GRB230307A_rest_frame.pdf
The analysis of KW data is ongoing and its results will be reported
elsewhere.
GCN Circular 33578
Subject
GRB 230307A: good match with kilonova models
Date
2023-04-06T14:41:22Z (2 years ago)
From
Cristiano Guidorzi at Ferrara U,Italy <guidorzi@fe.infn.it>
M. Bulla, A.E. Camisasca, C. Guidorzi (Ferrara U.), L. Amati, A. Rossi
(INAF-OAS), G. Stratta, P. Singh (Goethe U. Frankfurt) on behalf of a
larger collaboration report: We compared kilonova models computed with
the latest version of the radiative transfer code POSSIS (Bulla 2023,
MNRAS, 520, 2558) to photometric data of a faint source associated with
GRB 230307A as reported by Levan et al. (GCN 33569). Assuming a redshift
z=0.065 (Gillanders et al. GCN 33485) and a Galactic extinction of
E(B-V)=0.0743 mag (Schlafly & Finkbeiner 2011, ApJ, 737, 103), we find a
reasonably good match to observations in both the F150W and F444W
filters for a model viewed along the jet axis (face-on) and with two
ejecta components: 1) a dynamical ejecta component with a mass of 0.005
Msun, an average velocity of 0.25c and an average electron fraction
Ye=0.15; 2) and a disk-wind ejecta component with a mass of 0.05 Msun,
an average velocity of 0.1c and an average electron fraction Ye=0.3 (see
figure at the link below). This supports the claim of kilonova emission
by Levan et al. (GCN 33569) and strengthens the interpretation of GRB
230307A as a merger event, as also suggested by the properties of the
gamma-ray prompt emission (Camisasca et al. GCN 33577). Further analysis
is ongoing. Figure:
https://drive.google.com/file/d/1XhpfwCXQxWWS_G7WQ1fUSZKSiZXnwXiJ/view?usp=sharing
GCN Circular 33577
Subject
GRB 230307A: short mininum variability timescale compatible with a merger origin
Date
2023-04-06T11:06:22Z (2 years ago)
From
Cristiano Guidorzi at Ferrara U,Italy <guidorzi@fe.infn.it>
A.E. Camisasca, C. Guidorzi, M. Bulla (Ferrara U.), L. Amati, A. Rossi
(INAF-OAS), G. Stratta, P. Singh (Goethe U. Frankfurt) on behalf of a
larger collaboration report:
"We determined the minimum variability timescale (MVT) of GRB230307A
(Fermi GBM team, GCN 33405; Xiong et al., GCN 33406; Xiao & Krucker, GCN
33410; Cosentini et al., GCN 33412; Navaneeth et al., GCN 33415) from
the Fermi/GBM light curve (NaI detectors 10 and 6) following the
prescriptions of Camisasca et al. (2023), i.e. as the minimum full width
half maximum (FWHM_min) of all statistically significant pulses, and
found FWHM_min = 28 (-7, +10) ms. Combined with the T90=34.56 +- 0.6 s
(Fermi GBM team, GCN 33405), in the T90-FWHM_min plot GRB230307A (purple
star in the Figure below) lies in the region populated by other
long-lasting merger candidates, such as also GRB191019A (green star in
Figure; Levan et al. 2023; Lazzati et al. 2023). In particular, it lies
very close to the merger GRB211211A (Gompertz et al. 2023; Mei et al.
2022; Rastinejad et al. 2022; Troja et al 2022; Yang et al 2022).
Despite its long duration and complex light curve, its short MVT
therefore supports the merger origin for GRB230307A, as suggested by the
possible evidence for kilonova emission reported by Levan et al. (GCN
33569).
In addition, assuming a redshift z=0.065 (Gillanders et al. GCN 33485),
a fluence of 3.6e-3 erg cm-2 (Svinkin et al. GCN 33427) would correspond
to Eiso=3.7e52 erg. Combined with Ep~1 MeV (Svinkin et al.), the
position of GRB230307A in the Ep-Eiso plane seems to be more compatible
with short rather than long GRBs.
http://www.fe.infn.it/u/guidorzi/T90_vs_FWHMmin_neu.pdf���� (Figure
adapted from Camisasca et al. 2023)
References
- Camisasca et al., 2023, A&A, 671, A112,
https://doi.org/10.1051/0004-6361/202245657
- Gompertz et al., 2023, Nature Astronomy, 7, 67
- Lazzati et al., 2023, arXiv:2303.12935
- Levan et al., 2023, arXiv:2303.12912
- Mei et al., 2022, Nature, 612, 236
- Rastinejad et al., 2022, Nature, 612, 223
- Troja et al., 2022, Nature, 612, 228
- Yang et al., 2022, Nature, 612, 232
GCN Circular 33569
Subject
GRB 230307A: JWST observations consistent with the presence of a kilonova
Date
2023-04-05T19:08:10Z (2 years ago)
From
Andrew Levan at U.of Leicester <a.levan@astro.ru.nl>
A. J. Levan (Radboud), B. P. Gompertz (U. Birmingham), D. B. Malesani (Radboud/DAWN NBI), N. R. Tanvir (Leicester), E. Burns (LSU), R. Salvaterra (INAF/IASF-Mi), K. Ackley (U. Warwick), G. P. Lamb (LJMU), J. Fynbo (DAWN NBI), B. Schneider (MIT), P. Jakobsson (U. Iceland), L. Izzo (DARK/NBI), A. Fruchter (STScI), D. Watson (DAWN NBI), M. Kennedy (UCC), J. Hjorth (DARK/NBI), G. Pugliese (API UvA), K. Bhirombhakdi (STScI), V. S. Dhillon (Sheffield/IAC) report for a larger collaboration.
"We obtained observations of the exceptionally bright, long-duration GRB 230307A (Fermi GBM team, GCN 33405; Xiong et al., GCN 33406; Xiao & Krucker, GCN 33410; Cosentini et al., GCN 33412; Navaneeth et al., GCN 33415) with the James Webb Space Telescope on 5 April 2023 (about 28.8 days after the GRB). Observations were obtained with NIRCam in the F070W, F115W, F150W, F277W, F356W and F444W filters.
At the location of the optical afterglow (Levan et al., GCN 33439) we find a faint source with F150W(AB) ~ 28.4 +/- 0.3. From our provisional analysis, the source appears point-like, without any evident extension. It is thus unlikely to be due to an underlying host galaxy. The lack of a host galaxy in observations of this depth is unusual for a long GRB, particularly for one as bright as GRB 230307A.
In addition, observations in the redder bands show a much brighter source, with F444W(AB)~24.5 +/- 0.1, consistent with a power-law slope of approximately nu^-3 through the redder bands.
We suggest that the very red colour and the absence of a host galaxy make a kilonova the most likely interpretation. In this case the burst may arise from a compact binary ejected from the nearby galaxy at z=0.065, which is ~40 kpc away in projection (Gillanders et al. GCN 33485).3
Further analysis is ongoing.
We thank the staff of STScI for their work to get these observations rapidly scheduled, in particular Katey Alatalo, Alaina Henry, Armin Rest and Wilson Skipper."
GCN Circular 33558
Subject
GRB 230307A: Chandra late-time detection of the X-ray afterglow
Date
2023-04-03T17:31:15Z (2 years ago)
Edited On
2024-12-03T15:09:39Z (10 months ago)
From
Wen-fai Fong at Northwestern U <wfong@northwestern.edu>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Leo P. Singer at NASA/GSFC <leo.p.singer@nasa.gov>
A. Rouco Escorial (ESA/ESAC), B. Gompertz (U. Birmingham), W. Fong (Northwestern), A. J. Levan (Radboud), J. Rastinejad (Northwestern), E. Berger (Harvard) report:
"The Chandra X-ray Observatory observed the extremely bright long-duration GRB 230307A (Fermi GBM Team, GCN 33405; Xiong et al., GCN 33406; Dalessi et al., GCN 33407, 33411; Burns et al., GCN 33414) starting on 2023 April 1st 21:30:20 UT, with a median observation time of ~25.4 days post-trigger. We obtained an ACIS-S observation under Director's Discretionary Time (Proposal 24408902, ObsID 27778; PI: Fong), with an effective exposure time of ~16.8 ks.
At the XRT position (Evans et al. GCN 33429), we identify 4 net counts, compared to an expected background of ~0.2 counts. Using the method of Kraft, Burrows & Nousek (1991ApJ 374 444) for the confidence limits in the low counts regime this suggests the detection of a source at >3-sigma confidence. We infer a count rate of ~2.4E-4 counts/seconds. Performing a joint spectral fit with the Swift/XRT data we obtain an X-ray flux of FX ~ 1.1e-14 erg/s/cm2.
Combining this Chandra observation with earlier XRT data, we infer a power-law decline with a decay index (FX~t^alpha) of alpha~-1.3.
We thank Pat Slane, Harvey Tananbaum and the CXO staff for the rapid approval and planning of these observations."
GCN Circular 33551
Subject
GRB 230307A: Bad Time Intervals for Fermi GBM data
Date
2023-04-01T01:57:34Z (2 years ago)
From
Sarah Dalessi at UAH <sd0104@uah.edu>
S. Dalessi (UAH) reports on behalf of the Fermi GBM Team:
"The Fermi Gamma-ray Burst Monitor data for GRB 230307A has a period
of bad time intervals, affecting all data types. At particularly high
rates the TTE data has data loss due to the bandwidth limit between
the instrument and the spacecraft. CTIME and CSPEC data experience
deadtime but do not experience similar losses due to electronics
bandwidth. However, at particularly high rates both CTIME and CSPEC
are affected by pulse pile-up, which will distort the spectra (see
https://arxiv.org/abs/2303.14172). For CTIME and CSPEC, pulse pile-up
occurs for GRB pulses during the time interval of 2.5-11.0 seconds for
the BGO detector B1 and the interval 2.5-7.5 seconds for the NaI
detector Na, with T0 referenced to the GBM trigger time. The TTE
losses happen within these time intervals, with packet losses for
high-rate GRB pulses between 3 to 7 seconds. We recommend the
exclusion of these time intervals for GBM analysis of this burst, as
well as caution in using bins adjacent to these selections.
Additionally, due to the orientation of the burst, we recommend only
using BGO detector B1 and NaI detector Na for analysis of this burst.
All the other detectors either have >60deg source angles or are
blocked by the spacecraft itself."
GCN Circular 33485
Subject
GRB 230307A: Continued Gemini-South observations confirm rapid optical fading
Date
2023-03-17T16:06:24Z (3 years ago)
From
James Gillanders at University of Rome Tor Vergata <jhgillanders.astro@gmail.com>
J. Gillanders (UTV), B. O'Connor (UMD, GWU), S. Dichiara (PSU), and E.
Troja (UTV, ASU) report on behalf of a larger team:
We re-observed the field of GRB 230307A (GBM team GCN 33405, Xiong et al.
GCN 33406) with the GMOS-S spectrograph at Gemini-South through Director's
Discretionary Time (PI: O���Connor).
Our initial epoch was carried out at 2.4 d post-burst. We performed 4x1000 s
exposures with the R400 grating covering wavelengths 4100-9200 angstroms.
The brightness in the initial acquisition image (r~22 AB mag) was reported
in O'Connor et al. (GCN 33447). A weak trace is visible from this position
down to ~5300 angstroms, which sets an upper limit of z<4.3 to the GRB
redshift. No obvious emission or absorption features are visible in the
spectrum.
Our slit also covered a nearby bright galaxy at an offset of ~30���. We estimate
a redshift z~0.065 from Halpha, N II, and S II emission lines. If this galaxy
(RA=+60.8280, DEC=-75.3819) is the host, then the GRB would have a projected
offset of ~40 kpc. The probability of chance coincidence is ~0.08.
Our latest observations were carried out in z-band at approximately 8.4 d
post-burst. A faint source is significantly detected at the location of the
optical counterpart (Levan et al. GCN 33439, O'Connor et al. GCN 33447), and
indicates a rapid fading of the afterglow by approximately 2 mag with respect
to earlier measurements. This suggests that the source reported by Bom et al.
(GCN 33459) is not the GRB host galaxy. Additionally, the observed power-law
temporal slope of ~-2 appears consistent with a jet-break.
We thank Andrew Levan for providing an initial finding chart and the staff of
the Gemini Observatory for rapidly approving and executing these observations.
GCN Circular 33478
Subject
GRB 230307A: Far off-axis NuSTAR detection of the GRB
Date
2023-03-14T21:10:47Z (3 years ago)
From
Brian Grefenstette at Caltech/NuSTAR <bwgref@srl.caltech.edu>
B.W. Grefenstette (Caltech) on behalf of the NuSTAR Team
After notification of the GRB 230307A via numerous GCNs, we searched the NuSTAR event stream for signals near the time of the GRB. Using a nominal position of RA:60.819 Dec:-75.379 (GCN #33425) we estimate the GRB was ~140-deg away from the telescope boresight (e.g., coming through the side of the instrument).
Even so, we clearly see the GRB in the CsI anti-coincidence shields in both of the NuSTAR telescopes. In the 1-sec time resolution shield data we see bursts in excess of 25,000 cps above the LLD in the shield at 2023-03-07T15:44:07.5 and a brighter second peak at 2023-03-07T15:44:11.5, along with a dip at 2023-03-07T15:44:23.5 as also seen in the GRBAlpha (GCN 33418) lightcurves. The energy scale for the LLD on the CsI is not well calibrated for incident gamma-rays, but this can roughly be interpreted as counts above ~100 keV.
The GRB is also seen in the CdZnTe X-ray detectors of both telescopes. The high rate of shield hits and the temporal variations in the intrinsic flux makes interpreting the CdZnTe lightcurve difficult. NuSTAR detected roughly 1000 events per telescope during the burst, with measured rates on the order of 5 � 50 counts per second throughout the burst and energies ranging from a few keV up to the saturation level of the detectors around 250 keV.
We clearly see that the GRB is resolved into several peaks, with significant relative spectral evolution between the first and second peaks with the second peak seen to have slightly lower energies in the X-rays, though whether this is instrument or intrinsic remains to be seen.
GCN Circular 33475
Subject
GRB 230307A: ATCA radio detection
Date
2023-03-14T05:23:06Z (3 years ago)
From
Gemma Anderson at Curtin U <gemma.anderson@curtin.edu.au>
G. E. Anderson (Curtin Uni.), J. K. Leung (U. Sydney), T. Murphy (U. Sydney), E. Lenc (CSIRO)
L. Rhodes (U. Oxford), A. J. van der Horst (GWU), G. Rowell (U. Adelaide)
We observed GRB 230703A (Fermi GBM Team GCN 33405) with the Australia Telescope
Compact Array (ATCA) between 2023-03-12_02:30 UT and 2023-03-12_07:30 UT
(~4.5 days post-burst). In our preliminary analysis, we detect a radio source coincident
with the X-ray (Burrows et al. GCN 33429, GCN 33465) and optical (Levan et al. GCN 33439)
counterpart with a flux density of 120+/-30 microJy/beam at 9 GHz. We also obtain an
3 sigma upper limit of 90 microJy/beam at 5.5 GHz.
We thank CSIRO staff for supporting these observations.
The ATCA is part of the Australia Telescope National Facility which is funded by the Australian
Government for operation as a National Facility managed by CSIRO. We acknowledge the Gomeroi
people as the traditional owners of the Observatory site.
GCN Circular 33472
Subject
GRB 230307A: INTEGRAL upper limit on Hard X-ray afterglow
Date
2023-03-13T16:54:30Z (3 years ago)
From
Volodymyr Savchenko at ISDC,U of Geneve <savchenk@in2p3.fr>
At the time of the very bright GRB 230307A (GCN #33405, GCN #33406, GCN
#33407, GCN #33410, GCN #33411, GCN #33412, GCN #33413, GCN #33414, GCN
#33415, GCN #33416, GCN #33418, GCN #33419, GCN #33424, GCN #33425, GCN
#33427, GCN #33428, GCN #33429, GCN #33430, GCN #33431, GCN #33434, GCN
#33437, GCN #33438, GCN #33439, GCN #33442, GCN #33443, GCN #33444, GCN
#33447, GCN #33448, GCN #33449, GCN #33453, GCN #33459, GCN #33461, GCN
#33465, GCN #33466), INTEGRAL was pointing 74 deg from the GRB
direction. Such an exceptionally high flux lead to a detection in
various ratemeters of INTEGRAL often causing saturation. From moderately
saturated SPI-ACS observation, we can estimate a likely close lower
limit on the total flux in 75 - 2000 keV energy range at the level of
0.0015 erg cm-2 s-1 in the time range T0 to T0+130.0s where T0 =
2023-03-07T15:44:07.
We note that despite the GRB brightness, both SPI-ACS and PICsIT
observations do not reveal early afterglow and no emission past
T0+129~s, with an approximate upper limit on average 75-2000 keV flux
between T0+129s and of T0+259 s at the level of 5.8e-09 erg cm-2 s-1
(see also GCN#33431).
A ToO pointed observation was carried out from 2023-03-08 11:35:00 (T0 +
19.8 hours) to 2023-03-09 02:18:20 (T0 + 34.6 hours) with a total
exposure time of 28.2 ks (for ISGRI). Since the observation was
scheduled when the refined IPN localization was not yet available, the
position of the candidate GRB optical and X-ray afterglow ((GCN #33429,
GCN #33439, GCN #33443, GCN #33447, GCN #33449, GCN #33459, GCN #33465))
was observed at an offset of 1.3 deg, reducing somewhat the effective
exposure of JEM-X compared to an optimal pointing.
We do not find any significant signal, and put a limit on any source
within the IPN error box, including also to the possible X-ray and
optical afterglow, at the level of 4.2e-11 erg cm-2 s-1 in the 3-200 keV
energy range, assuming a powerlaw spectrum with a slope of -2. This
limit is about 1.2 orders of magnitude lower than the detection in the
case of GRB 221009A.
We are grateful to the INTEGRAL Ground Segment team for the quick
scheduling of these observations.
All of the results except PICsIT were produced MMODA platform
(https://www.astro.unige.ch/mmoda/).
GCN Circular 33471
Subject
GRB 230307A: Swift/UVOT detection
Date
2023-03-13T15:54:52Z (3 years ago)
From
Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>
A. A. Breeveld (UCL-MSSL), and C. Salvaggio (INAF-OAB) report on behalf
of the Swift/UVOT team:
The Swift/UVOT began observations of the field of GRB 230307A 99.5 ks
after the Fermi/GBM-detected trigger (Dalessi et al., GCN 33407).
A fading source consistent with the enhanced XRT position (Burrows et
al., GCN 33465) and consistent with the optical counterpart reported by
Levan et al. (GCN 33439), Lipunov et al. (GCN 33441), Fulton et al. (GCN
33443), O'Connor et al. (GCN 33447), Im et al. (GCN 33449), Vanderspek
et al. (GCN 33453) and Bom et al. (GCN 33459) is detected in the initial
UVOT exposures. Detections and 3 sigma upper limits are given in the
following table:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 99525 110441 2265 21.28 +/- 0.16
white 133031 208070 2931 22.09 +/- 0.32
white 212899 420530 3418 >22.25
u 83621 88252 422 >20.44
The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.084 in the direction of
the burst (Schlegel et al. 1998).
GCN Circular 33466
Subject
GRB 230307A: soft X-ray detection with LEIA
Date
2023-03-13T11:24:55Z (3 years ago)
From
LEIA Team at NAOC/CAS <ep_ta@bao.ac.cn>
M.J. Liu, Y.L. Wang, Y. Liu, C. Zhang, Z.X. Ling, H.Q. Cheng, C.Z. Cui, D.W. Fan,
H.B. Hu, J.W. Hu, M.H. Huang, C.C. Jin, D.Y. Li, J.Q. Li, H.Y. Liu, H. Sun, H.W. Pan,
W.X. Wang, Q.Y. Wu, X.P. Xu, Y.F. Xu, H.N. Yang, M. Zhang, W.D. Zhang, Z. Zhang,
D.H. Zhao, and W. Yuan (NAOC, CAS), report on behalf of the LEIA and Einstein Probe team:
The prompt emission of the extremely bright long-duration GRB 230307A (Fermi/GBM
detection: GCN 33405, 33407, 33411, 33414; GECAM-B detection: GCN 33406;
Solar Orbiter STIX detection: GCN 33410; AGILE/MCAL detection: GCN 33412, 33444;
IPN triangulation: GCN 33413; AstroSat detection: GCN 33415; BALROG
localization: GCN 33416; GRBAlpha detection: 33418, VZLUSAT-2: GCN 33424,
Konus-Wind GCN 33427, AstroSat CZIT: 33415, Swift/BAT upper limits: GCN 33431,
AstroSat LAXPC detection: GCN 33437, ASO-S/HXI detection: GCN 33438, MAXI/GSC
upper limit: GCN 33448) was detected by LEIA (Lobster Eye Imager for Astronomy)
in the soft X-ray 0.5-4 keV band during one of its monitoring observations of
the Large Magellanic Cloud.
The observation was conducted from 2023-03-07T15:43:41 (25 s earlier than the
Fermi GBM trigger time at 2023-03-07T15:44:06) to 2023-03-07T16:02:00 with
a net exposure of 761 s. The GRB was detected within the extended FoV
(about 0.6 deg outside the nominal 18.6deg x 18.6deg FoV) of LEIA, and the
on-ground calculated position is RA=60.6, Dec=-75.4, with an estimated 3-sigma
error of 10 arcmin, which is consistent with the IPN localizaition (GCN 33461).
The lightcurve shows a burst profile which peaked at 2023-03-07T15:44:13
in 0.5 - 4.0 keV, and droped quickly to a level comparable to the detection
sensitivity within about 200 s. Given that the source is outside the nominal FoV,
the estimation of the source flux is complex and subject to further
investigation and will be published later.
LEIA also conducted follow-up observations in 6 successive orbits covering
the entire IPN error box from 2023-03-09UT00:47:26 to 2023-03-09UT10:32:34.
The total good exposure is around 4000 s and no significant emission was detected.
The derived upper limit of the LEIA is around 1e-11 erg/cm^2/s
in the energy band of 0.5 - 4.0 keV.
LEIA (Zhang et al, ApJL, 941, 2) is a soft X-ray monitor (0.5 - 4.0 keV)
with a FoV of 340 square degrees aboard the SATech-01 satellite of the CAS,
launched on July 27, 2022. The above result is preliminary and the final
result will be published elsewhere.
GCN Circular 33465
Subject
GRB 230307A: Swift-XRT afterglow detection
Date
2023-03-13T11:21:46Z (3 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
D.N. Burrows (PSU), J. D. Gropp (PSU), J.P. Osborne (U. Leicester),
K.L. Page (U. Leicester), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti
(INAF-OAB), A. D'Ai (INAF-IASFPA), S. Dichiara (PSU) and P.A. Evans (U.
Leicester) report on behalf of the Swift-XRT team:
Swift-XRT has conducted further observations of the field of the
Fermi/GBM-detected burst GRB 230307A (Dalessi et al. GCN Circ. 33407).
The observations now extend from T0+83.6 ks to T0+437.2 ks.
Of the sources reported by Burrows et al. (GCN Circ. 33429), "Source 2"
is fading with >3-sigma significance, and is therefore likely the GRB
afterglow. Using 1252 s of PC mode data and 1 UVOT image, we find an
enhanced XRT position (using the XRT-UVOT alignment and matching UVOT
field sources to the USNO-B1 catalogue): RA, Dec = 60.85935, -75.37884
which is equivalent to:
RA (J2000): 04h 03m 26.24s
Dec(J2000): -75d 22' 43.8"
with an uncertainty of 3.2 arcsec (radius, 90% confidence). This
position is 13.3 arcsec from the IPN improved position (Kozyrev et al.
GCN Circ. 33461).
The light curve can be modelled with a power-law decay with a decay
index of alpha=1.1 (+0.6, -0.5).
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00021537.
The results of the full analysis of the tiled XRT observations are
available at https://www.swift.ac.uk/xrt_products/TILED_GRB00110.
This circular is an official product of the Swift-XRT team.
GCN Circular 33461
Subject
Further improved IPN localization for GRB 230307A
Date
2023-03-11T22:07:23Z (3 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin
on behalf of the MGNS/BepiColombo and HEND/Mars Odyssey teams,
J. Benkhoff on behalf of the BepiColombo team,
D. Svinkin, D. Frederiks, A. Ridnaia, A. Lysenko,
and T. Cline on behalf of the Konus-Wind team,
A. Goldstein, M. S. Briggs, C. Wilson-Hodge,
and E. Burns on behalf of the Fermi GBM team,
E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT team,
and
W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr,
and A.S. Gardner on on behalf of the GRS-Odyssey GRB team,
report:
Using the BepiColombo (MGNS) data we have further improved
the previous IPN box for GRB 230307A (Kozyrev et al., GCN Circ. 33425).
The coordinates of the updated 3 sigma error box are:
---------------------------------------------
RA(2000), deg Dec(2000), deg
---------------------------------------------
Center:
60.867 (04h 03m 28s) -75.382 (-75d 22' 57")
Corners:
60.846 (04h 03m 23s) -75.417 (-75d 25' 03")
61.006 (04h 04m 01s) -75.357 (-75d 21' 26")
60.889 (04h 03m 33s) -75.348 (-75d 20' 51")
60.728 (04h 02m 55s) -75.408 (-75d 24' 28")
---------------------------------------------
The error box area is 8 sq. arcmin, and its maximum
dimension is 5 arcmin (the minimum one is 1.8 arcmin).
The Sun distance was 80 deg.
This box may be further improved.
The distance between the IPN box center and X-ray/optical
transient position (X-ray Source #2 in Burrows et al., GCN Circ. 33429;
Levan et al., GCN Circ. 33439; Lipunov et al. GCN Circ. 33441;
O'Connor et al., GCN Circ. 33447; Im et al., GCN Circ. 33449;
Vanderspek et al., GCN Circ. 33453)
is 15 arcsec, which further strengthen the interpretation of transient as
the burst afterglow.
An updated triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB230307_T56646/IPN
GCN Circular 33459
Subject
GRB 230307A: SOAR/Goodman detection of the possible host galaxy
Date
2023-03-11T21:13:45Z (3 years ago)
From
Charles Kilpatrick at Northwestern U <ckilpatrick@northwestern.edu>
C. R. Bom (CBPF), C. D. Kilpatrick (Northwestern), R. Santucci (Universidade Federal de Goi��s), A. J. Castro-Tirado (IAA-CSIC and UMA), I. P��rez-Garc��a, Y.-D. Hu (IAA-CSIC), F. Navarete (IAG-USP, RSS/NOIRLab), and M. Makler (UNSAM/CBPF), on behalf of a larger collaboration, report:
Following the detection of the very bright GRB 230307A (Burns et al. GCNC 33414) by Fermi/GBM (the Fermi GBM team, GCNC 33405; Dalessi, GCNC 33407; Dalessi and Roberts, GCNC 33411), GECAM (Xiong et al., GCNC 33406), Solar Orbiter/STIX (Xiao and Krucker, GCNC 33410), AGILE/MCAL (Casentini et al., GCNC. 33412), INTEGRAL/SPI-ACS, Mars-Odyssey/HEND (Kozyrev et al. GCNC 33413), AstroSat/CZTI (Navaneeth et al. GCNC 33415), GRBAlpha (Dafcikova et al. GCNC 33418), VZLUSAT-2 (Ripa et al. GCNC 33424), Konus-WIND (Svinkin et al. GCNC 33427) Swift-BAT (Tohuvavohu, GCNC 33431) and ASO-S/HXI (Li et al. GCNC 33438), we report z-band imaging and optical spectroscopy of the GRB 230307A from 9 and 10 March 2023 with the Goodman high-throughput imaging spectrograph on the SOAR 4.1m telescope at Cerro Pach��n, Chile. The z-band imaging consisted of a cumulative 310s of exposure starting at 2023-03-10T00:13:45 (MJD 60013.0095, 56.5 hr from burst) and 600s starting at 2023-03-11T00:19:08 (MJD 60014.0133, 80.5 hr from burst) at the site of the reported optical counterpart to GRB 230307A (Levan et al. GCNC 33439, Lipunov et al. GCN 33441, Fulton et al. GCNC 33443, O'Connor et al. GCNC 33447, Im et al. GCNC 33449, Vanderspek et al. GCNC 33453). Using forced photometry at the site of the counterpart (RA=04:03:25.83, Dec=-75:22:42.7), we obtained a marginal detection in both epochs of z=21.8+/-0.3 AB mag. The lack of any change between the two epochs suggests we may be seeing a faint background source consistent with the host galaxy of GRB 230307A.
We also obtained spectroscopy at the site of the counterpart at 2023-03-10T00:28:17 with the 400 l/mm grating on SOAR/Goodman covering a wavelength range of 3000-7000 angstroms for a cumulative exposure time of 1500s. We oriented the 1.0" Goodman long slit to simultaneously observe the optical afterglow of GRB 230307A and the red source roughly 3 arcseconds to the southwest reported in Levan et al. (GCNC 33439) as a possible host galaxy. There is no signature of emission from the GRB afterglow in our spectra, but we detect red continuum emission from 6000-7000 angstroms consistent with the r=20.8 mag, i=19.5 mag, z=18.9 mag (Legacy Survey DR10; Dey et al., 2019, AJ, 157, 168) to the southwest. Combined with the fact that this source is unresolved in our imaging and has a significant parallax in the Gaia DR3 catalog (Gaia Collaboration et al., 2022), we consider this source to be a foreground star as pointed out by Lipunov et al. (GCNC 33441) and not the host galaxy of GRB 230307A.
Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Minist��rio da Ci��ncia, Tecnologia e Inova����es do Brasil (MCTI/LNA), the US National Science Foundation���s NOIRLab, the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).
GCN Circular 33453
Subject
TESS Detection of the Optical Afterglow of GRB230307A
Date
2023-03-11T16:52:38Z (3 years ago)
From
Roland Vanderspek at MIT <roland@space.mit.edu>
R. Vanderspek, M.M. Fausnaugh, R. Jayaraman, G.R. Ricker (MIT), K. Colon and A. Youngblood (GSFC), on behalf of the TESS Team, report:
The Transiting Exoplanet Survey Satellite (TESS; Ricker et al. 2015) observed the location of the bright gamma-ray burst GRB230307A during the second orbit of Observation Sector 62. Images of the burst region, located in TESS Camera 4, CCD 4, were captured in the TESS full-frame images (FFIs). The observations of the field were made at a cadence of 200 seconds and were continuous from 3 days before the trigger to 3 days after the trigger.
Analysis of the TESS FFIs using TICA (Fausnaugh et al. 2020; doi:10.3847/2515-5172/abd63a <https://ui.adsabs.harvard.edu/link_gateway/2020RNAAS...4..251F/doi:10.3847/2515-5172/abd63a>) data confirms the existence of the optical counterpart reported by Levan et al. (GCN Circular 33439), Lipunov et al. (GCN Circular 33441), O'Conner et al. (GCN Circular 33447), and Im et al. (GCN Circular 33449). The signal is seen as a point source brighter than 15th magnitude in a single 200s FFI. The measured position is 4:03:26.5, -75:22:45 with an estimated 1-sigma error of 4���, consistent with previously-reported localizations.
TICA data can be found at https://archive.stsci.edu/hlsp/tica.
GCN Circular 33449
Subject
GRB 230307A: GECKO optical observations and detections of the afterglow
Date
2023-03-10T07:42:47Z (3 years ago)
From
Myungshin Im at Seoul Nat U <mim@astro.snu.ac.kr>
Myungshin Im, Gregory S.-H. Paek, Mankeun Jeong, Seo-Won Chang, Hyeonho
Choi (SNU), and Chung-Uk Lee (KASI)
We covered the localization areas of GRB 230307A (GBM team GCN 33405, Xiong
et al. GCN 33406) with the RASA36 telescope at the El Sauce observatory in
Chile, and the KMTNet telescopes in SSO, Australia, and SAAO, South Africa.
The RASA36 observation started at 2023-03-08-00:52 (UT) or about 9.11 hrs
after the burst alert, taking a series of r-band images for about 20 min.
The starting times of the KMTNet SSO and SAAO stations are 2023-03-08-09:39
(UT) and 2023-03-08-18:30 (UT) or 17.89 hrs and 26.74 hrs respectively,
taking a series of R- and I-band images for about 1 hr at each location.
We clearly identify the afterglow (Levan et al. GCN 33439, Lipunov et al.
GCN 33441, O'Conner et al. 33447) and confirm its fading nature in all of
the time-series KMTNet images, with the photometry roughly consistent with
that of the Levan et al. (GCN 33439) report. A weak signal is found in the
RASA36 image.
Further observations and analysis are being carried out.
We thank the KMTNet operators for their support for the KMTNet observations.
GCN Circular 33448
Subject
GRB 230307A: MAXI/GSC upper limit
Date
2023-03-10T04:03:34Z (3 years ago)
From
Motoko Serino at Aoyama Gakuin U. <serino@phys.aoyama.ac.jp>
S. Sugita, M. Serino (AGU), H. Negoro (Nihon U.), T. Mihara (RIKEN),
M. Nakajima, K. Kobayashi, M. Tanaka, Y. Soejima (Nihon U.),
T. Kawamuro, S. Yamada, T. Tamagawa, M. Matsuoka (RIKEN),
T. Sakamoto, H. Hiramatsu, H. Nishikawa, A. Yoshida (AGU),
Y. Tsuboi, J. Kohara, S. Urabe, S. Nawa, N. Nemoto (Chuo U.),
M. Shidatsu, M. Iwasaki (Ehime U.),
N. Kawai, M. Niwano, R. Hosokawa, Y. Imai, N. Ito, Y. Takamatsu (Tokyo Tech),
S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, T. Kurihara (JAXA),
Y. Ueda, S. Ogawa, K. Setoguchi, T. Yoshitake, K. Inaba, Y. Nakatani (Kyoto U.),
M. Yamauchi, T. Sato, R. Hatsuda, R. Fukuoka, Y. Hagiwara, Y. Umeki (Miyazaki U.),
K. Yamaoka (Nagoya U.),
Y. Kawakubo (LSU),
M. Sugizaki (NAOC) ,
W. Iwakiri (Chiba U.)
report on behalf of the MAXI team:
We report the non-detection of MAXI/GSC of GRB 230307A
(Fermi-GBM GCN #33405, #33407 #33411; GECAM GCN #33406,
Solar Orbiter STIX GCN #33410; AGILE/MCAL GCN #33412;
HEND/Mars Odyssey, INTEGRAL SPI-ACS, Swift/BAT GCN #33413;
AstroSat CZTI GCN #33415; GRBAlpha GCN #33418;
VZLUSAT-2 GCN #33424; Konus-Wind GCN #33427;
AstroSat LAXPC GCN #33437; ASO-S/HXI GCN #33438;
).
At 15:58:54 UT on 2023-03-07 (888s after the Fermi/GBM trigger),
MAXI/GSC scanned the error region of the event.
The scan time of the five consecutive scans were
17:31:49 (t0+6463s), 19:04:40 (t0+12034s), 20:37:36 (t0+17610s),
22:10:27 (t0+23181s), and 23:43:22 (t0+28756s).
No significant excess emission was detected from the region.
Typical 1-sigma upper limits in 2-20 keV for one scan (and six scans) are
20 mCrab (and 8 mCrab).
GCN Circular 33447
Subject
GRB 230307A: Gemini-South Confirmation of the Optical Afterglow
Date
2023-03-10T03:37:36Z (3 years ago)
From
Brendan O'Connor at UMD <oconnorb@umd.edu>
B. O'Connor (UMD, GWU), S. Dichiara (PSU), E. Troja (UTV, ASU),
J. Gillanders (UTV), S. B. Cenko (NASA, UMD), C. Kouveliotou (GWU):
We observed GRB 230307A (GBM team GCN 33405, Xiong et al. GCN 33406,
Kozyrev et al. GCN 33425) with the GMOS-S instrument mounted on
Gemini-South in Cerro Pachon, Chile through Director's Time.
Observations began at 00:06:47 UT on 2023-03-10, corresponding to
2.35 d after the GRB trigger.
In a 30 s acquisition image, we detect the optical afterglow reported
by Levan et al. (GCN 33439) and Lipunov et al. (GCN 33441). With
preliminary photometry calibrated to the SkyMapper catalog we derive
a magnitude of r~22.0+/-0.3 mag. This confirms fading of the reported
counterpart and solidifies the connection to the GRB.
Analysis of the spectroscopic observations is underway.
We thank the staff of the Gemini Observatory for rapidly approving and
executing these observations.
GCN Circular 33444
Subject
GRB 230307A: AGILE/MCAL analysis
Date
2023-03-09T19:41:32Z (3 years ago)
From
Claudio Casentini at INAF-IAPS <claudio.casentini@inaf.it>
C. Casentini (INAF/IAPS), F. Verrecchia (SSDC, and INAF/OAR),
A.Ursi (ASI), C. Pittori (SSDC, and INAF/OAR),
M. Tavani (INAF/IAPS and Uni. Roma Tor Vergata),
F. Lucarelli (SSDC, and INAF/OAR), A. Argan, M. Cardillo, Y. Evangelista,
L. Foffano, G. Piano (INAF/IAPS), A. Addis, L. Baroncelli, A. Bulgarelli,
A. Di Piano, V. Fioretti, G.Panebianco, N. Parmiggiani (INAF/OAS-Bologna),
M. Romani (INAF/OA-Brera), M. Marisaldi (INAF/OAS-Bologna, Bergen
University),
M. Pilia, A. Trois (INAF/OA Cagliari), I. Donnarumma, E. Menegoni,
A. Giuliani (INAF/IASF-Mi) and P. Tempesta (TeleSpazio),
report on behalf of the AGILE Team:
We carried out further analysis of the AGILE/MCAL data of GRB 230307A
(GCNs #33405, #33406, #33407, #33410, #33411, #33412, #33413, #33414,
#33415, #33416, #33418, #33419, #33424, #33425, #33427, #33428, #33429
#33430, #33431, #33434, #33437, #33438, #33439, 33442, 33443)
The burst released 229697 counts in the detector in 18s, above a background
rate of 545 Hz.
The spectral analysis shows a clear component up to 8 MeV.
The time-integrated spectrum of the burst can be fitted in the energy range
0.6-6.5 MeV with a Band model with alpha = -0.43 (+/-0.06),
beta = -5.1 (+/-0.7), peak energy Epeak = 1260 keV (+/- 42 keV).
The fit results in a reduced chi-squared of 1.607 (34 d.o.f.) and a
fluence of 1.3e-03 erg/cm^2, in the same energy range.
MCAL spectrum in the selected 18 s time interval can be found at:
http://www.agilescienceapp.it/notices/GRB230307A_AGILE-MCAL_spectral_analysis.png
Additional analysis of AGILE data is in progress. Automatic MCAL GRB alert
Notices can be found at: https://gcn.gsfc.nasa.gov/agile_mcal.html.
GCN Circular 33443
Subject
GRB 230307A: ATLAS information on the ULTRACAM optical afterglow candidate
Date
2023-03-09T18:19:09Z (3 years ago)
From
Stephen Smartt at Queen's U/Belfast <s.smartt@qub.ac.uk>
M. D. Fulton, K. W. Smith, S. Srivastav, D. R. Young, M. Nicholl, M.
McCollum, T. Moore, J. Weston (QUB), S. J. Smartt (Oxford/QUB), L.
Shingles (GSI/QUB), J. Sommer (LMU/QUB), L. Rhodes (Oxford), L.
Denneau, J. Tonry, H. Weiland, A. Lawrence, R. Siverd (IfA, University
of Hawaii), N. Erasmus, W. Koorts (South African Astronomical
Observatory), A. Jordan, V. Suc (UAI, Obstech), A. Rest (STScI), T.-W.
Chen (TUM/MPA), C. Stubbs (Harvard)
We report optical observations in the field of the
Fermi/GBM-discovered GRB 230307A (Dalessi et al. GCN Circ. 33407) in
the context of the detection of a possible optical afterglow by Levan
et al. (GCN Circ. 33439).
ATLAS is a quadruple 0.5m telescope system with two units in Hawaii,
one in Chile and one South Africa (see Tonry et al. 2018,
PASP,130:064505), routinely surveying the visible sky on a daily
basis. We promptly process all data with our transient science server
(Smith et al. 2020, PASP, 132:085002). The ATLAS system observed the
field of the GRB 230307A in normal survey mode before the GRB trigger
date of MJD 60010.655 (=2023-03-07 15:44:06.67 UT). We forced the
photometry at the proposed position of the optical afterglow
RA=04:03:25.83, Dec=-75:22:42.7 (J2000) (Levan et al. GCN Circ. 33439;
Source 2 from Evans et al. GCN Circ. 33429) thorough our ATLAS forced
photometry server (Shingles et al. AstroNote #2021-7, Smith et al.
2020, PASP, 132:085002). We found no historical detections of any
excess optical flux at this position.
Forced photometry at those coordinates results in the following most
recent non-detections in the o-band filter. These measurements are not
corrected for any galactic dust extinction. The AB mag are quoted as
2 sigma.
+-----------+------------+-----------------+-------------------+
| MJD | Flux (uJy) | Flux Err (duJy) | AB Mag Limit (2��) |
+-----------+------------+-----------------+-------------------+
| 60002.781 | 6.0 | 6.8 | >21.1 |
+-----------+------------+-----------------+-------------------+
| 60004.034 | -8.8 | 8.6 | >20.8 |
+-----------+------------+-----------------+-------------------+
| 60008.087 | 1.1 | 11.9 | >20.5 |
+-----------+------------+-----------------+-------------------+
The candidate optical afterglow from Levan et al. (GCN Circ. 33439)
was r=20.5 at MJD=60012.1. We find no sign of the object to similar
flux levels before the GRB, which suggests the source is a new
transient occurring after MJD 60008. This supports it being the
candidate optical afterglow of GRB 230307A.
GCN Circular 33442
Subject
GRB 230307A: Erratum of the GCN 33441
Date
2023-03-09T17:33:43Z (3 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
V.Lipunov (Lomonosov MSU)
I am sorry for my mistake in Subject.
Correct subject is
GRB 230307A: MASTER detection of an object near NTT Optical Afterglow Candidate
GCN Circular 33439
Subject
GRB 230307A: Possible optical afterglow
Date
2023-03-09T15:14:27Z (3 years ago)
From
Andrew Levan at U.of Leicester <a.levan@astro.ru.nl>
A.J. Levan (Radboud), B. Gompertz (U. Birmingham), K. Ackley (U. Warwick), M. Kennedy (University College Cork), V. Dhillon (U. Sheffield) report on behalf of a larger collaboration:
"We observed the IPN localisation (Kozyrev et al. GCN 33425) of GRB 230307A (GBM team GCN 33405, Xiong et al. GCN 33406) with ULTRACAM, mounted on the NTT at La Silla. A total of 200s of exposure (10 x 20s) were obtain simultaneously in the u, g and r filters starting at 01:58:33 UTC approximately 34.3 hours post burst. Observations covered the entirety of the refined IPN localisation. A comparison of the observation with DSS and legacy survey image reveals a weak new optical source at a location of
RA(J2000): 04:03:25.83
DEC(J2000): -75:22:42.7
(+/- 0.5���)
The source has an r-band magnitude of approximately r=20.5 at the time of these observations. We note that the source is co-incident (1.9��� offset) with source 2 identified by the Swift-XRT (Evans, GCN 33419). Combined with the absence of the source in pre-imaging we suggest that this is the afterglow of GRB 230307A.
We note that the source has a modest offset (3���) from a very red source identified in the legacy survey and WISE. It is possible that this is host galaxy of the GRB. Spectroscopic observations to obtain the redshift of both afterglow and nearby source are encouraged. "
GCN Circular 33438
Subject
GRB 230307A: ASO-S/HXI detection
Date
2023-03-09T14:33:56Z (3 years ago)
From
Tianrui Sun at Purple Mountain Obs,CAS <trsun@pmo.ac.cn>
Zhentong Li, Yang Su on behalf of the HXI team report:
At 2023-03 07 15:44:09 UT, HXI detected the bright GRB 230307A (Burns et al. GCNC 33414) which was also reported by Fermi/GBM (Fermi GBM Team et al. GCNC 33405; Dalessi, GCNC 33407; Dalessi et al. , GCNC 33411; Dalessi et al. GCNC 33411), GECAM (Xiong et al. GCNC 33406), STIX (Xiao et al. GCNC 33410), AGILE/MCAL (Claudio et al. GCNC 33412), IPN (Kozyrev et al. GCNC 33413, Kozyrev et al. GCNC 33425), AstroSat CZTI (Gaurav et al. GCNC 33415), BARLOG (Jochen et al. GCNC 33416), GRBAlpha (Marianna et al. GCNC 33418), VZLUSAT-2 (Ripa et al. GCNC 33424), Konus-WIND (Svinkin et al. GCNC 33427), Swift (Phil et al. GCNC 33419, GCNC 33431), IceCube (Jessie et al. GCNC 33430) and BOOTES (Alberto et al. GCNC 33434).
The GRB signal is spiky with significant responses at energies from ~20 keV to the detection upper limit 300 keV of the HXI scintillation detectors. The signal displays a major peak (> 570 cts/s/detetor) and a faint secondary peak (> 230 cts/s/detetor, with an in-orbit background of ~130 cts/s/detetor). The duration of the major peak is ~16 s and the whole signal lasts for ~40 s. The time resolution of the observed signal is 4 s. The burst mode (res. as high as 0.125s) was not triggered because the GRB was detected by both total flux monitor and background monitor.
By examining the count rate distribution of the 99 detectors of HXI, the direction of the GRB was roughly deduced. Hard X-ray Imager (HXI) is one of the three scientific payloads onboard the Advanced Space-based Solar Observatory (ASO-S) satellite, which is China���s first comprehensive solar dedicated space science mission. HXI is designed to investigate the non-thermal high-energy electrons accelerated in solar flares by providing X-ray spectra and images of solar flaring regions in the energy range from 15 to 300 keV. ��It started to work on ��2022-Oct-17 and is currently in the inflight testing phase. The science data will be completely open to the community after the testing phase, i.e., around mid-April 2023.
More information about HXI can be found on the ASO-S website: http://aso-s.pmo.ac.cn/en_index.jsp
GCN Circular 33437
Subject
GRB 230307A: AstroSat LAXPC detection
Date
2023-03-09T13:15:29Z (3 years ago)
From
Tilak Katoch at TIFR <tilak@tifr.res.in>
Tilak Katoch, H. M. Antia and Parag Shah TIFR, Mumbai, India.
Analysis of AstroSat LAXPC data showed the clear detection of a long GRB
230307A. The lightcurve shows the multiple burst profile with the peak
triggered at T0 = 15h 44m 03s UT on 07 Mar 2023. The satellite was in a
normal operating mode and well before the entry into the SAA region.
The lightcurve has a burst profile with T90 = 36 sec. The strongest peak
measured have a count rate above the background with 13321 +/- 117
count/sec in LAXPC10 and 4415 +/- 68 count/sec in LAXPC20 at T0+7 sec.
Both LAXPC instruments (LAXPC10 and LAXPC20) have registered this burst
profile in the light curve. For LAXPC20, the nominal energy range is
3-100 keV, but due to the lower gain in LAXPC10 the energy range is
about 30-400 keV.
The background subtracted lightcurve with 1 sec time-bin is available at
the website:
https://www.tifr.res.in/~astrosat_laxpc/grb230307alc.jpg [1]
LAXPC was built by TIFR in collaboration with the Indian Space Research
Organisation. The Indian Space Research Organisation funded, managed and
facilitated the project.
Links:
------
[1] https://www.tifr.res.in/~astrosat_laxpc/grb230106lc.jpg
GCN Circular 33434
Subject
GRB 230307A: optical upper limit
Date
2023-03-09T09:51:32Z (3 years ago)
From
Alberto J. Castro-Tirado at IAA-CSIC <ajct@iaa.es>
I. P��rez-Garc��a (IAA-CSIC Granada, Spain), A. Maury (Space Obs, Chile),
E. Fern��ndez-Garc��a, Y.-D. Hu and A. J. Castro-Tirado (IAA-CSIC and
UMA), on behalf of a larger collaboration, report:
���Following the detection of the very bright GRB 230307A (Burns et al.
GCNC 33414) by Fermi/GBM (the Fermi GBM team, GCNC 33405; Dalessi, GCNC
33407; Dalessi and Roberts, GCNC 33411), GECAM (Xiong et al., GCNC
33406), Solar Orbiter/STIX (Xiao and Krucker, GCNC 33410), AGILE/MCAL
(Casentini et al., GCNC. 33412), INTEGRAL/SPI-ACS, Mars-Odyssey/HEND
(Kozyrev et al. GCNC 33413), AstroSat/CZTI (Navaneeth et al. GCNC
33415), GRBAlpha (Dafcikova et al. GCNC 33418), VZLUSAT-2 (Ripa et al.
GCNC 33424), Konus-WIND (Svinkin et al. GCNC 33427) and Swift-BAT
(Tohuvavohu, GCNC 33431), we observed 60% of the preliminary IPN error
box (Kozyrev et al. GCNC 33413) with a 0.5m wide-field telescope in the
vicinity of the BOOTES-7 astronomical station at San Pedro de Atacama
Space Observatory. No optical candidate down to 17.4 mag is found on the
images (clear filter, 1.6h co-add) starting at 4:36 on Mar 8 UT (i.e.
12.9 h postburst) within the entire improved IPN position (Kozyrev et
al. GCNC 33425).���
This message can be quoted.
GCN Circular 33431
Subject
GRB 230307A: Swift/BAT upper limits on the early afterglow
Date
2023-03-09T01:49:22Z (3 years ago)
From
Aaron Tohuvavohu at U Toronto <aaron.tohu@gmail.com>
Aaron Tohuvavohu (U Toronto), Jimmy DeLaunay (U Alabama), Samuele Ronchini
(Penn State), Tyler Parsotan (GSFC/UMBC), Chris Matzner (U Toronto) report:
The extremely bright GRB 230307A (GCN 33425) was detected in prompt
emission by Swift/BAT outside the coded field of view, as reported
previously.
Soon after, a pre-planned observation serendipitously landed the GRB
position near the center of the BAT field of view, with settled
observations beginning at T0+910s. Using the BAT survey mode data, 300s
duration 80-channel Detector Plane Histograms, we search for any detection
of continued emission or bright afterglow from the burst between 910 to
1210 seconds after the burst.
No emission is detected at the IPN position of the GRB, with a 5 sigma
upper limit of 0.00656 mask-weighted counts/s (15-50 keV).
Assuming an afterglow spectrum that can be described as a power law with
photon index of 2.08 (as found for the BAT afterglow detection in GRB
221009A, Williams et al. 2023), this corresponds to an upper limit of
2.389e-9 erg/cm^2/s (15-50 keV).
This constrains GRB 230307A's early afterglow (at T0+1 ks) to be at least
~1.5 orders of magnitude fainter than that of GRB 221009A at comparable
times.
GCN Circular 33430
Subject
GRB 230307A: Upper limits from a neutrino search with IceCube
Date
2023-03-09T00:17:46Z (3 years ago)
From
Jessie Thwaites at IceCube/U Wisc-Madison <thwaites@wisc.edu>
The IceCube Collaboration (http://icecube.wisc.edu/) reports:
IceCube has performed a search for track-like muon neutrino events arriving from the direction of GRB 230307A (GCN 33405<https://gcn.gsfc.nasa.gov/gcn/gcn3/33405.gcn3> (Fermi-GBM)) in a time range of -1 hour/+2 hours from the initial trigger reported by Fermi-GBM (2023-03-07 15:44:06.67 UTC), using the localization area reported by IPN (GCN 33425<https://gcn.gsfc.nasa.gov/gcn/gcn3/33425.gcn3>), during which IceCube was collecting good quality data. Zero track-like events are found coincident with the position of the GRB. We accordingly derive a time-integrated muon-neutrino flux upper limit for this source of E^2 dN/ dE = 1.0 GeV cm^-2 at 90% CL, under the assumption of an E^-2 power law. 90% of events IceCube would detect from a source at this declination with an E^-2 spectrum have energies in the approximate energy range between 90 TeV and 20 PeV.
A subsequent search was performed including 2 days of data centered on the Fermi-GBM trigger (2023-03-06 15:44:06.67 UTC to 2023-03-08 15:44:06.67 UTC). In this case, we report a p-value of 1.0, consistent with background expectation. We accordingly derive a time-integrated muon-neutrino flux upper limit for this source of E^2 dN/ dE = 1.1 GeV cm^-2 at 90% CL, under the assumption of an E^-2 power law.
The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc@icecube.wisc.edu<mailto:roc@icecube.wisc.edu>.
[1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021)
GCN Circular 33429
Subject
GRB 230307A: Swift-XRT observations
Date
2023-03-08T23:17:17Z (3 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
D.N. Burrows (PSU), J. D. Gropp (PSU), J.P. Osborne (U. Leicester),
K.L. Page (U. Leicester), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti
(INAF-OAB), A. D'Ai (INAF-IASFPA), S. Dichiara (PSU) and P.A. Evans (U.
Leicester) report on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the
Fermi/GBM-detected burst GRB 230307A (Dalessi et al. GCN Circ. 33407)
in a series of observations tiled on the sky. The total exposure time
is 8.6 ks, distributed over 32 tiles; the maximum exposure at a single
sky location was 1.6 ks. The data were collected between T0+76.4 ks and
T0+100.9 ks, and are entirely in Photon Counting (PC) mode.
Two X-ray sources have been detected within the improved IPN error box
(Kozyrev et al., GCN Circ. 33425), that has been fully covered by
Swift/XRT observations.
Source 2:
RA (J2000): 04h 03m 26.24s = 60.85935��
Dec (J2000): -75�� 22��� 43.8��� = -75.3788��
Error: 3.4��� (radius, 90% conf., enhanced)
Count-rate: 0.019 (��0.004) ct s-1
Distance: 36.6 arcsec from IPN position
Source 3:
RA (J2000): 04h 03m 57.93s = 60.99137��
Dec (J2000): -75�� 21��� 26.8��� = -75.3574��
Error: 7.1��� (radius, 90% conf.)
Count-rate: 2.6 (+1.9, -1.3) ��10-3 ct s-1
Distance: 175 arcsec from IPN position
Source 2 is below the RASS limit and shows no definitive signs of
fading. Therefore, at the present time we cannot confirm this as the
afterglow. Source 3 is at a position consistent with a QSO candidate
(Wu et al., 2023, RAA, 23, 025006) and therefore is likely unrelated to
GRB 230307A. Further observations are ongoing.
The results of the XRT-team automatic analysis of the tiled XRT
observations, including a position-specific upper limit calculator, are
available at https://www.swift.ac.uk/xrt_products/TILED_GRB00110.
This circular is an official product of the Swift-XRT team.
GCN Circular 33428
Subject
Fermi GRB 230307A: Global MASTER-Net observations report
Date
2023-03-08T22:20:57Z (3 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 230307A ( Fermi GBM team, GCN 33405) errorbox 1 days 7520 sec after notice time and 1 days 7572 sec after trigger time at 2023-03-08 17:50:19 UT, with upper limit up to 19.0 mag. Observations started at twilight. The observations began at zenith distance = 46 deg. The sun altitude is -10.1 deg.
The galactic latitude b = -37 deg., longitude l = 292 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2202708
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
94063 | 2023-03-08 17:50:19 | MASTER-SAAO | (04h 06m 50.07s , -74d 51m 54.3s) | C | 180 | 17.4 |
94063 | 2023-03-08 17:50:19 | MASTER-SAAO | (04h 09m 51.53s , -74d 51m 58.1s) | C | 180 | 17.1 |
94274 | 2023-03-08 17:53:51 | MASTER-SAAO | (04h 06m 44.57s , -76d 46m 43.0s) | C | 180 | 17.9 |
94274 | 2023-03-08 17:53:51 | MASTER-SAAO | (04h 10m 11.69s , -76d 46m 46.6s) | C | 180 | 17.7 |
94909 | 2023-03-08 18:04:25 | MASTER-SAAO | (03h 08m 23.27s , -74d 51m 18.2s) | C | 180 | 18.5 |
94909 | 2023-03-08 18:04:25 | MASTER-SAAO | (03h 11m 26.50s , -74d 51m 25.8s) | C | 180 | 18.5 |
95120 | 2023-03-08 18:07:56 | MASTER-SAAO | (04h 06m 35.42s , -76d 44m 20.5s) | C | 180 | 19.0 |
95120 | 2023-03-08 18:07:56 | MASTER-SAAO | (04h 10m 04.25s , -76d 44m 25.9s) | C | 180 | 18.8 |
95754 | 2023-03-08 18:18:31 | MASTER-SAAO | (03h 08m 25.33s , -74d 51m 41.6s) | C | 180 | 18.7 |
95754 | 2023-03-08 18:18:31 | MASTER-SAAO | (03h 11m 30.09s , -74d 51m 50.8s) | C | 180 | 18.7 |
106819 | 2023-03-08 21:23:55 | MASTER-SAAO | (03h 03m 53.63s , -76d 38m 21.4s) | C | 60 | 18.5 |
106819 | 2023-03-08 21:23:55 | MASTER-SAAO | (03h 00m 21.60s , -76d 38m 10.8s) | C | 60 | 18.6 |
107112 | 2023-03-08 21:28:48 | MASTER-SAAO | (03h 38m 39.03s , -76d 38m 02.4s) | C | 60 | 18.5 |
107112 | 2023-03-08 21:28:48 | MASTER-SAAO | (03h 35m 05.28s , -76d 37m 50.0s) | C | 60 | 18.5 |
107204 | 2023-03-08 21:30:20 | MASTER-SAAO | (03h 34m 06.25s , -78d 31m 42.8s) | C | 60 | 18.4 |
107204 | 2023-03-08 21:30:20 | MASTER-SAAO | (03h 29m 57.72s , -78d 31m 30.2s) | C | 60 | 18.4 |
107284 | 2023-03-08 21:31:41 | MASTER-SAAO | (04h 14m 36.07s , -78d 32m 15.3s) | C | 60 | 18.5 |
107284 | 2023-03-08 21:31:41 | MASTER-SAAO | (04h 10m 26.79s , -78d 32m 04.8s) | C | 60 | 18.5 |
107714 | 2023-03-08 21:37:50 | MASTER-SAAO | (03h 39m 18.35s , -76d 34m 01.4s) | C | 180 | 18.9 |
107714 | 2023-03-08 21:37:50 | MASTER-SAAO | (03h 35m 45.53s , -76d 33m 46.1s) | C | 180 | 19.0 |
107926 | 2023-03-08 21:41:22 | MASTER-SAAO | (03h 24m 25.90s , -76d 32m 40.7s) | C | 180 | 18.7 |
107926 | 2023-03-08 21:41:22 | MASTER-SAAO | (03h 20m 53.73s , -76d 32m 24.2s) | C | 180 | 18.9 |
108138 | 2023-03-08 21:44:54 | MASTER-SAAO | (03h 24m 23.20s , -76d 33m 24.5s) | C | 180 | 18.7 |
108138 | 2023-03-08 21:44:54 | MASTER-SAAO | (03h 20m 50.60s , -76d 33m 07.7s) | C | 180 | 18.8 |
108349 | 2023-03-08 21:48:25 | MASTER-SAAO | (03h 39m 21.23s , -76d 32m 07.5s) | C | 180 | 18.7 |
108349 | 2023-03-08 21:48:25 | MASTER-SAAO | (03h 35m 48.38s , -76d 31m 51.0s) | C | 180 | 18.9 |
108559 | 2023-03-08 21:51:55 | MASTER-SAAO | (03h 39m 29.26s , -76d 33m 05.1s) | C | 180 | 18.7 |
108559 | 2023-03-08 21:51:56 | MASTER-SAAO | (03h 35m 56.14s , -76d 32m 48.9s) | C | 180 | 18.9 |
108771 | 2023-03-08 21:55:27 | MASTER-SAAO | (03h 38m 53.42s , -74d 34m 06.9s) | C | 180 | 18.6 |
108771 | 2023-03-08 21:55:27 | MASTER-SAAO | (03h 35m 47.35s , -74d 33m 50.3s) | C | 180 | 18.8 |
108982 | 2023-03-08 21:58:58 | MASTER-SAAO | (03h 35m 55.42s , -74d 33m 24.8s) | C | 180 | 18.6 |
108982 | 2023-03-08 21:58:58 | MASTER-SAAO | (03h 39m 01.23s , -74d 33m 41.8s) | C | 180 | 18.5 |
109194 | 2023-03-08 22:02:30 | MASTER-SAAO | (03h 39m 51.43s , -77d 32m 08.3s) | C | 180 | 18.6 |
109194 | 2023-03-08 22:02:30 | MASTER-SAAO | (03h 36m 01.98s , -77d 31m 51.5s) | C | 180 | 18.8 |
109405 | 2023-03-08 22:06:01 | MASTER-SAAO | (03h 36m 04.38s , -77d 33m 31.5s) | C | 180 | 18.8 |
109405 | 2023-03-08 22:06:01 | MASTER-SAAO | (03h 39m 54.39s , -77d 33m 48.0s) | C | 180 | 18.7 |
109617 | 2023-03-08 22:09:33 | MASTER-SAAO | (03h 49m 04.44s , -77d 31m 38.2s) | C | 180 | 18.7 |
109617 | 2023-03-08 22:09:33 | MASTER-SAAO | (03h 52m 54.28s , -77d 31m 54.1s) | C | 180 | 18.7 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 33427
Subject
Konus-Wind detection of GRB 230307A
Date
2023-03-08T21:50:47Z (3 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
D. Svinkin, D. Frederiks, M. Ulanov, A. Tsvetkova,
A. Lysenko, A. Ridnaia, and T. Cline
on behalf of the Konus-Wind team, report:
The very intense, long-duration GRB 230307A
(Fermi-GBM detection: the Fermi GBM team, GCN Circ. 33405;
Dalessi, GCN Circ. 33407; Dalessi and Roberts, GCN Circ. 33411;
GECAM detection: Xiong et al., GCN Circ. 33406;
Solar Orbiter STIX detection: Xiao and Krucker, GCN Circ. 33410;
AGILE-MCAL detection: Casentini et al., GCN Circ. 33412;
IPN triangulation: Kozyrev et al., GCN Circ. 33413 and 33425;
AstroSat CZTI detection: Navaneeth et al., GCN Circ. 33415;
GRBAlpha detection: Dafcikova et al., GCN Circ. 33418;
VZLUSAT-2 detection: Ripa et al., GCN Circ. 33424)
triggered Konus-Wind at T0=56645.615 s UT (15:44:05.615).
The burst light curve shows a multipeaked structure
which starts at ~T0 and has a total duration of ~196 s.
The emission is seen up to ~10 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB230307_T56645/
As observed by Konus-Wind, the burst
had a fluence of 3.58(-0.08,+0.08)x10^-3 erg/cm2,
and a 64-ms peak flux, measured from T0+6.224 s,
of 6.66(-0.42,+0.46)x10^-4 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst
(measured from T0 to T0+71.424 s)
is best fit in the 530 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.60(-0.08,+0.08)
and Ep = 1000(-16,+15) keV (chi2 = 41/42 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -5.4
(chi2 = 41/41 dof).
The spectrum near the maximum count rate
(measured from T0+6.144 to T0+6.400 s)
is best fit in the 530 keV - 10 MeV range
by a power law with exponential cutoff model:
with alpha = -0.13(-0.31,+0.35)
and Ep = 1321(-62,+60) keV (chi2 = 19/21 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -4.3
(chi2 = 19/20 dof).
The energy fluence of the burst is the second highest
(after BOAT GRB 221009A) and the energy peak flux is the 5th highest
observed for GRBs for almost 28 years of the KW operation.
This supports the results reported in Burns et al., GCN Circ. 33414.
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
GCN Circular 33425
Subject
Improved IPN localization for GRB 230307A
Date
2023-03-08T20:16:29Z (3 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin
on behalf of the HEND/Mars Odyssey team,
D. Svinkin, D. Frederiks, A. Ridnaia, A. Lysenko,
and T. Cline on behalf of the Konus-Wind team,
A. Goldstein, M. S. Briggs, C. Wilson-Hodge,
and E. Burns on behalf of the Fermi GBM team,
E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT team,
and
W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr,
and A.S. Gardner on on behalf of the GRS-Odyssey GRB team,
report:
Using the Konus-Wind data we have triangulated GRB 230307A
(GCNs 33405, 33406, 33407, 33410, 33411, 33412, 33413, 33414,
33415, 33416, 33418, 33424)
to the 3 sigma error box whose coordinates are:
---------------------------------------------
RA(2000), deg Dec(2000), deg
---------------------------------------------
Center:
60.819 (04h 03m 17s) -75.379 (-75d 22' 43")
Corners:
61.075 (04h 04m 18s) -75.436 (-75d 26' 10")
61.016 (04h 04m 04s) -75.358 (-75d 21' 29")
60.565 (04h 02m 16s) -75.321 (-75d 19' 14")
60.622 (04h 02m 29s) -75.399 (-75d 23' 56")
---------------------------------------------
The error box area is 30 sq. arcmin, and its maximum
dimension is 10 arcmin (the minimum one is 4.2 arcmin).
The Sun distance was 80 deg.
This box may be further improved.
The Swift ToO is ongoing.
An updated triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB230307_T56646/IPN
GCN Circular 33424
Subject
GRB 230307A: VZLUSAT-2 detection
Date
2023-03-08T18:13:06Z (3 years ago)
From
Jakub Ripa at Masaryk University <245487@mail.muni.cz>
J. Ripa (Masaryk U.), M. Dafcikova, A. Pal (Konkoly Observatory), N.
Werner�� (Masaryk U.), M. Ohno (Hiroshima U.),�� L. Meszaros, B. Csak
(Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M.
Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec,
J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo
(Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida
(ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K.
Hirose, H. Matake (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe
(Rikkyo U.), L. L. Kiss (Konkoly Observatory),�� T. Mizuno (Hiroshima
U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), K. Torigoe
(Hiroshima U.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes
(VZLU), I. Vertat (FEL ZCU)�� -- the VZLUSAT-2/GRB payload collaboration.
The extremely bright long-duration GRB 230307A (Fermi/GBM detection: GCN
33405, 33407, 33411, 33414; GECAM-B detection: GCN 33406; Solar Orbiter
STIX detection: GCN 33410; AGILE/MCAL detection: GCN 33412; IPN
triangulation: GCN 33413; AstroSat detection: GCN 33415; BALROG
localization: GCN 33416; GRBAlpha detection: GCN 33418) was detected by
the GRB detectors on board of the VZLUSAT-2 3U CubeSat
(https://www.vzlusat2.cz/en/).
The data acquisition was performed by GRB detector units no. 0 and no.
1. The detection was confirmed at the peak time 2023-03-07 15:44:11 UTC.
The T90 duration measured by VZLUSAT-2 is 28 s (34 s) and the
significance during T90 reaches 219 sigma (213 sigma) for detector unit
no. 0 (no. 1).
The light curves obtained by VZLUSAT-2 is available here:
https://vzlusat2.konkoly.hu/static/share/GRB230307A_GCN_VZLUSAT2.pdf
All VZLUSAT-2 detections are listed at:
https://monoceros.physics.muni.cz/hea/VZLUSAT-2/
The GRB detectors on VZLUSAT-2 are a demonstration payload for a future
CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules
of VZLUSAT-2 are placed in a perpendicular manner and each consists of a
75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the
energy range from ~40 keV to ~1000 keV. VZLUSAT-2 was launched on 2022
January 13 from Cape Canaveral.
GCN Circular 33419
Subject
GRB 230307A: Tiled Swift observations
Date
2023-03-08T12:57:43Z (3 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a series of observations, tiled on the sky, of the
Fermi/GBM GRB 230307A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00110
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the Fermi/GBM event is high: any X-ray source
considered to be a probable afterglow candidate will be reported via a GCN Circular
after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
GCN Circular 33418
Subject
GRB 230307A: Detection by GRBAlpha
Date
2023-03-08T11:23:01Z (3 years ago)
From
Marianna Dafcikova at Masaryk University <500025@mail.muni.cz>
M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner
(Masaryk U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, B. Csak
(Konkoly Observatory), N. Husarikova, F. Munz , M. Topinka, M. Kolar, J.-P.
Breuer, F. Hroch (Masaryk U.), T. Urbanec, M. Kasal, A. Povalac (Brno U.
of Technology), J. Hudec, J. Kapus, M. Frajt (Spacemanic s.r.o), R. Laszlo,
M. Koleda (Needronix s.r.o), M. Smelko, P. Hanak, P. Lipovsky (Technical U.
of Kosice), G. Galgoczi (Wigner Research Center/Eotvos U.), Y. Uchida, H.
Poon, H. Matake (Hiroshima U.), N. Uchida (ISAS/JAXA), T. Bozoki (Eotvos
U.), G. Dalya (Eotvos U.), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), G.
Friss (Eotvos U.), Y. Fukazawa, K. Hirose (Hiroshima U.), S. Hisadomi
(Nagoya U.), Y. Ichinohe (Rikkyo U.), K. Kapas (Eotvos U.), L. L. Kiss
(Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.),
H. Odaka (Univ of Tokyo), J. Takatsy (Eotvos U.), K. Torigoe (Hiroshima
U.), N. Kogiso, M. Yoneyama (Osaka Metropolitan U.), M. Moritaki (U.
Tokyo), T. Kano (U. Michigan) -- the GRBAlpha collaboration.
The extremely bright long-duration GRB 230307A (Fermi/GBM detection: GCN
33405, 33407, 33411, 33414; GECAM-B detection: GCN 33406; Solar Orbiter
STIX detection: GCN 33410; AGILE/MCAL detection: GCN 33412; IPN
triangulation: GCN 33413; AstroSat detection: GCN 33415; BALROG
localization: GCN 33416) was observed by the GRBAlpha 1U CubeSat (Pal et
al. Proc. SPIE 2020).
The detection was confirmed at the peak time 2023-03-07 15:44:12 UTC. The
T90 duration measured by GRBAlpha is 25 s and the overall significance
during T90 reaches 305 sigma. GRBAlpha entered the outer Van Allen
radiation belt during the tail part of the burst.
The peak count rate detected by GRBAlpha reaches almost 10 000 counts/s,
which is nearly half of the peak count rate of 22 000 counts/s measured for
GRB221009A.
The light curve obtained by GRBAlpha is available here:
https://grbalpha.konkoly.hu/static/share/GRB230307A_GCN.pdf
All GRBAlpha detections are listed at:
https://monoceros.physics.muni.cz/hea/GRBAlpha/
GRBAlpha, launched on 2021 March 22, is a demonstration mission for a
future CubeSat constellation (Werner et al. Proc. SPIE 2018). The detector
of GRBAlpha consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a
SiPM array, covering the energy range from ~50 keV to ~1000 keV. To
increase the duty cycle and the downlink rate, the upgrade of the on-board
data acquisition software stack is in progress. The ground segment is also
supported by the radio amateur community and it takes advantage of the
SatNOGS network for increased data downlink volume.
GCN Circular 33416
Subject
GRB 230307A: BALROG localization (Fermi Trigger 699896651/ GRB 230307656)
Date
2023-03-08T09:20:58Z (3 years ago)
From
Jochen Greiner at MPE,Garching <jcg@mpe.mpg.de>
B. Biltzinger, F. Kunzweiler, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
699896651 at 15:44:06 on 07 March 2023 were fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).
The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 41.8+/-0.4 deg
Decl.(2000.0) = -71.5+/-0.1 deg
We estimate an additional systematic error of 2 deg.
The position is in agreement with the IPN localization (GCN Circ. 33413).
We note that the determined localization is close to the Earth horizon, which could be an additional source of systematic errors.
Further details are available at:
https://grb.mpe.mpg.de/grb/GRB230307656/?data_version=h01
The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/media/data/GRB230307656/data_files/230308_090913782213_GRB230307656_healpixSysErr_trigdat_h01.fits
The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB230307656/json
GCN Circular 33415
Subject
GRB 230307A: AstroSat CZTI detection
Date
2023-03-08T06:17:52Z (3 years ago)
From
Gaurav Waratkar at IIT,Bombay <gauravwaratkar@iitb.ac.in>
P K. Navaneeth (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V.
Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao
(IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat
CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al.,
2021, JApA, 42, 73) showed the detection of the extremely bright long
GRB 230307A which was also detected by Fermi-GBM (Fermi GBM team, GCN
33405), GECAM (Xiong et al., GCN 33406), Solar Orbiter STIX (Xiao et
al., GCN 33410), AGILE/MCAL (Casentini et al., GCN 33412) and IPN
(Kozyrev et al., GCN 33413).
The source was clearly detected in the 20-200 keV energy range. The
light curve showed multiple peaks of emission with the strongest peak at
2023-03-07 15:44:10.0 UTC. The measured peak count rate associated with
the burst is 4041 (+33, -37) counts/s above the background in the
combined data of all quadrants, with a total of 90900 (+758, -850)
counts. The local mean background count rate was 453 (+1, -1) counts/s.
Using cumulative rates, we measure a T90 of 33 (+1, -1) s. In the
preliminary analysis, we find 5484 Compton events associated with this
event.
It was also clearly detected in the CsI anticoincidence (Veto) detector
in the 100-500 keV energy range. The light curve showed multiple peaks
of emission with the strongest peak at 2023-03-07 15:44:15.17 UTC. The
measured peak count rate is 276156 (+268, -300) counts/s above the
background in the combined Veto data of all quadrants, with a total of
5571313 (+4953, -6044) counts. The local mean background count rate was
14750 (+7, -6) counts/s. We measure a T90 of 40 (+0.2, -0.2) s from the
cumulative Veto light curve.
CZTI is built by a TIFR-led consortium of institutes across India,
including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research
Organisation funded, managed, and facilitated the project. CZTI GRB
detections are reported regularly on the payload site at:
http://astrosat.iucaa.in/czti/?q=grb
GCN Circular 33414
Subject
GRB 230307A: possibly the second highest GRB energy fluence ever identified
Date
2023-03-08T05:41:31Z (3 years ago)
From
Eric Burns at LSU <erickayserburns@gmail.com>
E. Burns (LSU), A. Goldstein (USRA), S. Lesage (UAH), and S. Dalessi (UAH)
report on behalf of the Fermi-GBM Team.
The very bright long GRB 230307A has been detected by many prompt GRB
monitors (GCN Circ. 33405; Dalessi, GCN Circ. 33407; Dalessi and Roberts,
GCN Circ. 33411; GECAM detection: Xiong etal., GCN Circ. 33406; Solar
Orbiter STIX detection: Xiao and Krucker, GCN Circ. 33410; AGILE-MCAL
detection: Casentini et al., GCN Circ. 33412) at 15:44:07.
Fermi-GBM reports a preliminary 10-1000 keV fluence of
(2.951 +/- 0.004)E-03 erg/cm^2 (Dalessi and Roberts, GCNCirc. 33411) with
a best-fit Comptonized spectrum with Epeak = 936 +/- 3 keV and alpha
-1.07 +/- 0.01. Utilizing this spectrum, this corresponds to a bolometric
fluence of 4.56E-3 erg/cm^2, with negligible error.
For reported GRB energy fluence values, only GRB 221009A is higher.
GRB 130427A has a reported fluence of 2.83E-3 erg/cm^2, 840304 of
~2.8E-3 erg/cm^2, and 830801 of >2.0e-3erg/cm^2. Noting that these three
values have some uncertainty due to detector issues and that this initial
value for GRB 230307A is preliminary, from these base values GRB 230307A
has the second highest reported value.
Follow-up is thus strongly encouraged. The best current localization is
from the IPN, reported in GCN 33413.
GCN Circular 33413
Subject
IPN triangulation of GRB 230307A (long/very bright)
Date
2023-03-07T23:33:26Z (3 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin
on behalf of the HEND/Mars Odyssey team,
D. Svinkin, A. Lysenko, A. Ridnaia on behalf of the IPN,
A. Goldstein, M. S. Briggs, C. Wilson-Hodge,
and E. Burns on behalf of the Fermi GBM team,
E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT team,
and
W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr,
and A.S. Gardner on on behalf of the GRS-Odyssey GRB team,
report:
The very bright, long-duration GRB 230307A
(Fermi-GBM detection: the Fermi GBM team, GCN Circ. 33405;
Dalessi, GCN Circ. 33407; Dalessi and Roberts, GCN Circ. 33411;
GECAM detection: Xiong et al., GCN Circ. 33406;
Solar Orbiter STIX detection: Xiao and Krucker, GCN Circ. 33410;
AGILE-MCAL detection: Casentini et al., GCN Circ. 33412)
has been detected by Fermi(GBM trigger 699896651), GECAM,
INTEGRAL (SPI-ACS), Swift (BAT), Solar Orbiter (STIX), AGILE (MCAL),
and Mars-Odyssey (HEND), so far, at about 56647 s UT (15:44:07).
The burst was outside the coded field of view of the BAT.
We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
------------------------------
RA(2000), deg Dec(2000), deg
------------------------------
Center:
59.233 -75.226
Corners:
70.905 -76.077
38.996 -71.948
38.440 -72.064
73.041 -76.146
--------------------------------
The error box area is 1.948 sq. deg, and its maximum
dimension is 9.6 deg (the minimum one is 11.6 arcmin).
The Sun distance was 100 deg.
This box may be improved.
The IPN localization is consistent with, but reduces the area of,
the Fermi-GBM final localization (GCN 33407).
A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB230307_T56646/IPN
GCN Circular 33412
Subject
GRB 230307A: AGILE/MCAL detection
Date
2023-03-07T22:40:47Z (3 years ago)
From
Claudio Casentini at INAF-IAPS <claudio.casentini@inaf.it>
C. Casentini (INAF/IAPS), M. Tavani (INAF/IAPS, and Uni.Roma Tor Vergata),
C. Pittori, F. Lucarelli, F. Verrecchia (SSDC, and INAF/OAR)
A. Argan, M. Cardillo, Y. Evangelista, L. Foffano, G. Piano (INAF/IAPS),
A. Addis, L. Baroncelli, A. Bulgarelli, A. Di Piano, V. Fioretti,
G. Panebianco, N. Parmiggiani (INAF/OAS-Bologna),
F. Longo (Uni. Trieste, INFN Trieste), M. Romani (INAF/OA-Brera),
M. Marisaldi (INAF/OAS-Bologna, Bergen University), M. Pilia,
A. Trois (INAF/OA Cagliari), I. Donnarumma, E. Menegoni, A.Ursi (ASI),
A. Giuliani (INAF/IASF-Mi) and P. Tempesta (TeleSpazio),
report on behalf of the AGILE Team:
The AGILE satellite detected the long GRB 230307A at
T0 = 2023-03-07 15:44:06 (UTC), reported by Fermi/GBM (GCN #33405 and
GCN #33407), GECAM (GCN #33406) and Stix (GCN #33410).
The burst is clearly visible in the AGILE scientific ratemeters of the
MiniCALorimeter (MCAL; 0.4-100 MeV), and in all the panels of the
AntiCoincidence detectors (AC Top, 50-200 keV; AC Lat, 80-200 keV).
The event lasted about 30 s and it released a total number of 527069 counts
in the MCAL detector (above a background rate of 1154 Hz), and 920952 counts
in the AC Top detector (above a background rate of 2959 Hz).
The AGILE ratemeters light curves can be found at:
http://www.agilescienceapp.it/notices/GRB230307A_AGILE_RM_ND.png .
The event also triggered a high-time resolution MCAL data acquisition,
from T0 to T0+22 s (UTC), and released 241403 counts in the detector,
above a background rate of 510 Hz. The MCAL light curve can be found at:
http://www.agilescienceapp.it/notices/GRB230307A_082567_605288646.000000.png
.
At the T0, the event was 54 deg off-axis.
Additional analysis of AGILE data is in progress.
Automatic MCAL GRB alert Notices can be found at:
https://gcn.gsfc.nasa.gov/agile_mcal.html
GCN Circular 33411
Subject
GRB 230307A: Fermi GBM Observation of a very bright burst
Date
2023-03-07T22:31:41Z (3 years ago)
From
Sarah Dalessi at UAH <sd0104@uah.edu>
S. Dalessi(UAH), O.J. Roberts (USRA), and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:
"At 15:44:06.67 UT on 07 March 2023, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 230307A (trigger 699896651 / 230307656). This burst
was also detected by Solar Orbiter STIX (Xiao et al. 2023, GCN 33410), and
GECAM (Xiong et al. 2023, GCN 33406). The Fermi GBM Final Real-time
Localization (GBM team 2023, GCN 33405) is consistent with the GECAM position.
The angle from the Fermi LAT boresight at the GBM trigger time is 142.0 degrees.
The GBM light curve consists of a single burst with a duration (T90)
of about 35 s (10-1000 keV). The time-averaged spectrum
from T0 to T0+148 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.07 +/- 0.01 and the cutoff energy,
parameterized as Epeak, is 936 +/- 3 keV.
The event fluence (10-1000 keV) in this time interval is
(2.951 +/- 0.004)E-03 erg/cm^2. The 1s peak photon flux measured
starting from T0+5.8 s in the 10-1000 keV band is 791 +/- 4 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 33410
Subject
Solar Orbiter STIX observation of GRB 230307A
Date
2023-03-07T20:59:04Z (3 years ago)
From
Hualin Xiao at FHNW <hualin.xiao@fhnw.ch>
Hualin Xiao, S�m Krucker on behalf of the STIX team report:
At 2023-03-07T15:44:09Z UT (Solar Orbiter onboard time), STIX detected GRB 230307A, when Solar Orbiter was 0.53 AU from the earth. The one-way light time between the earth and the Solar Orbiter was 264.46 sec.
The gamma-ray burst signal can be clearly seen in the STIX quick-look light curves in the range between 10 - 84 keV. The GRB has a single peak and a duration of about 40 seconds.
The STIX light curves for this GRB can be found here:
https://datacenter.stix.i4ds.net/view/plot/lightcurves?start=1678203251&span=1200
By using the light time difference information, we also estimated the possible locations of the GRB.
The result can be found here:
https://datacenter.stix.i4ds.net/pub/GRB/GRB230307A/GRB230307A_loc.png
The analysis results presented above are preliminary. The science data will only be down-linked from the instrument in a month or two. Detailed analysis of the event will be started after downloading the science data.
The Solar Orbiter (SolO) is a Sun-observing satellite developed by the European Space Agency, it was launched on 10th Feb. 2020. It has a unique elliptical orbit around the sun, with distances varying from 0.3 - 1 AU. The Spectrometer Telescope for Imaging X-rays (STIX) is one of the ten instruments onboard the Solar Orbiter. It measures X-rays emitted during solar flares in the energy range of 4 � 150 keV and takes X-ray images by using an indirect imaging technique, based on the Moir� effect. Its detectors consist of thirty-two pixelated CdTe detectors with a total effective area of 6 cm^2.
More information about STIX can be found on the STIX data center website: https://datacenter.stix.i4ds.net/
GCN Circular 33407
Subject
GRB 230307A: Fermi GBM detection of a very bright GRB
Date
2023-03-07T17:10:32Z (3 years ago)
From
Sarah Dalessi at UAH <sd0104@uah.edu>
S. Dalessi(UAH)
report on behalf of the Fermi GBM Team:
"At 15:44:06.67 UT on 07 March 2023, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 230307A (trigger 699896651 / 230307656).
This event is one of the brightest among the GBM detected
GRBs. Follow-up across all wavelengths is encouraged.
The on-ground calculated location, using the GBM trigger
data, is RA = 54.06, DEC = -76.61 (J2000 degrees,
equivalent to J2000 03h 36m, -76d 35'), with a statistical uncertainty
of 1 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which we have characterized as a core-plus-tail model, with 90% of
GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg
systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ).
The angle from the Fermi LAT boresight at the GBM trigger time is 142.0 degrees.
A full GCN of the Fermi-GBM analysis of this event will follow in a
later GCN, once the data has become available.
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 33406
Subject
GRB 230307A: GECAM detection of an extremely bright burst
Date
2023-03-07T16:53:45Z (3 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
Shaolin Xiong, Chenwei Wang, Yue Huang, report on behalf of the GECAM team:
GECAM-B was triggered in-flight by the extremely bright long burst at
2023-03-07T15:44:06.650 UTC (T0), which was also observed by Fermi/GBM
(GCN 33405).
The GECAM-B ground calculated location (J2000) is:
R.A.: 28.03 [deg]
Dec.: -81.51 [deg]
Error: 1 [deg] (1-sigma, statistical only)
The systematic error of this location is estimated to be ~2 degrees.
This GECAM location is consistent with the Fermi/GBM one within error.
The GECAM-B light curve shows a roughly FRED shape with a possible
precursor, with a total duration of ~100 sec. The time-averaged spectrum
analysis on the trigger alert data shows this burst has a fluence of
about 1E-3 erg/cm2 in 20-1000 keV, which is notably high, and comparable
to GRB 130427A. We caution that this analysis is very preliminary.
Refined analysis will be reported later.
Follow-up observations are encouraged.
GCN Circular 33405
Subject
GRB 230307A: Fermi GBM Final Real-time Localization
Date
2023-03-07T15:54:24Z (3 years ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
The Fermi GBM team reports the detection of a likely LONG GRB
At 15:44:06 UT on 7 Mar 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 230307A (trigger 699896651.671248 / 230307656).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 54.1, Dec = -76.6 (J2000 degrees, equivalent to J2000 03h 36m, -76d 35'), with a statistical uncertainty of 1.0 degrees.
The angle from the Fermi LAT boresight is 142.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230307656/quicklook/glg_skymap_all_bn230307656.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230307656/quicklook/glg_healpix_all_bn230307656.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230307656/quicklook/glg_lc_medres34_bn230307656.gif