GRB 230906A
GCN Circular 34704
Subject
GRB 230906A: optical counterpart
Date
2023-09-15T21:21:52Z (2 years ago)
From
corinna.pena@utah.edu
Via
Web form
C. Peña (Univ. of Utah), D. B. Malesani (Radboud univ. and DAWN/NBI), A. Rossi (INAF), A. J. Levan (Radboud univ.), and G. Pugliese (API, Amsterdam), report on behalf of the Stargate collaboration:
Following the Chandra X-ray localization (O’Connor et al., GCN 34672) of the Fermi/GBM short GRB 230906A (Fermi GBM team, GCN 34631; Frederiks et al., GCN 34638), we observed the GRB afterglow with the ESO Very Large Telescope equipped with the HAWK-I near infrared camera and with the FORS2 optical camera. Observations in the HAWK-I Ks band consisted in 30 minute exposure with a mean time of 6.84 days after the GRB. Observations in the FORS2 R band consisted in 40 minute exposure with a mean time of 6.76 days after the GRB. Sky conditions were modest, with a delivered seeing of ~2" in the R band.
Consistent with the position of the X-ray afterglow discovered by Chandra (O’Connor et al., GCN 34672), we detect a weak source in the stacked R-band image, at J2000 coordinates (~0.5" error):
RA = 05:19:01.57
Dec = -47:53:32.3
We measure for this source an AB magnitude R = 25.44 ± 0.25, calibrated against nearby SkyMapper stars. In the Ks band, we can only set an upper limit with AB magnitude > 23.3. As noted by O’Connor et al. (GCN 34672), there is no detected host galaxy in the Legacy Survey, which has however a depth shallower than our measurement.
While the spatial association with the X-ray counterpart suggests a physical connection with the GRB, it is unclear whether the source is dominated by transient light or is a faint host galaxy. We note that the R-K color is not as red as was AT 2017gfo at a comparable epoch after explosion (e.g. Villar et al. 2017, ApJ, 851, L21).
We acknowledge the support of the observing staff at Paranal, in particular Ana Escorza, Linda Schmidtobreick, and Fuyan Bian.
GCN Circular 34672
Subject
GRB 230906A: Chandra detection of the X-ray afterglow
Date
2023-09-11T23:51:20Z (2 years ago)
From
Brendan O'Connor at CMU <oconnorb@umd.edu>
Via
Web form
B. O'Connor (CMU), S. Dichiara (PSU), E. Troja (UTV), report on behalf of a larger collaboration:
We carried out a Chandra Target of Opportunity (ToO) observation of the IPN localized short GRB 230906A (Fermi GBM team, GCN 34631; Kozyrev et al., GCN 34637) under program 24500202 (PI: S. Dichiara). We used the ACIS-S camera with a total exposure of 19.8 ks beginning on 2023-09-11 04:58:29 UT, corresponding to ~4.7 days after the initial trigger.
At the location of the Swift XRT candidate afterglow (Beardmore et al., GCN 34639) uncovered during tiled observations of the IPN localization (Evans et al., GCN 34636), we detect a clear X-ray source at the North-East edge of the XRT localization. The source is located at
RA, DEC = 05:19:01.52, -47:53:32.66
with an uncertainty of 0.8" (systematic + statistical). The source shows signs of fading compared to previous XRT observations. We note that there is no obvious host galaxy at this location in the Legacy Survey, although multiple sources exist within a few arcseconds.
We would like to thank Patrick Slane, Harvey Tananbaum, Dan Schwartz, Jack Steiner, Brad Wargelin, and the entire CXO staff for rapidly approving and planning this observation.
GCN Circular 34651
Subject
GRB 230906A: BlackGEM upper limits
Date
2023-09-10T15:28:47Z (2 years ago)
From
Simon de Wet at University of Cape Town <simdewet@gmail.com>
Via
Web form
S. de Wet (UCT), D. Pieterse (Radboud), P.J. Groot (Radboud/UCT/SAAO) and P.M. Vreeswijk (Radboud) report on behalf of the BlackGEM consortium:
Following the IPN localisation of the short GRB 230906A (Fermi GBM team, GCN 34631) by the Interplanetary Network (Kozyrev et al., GCN 34637), the BlackGEM Unit Telescope 3 (BG3-Opal) located at ESO La Silla, Chile, obtained 2 x 300 s exposures in the q-band (440-720 nm) of the IPN triangulation region. The first observation started at 08:00:42 UT on 2023 September 7, 19.1 hours after the Fermi GBM trigger.
We detect no new transients within the IPN triangulation error region nor at the position of the Swift XRT source (Beardmore et al., GCN 34639) down to a 5-sigma limiting AB magnitude of q=21.53, consistent with the upper limits reported by Swift/UVOT (Oates and Moss, GCN 34643). The depth of our images was negatively affected by ~3 arcsecond seeing.
BlackGEM is an array of wide-field telescopes designed, built and operated by a consortium consisting of Radboud University, the Netherlands Research School for Astronomy NOVA, KU Leuven, the University of Manchester, Tel Aviv University, the Weizmann Institute, the Hebrew University of Jerusalem, the University of Potsdam, Texas Tech University, the University of California at Davis, the Danish Technical University and the Armagh Observatory and Planetarium.
GCN Circular 34649
Subject
GRB 230906A: AstroSat CZTI detection
Date
2023-09-10T05:39:19Z (2 years ago)
From
Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in>
Via
Web form
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 short GRB 230906A which was also detected by Fermi (Fermi GBM team, GCN Circ. 34631), Konus-Wind (Frederiks et al., GCN Circ. 34638) with IPN localization (Kozyrev et al., GCN Circ. 34637).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed a multi-peak structure that peaked at 2023-09-06 12:55:07.82 UTC. The measured peak count rate associated with the burst is 3406 (+1081, -773) counts/s above the background in the combined data of all quadrants, with a total of 163 (+35, -34) counts. The local mean background count rate was 545 (+43, -67) counts/s. Using cumulative rates, we measure a T90 of 0.09 (+0.03, -0.03) s.
The source was also clearly detected in the CsI anticoincidence (Veto) detectors in the 100-500 keV energy range. The light curve peaks at 2023-09-06 12:55:07.01 UTC. The measured peak count rate associated with the burst is 1048 (+81, -90) counts/s above the background in the combined data of all quadrants, with a total of 823 (+634, -729) counts. The local mean background count rate was 1430 (+7, -8) counts/s. Due to the intrinsic 1 s binning of Veto data, we cannot reliably estimate a T90 from it.
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 34643
Subject
GRB 230906A: Swift/UVOT Upper Limits
Date
2023-09-09T10:53:16Z (2 years ago)
From
Samantha Oates at University of Birmingham <samantha.oates@alumni.ucl.ac.uk>
Via
email
S. R. Oates (Lancaster U. ) and M. J. Moss (GSFC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 230906A
93 ks after IPN-detection (Kozyrev et al., GCN Circ 34637). No optical
afterglow consistent with the XRT position (Beardmore et al., GCN
Circulars 34639), 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 93297 106009 4648 >22.8
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.021 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 34639
Subject
GRB 230906A: Swift-XRT observations
Date
2023-09-07T23:22:03Z (2 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
legacy email
A.P. Beardmore (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), J.P. Osborne (U. Leicester) and P.A. Evans
(U. Leicester) reports on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the IPN-detected
burst GRB 230906A (Kozyrev et al., GCN Circ 34637), collecting 4.7 ks
of Photon Counting (PC) mode data between T0+93.0 ks and T0+106.0 ks.
One uncatalogued X-ray source has been detected, it is below the RASS
limit and shows no definitive signs of fading. Therefore, at the
present time we cannot confirm this as the afterglow. Details of this
source are given below:
Source 1:
RA (J2000.0): 79.7533 = 05:19:0.79
Dec (J2000.0): -47.8930 = -47:53:34.9
Error: 6.4 arcsec (radius, 90% conf.)
Count-rate: (1.73 [+0.88, -0.67])e-3 ct s^-1
Distance: 23 arcsec from IPN position.
The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
https://www.swift.ac.uk/ToO_GRBs/00021621.
This circular is an official product of the Swift-XRT team.
GCN Circular 34638
Subject
Konus-Wind detection of GRB 230906A (short)
Date
2023-09-07T16:26:29Z (2 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
Via
legacy email
D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin,
A. Tsvetkova, M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:
The short GRB 230906A (Fermi GBM detection: the Fermi GBM team, GCN Circ 34631;
IPN triangulation: Kozyrev et al., GCN Circ 34637)
triggered Konus-Wind (KW) at T0=46507.186 s UT (12:55:07.186).
The burst light curve shows a multi-peaked structure
which starts at ~T0-0.256 s and has a duration of ~0.29 s.
The emission is seen up to ~2 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB230906_T46507/
As observed by Konus-Wind, the burst had
a total fluence of (2.55 ± 0.23)x10^-6 erg/cm^2 and
a 16-ms peak energy flux, measured from T0,
of (3.48 ± 0.34)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The spectrum of the burst (measured from T0 to T0+0.128 s)
is best fit in the 20 keV - 15 MeV range by a power law with exponential
cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.56(-0.13,+0.14) and Ep = 522(-56,+65) keV (chi2 = 27/35 dof).
Fitting this spectrum by a Band function yields the same values of alpha and Ep,
and an upper limit on the high energy photon index beta of -2.1 (chi2 = 27/34 dof).
All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.
GCN Circular 34637
Subject
IPN triangulation of GRB 230906A (short)
Date
2023-09-07T14:58:27Z (2 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
Via
legacy email
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. Lysenko, A. Ridnaia,
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,
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 bright, short-duration GRB 230906A
(Fermi-GBM detection: The Fermi GBM team, GCN Circ. 34631)
was detected by Fermi (GBM trigger 715697712), INTEGRAL (SPI-ACS),
Konus-Wind, and Mars-Odyssey (HEND) at about 46507 s UT (12:55:07).
We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
---------------------------------------------
RA(2000), deg Dec(2000), deg
---------------------------------------------
Center:
79.757 (05h 19m 02s) -47.887 (-47d 53' 13")
Corners:
79.710 (05h 18m 50s) -47.945 (-47d 56' 41")
79.748 (05h 19m 00s) -47.986 (-47d 59' 08")
79.803 (05h 19m 13s) -47.829 (-47d 49' 45")
79.765 (05h 19m 04s) -47.788 (-47d 47' 17")
---------------------------------------------
The error box area is 20 sq. arcmin, and its maximum
dimension is 12 arcmin (the minimum one is 2 arcmin).
The Sun distance was 91 deg.
The IPN localization is consistent with, but reduces the area of,
the Fermi-GBM final localization (glg_healpix_all_bn230715190_v00).
Swift ToO has been submitted (GCN 34636).
This localization may be improved.
A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB230906_T46507/IPN/
The Konus-Wind time history and spectrum will be given
in a forthcoming GCN Circular.
GCN Circular 34636
Subject
GRB 230906A: Swift ToO observations
Date
2023-09-07T14:44:50Z (2 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the IPN GRB 230906A.
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021621
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the IPN event. 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 34634
Subject
Fermi GRB 230906A: Global MASTER-Net observations report
Date
2023-09-07T03:30:54Z (2 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
legacy email
V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik, D. Vlasenko,
G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij
(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. Gress, N.M. Budnev, O.Ershova
(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),
V. Yurkov, A. Gabovich
(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 230906A ( Fermi GBM team, GCN 34631) errorbox 30270 sec after notice time and 30304 sec after trigger time at 2023-09-06 21:20:11 UT, with upper limit up to 18.4 mag. The observations began at zenith distance = 79 deg. The sun altitude is -58.8 deg.
The galactic latitude b = -34 deg., longitude l = 254 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2266531
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
30334 | 2023-09-06 21:20:11 | MASTER-SAAO | (05h 00m 24.99s , -46d 27m 50.7s) | C | 60 | 18.0 |
30505 | 2023-09-06 21:23:02 | MASTER-SAAO | (05h 12m 37.40s , -50d 13m 19.5s) | C | 60 | 18.3 |
30755 | 2023-09-06 21:27:12 | MASTER-SAAO | (05h 11m 27.14s , -48d 21m 19.4s) | C | 60 | 18.4 |
30835 | 2023-09-06 21:28:32 | MASTER-SAAO | (05h 23m 34.07s , -48d 20m 18.0s) | C | 60 | 18.1 |
30927 | 2023-09-06 21:30:03 | MASTER-SAAO | (05h 23m 47.74s , -50d 14m 12.7s) | C | 60 | 18.2 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 34631
Subject
GRB 230906A: Fermi GBM Final Localizationn
Date
2023-09-06T15:07:02Z (2 years ago)
From
Elisabetta Bissaldi at Politecnico and INFN Bari <elisabetta.bissaldi@ba.infn.it>
Via
email
The Fermi GBM team reports the detection of a likely SHORT GRB
"At 12:55:07.15 UT on 06 September 2023, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 230906A (trigger 715697712/230906538).
The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 81.37, Dec = -47.41 (J2000 degrees, equivalent to J2000 05h 25m, -47d 24'),
with a statistical uncertainty of 2.79 degrees.
The angle from the Fermi LAT boresight is 55.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230906538/quicklook/glg_skymap_all_bn230906538.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/bn230906538/quicklook/glg_healpix_all_bn230906538.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230906538/quicklook/glg_lc_medres34_bn230906538.gif "