GRB 240912A
GCN Circular 37978
Subject
GRB 240912A: radio detection with the VLA
Date
2024-10-30T17:05:06Z (a year ago)
From
Stefano Giarratana at INAF-OAB <s.giarratana@ira.inaf.it>
Via
email
S. Giarratana (INAF-OAB), M. Giroletti (INAF-IRA),
G. Ghirlanda (INAF-OAB), N. Di Lalla (Stanford Univ.),
N. Omodei (Stanford Univ.), O. S. Salafia (INAF-OAB)
At 16:50:36 UT on 2024 Oct 8 (T_mid = 26.7 days post-burst)
the Karl G. Jansky VLA observed the field of GRB 240912A
(Fermi GBM team, GCN 37465; Evans et al., GCN 37466; Pawar
et al., GCN 37473; SVOM team, GCN 37484; Konus-Wind team,
GCN 37624) in three bands, with central frequencies of 6,
10 and 15 GHz.
The standard 3C286 was used as bandpass and flux density
calibrator, while J0815+3635 was used as phase calibrator.
From a preliminary analysis, an unresolved radio source
is clearly detected at a position:
RA: 08:18:32.389 +- 0.001
Dec: 33:59:56.13 +- 0.02
consistent with the optical (Evans et al., GCN 37466)
and X-ray (Goad et al., GCN 37470) transient.
The preliminary analysis yields the following results:
+-----------+-----------------------+--------------+-----------+-----------+
| Frequency | Peak surf. brightness | r.m.s. noise | Beam size | Beam P.A. |
| (GHz) | (uJy/beam) | (uJy/beam) | arcsec^2 | deg |
+-----------+-----------------------+--------------+-----------+-----------+
| 6 | 171 | 8 | 1.34x0.28 | 60 |
| 10 | 138 | 7 | 0.93x0.17 | 57 |
| 15 | 128 | 7 | 0.54x0.12 | 62 |
+-----------+-----------------------+--------------+-----------+-----------+
No source is detected with a >3sigma confidence at the
aforementioned position in previous radio surveys (FIRST,
VLASS, RACS), all of which have r.m.s. noise levels above
100 uJy/b.
We would like to thank the staff of the VLA for approving, executing,
and processing the observations.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc.
These observations were carried out as part of project SF171028,
approved in the framework of the Fermi - NRAO joint program agreement.
GCN Circular 37624
Subject
Konus-Wind detection of GRB 240912A
Date
2024-09-29T14:14:30Z (a year ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
Via
Web form
D. Svinkin, D. Frederiks, M. Ulanov, A. Tsvetkova,
A. Lysenko, A. Ridnaia, and T. Cline
on behalf of the Konus-Wind team, report:
The long-duration GRB 240912A
(Fermi-GBM detection: The Fermi GBM Team, GCN 37465;
Smith and Meegan, GCN 37478;
Swift-BAT detection: Evans et al., GCN 37466;
Parsotan et al., GCN 37539;
INTEGRAL-SPI-ACS detection: Pawar et al., GCN 37473;
SVOM-GRM detection: Zheng et al., GCN 37484)
triggered Konus-Wind at T0 = 6454.746 s UT (01:47:34.746).
The burst light curve shows a multipeaked structure
which starts at ~T0-60 s and has a total duration of ~118 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/GRB240912_T06454/
As observed by Konus-Wind, the burst
had a fluence of 9.57(-0.96,+0.88)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+2.496 s,
of 7.32(-1.90,+1.87)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst
(measured from T0 to T0+60.928 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.36(-0.11,+0.12),
the high energy photon index beta = -2.44(-0.54,+0.18),
the peak energy Ep = 196(-27,+37) keV
(chi2 = 90/96 dof).
The spectrum near the maximum count rate
(measured from T0+0.256 s to T0+6.144 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.12(-0.15,+0.16),
the high energy photon index beta = -2.59(-7.41,+0.35),
the peak energy Ep = 358(-77,+124) keV
(chi2 = 89/72 dof).
Assuming the redshift z=1.234 (de Ugarte Postigo et al., GCN 37469)
and a standard cosmology 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 4.0(-0.4,+0.4)x10^53 erg,
the peak luminosity L_iso is 6.8(-1.8,+1.7)x10^52 erg/s,
the rest-frame peak energy of the time-averaged spectrum
Ep,i,z is 437(-60,+82) keV, and the spectrum near the maximum count rate
Ep,p,z is 799(-172,+277) keV.
With the obtained estimates, GRB 240912A is inside 68% prediction bands
for 'Amati' and 'Yonetoku' relations, for the sample of >300 long KW
GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021),
see http://www.ioffe.ru/LEA/GRBs/GRB240912_T06454/GRB240912A_rest_frame.pdf
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
GCN Circular 37539
Subject
GRB 240912A: Swift-BAT refined analysis
Date
2024-09-17T23:48:22Z (a year ago)
From
Mike Moss at NASA GSFC <mikejmoss3@gmail.com>
Via
Web form
T. Parsotan (GSFC), S. D. Barthelmy (GSFC),
P. A. Evans (U Leicester), R. Gupta (GSFC),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
M. J. Moss (GSFC), D. M. Palmer (LANL),
D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU)
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 240912A (trigger #1253910)
(P. A. Evans, et al., GCN Circ. 37466). The BAT ground-calculated position is
RA, Dec = 124.625, 33.999 deg which is
RA(J2000) = 08h 18m 29.9s
Dec(J2000) = +33d 59' 56.2"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 86%.
The light curve displays an interval of weak flat emission for ~45 seconds before
a bright multi-pulsed emission period. There is a possible shallow rise of emission
at ~T0+280 seconds coincident with the flare seen in the XRT afterglow.
T90 (15-350 keV) is 113.24 +- 7.83 sec (estimated error including systematics).
The time-averaged spectrum from T-2.35 to T+373.02 sec is best fit by a power law
with an exponential cutoff. This fit gives a photon index 1.43 +- 0.11,
and Epeak of 140.5 +- 41.0 keV (chi squared 27.79 for 56 d.o.f.). For this
model the total fluence in the 15-150 keV band is 3.4 +- 0.0 x 10^-05 erg/cm2
and the 1-sec peak flux measured from T+76.05 sec in the 15-150 keV band is
15.8 +- 0.5 ph/cm2/sec. A fit to a simple power law gives a photon index
of 1.68 +- 0.03 (chi squared 43.74 for 57 d.o.f.). All the quoted errors
are at the 90% confidence level.
The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1253910
GCN Circular 37487
Subject
GRB 240912A: Swift/UVOT Detection
Date
2024-09-13T13:30:34Z (a year ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
Via
Web form
M. H. Siegel (PSU) and P. A. Evans (U. Leicester)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 240912A
115 s after the BAT trigger (Evans et al., GCN Circ. 37466).
A fading source consistent with the XRT position (Goad et al.,
GCN Circ. 37470) is detected in the initial UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 08:18:32.40 = 124.63499 (deg.)
Dec (J2000) = +33:59:56.3 = 33.99897 (deg.)
with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white (fc) 117 265 144 17.44+/-0.05
white 608 1031 186 17.87+/-0.06
white 1185 1379 38 18.06+/-0.16
v 657 1430 97 17.78+/-0.28
b 583 5154 205 19.08+/-0.25
u (fc) 328 577 245 16.68+/-0.05
u 731 5018 274 18.14+/-0.13
uvw1 707 1479 77 17.76+/-0.25
uvm2 1086 1106 19 >17.18
uvw2 633 1406 97 18.47+/-0.30
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.054 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 37484
Subject
GRB 240912A: SVOM/GRM observation
Date
2024-09-13T08:38:52Z (a year ago)
From
Chenwei Wang at IHEP <cwwang@ihep.ac.cn>
Via
Web form
SVOM/GRM team: Chao Zheng, Wen-Jun Tan, Chen-Wei Wang, Wen-Long Zhang, Yong-Wei Dong, Jiang-Tao Liu, Shi-Jie Zheng, Jian-Chao Sun, Yue Huang, Jiang He, Min Gao, Hao-Xuan Guo, Lu Li, Yong-Ye Li, Hong-Wei Liu, Xin Liu, Hao-Li Shi, Li-Ming Song, You-Li Tuo, Hao-Xi Wang, Jin Wang, Jin-Zhou Wang, Ping Wang, Rui-Jie Wang, Yu-Xi Wang, Bo-Bing Wu, Shao-Lin Xiong, Jian-Ying Ye, Yi-Tao Yin, Wen-Hui Yu, Fan Zhang, Li Zhang, Peng Zhang, Shuang-Nan Zhang, Yan-Ting Zhang, Yan-Qiu Zhang, Shu-Min Zhao, Xiao-Yun Zhao (IHEP), Maria-Grazia Bernardini (LUPM/INAF-OAB), Laurent Bouchet (IRAP), David Corre (CEA), Tais Maiolino (LUPM), Frédéric Piron (LUPM), Stéphane Schanne (CEA), Jingwei Wang (IAP)
SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), JeanLuc Attéia (IRAP), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), Andrea Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Bing Zhang (UNLV)
report on behalf of the SVOM team:
During the commissioning phase, the SVOM/GRM was triggered in-flight by a long GRB 240912A (SVOM trigger reference: sb24091203) at 2024-09-12T01:47:37.000 UT (T0), which also triggered Fermi/GBM (Fermi GBM team, GCN 37465), Swift/BAT (Evans et al., GCN 37466) and INTEGRAL SPI ACS (Pawar, GCN 37473).
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple pulses with a duration of about 79 s.
The GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb240912A.png
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.
The SVOM point of contact for this burst is: Chao Zheng (IHEP)(zhengchao97@ihep.ac.cn)
GCN Circular 37480
Subject
GRB 240912A: J-band observations with WINTER
Date
2024-09-12T22:02:51Z (a year ago)
From
Geoffrey Mo at MIT <gmo@mit.edu>
Via
Web form
Geoffrey Mo (MIT), Tomas Ahumada (Caltech), Benjamin Schneider (MIT), Viraj Karambelkar (Caltech), Danielle Frostig (CfA), Robert Stein (Caltech), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report:
We observed the field of GRB 240912A (Fermi GBM Team, GCN 37465; Evans et al., GCN 37466; Pawar et al., GCN 37473; Smith et al., GCN 37478) in the near-infrared J-band with the Palomar 1-m telescope, equipped with the 1 square degree WINTER camera (Lourie et al. 2020).
Observations began at 2024-09-12T10:58:40 UTC (~9.2 hours after the GRB) and consisted of 15 x 120 s exposures. The images were processed using the WINTER data reduction pipeline (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565).
We do not detect a source at the optical and refined Swift/XRT counterpart location (Evans et al., GCN 37466; de Ugarte Postigo et al., GCN 37469; Goad et al., GCN 37470; An et al., GCN 37471; Pérez-Fournon et al., GCN 37476; Lipunov et al., GCN 37477; Burrows et al., GCN 37479). We obtain the following 5-sigma upper limit: J ~ 18.7 mag (AB).
WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucille Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research.
GCN Circular 37479
Subject
GRB 240912A: Swift-XRT refined Analysis
Date
2024-09-12T18:50:53Z (a year ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
D.N. Burrows (PSU), M. A. Williams (PSU), S. Dichiara (PSU), J.P.
Osborne (U. Leicester), K.L. Page (U. Leicester), A. Melandri
(INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB) and P.A.
Evans report on behalf of the Swift-XRT team:
We have analysed 6.9 ks of XRT data for GRB 240912A, from 99 s to 45.7
ks after the BAT trigger. The data comprise 939 s in Windowed Timing
(WT) mode (the first 5 s were taken while Swift was slewing) with the
remainder in Photon Counting (PC) mode.
The late-time light curve (from T0+4.8 ks) can be modelled with a
power-law decay with a decay index of alpha=0.82 (+/-0.07).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.925 (+/-0.020). The
best-fitting absorption column is 2.61 (+/-0.29) x 10^21 cm^-2, at a
redshift of 1.234, in addition to the Galactic value of 5.6 x 10^20
cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index
of 1.86 (+/-0.09) and a best-fitting absorption column of 9 (+11, -9) x
10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum is 3.6 x 10^-11 (4.1 x
10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Galactic foreground: 5.6 x 10^20 cm^-2
Intrinsic column: 9 (+11, -9) x 10^20 cm^-2 at z=1.234
Photon index: 1.86 (+/-0.09)
If the light curve continues to decay with a power-law decay index of
0.82, the count rate at T+24 hours will be 0.12 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.3 x
10^-12 (4.9 x 10^-12) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01253910.
This circular is an official product of the Swift-XRT team.
GCN Circular 37478
Subject
GRB 240912A: Fermi GBM Observation
Date
2024-09-12T18:37:53Z (a year ago)
From
Jacob Smith at Fermi-GBM Team <jrs0118@uah.edu>
Via
Web form
J. Smith (UAH) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 01:46:40.59 UT on 12 September 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 240912A (trigger 747798405/240912074).
which was also detected by Swift BAT and XRT (P. A. Evans et al. 2024, GCN 37466), INTEGRAL SPI ACS (D. Pawar 2024, GCN 37473), OSIRIS+/GTC (A. de Ugarte Postigo et al. 2024, GCN 37469), and NOT (J. An et al. 2024, GCN 37471).
The Fermi GBM on-ground location is consistent with the Swift BAT/XRT position.
The angle from the Fermi LAT boresight is 71 degrees.
The GBM light curve single emission episode with a duration (T90)
of about 88.6 s (50-300 keV). The time-averaged spectrum
from T0+0 to T0+124.930 s is best fit by
a Band function
with Epeak = 147 +/- 7 keV, alpha = -1.31 +/- 0.02,
and beta = -2.21 +/- 0.05.
The event fluence (10-1000 keV) in this time interval is
(8.953 +/- 0.089)E-05 erg/cm^2. The 1.024-s peak photon flux measured
starting from T0+60.2 s in the 10-1000 keV band is 26.43 +/- 0.4 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 37477
Subject
Swift GRB 240912A: Global MASTER-Net observations report
Date
2024-09-12T18:14:29Z (a year 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-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the Swift GRB 240912A ( P. A. Evans et al., GCN 37466) errorbox 58397 sec after notice time and 58417 sec after trigger time at 2024-09-12 18:00:16 UT, with upper limit up to 18.1 mag. The observations began at zenith distance = 80 deg. The sun altitude is -33.7 deg.
The galactic latitude b = 33 deg., longitude l = 188 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2598499
We obtain a following upper limits.
Tmid-T0 | Site |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________
58507 | MASTER-Tunka | C | 180 | 13.3 |
58898 | MASTER-Tunka | C | 180 | 18.1 |
59089 | MASTER-Tunka | C | 180 | 17.4 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 37476
Subject
GRB 240912A: LCOGT detection and Legacy Surveys likely host galaxy
Date
2024-09-12T17:23:35Z (a year ago)
From
Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf@iac.es>
Via
Web form
I. Pérez-Fournon and F. Poidevin (IAC and ULL)
Report on LCOGT follow-up observations of the optical afterglow of GRB 240912A, detected by
the Fermi Gamma-ray Burst Monitor (GBM) (Fermi GBM team, GCN 37465); Swift BAT, XRT, and UVOT (Evans et al., GCN 37466; an enhanced Swift XRT position is given by Goad et al., GCN 37470); and with INTEGRAL ACS SPI (Pawar, GCN 37473). Spectroscopy of the optical afterglow reported by de Ugarte Postigo et al. (GCN 37469) and An et al. (GCN 37471) provides a redshift of z = 1.234, measured from absorption features.
We observed the field of GRB 240912A with one of the 1-meter telescopes at the Las Cumbres Observatory node located at McDonald Observatory (Texas), with a single 500-sec exposure in the SDSS-r' band starting at 2024-09-12T11:13:18 (UTC), ~ 9.44 hours after the Fermi GBM trigger.
We detect a point-like source at RA = 08:18:32.39, Dec = +33:59:56.1 (J2000) with an uncertainty of ~ 0.4", after astrometric calibration with Gaia DR3 stars, at a magnitude r' = 19.88 +/- 0.05, calibrated with PanSTARRS and not corrected for Galactic extinction.
We report also the identification of the likely GRB host galaxy in archival Legacy Surveys DR10 imaging at RA = 08:18:32.38, Dec = +33:59:55.3 (J2000) and magnitudes g = 23.08, r = 22.88; and z = 22.01.
The position of the optical afterglow on our LCOGT image is at about 0.2" from the Swift UVOT afterglow position and 0.8" from the DESI galaxy position.
This work makes use of observations from the Las Cumbres Observatory global telescope network (program IAC2024B-004).
GCN Circular 37473
Subject
GRB 240912A : INTEGRAL SPI ACS LIGHT CURVE
Date
2024-09-12T14:44:39Z (a year ago)
From
Devraj Pawar at R. J. College, Mumbai - 86, India <devrajdp@gmail.com>
Via
Web form
Devraj Pawar (R. J. College, Mumbai-86, India) on behalf of a collaboration studying transients.
The Fermi GBM team reported detection of GRB 240912A in GCN 37465. We analyzed the INTEGRAL SPI ACS data around the given T0 and detected a multi-peak burst. The light curve is given on the following link and further outcomes will be updated on the same page. The SPI ACS is sensitive above 80 keV; the burst peaks at ~4200 counts/s above a steady rate of 3400 counts/s, this may be affected by the instruments orientation with respect to the direction of the source.
[https://docs.google.com/document/d/1e3pSUtLecDZTZkkMOuYGc6L4t64F4V-tjK1KT3_N7GE/edit?usp=sharing]()
This work is based on observations with INTEGRAL, an ESA project with instruments and a science data center funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), and with the participation of Russia and the USA. The SPI-ACS detector system has been provided by MPE Garching/Germany.
GCN Circular 37471
Subject
GRB 240912A: NOT optical spectroscopy
Date
2024-09-12T09:45:30Z (a year ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
Via
Web form
J. An (NAOC), J.P.U. Fynbo (DAWN/NBI), S.Y. Fu, Z.P. Zhu, S.Q. Jiang, X. Liu, D. Xu (NAOC), Niilo Koivisto (NOT) report on behalf of a large collaboration:
We carried out the spectroscopy of the optical afterglow of GRB 240912A detected by Fermi/GBM (Fermi GBM team, GCN 37465) and Swift/BAT (Evans et al., GCN 37466), using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera, at a mean time of 2024-09-12T05:20:43, i.e., ~ 3.57 hrs after the Swift/BAT trigger, covering the wavelength range between ~ 3600 AA and ~ 8000 AA.
A total of 970 s spectral exposure was obtained. A continuum is throughout the whole spectral wavelength range, superimposed with three relatively strong absorption features, which can be interpreted as due to Fe II, Mg II and Mg I at a common redshift of z = 1.23, in agreement with the GTC measurement (de Ugarte Postigo et al., GCN 37469).
GCN Circular 37470
Subject
GRB 240912A: Enhanced Swift-XRT position
Date
2024-09-12T07:11:06Z (a year ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester)
report on behalf of the Swift-XRT team.
Using 328 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 240912A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 124.63469, +33.99901 which is equivalent
to:
RA (J2000): 08h 18m 32.32s
Dec (J2000): +33d 59' 56.4"
with an uncertainty of 2.5 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the
Swift-XRT team.
GCN Circular 37469
Subject
GRB 240912A: Redshift from OSIRIS+/GTC
Date
2024-09-12T06:32:02Z (a year ago)
From
Antonio de Ugarte Postigo at LAM/OCA, CNRS <deugarte@oca.eu>
Via
email
A. de Ugarte Postigo (LAM/OCA, CNRS), J. F. Agui Fernandez (CAHA), C. C. Thoene (ASU-CAS), N. A. Rakotondrainibe (LAM), N. R. Tanvir (U. Leicester), L. Izzo (INAF-OACn & DARK/NBI), S. Geier (GTC), G. Lombardi (GTC), J. P. U. Fynbo (DAWN/NBI), A. Martin-Carrillo (UCD), A. Garcia Rodriguez (GTC), A. Perez Romero (GTC) report,
We observed the afterglow of GRB 240912A (Fermi GBM team GCN 37465; Evans et al. GCN 37466) using OSIRIS+ on the 10.4 m GTC telescope, at the Roque de los Muchachos Observatory (La Palma, Spain). The observation consisted in 2 acquisition images in r-band, followed by a single 600 s spectra obtained just before the twilight became too bright to continue with observations. The spectrum was obtained with grism R1000B, covering the spectral range between 3650 and 7800 AA at a resolving power of 600.
The acquisition image, obtained at 2024-09-12T05:34:23 UT, 3.798 hrs after the burst, shows the afterglow at r(AB) = 19.15 +/- 0.08 mag, as compared to SDSS field stars. The spectrum has a strong continuum throughout the complete range with absorption features due to AlII, AlIII, FeII, MnII, MgII and MgI at a common redshift of 1.234, which we propose as the redshift of GRB 240912A.
GCN Circular 37466
Subject
GRB 240912A: Swift detection of a burst with an optical counterpart
Date
2024-09-12T02:13:06Z (a year ago)
From
K.L. Page at U Leicester <klp5@leicester.ac.uk>
Via
email
P. A. Evans (U Leicester), R. Gupta (NASA GSFC), J. A. Kennea (PSU),
K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of
the Neil Gehrels Swift Observatory Team:
At 01:46:39 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 240912A (trigger=1253910). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 124.633, +33.995 which is
RA(J2000) = 08h 18m 32s
Dec(J2000) = +33d 59' 42"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a complex
structure with a duration of at least 150 sec, extending into
the observation times of the XRT and UVOT. The peak count rate
was ~17000 counts/sec (15-350 keV), at ~69 sec after the trigger.
The XRT began observing the field at 01:48:25.2 UT, 106.0 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 124.63711,
33.99865 which is equivalent to:
RA(J2000) = 08h 18m 32.91s
Dec(J2000) = +33d 59' 55.1"
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This
location is 17 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at https://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (5.53 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.2
(+2.90/-2.49) x 10^21 cm^-2 (90% confidence).
The initial flux in the 0.1 s image was 8.64e-08 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 115 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 08:18:32.40 = 124.63502
DEC(J2000) = +33:59:56.3 = 33.99896
with a 90%-confidence error radius of about 0.75 arc sec. This position is 8.0
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.40 with a 1-sigma error of about 0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.054.
Burst Advocate for this burst is P. A. Evans (pae9 AT leicester.ac.uk).
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)
GCN Circular 37465
Subject
GRB 240912A: Fermi GBM Final Real-time Localization
Date
2024-09-12T01:57:11Z (a year ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely LONG GRB
At 01:46:40 UT on 12 Sep 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240912A (trigger 747798405.59471 / 240912074).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 153.1, Dec = 23.8 (J2000 degrees, equivalent to J2000 10h 12m, 23d 48'), with a statistical uncertainty of 4.2 degrees.
The angle from the Fermi LAT boresight is 81.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240912074/quicklook/glg_skymap_all_bn240912074.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240912074/quicklook/glg_healpix_all_bn240912074.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240912074/quicklook/glg_lc_medres34_bn240912074.gif