GRB 241223A

The Fermi GBM team reports the detection of a likely LONG GRB

At 12:08:46 UT on 23 Dec 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 241223A (trigger 756648531.631546 / 241223506).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 159.9, Dec = -34.8 (J2000 degrees, equivalent to J2000 10h 39m, -34d 47'), with a statistical uncertainty of 1.0 degrees.

The angle from the Fermi LAT boresight is 67.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn241223506/quicklook/glg_skymap_all_bn241223506.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/bn241223506/quicklook/glg_healpix_all_bn241223506.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn241223506/quicklook/glg_lc_medres34_bn241223506.gif

T. Preis, B. Biltzinger, J. Burgess & J. Greiner (all MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
756648531 at 12:08:46 on 23 Dec. 2024 were automatically 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 is:
RA(2000.0) = 160.4 deg
Decl.(2000.0) = -34.3 deg
The 1 sigma statistical error radius is 0.8 deg.
We estimate an additional systematic error of 2 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB241223506/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB241223506/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB241223506/json

                        

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the Fermi/GBM GRB 241223A. 
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021749

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 Fermi/GBM 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.

A. Kumar, D. O’Neill, B. P. Gompertz, G. Ramsay, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, F. Jimenez-Ibarra, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Palle and D. Pollacco report on behalf of the GOTO collaboration:

We report on observations with the Gravitational-wave Optical Transient Observer (GOTO, Steeghs et al. 2022; Dyer et al. 2024) in response to the Fermi GBM detected GRB 241223A (Fermi GBM team, GCN 38650
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 ). Targeted observations were performed beginning at 2024-12-23 14:11:18, (+2.04h post trigger) and continued through to 2024-12-23 17:28:07 UT (+5.23h post trigger). 87 images were taken, across 5 unique pointings, covering 151.2 square degrees within the 90% localisation contour, distributed over three epochs. ~88.1% of the total 2D localisation probability was covered, with an average 5-sigma depth of 20.7 mag. Each observation consisted of 8x90s exposures. We also had serendipitous coverage in the all-sky survey mode which consisted of 4x45s exposures. All images were taken in the GOTO L-band (400-700 nm).

Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using recent survey observations of the same pointings. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogues. Human vetting was carried out in real time on any candidates that passed the above checks.

We identified AT 2024aera
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 /GOTO24jht (RA = 10:43:01.030 and Dec = -37:32:47.95) as a possible optical counterpart within the GBM 90% localisation region. The first epoch of GOTO24jht was obtained at 2024-12-23 14:16:04 UT (+2.12h post-trigger), which showed its magnitude to be L = 17.13 ± 0.01 (AB). We found no evidence of this source prior to the GRB trigger time in previous GOTO observations taken -44.73h pre-trigger down to a 3-sigma limiting magnitude of L > 20.0, or in the ATLAS forced photometry server (Shingles et al. 2021). 

Before a second epoch could be taken to confirm a decay, GOTO-south was forced to shut due to wind. Based on the available evidence, a Swift ToO was requested (Evans, GCN 38653
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 ) to confirm whether or not the source was the afterglow. However, conditions subsequently improved and GOTO-south reopened approximately 1 hour later. The second and third epochs were obtained at 2024-12-23 16:06:14 (+3.96h post-trigger) and 17:20:34 (+5.20h post-trigger) UTs. These showed the source had brightened to L = 16.84 ± 0.01 and L = 16.71 ± 0.01 AB magnitudes, respectively. Coupled with the position of the source close to the galactic plane (+18.7 degrees latitude), this suggests that AT 2024aera
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 /GOTO24jht is likely an unrelated CV and not the afterglow of GRB 241223A.

We also note 2 additional newly-reported transients (AT 2024aerb
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 /GOTO24jhu and AT 2024aerc
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 /GOTO24jhv) within the GBM 90% localisation region. However, these sources have exhibited fluctuating flux in both ATLAS and GOTO observations over the past week; hence these objects are unlikely to be related to GRB 241223A.

Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and were not corrected for Galactic extinction.

GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC).

V.Lipunov, E.Gorbovskoy, N.Tiurina,  P.Balanutsa, , D.Vlasenko, I.Panchenko,
A.Kuznetsov,  G.Antipov,  A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin,
V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile,  F. Podesta, R.Podesta, E. Gonzalez  (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) 

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 241223A ( Fermi GBM team, GCN 38650
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 ) errorbox  29603 sec after notice time and 29637 sec after trigger time at 2024-12-23 20:22:44 UT, with upper limit up to  18.4 mag. The observations began at zenith distance = 79 deg. The sun  altitude  is -25.8 deg. 

The galactic latitude b = 21 deg., longitude l = 275 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2719951

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   29667 | 2024-12-23 20:22:44 |         MASTER-SAAO | (10h 31m 23.22s , -34d 45m 27.5s) |   C |    60 | 17.9 |        
   31507 | 2024-12-23 20:53:23 |         MASTER-SAAO | (10h 31m 16.29s , -34d 45m 04.3s) |   C |    60 | 18.3 |        
   32074 | 2024-12-23 21:02:50 |         MASTER-SAAO | (10h 40m 01.52s , -34d 44m 52.8s) |   C |    60 | 18.4 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.

R. Sonawane (IISER, TVM) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 12:08:46.63 UT on 23 December 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 241223A (trigger 756648531/241223506).

The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 159.85, Dec = -34.80 (J2000 degrees, equivalent to
J2000 10h 39m, -34d 47'), with a statistical uncertainty of 1.00 degrees.
(radius, 1-sigma containment, statistical only; there is additionally a
systematic error which we have characterized as a mixture of two Gaussians,
one with a radius of 1.8 degrees (52% contribution) and one with a radius
of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]).

The angle from the Fermi LAT boresight is 67 degrees.

The GBM light curve consist of one weak emission episode (possibly a precursor) followed by a strong emission episode with a duration (T90)
of about 30.5 s (50-300 keV). The time-averaged spectrum
from T0+0.003 to T0+47.489 s is best fit by
a Band function with Epeak = 239 +/- 5 keV,
alpha = -0.66 +/- 0.02, and beta = -2.42 +/- 0.06.

The event fluence (10-1000 keV) in this time interval is
(6.28 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+26 s in the 10-1000 keV band is 34.4 +/- 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/"

B. Sbarufatti (INAF-OAB), C. Salvaggio (INAF-OAB), S. Dichiara (PSU),
J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P.
Beardmore (U. Leicester), M. Ferro (INAF-OAB) and P.A. Evans (U.
Leicester) reports on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Fermi/GBM-detected burst GRB 241223A, collecting  2.2 ks of Photon
Counting (PC) mode data between T0+20.5 ks and T0+99.8 ks. 

No X-ray sources have been detected at the position of the GOTO optical
source (GCN Circ. 38655
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 ). The 3-sigma upper limit in the field ranges
from ~0.005 to ~0.006 ct s^-1, corresponding to a 0.3-10 keV observed
flux of 2.0e-13 to 2.5e-13 erg cm^-2 s^-1 (assuming a typical GRB
spectrum).

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/00021749.

This circular is an official product of the Swift-XRT team.

M. Dafcikova, J. Ripa, M. Kolar (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. Duriskova, L. Szakszonova, 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 long-duration GRB 241223A (Fermi/GBM detection: GCN 38650
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 ; INTEGRAL/SPI-ACS detection: trigger no. 11006) was observed by the GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; https://ui.adsabs.harvard.edu/abs/2023A%26A...677A..40P/abstract).

The detection was confirmed at the peak time 2024-12-23 12:09:12.5 UTC. The T90 duration measured by GRBAlpha is 27.5 s and the overall significance during T90 reaches 29 sigma.

The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB241223A_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.

A. Bogomolov, V. Bogomolov, A. Iyudin, S. Svertilov, N. Vasiliev 
on behalf of the MSU “Sozvezdie-270” team, report:

At 2024-12-23 ~12:08:45 UT the long-duration GRB 241223A (Fermi GBM detection: GCN #38650
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 ; GRBAlpha detection: GCN #38678
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 ) was detected by the DeCoR-1 and DeCoR-3 instruments on the cubesat Avion of the Moscow University project “Constellation-270” [1].  
Total amount of photons detected by Avion is 620 (DeCoR-1, energy band 40-500 keV) and ~1540 (DeCoR-3, >30 keV), it corresponds to a fluence of ~7*10^(-6) erg/cm^2 in the range 30-500 keV.
LC in the energy range of 30-500 keV has two main episodes with a maximum flux of ~1.6 phot/(cm^2*s) in the 1st peak with a duration of ~11 s, and ~11.7 phot/(cm^2*s) in the 2nd peak with a duration of ~12 s.

А total duration (T90) of the burst is ~31 s.
The light curve obtained by Avion is available here:
https://swx.sinp.msu.ru/models/grb_cat/data/pictures/GRB20241223A_Acion_Decor3_s.png
Parameters of GRB 241223A as well as other GRBs detected by Moscow University cubesats are listed at: https://swx.sinp.msu.ru/models/grb_cat/grb.php?lang=en
Avion is one of 5 cubesats of the Moscow University project “Constellation-270” [1] launched on 2023 June 27. The payload of Avion is a set of scintillation gamma-ray detectors DeCoR [2], the energy range is >30 keV, the time resolution is 0.5s. 
[1] Svertilov et al. 2023  https://link.springer.com/chapter/10.1007/978-3-031-50248-4_21
[2] Bogomolov et al. 2022 Universe 8, 282 https://www.mdpi.com/2218-1997/8/5/282