GRB 240123B

L. Scotton (UAH) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 17:48:03.22 UT on 23 January 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 240123B (trigger 727724888/240123742).
which was also detected by Swift/BAT-GUANO (Ronchini et al. 2024, GCN 35629
Loading...
 
 ).
The Fermi GBM Final Real-time Localization was reported in GCN 35608
Loading...
 
 .

The angle from the Fermi LAT boresight is 51 degrees.

The GBM light curve consists of a single emission episode with a duration (T90)
of about 12 s (50-300 keV). The time-averaged spectrum
from T0-0.5 to T0+11.5 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.6 +/- 0.2 and the cutoff energy,
parameterized as Epeak, is 250 +/- 30 keV.

The event fluence (10-1000 keV) in this time interval is
(2.6 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+4.9 s in the 10-1000 keV band is 2.4 +/- 0.2 ph/s/cm^2.

A Band function fits the spectrum equally well
with Epeak= 130 +/- 30 keV, alpha = 0.1 +/- 0.4 and beta = -1.9 +/- 0.1.

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/"

Samuele Ronchini (PSU), James DeLaunay (PSU), Gayathri Raman (PSU), Aaron Tohuvavohu (U Toronto), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC) report:

Swift/BAT did not localize GRB 240123B onboard (T0: 2024-01-23T17:48:03.22 UTC, Fermi GCN 35608
Loading...
 
 ). 

The Fermi notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1). 

Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground.

The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 15.5 in a 8.192 s analysis time bin, starting at T0 - 2.05 s. 

NITRATES results, independently, are ambiguous with respect to whether this burst originates from in or outside the BAT coded FOV, with a DeltaLLHOut of 2.75.

See Section 9.1 and Figures 10 and 17 in the NITRATES paper for brief descriptions and interpretation of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut.

GUANO is a fully autonomous, extremely low latency, spacecraft
commanding pipeline designed for targeted recovery of BAT event mode
data around the times of compelling astrophysical events to enable
more sensitive GRB searches.

A live reporting of Swift/BAT event data recovered by GUANO can be
found at: https://www.swift.psu.edu/guano/

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) started inspect of the Fermi GRB 240123B ( Fermi GBM team, GCN 35608
Loading...
 
 ) errorbox  17492 sec after notice time and 17523 sec after trigger time at 2024-01-23 22:40:06 UT, with upper limit up to  17.1 mag. The observations began at zenith distance = 79 deg. The sun  altitude  is -21.0 deg. 

The galactic latitude b = -17 deg., longitude l = 64 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2363736

We obtain a following upper limits.  

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

   17534 | 2024-01-23 22:40:06 |        MASTER-Tunka | (20h 45m 43.98s , +25d 49m 07.9s) |   C |    20 | 16.9 |        
   17626 | 2024-01-23 22:41:41 |        MASTER-Tunka | (20h 25m 46.01s , +22d 02m 50.8s) |   C |    15 | 16.9 |        
   17669 | 2024-01-23 22:42:23 |        MASTER-Tunka | (20h 26m 42.78s , +23d 55m 03.1s) |   C |    15 | 17.1 |        
Filter C is a clear (unfiltred) band. 


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

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

At 17:48:03 UT on 23 Jan 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240123B (trigger 727724888.218344 / 240123742).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 312.7, Dec = 17.3 (J2000 degrees, equivalent to J2000 20h 50m, 17d 18'), with a statistical uncertainty of 6.9 degrees.

The angle from the Fermi LAT boresight is 51.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240123742/quicklook/glg_skymap_all_bn240123742.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/bn240123742/quicklook/glg_healpix_all_bn240123742.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240123742/quicklook/glg_lc_medres34_bn240123742.gif