GRB 240112C

R. A. J. Eyles-Ferris (U Leicester), J.D. Gropp (PSU),
S. Laha (GSFC/UMBC), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL), M. H. Siegel (PSU) and
M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 17:37:24 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 240112C (trigger=1208389).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 270.644, +24.487 which is 
   RA(J2000) = 18h 02m 35s
   Dec(J2000) = +24d 29' 12"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  Due to a telemetry gap, the BAT lightcurve
is not immediately available. 

The XRT began observing the field at 17:39:18.9 UT, 114.0 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 270.64225, 24.48830 which is equivalent
to:
   RA(J2000)  = 18h 02m 34.14s
   Dec(J2000) = +24d 29' 17.9"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 7.4 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.  We cannot determine whether the source
is fading at the present time. No spectrum from the promptly downlinked
event data is yet available to determine the column density. 

UVOT took a finding chart exposure of 115 seconds with the White filter
starting 120 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	18:02:34.59 = 270.64414
  DEC(J2000) = +24:29:21.2  =  24.48923
with a 90%-confidence error radius of about 0.75 arc sec. This position is 7.4
arc sec. from the center of the XRT error circle. The estimated magnitude is
16.73 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.108. 

Burst Advocate for this burst is R. A. J. Eyles-Ferris (raje1 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/)

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 240112C ( R. A. J. Eyles-Ferris et al., GCN 35522
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 ) errorbox  8981 sec after notice time and 9002 sec after trigger time at 2024-01-12 20:07:27 UT, with upper limit up to  15.4 mag. The observations began at zenith distance = 85 deg. The sun  altitude  is -45.5 deg. 

The galactic latitude b = 21 deg., longitude l = 51 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2354458

We obtain a following upper limits.  

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

    9040 |        MASTER-Tunka |   C |    75 | 12.4 |        
    9124 |        MASTER-Tunka |   C |    70 | 15.4 |        
Filter C is a clear (unfiltred) band. 


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

A. S. Moskvitin and O. A. Maslennikova (SAO RAS)
report on behalf of the GRB follow-up team.

We observed the field of Swift GRB 240112C (Eyles-Ferris et al.,
GCN #35522
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 ) with the 1-m telescope of SAO RAS equipped with the CCD
photometer. We obtained 21 x 60 sec. images in Rc band on January 13,
03:00:16--03:34:31 UT (t_mid - T0 = 0.40277 days) under mediocre
weather conditions.

We did not detect any significant source at the OT position
down to the limiting magnitude R_lim = 21.1
(based on R2 magnitudes of nearby USNO-B1 stars).

K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), P. D'Avanzo
(INAF-OAB), M.G. Bernardini (INAF-OAB), E. Ambrosi  (INAF-IASFPA) ,
J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), D.N. Burrows (PSU) and
P.A. Evans report on behalf of the Swift-XRT team:

We have analysed 6.3 ks of XRT data for GRB 240112C, from 97 s to 45.8
ks after the  BAT trigger. The data comprise 39 s in Windowed Timing
(WT) mode (the first 10 s were taken while Swift was slewing) with the
remainder in Photon Counting (PC) mode. Using 2660 s of PC mode data
and 6 UVOT images, we find an enhanced XRT position (using the XRT-UVOT
alignment and matching UVOT field sources to the USNO-B1 catalogue):
RA, Dec = 270.64402, +24.48893 which is equivalent to:

RA (J2000): 18h 02m 34.56s
Dec(J2000): +24d 29' 20.2"

with an uncertainty of 2.0 arcsec (radius, 90% confidence).

The light curve can be modelled with an initial power-law decay with an
index of alpha=0.61 (+0.04, -0.48), followed by a break at T+5970 s to
an alpha of 1.30 (+0.18, -0.20).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.92 (+0.14, -0.13). The
best-fitting absorption column is  2.0 (+0.5, -0.4) x 10^21 cm^-2, in
excess of the Galactic value of 1.3 x 10^21 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.6 x 10^-11 (4.8 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     2.0 (+0.5, -0.4) x 10^21 cm^-2
Galactic foreground: 1.3 x 10^21 cm^-2
Excess significance: 2.5 sigma
Photon index:	     1.92 (+0.14, -0.13)

If the light curve continues to decay with a power-law decay index of
1.30, the count rate at T+24 hours will be 0.015 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.3 x
10^-13 (7.0 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01208389.

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

P. Veres (UAH), R. Hamburg (CNRS/IN2P3), A. Myers (NPP/GSFC) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 17:37:25.12 UT on 12 January 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 240112C (trigger 726773850/240112734). GRB 240112C 
was also localized by Swift BAT and XRT (Eyles-Ferris et al., GCN #35522
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 ).
The Fermi GBM on-ground Localization is consistent with the Swift position.


The angle from the Fermi LAT boresight is 43 degrees.

The GBM light curve consists of two pulses with a duration (T90)
of about 5.3 s (50-300 keV). The time-averaged spectrum
from T0-0.6 to T0+6.3 s is best fit by
a Band function with with Epeak= 71 +/- 6 keV, alpha = -1.26 +/- 0.08 
and beta = -2.34 +/- 0.10.


The event fluence (10-1000 keV) in this time interval is
(4.8 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.064 s in the 10-1000 keV band is 20.2 +/- 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/"

N. P. M. Kuin (UCL-MSSL) and Eyles-Ferris (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 240112C
121 s after the BAT trigger (Eyles-Ferris et al., GCN Circ. 35522
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 ).
A source consistent with the XRT position is detected in the initial
UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  18:02:34.58 = 270.64410 (deg.)
    Dec (J2000) = +24:29:21.3  =  24.48925 (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              121          236          113         16.98 +/- 0.04
v                 4955         5126          169        >18.6
b                 4340         4539          197         19.35 +/- 0.16
u                 4134         4334          197         19.11 +/- 0.18
w1                3930         4129          197         19.13 +/- 0.24

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.108 in the direction of the burst
(Schlegel et al. 1998).

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, 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 240112C (Swift/BAT detection: GCN 35522
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 ; Fermi/GBM detection: GCN 35533
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 ; INTEGRAL/SPI-ACS detection: trigger no. 10466; Konus/Wind trigger at 2024-01-12 17:37:21.633 UT) was observed by the GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; arXiv:2302.10048
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 ).

The detection was confirmed at the peak time 2024-01-12 17:37:25 UTC. The T90 duration measured by GRBAlpha is 5 s and the overall significance during T90 reaches 12 sigma.

The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB240112C_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. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin,
A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The long-duration GRB 240112C
(Swift-BAT detection: Eyles-Ferris et al., GCN 35522
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 ;
Fermi-GBM detection: Veres at al., GCN 35533
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 ;
GRBAlpha detection: Dafcikova et al., GCN 34436
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 )
triggered Konus-Wind at T0=63441.633 s UT (17:37:21.633).

The burst light curve shows a double-peaked structure,
which starts at ~T0-0.5 s and has a total duration of ~4 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/GRB240112_T63441/

As observed by Konus-Wind, the burst
had a fluence of 3.70(-0.39,+0.46)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0+2.384 s,
of 3.30(-0.84,+0.88)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+8.448 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.59(-0.22,+0.26)
and Ep = 79(-18,+18) keV (chi2 = 66/74 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.3
(chi2 = 64/73 dof).

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.

M. Dafcikova, J. Ripa (Masaryk U.), 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 long-duration GRB 240112C (Swift/BAT detection: GCN 35522
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 ; Fermi/GBM detection: GCN 35533
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 ; GRBAlpha detection: GCN 35536
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 ; Konus/Wind detection: GCN 35539
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 ; INTEGRAL/SPI-ACS detection: trigger no. 10466) was detected by the GRB detector on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/).

The data acquisition was performed by the GRB detector unit no. 1. The detection was confirmed at the peak time 2024-01-12 17:37:27 UTC. The T90 duration is 3 s and the significance during T90 reaches 14 sigma.

The light curve obtained by VZLUSAT-2 is available here:
https://vzlusat2.konkoly.hu/static/share/GRB240112C_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 ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral.

C.C. Cheung, M. Kerr, J. E. Grove, R. Woolf (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge (MSFC), and M.S. Briggs (UAH) report:                                                                                                                                                                                                                                                   
 
The Glowbug gamma-ray telescope [1,2], operating on the International Space Station, reports the detection of GRB 240112C, which was also detected by Swift/BAT, Fermi/GBM, GRBAlpha, Konus-Wind, VZLUSAT-2 (GCN #35522
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 , #35533
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 , #35536
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 , #35539
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 , #35545
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 ), and INTEGRAL/SPI-ACS (Trigger no. 10466).
 
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2024-01-12 17:37:23.592 with a duration of 4.10 s and a total significance of about 20.1 sigma.  The light curve comprises two primary peaks.
 
Using a standard power-law function with an exponential high-energy cutoff [3] to model the emission over this duration results in a photon index dN/dE~E^x of x=1.6 and a cutoff energy ("Epeak") of 185 keV.  The modeled 10-10000 keV fluence is 7.5e-07 erg/cm^2.
 
The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS.
 
Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC.  It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS.  The detector comprises 12 large-area (15 cm x 15 cm) CsI:Tl panels covering the surface of a half cube, and two hexagonal (5-cm diameter, 10-cm length) CLLB scintillators, giving it a large field of view (instantaneous FoV ~2/3 sky) over a wide energy band of 50 keV to >2 MeV.
 
[1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959
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[2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O
[3] Goldstein, A. et al. 2020, ApJ 895, 40, arXiv :1909.03006
 
Distribution Statement A: Approved for public release.  Distribution is unlimited.