GRB 240128A

P. D'Avanzo (INAF-OAB), K.L. Page (U. Leicester) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:

Swift-XRT has performed further follow-up observations of the MAXI-detected burst GRB 240128A (Yamaoka et al., GCN Circ. 35646
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 ; 
Yoshida et al., GCN Circ. 35647
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 ; Dafcikova et al., GCN Circ. 35649
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 ; Cheung et al., GCN Circ. 35651
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 ). The data were collected between T0+553.6 ks and T0+1237.1 ks, and are entirely in Photon Counting (PC) mode for a total exposure time of 8.0 ks. 

The uncatalogued X-ray source reported by Perri et al. ("Source 1"; GCN Circ. 35650
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 ), is still detected at an average count rate of 
~ 4e-2 ct/s and shows no definitive signs of fading. Therefore, we conclude that it is likely a field source unrelated with the GRB. 

The results of the XRT-team automatic analysis of the XRT observations for this GRB, including a position-specific upper limit calculator, 
are available at https://www.swift.ac.uk/xrt_products/TILED_GRB00120 <https://www.swift.ac.uk/xrt_products/TILED_GRB00120>.

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

C.C. Cheung, M. Kerr, J.E. Grove, R. Woolf (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (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 240128A, which was also detected by MAXI/GSC (GCN 35646
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 ), CALET/CGBM (GCN 35647
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 ), GRBAlpha (GCN 35649
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 ), and INTEGRAL/SPI-ACS (Trigger 10493).
 
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2024-01-28 15:13:35.064 with a duration of 18.4 s and a total significance of about 44.8 sigma.  The light curve comprises a multi-peaked structure similar to that observed by CALET/CGBM (GCN 35647
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 ).
 
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=1.9 and a cutoff energy ("Epeak") of 176 keV.  The modeled 10-10000 keV fluence is 2.0e-06 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.

M. Perri (SSDC & INAF-OAR), S. Dichiara (PSU), J.A. Kennea (PSU), A.
Tohuvavohu (U. Toronto), K.L. Page (U. Leicester), A.P. Beardmore (U.
Leicester), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (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 MAXI-detected
burst GRB 240128A in a series of observations tiled on the sky. The
total exposure time is 1.4 ks, distributed over 6 tiles; the maximum
exposure at a single sky location was 460 s. The data were collected
between T0+46.4 ks and T0+52.4 ks, and are entirely in Photon Counting
(PC) mode. 

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):  140.1536  =  09:20:36.87
  Dec (J2000.0): -5.2004  =  -05:12:01.5
  Error: 8.8 arcsec (radius, 90% conf.)
  Count-rate: 0.0149 [+0.0080, -0.0059] ct s^-1   
  Distance: 1224 arcsec from MAXI position.
  Flux: (2.9 [+1.6, -1.2])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

A catalogued source was also detected.

The results of the XRT-team automatic analysis of the tiled XRT
observations, including a position-specific upper limit calculator, are
available at https://www.swift.ac.uk/xrt_products/TILED_GRB00120.

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

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 240128A (MAXI/GSC detection: GCN 35646
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 ; CALET/CGBM detection: GCN 35647
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 ; INTEGRAL/SPI-ACS trigger no. 10493) 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 2024-01-28 15:13:46 UTC. The T90 duration measured by GRBAlpha is 13 s and the overall significance during T90 reaches 8 sigma.

The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB240128A_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. 

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

Swift has initiated a series of observations, tiled on the sky, of the
MAXI GRB 240128A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00120

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the MAXI event is high: 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. Yoshida, T. Sakamoto, S. Sugita (AGU), Y. Kawakubo (LSU),
K. Yamaoka (Nagoya U), S. Nakahira (JAXA),
Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC),
M. L. Cherry (LSU), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:

The long GRB 240128A (MAXI/GSC detection, Yamaoka et al., 
GCN Circ. 35646
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 ) triggered the CALET Gamma-ray Burst Monitor
(CGBM) at 15:13:34.34 UTC on 28 January 2024
(http://cgbm.calet.jp/cgbm_trigger/flight/1390489809/).
The burst signal was seen by all CGBM detectors.

The burst light curve shows a multi-peaked structure that starts
at T+1.4 sec, peaks at T+10.8 sec, and ends at T+15.2 sec.
The T90 and T50 durations measured by the SGM data are 12.5 +/- 0.6 sec
and 7.2 +/- 0.6 sec (40-1000 keV), respectively.

The ground-processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1390489809/index.html

The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at Waseda University.

K. Yamaoka (Nagoya U.), H. Negoro (Nihon U.), M. Serino (AGU),
W. Iwakiri (Chiba U.), M. Nakajima, K. Kobayashi, M. Tanaka, 
Y. Soejima, Y. Kudo (Nihon U.), T. Mihara, T. Kawamuro, S. Yamada, 
T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita,
H. Hiramatsu, H. Nishikawa, A. Yoshida (AGU), Y. Tsuboi, S. Urabe, 
S. Nawa, N. Nemoto, E.Goto (Chuo U.), M. Shidatsu, Y. Niida (Ehime U.),
I. Takahashi, M. Niwano, S. Sato, N. Higuchi, Y. Yatsu (Tokyo Tech),
S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, T. Kurihara (JAXA),
Y. Ueda, K. Setoguchi, T. Yoshitake, Y. Nakatani, Y. Okada (Kyoto U.),
M. Yamauchi, Y. Hagiwara, Y. Umeki, Y. Otsuki (Miyazaki U.),
Y. Kawakubo (LSU), and M. Sugizaki (NAOC)


The MAXI/GSC nova alert system triggered on an uncatalogued X-ray
transient source at 15:14:03 UT on January 28, 2024.
Because our localization program did not run, we can not provide a
precise error region.
The source position determined with the nova alert system (Negoro et
al. 2016) is

(R.A., Dec) = (139.846 deg, -5.053 deg) = (09 19 23.04, -05 03 10.8) (J2000)

with an uncertainty of more than 30 arc-min. The burst duration is
about 30 sec, and the averaged X-ray flux in the 2-10 keV range was about 600 mCrab.
This event was also detected by INTEGRAL SPI-ACS. 
There was no significant excess flux in the previous transit at 13:37 UT
with an upper limit of 20 mCrab.