TITLE: GCN CIRCULAR
NUMBER: 35810
SUBJECT: GRB 240225B: Swift-XRT observations
DATE: 24/02/26 22:22:37 GMT
FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk>
A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB),
J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), D.N. Burrows (PSU), J.P.
Osborne (U. Leicester), K.L. Page (U. Leicester) and P.A. Evans (U.
Leicester) and A. A. Breeveld (UCL-MSSL) reports on behalf of the
Swift-XRT and the Swift-UVOT team:
Swift-XRT has performed follow-up observations of the MAXI-detected
burst GRB 240225B in a series of observations tiled on the sky. The
total exposure time is 1.8 ks, distributed over 7 tiles; the maximum
exposure at a single sky location was 693 s. The data were collected
between T0+29.1 ks and T0+30.9 ks, and are entirely in Photon Counting
(PC) mode.
Two uncatalogued X-ray sources are detected, of which one ("Source 1")
is above the RASS 3-sigma upper limit at this position. The position of
this source is RA, Dec=128.3629, +27.0746 which is equivalent to:
RA (J2000): 08:33:27.11
Dec(J2000): +27:04:28.5
with an uncertainty of 4.4 arcsec (radius, 90% confidence). This
position is 25.3 arcmin from the MAXI position. At the present time the
light curve of Source 1 shows no signs of fading and we can not
confirm this source as the GRB afterglow.
The results of the full analysis of the tiled XRT observations are
available at https://www.swift.ac.uk/xrt_products/TILED_GRB00124.
Source 1 was out of the field of view for UVOT so we can't say anything
about optical properties.
This circular is an official product of the Swift team.
View this GCN Circular online at https://gcn.nasa.gov/circulars/35810.
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TITLE: GCN CIRCULAR
NUMBER: 35808
SUBJECT: Transient EPW20240219aa: Kp-band imaging observations with NIRES
DATE: 24/02/26 21:05:11 GMT
FROM: Viraj Karambelkar at Indian Inst of Tech,Bombay <karambelkarvraj21197(a)gmail.com>
Viraj Karambelkar (Caltech), Tomas Ahumada (Caltech), Mansi Kasliwal
(Caltech)
We observed the location of the X-ray flare EPW20240219aa (Zhang et al.,
ATel #16463; Zhang et al., GCN #35773) in the near-infrared K prime-band
(Kp) with the NIRES acquisition camera on the Keck II telescope starting
UTC 2024-02-25T05:12:12.45.
We obtained four 300 second exposures that covered the locations of the VLA
radio sources # 1-6 reported in GCN #35788. The Kp-band observations
reached a depth of ~19.5 mag (Vega). We use an archival Ks-band image of
the field from the UKIRT Galactic Plane Survey (Lucas et al. 2008) to
calibrate the NIRES images. The depth of the UKIRT image is ~19 mag (Vega).
We detect sources at the locations of the VLA sources #1, 2, 3 and 6 in the
NIRES image.
VLA-1 : We detect a source with m_Kp ~ 19 mag (Vega) that is ~0.8 arcsec
offset from the VLA position reported in GCN #35788. The source is also
marginally visible in the archival UKIRT image (which is shallower than the
new NIRES image.)
VLA-2 has m_Kp ~ 17 mag (Vega) and appears as an extended source in the
NIRES as well as archival UKIRT image. There is no substantial variation
between the two epochs.
VLA-3 has m_Kp ~ 19 mag (Vega) and is not detected in the archival image
(limit ~19 mag).
VLA-4 and VLA-5 are not detected in our images.
VLA-6 is clearly detected as an extended source in both the NIRES and
archival images. As reported in GCN #35803, this source does not show any
variations, and is likely a galaxy unrelated to the transient.
VLA-7 was not covered by our observations.
In addition to these, we do not detect any new sources in the NIRES
observations.
VLA-3 is the most promising source in terms of association with the X-ray
transient. We encourage further follow-up.
View this GCN Circular online at https://gcn.nasa.gov/circulars/35808.
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TITLE: GCN CIRCULAR
NUMBER: 35807
SUBJECT: Transient EPW20240219aa: J-band upper limits from WINTER
DATE: 24/02/26 21:05:09 GMT
FROM: Viraj Karambelkar at Indian Inst of Tech,Bombay <karambelkarvraj21197(a)gmail.com>
Viraj Karambelkar (Caltech), Danielle Frostig (MIT), Robert Stein
(Caltech), Nathan Lourie (MIT), Geoffrey Mo (MIT), Tomas Ahumada (Caltech),
Robert Simcoe (MIT), Mansi Kasliwal (Caltech)
We observed the location of the X-ray flare EPW20240219aa (Zhang et al.,
ATel #16463; Zhang et al., GCN #35773) in the near-infrared J-band with the
Palomar 1-m telescope, equipped with the 1 square degree WINTER camera
(Lourie et al. 2020).
Our observations started at UTC 2024-02-25T03:24:23, and covered the 3
arcmin localization region of the X-ray flare. The images were processed
through the WINTER data reduction pipeline implemented using mirar (
https://github.com/winter-telescope/mirar), with image subtraction
performed relative to reference images built from the UKIRT Galactic Plane
Survey (Lucas et al. 2008).
No new sources are detected to a depth of J = 18.5 mag (AB). Of the 7 radio
sources detected by the VLA in this region (Ho et al. GCN #35788), source 6
is detected in both the WINTER and archival UKIRT images, but does not show
significant variability between the two epochs (consistent with that
reported in Ferro et al. GCN #35803).
View this GCN Circular online at https://gcn.nasa.gov/circulars/35807.
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TITLE: GCN CIRCULAR
NUMBER: 35806
SUBJECT: GRB 240225C: CALET Gamma-Ray Burst Monitor detection
DATE: 24/02/26 20:51:06 GMT
FROM: Yuta Kawakubo at Louisiana State University <kawakubo1(a)lsu.edu>
S. Sugita , A. Yoshida, T. Sakamoto (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 240225C (INTEGRAL SPI ACS Trigger: Trigger Num. 10590;
IPN RAW NOTICE (KONUS/Wind); AstroSat CZTI detection: Joshi et al.,
GCN Circ. 35799; GRBAlpha detection: Ripa et al., GCN Circ. 35802)
triggered the CALET Gamma-ray Burst Monitor (CGBM) at 05:19:32.73
UTC on 25 February 2024
(http://cgbm.calet.jp/cgbm_trigger/flight/1392873321/index.html).
The burst signal was seen by all CGBM detectors.
The burst light curve shows a single pulse that starts
at T+2.6 sec, peaks at T+4.2 sec, and ends at T+22.6 sec.
The T90 and T50 durations measured by the SGM data are 13.1 +/- 3.4 sec
and 4.6 +/- 0.4 sec (40-1000 keV), respectively.
The ground-processed light curve is available at
http://cgbm.calet.jp/cgbm_trigger/ground/1392873321/index.html
The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at Waseda University.
View this GCN Circular online at https://gcn.nasa.gov/circulars/35806.
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TITLE: GCN CIRCULAR
NUMBER: 35805
SUBJECT: GRB 240225B: GOTO detection of a candidate optical afterglow
DATE: 24/02/26 20:45:40 GMT
FROM: Ben Gompertz at U of Birmingham <b.gompertz(a)bham.ac.uk>
B. P. Gompertz, R. L. C. Starling, M. Kennedy, G. Ramsay, D. B. Malesani, B. Godson, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, F. Jimenez-Ibarra, A. Kumar, D. O'Neill, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Pall'e and D. Pollacco report on behalf of the GOTO collaboration:
We report on observations of the MAXI-discovered GRB 240225B (Nakajima et al, GCN 35796) with the Gravitational-wave Optical Transient Observer (GOTO, Steeghs et al. 2022). GOTO-North serendipitously tiled the MAXI localisation at 21:45:51 UT on 2024-02-25, 1.5 hours after trigger. The observation consisted of 4x45 s exposures 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 identify a new optical source (GOTO24tz/AT2024dgu) with a magnitude of L = 17.12 +/- 0.04 at RA 08:33:26.67, Dec +27:04:32.71 (J2000). The optical source is close to the probable X-ray afterglow identified in tiled Swift observations (Evans, GCN 35797), offset by 7.2”, whilst formally outside the 4.4” 90% confidence contour of the X-ray localisation. This source was not present in the previous GOTO epoch, taken one day prior at 22:05:36 UT on 2024-02-24, to a limiting magnitude of L > 18.7. Given the tight pre-burst limit and close proximity with a new X-ray source, we propose this as a strong candidate afterglow of GRB 240225B.
Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are 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).
View this GCN Circular online at https://gcn.nasa.gov/circulars/35805.
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TITLE: GCN CIRCULAR
NUMBER: 35803
SUBJECT: Transient EPW20240219aa: REM optical/NIR upper limits
DATE: 24/02/26 19:27:31 GMT
FROM: Matteo Ferro <matteo.ferro(a)inaf.it>
M. Ferro, R. Brivio, Y.-D. Hu, P. D’Avanzo, S. Covino, D. Fugazza (INAF-OAB) on behalf of the REM team, report:
We observed the field of the transient EPW20240219aa (Zhang et al., ATel 16463; Zhang et al., ATel 16472; Zhang et al., GCN 35773) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, H bands, starting on 2024 February 25 at 00:16:54 UT (i.e. 5.75 days after the event), and lasting for about 20 minutes.
We find no clear afterglow candidate within the Einstein Probe error circle, nor at the positions of the radio sources reported by Ho et al. (GCN 35788), down to the following 3sigma magnitude upper limits:
H > 17.3 (Vega; calibrated against the 2MASS catalogue)
r > 19.9 (AB; calibrated against the Pan-STARRS catalogue)
at the common mid-time of t - t0 = 5.75 days after the EP trigger.
We report a detection of VLA sources #6 and #7 in the co-added REM H-band image with magnitudes H ~ 16.7 and H ~ 16.5, respectively (AB). We note however that both sources are reported in the UKIDSS survey with similar magnitudes.
View this GCN Circular online at https://gcn.nasa.gov/circulars/35803.
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TITLE: GCN CIRCULAR
NUMBER: 35802
SUBJECT: GRB 240225C: GRBAlpha detection
DATE: 24/02/26 18:27:13 GMT
FROM: Jakub Ripa <ripa.jakub(a)gmail.com>
J. Ripa, M. Dafcikova, 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, 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 240225C (AstroSat detection: GCN 35799; CALET/CGBM detection: trigger no. 1392873321; INTEGRAL/SPI-ACS detection: trigger no. 10590) 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 2024-02-25 05:19:36.5 UTC. The T90 duration measured by GRBAlpha is 8.5 s and the overall significance during T90 reaches 5.5 sigma.
The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB240225C_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.
View this GCN Circular online at https://gcn.nasa.gov/circulars/35802.
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TITLE: GCN CIRCULAR
NUMBER: 35801
SUBJECT: GRB 240222A: ATCA radio observations
DATE: 24/02/26 17:22:04 GMT
FROM: jamesk.leung(a)utoronto.ca
J. K. Leung (U. Toronto/HUJI), G. E. Anderson (Curtin University),
S. Chastain (UNM), A. Gulati (U. Sydney), L. Rhodes (U. Oxford),
A. J. van der Horst (GWU) on behalf of the PanRadio GRB collaboration
The Australia Telescope Compact Array (ATCA) performed observations
of GRB 240222A (Fermi GBM Team, GCN 35769; D'Avanzo et al., GCN 35770)
at 5.5, 9, 16.7 and 21.2 GHz as part of the Large ATCA "PanRadio GRB"
follow-up programme C3542 (PI. Anderson). ATCA observed from
2024-02-24 12:00 UT to 22:00 UT. In our preliminary analysis, we find
no radio source coincident with the refined XRT position (Beardmore
et al., GCN 35780) with 3 sigma upper limits of 75, 54, 69 and 159
microJy/beam at 5.5, 9.0, 16.7 and 21.2 GHz, respectively.
We thank the CSIRO Space and Astronomy staff for supporting these
observations. We acknowledge the Gomeroi people as the traditional
owners of the Observatory site. The Australia Telescope Compact Array is
part of the Australia Telescope National Facility
(https://ror.org/05qajvd42) which is funded by the Australian Government
for operation as a National Facility managed by CSIRO.
View this GCN Circular online at https://gcn.nasa.gov/circulars/35801.
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