TITLE: GCN CIRCULAR
NUMBER: 35984
SUBJECT: IceCube-240327B - IceCube observation of a high-energy neutrino candidate track-like event
DATE: 24/03/27 18:11:03 GMT
FROM: Giacomo Sommani at Ruhr-Universität Bochum <gsommani(a)icecube.wisc.edu>
The IceCube Collaboration (http://icecube.wisc.edu/) reports:
On 2024-03-27, at 16:12:30.47 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_BRONZE alert stream. The average astrophysical neutrino purity for Gold alerts is 30%. This alert has an estimated false alarm rate of 2.420 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection.
After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/139205_9784024.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:
Date: 2024-03-27
Time: 16:12:30.47 UT
RA: 89.21 (+1.36, -1.55 deg 90% PSF containment) J2000
Dec: 0.93 (+1.23, -1.47 deg 90% PSF containment) J2000
We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino.
Five known gamma-ray sources listed in the Fermi 4FGL-DR4 or 3FHL catalogs are located within the 90% uncertainty region of the event. The nearest one to the neutrino alert position is 4FGL J0555.9+0030, located at RA = 89.00 deg, Dec = 0.51 deg J2000, 0.47 deg away from the best-fit alert position.
The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu
View this GCN Circular online at https://gcn.nasa.gov/circulars/35984.
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TITLE: GCN CIRCULAR
NUMBER: 35983
SUBJECT: IceCube-240327A - IceCube observation of a high-energy neutrino candidate track-like event
DATE: 24/03/27 13:44:38 GMT
FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu>
The IceCube Collaboration (http://icecube.wisc.edu/) reports:
On 2024-03-27 at 11:04:49.50 UT IceCube detected a track-like event with a high probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_GOLD alert stream. The average astrophysical neutrino purity for Gold alerts is 50%. This alert has an estimated false alarm rate of 1.0306 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection.
After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/139204_39158985.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:
Date: 2024-03-27
Time: 11:04:49.50 UT
RA: 25.40 (+1.86, -2.36 deg 90% PSF containment) J2000
Dec: 7.78 (+0.69, -0.68 deg 90% PSF containment) J2000
We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino.
No known gamma-ray sources listed in the Fermi 4FGL-DR4 or 3FHL catalogs are located within the 90% uncertainty region of the event.
The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu
View this GCN Circular online at https://gcn.nasa.gov/circulars/35983.
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TITLE: GCN CIRCULAR
NUMBER: 35982
SUBJECT: X-ray transient EP 240315a: Second epoch Chandra observations
DATE: 24/03/27 09:06:39 GMT
FROM: Andrew Levan at Radboud University <a.levan(a)astro.ru.nl>
A.J. Levan (Radboud & Warwick), P.G. Jonker (Radboud), D.B. Malesani (DAWN/NBI & Radboud), N.R. Tanvir (Leicester), B.P. Gompertz (Birmingham), A. Saccardi (GEPI/Obs. de Paris), A. de Ugarte Postigo (CNRS/OCA & LAM), A. Martin-Carrillo (UCD), D. Perley (LJMU), D. Xu (NAOC), G. Tagliaferri (INAF, Brera), J. Palmerio (GEPI/Obs. de Paris)), K.E. Heintz (DAWN/NBI), K. Wiersema (Hertfordshire), M. Grazia Bernardini (INAF, Brera), M. Ferro (INAF, Brera), P. Jakobbson (U. Iceland), P. D’Avanzo (INAF, Brera), R. Salvaterra (INAF, Milan), S. Vergani (GEPI/Obs. de Paris), G. Pugliese (API, Amsterdam), Y. Julakanti (Leicester) report for the Stargate collaboration:
We obtained a second epoch of Chandra observations of EP240315a (Zhang et al., GCN 35931; Chen et al., GCN 35951) beginning at 04:34 on 26 March 2024, approximately 10.4 days after the transient detection and 6 days from the first epoch of observations (Levan et al., GCN 35963). A total of 18.5 ks of observations were obtained (compared to 10 ks at the first epoch). At the location of AT2024eju (Srivastav et al. GCN 35932) we do not detect any source. More formally, we identify a single photon at the source location, and set a 2-sigma upper limit of <2.4e-4 count s^-1 at this epoch.
The inferred decay rate from 3 days to 10.4 days is steeper than t^-2.1, and suggests a relatively rapid decay. This is consistent with the post-jet break decay rate for a GRB afterglow.
We again thank Pat Slane, Vinay Kashyap and the staff of the CXC for their excellent support and rapid scheduling of these observations.
View this GCN Circular online at https://gcn.nasa.gov/circulars/35982.
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TITLE: GCN CIRCULAR
NUMBER: 35980
SUBJECT: X-ray transient EP240315a: e-MERLIN radio observations
DATE: 24/03/26 14:45:28 GMT
FROM: Gabriele Bruni at INAF <gabriele.bruni(a)inaf.it>
G. Bruni (INAF-IAPS), L. Rhodes (Oxford), L. Piro, G. Gianfagna, A.L. Thakur (INAF-IAPS), J. Bright, F. Carotenuto, S. Smartt, R. Fender (Oxford), P. Jonker (Radboud) report:
We observed the new Fast X-ray Transient EP240315a (Zhang et al., GCN 35931) with the e-Merlin radio telescope under the projects DD17003 (PI: Piro) and DD17004 (PI: Rhodes) at 5 GHz for a total of ~16 hours using a combination of two runs in two consecutive nights (from ~17:30 UT to ~02.00 UT, on March 20 and 21, 2024).
3C286 was used for flux scale calibration, and 0933-0819 for complex gain, respectively. The beam size was 275x104 milli-arcsec. Data was reduced with the e-MERLIN pipeline and imaged with CASA. The image RMS was 15 uJy/beam.
We did not find statistically significant emission at a level above 5-sigma at the position of the optical counterpart (AT2024eju, Srivastav et al., GCN 35932). Thus, we estimated a 5-sigma upper limit of 75 uJy at 5 GHz. Scintillation could be a possible explanation for the large variability with respect to the previous radio detection at the same frequency (Leung et al., GCN 35968).
Further e-Merlin observations are planned. We thank the e-Merlin staff for their excellent support.
View this GCN Circular online at https://gcn.nasa.gov/circulars/35980.
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TITLE: GCN CIRCULAR
NUMBER: 35979
SUBJECT: X-ray transient EP240315a: Ondrejov D50 optical limit
DATE: 24/03/26 11:07:49 GMT
FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov <martin.jelinek(a)asu.cas.cz>
Alzbeta Malenakova, Jan Strobl, Martin Jelinek, Rene Hudec and Cyril Polasek
(ASU CAS Ondrejov, CZ), report:
We observed the field of the fast X-ray transient EP240315a detected by Einstein Probe (Zhang et al., GCN 35931) and its optical counterpart AT2024eju detected by ATLAS (Srivastav et al., GCN 35932) with the 50 cm robotic telescope (D50) of Ondrejov observatory in Czech Republic. We obtained a set of 120s SDSS-r' exposures starting at 23:03 UT on March 16.
We measure the optical limit r' > 21.1 in a combined 26x120s image with a mean time T-T0 27.43h post detection, which is in agreement with other observations at similar epoch (e.g. Chen et al., GCN 35938, Leonini et al., 35944).
View this GCN Circular online at https://gcn.nasa.gov/circulars/35979.
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TITLE: GCN CIRCULAR
NUMBER: 35978
SUBJECT: Transient EPW20240219aa: REM optical/NIR further observations
DATE: 24/03/26 09:04:38 GMT
FROM: Matteo Ferro <matteo.ferro(a)inaf.it>
M. Ferro, Y.-D. Hu, P. D’Avanzo, R. Brivio, S. Covino, D. Fugazza (INAF-OAB) on behalf of the REM team, report:
We observed for a second epoch 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 March 15 at 23:53:40 UT (i.e. 25.73 days after the event), and lasting for about 30 minutes.
In order to identify a possible supernova we performed image subtraction between these observations and the first epoch (taken 5.75 days after the event, Ferro et al., GCN 35803). We find no clear transient 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 > 18.1 (Vega; calibrated against the 2MASS catalogue)
r > 19.8 (AB; calibrated against the Pan-STARRS catalogue)
View this GCN Circular online at https://gcn.nasa.gov/circulars/35978.
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