IceCube-240424A
GCN Circular 36283
Subject
IceCube-240424A - IceCube observation of a high-energy neutrino candidate track-like event
Date
2024-04-24T14:00:19Z (a year ago)
From
A. Zegarelli at Ruhr University Bochum <azegarelli@icecube.wisc.edu>
Via
Web form
The IceCube Collaboration (http://icecube.wisc.edu/) reports:
On 2024-04-24 at 01:49:26.0 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 1.225 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/139315_50057906.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:
Date: 2024-04-24
Time: 01:49:26.0 UT
RA: 327.08 (+2.06, -1.70 deg 90% PSF containment) J2000
Dec: 3.06 (+1.37, -1.33 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.
Two Fermi-LAT sources (listed in the 4FGL-DR4 or 3FHL catalogs) are located in the 90% uncertainty region. The nearest gamma-ray source in either catalog is 4FGL J2149.6+0323 (J2149.8+0322 in the 3FHL catalog) at RA: 327.42 deg and DEC: 3.40 deg (0.5 deg away from the best-fit position). The second one is 4FGL J2146.8+0425 at RA: 326.71 deg and DEC: 4.43 deg, 1.4 deg away from the best-fit position. The former source is associated with a BL Lac object, while the latter is a blazar candidate of uncertain type.
Additionally, we note that a recent GRB triggered by the Swift Burst Alert Catalog (BAT) on April 19, 2024 (GRB 240419B, detection time 2024-04-19 12:22:52 UT, GCN Circular #36180), is contained within the 90% uncertainty region of the neutrino candidate event, ~1.7 deg from its best-fit 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@icecube.wisc.edu
GCN Circular 36309
Subject
IceCube-240424A: Upper limits from a search for additional neutrino events in IceCube
Date
2024-04-25T20:37:57Z (a year ago)
From
Alicia Mand at IceCube/UW-Madison <aemand@wisc.edu>
Via
Web form
The IceCube Collaboration (http://icecube.wisc.edu/) reports:
IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-240424A (https://gcn.nasa.gov/circulars/36283) in a time range of 1000 seconds centered on the alert event time (2024-04-24 01:41:06.000 UTC to 2024-04-24 01:57:46.000 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-240424A. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-240424A is 1.4e-01 GeV cm^-2 in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 3e+02 GeV and 2e+05 GeV.
A subsequent search was performed including 2 days of data centered on the alert event time (2024-04-23 01:49:26.000 UTC to 2024-04-25 01:49:26.000 UTC). In this case, we report a p-value of 1.00, consistent with no significant excess of track events. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-240424A is 1.6e-01 GeV cm^-2 in a 2 day time window.
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@icecube.wisc.edu.
[1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021)
GCN Circular 36349
Subject
Fermi-LAT gamma-ray observations of IceCube-240424A
Date
2024-04-29T19:18:19Z (a year ago)
From
Sara Buson at DESY, Univ. of Wurzburg <sara.buson@gmail.com>
Via
Web form
S. Garrappa (Weizmann Institute of Science), C. Bartolini (INFN Bari), S. Buson (Univ. of Wuerzburg), L. Pfeiffer (Univ. of Wuerzburg) and J. Sinapius (DESY) on behalf of the Fermi-LAT collaboration:
We report an analysis of observations of the vicinity of the IC240424A high-energy neutrino event (GCN 36283) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 2024-04-24 at 01:49:26 UT (T0) with J2000 position RA = 327.08 (+2.06, -1.70) deg, Decl. = +3.06 (+1.37, -1.33) deg (90% PSF containment). Two catalogued gamma-ray (>100 MeV; 4FGL, The Fermi-LAT collaboration 2022, ApJS, 260, 53) sources are located within the 90% IC240204A localization region. These are 4FGL J2149.6+0323 (associated with the FSRQ PKS B2147+031) and 4FGL J2146.8+0425 (associated with the FSRQ MG1 J214653+0427). Based on a preliminary analysis of the LAT data over the timescales of 1-month and 1-day prior to T0, these objects are not significantly detected (> 5 sigma).
We searched for intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (> 5 sigma) new excess emission (> 100 MeV) at the IC240424A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC240424A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 1.2e-10 ph cm^-2 s^-1 for ~15-years (2008-08-04 to 2024-04-24 UTC), and < 2.2e-8 (<3.2e-8) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0.
In the analysis of the ~15-years integrated LAT data (100 MeV - 1 TeV), a 4.5 sigma new excess of gamma rays, Fermi J2151.3+0220 was detected 1 deg offset from the best-fit IC240424A position and within the 90% confidence localization of the direction of the neutrino. Assuming a power-law spectrum, the best-fit localization is (J2000) RA: 327.83 deg, Dec: 2.34 deg (10 arcmin 99% containment, 5 arcmin 68% containment). The gamma-ray best-fit spectral parameters are flux = (2.5 +/- 1.9)e-9 ph cm^-2 s^-1 and index = 1.7+/-0.2. In a preliminary analysis of the LAT data over 1-day and 1-month prior T0, Fermi J2151.3+0220 is not significantly detected in the LAT data. All values include the statistical uncertainty only. The statistical significance is calculated following the prescription adopted in the 4FGL.
Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this region will continue. For these observations the Fermi-LAT contact persons is S. Garrappa (simone.garrappa at weizmann.ac.il).
The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
GCN Circular 36396
Subject
IceCube-240424A: GRANDMA Optical Upper Limit of Fermi J2151.3+0220
Date
2024-05-05T10:09:59Z (a year ago)
From
Dalya Akl at American Uni. SHJ <dalyaakl.d@gmail.com>
Via
Web form
D. Akl (AUS), T. Pradier (Unistra/IPHC), T. Jegou du Laz (Caltech), M. Molham (NRIAG), S. Antier (OCA), I. Tosta e Melo (UniCT-DFA), P. Hello (IJCLAB), S. Karpov (FZU), M. Coughlin (UMN), C. Andrade (UMN), P-A Duverne (APC), D. Turpin (CEA-Saclay/Irfu), N. Guessoum (AUS), E. G. Elhosseiny (NRIAG), D. Dornic (CPPM), M. Pillas, J. Dibasso (Berkeley), W. Corradi, N. Sasaki, F. Navarete, L. De Almeida, L. Fraga (LNA), Z. Benkhaldoun, A. Kaeouch (OUCA, KNC) on behalf of GRANDMA collaboration:
We observed the localization region of the neutrino event IceCube-240424A (Zegarelli, GCN 36283; Mand, GCN 36309) primarily at the location of the gamma-ray source Fermi J2151.3+0220 (Garrappa et. al, GCN 36349; RA: 327.83 deg, DEC: 2.34 deg). We considered T0 as 2024-04-24 01:49:26.0 UT.
We did not find any optical counterpart in our images within a 10 arcmin radius around the J2151.3+0220 position for the ASO telescope, and within a 5 arcmin radius for the OPD telescope.
In the following table, we report a subset of the preliminary photometry of our observations of J2151.3+0220. Upper limits are reported in the Vega system.
| T-T0 [day] | MJD | Telescope | Exposure | Filter | Upperlimit (5 sig.) |
+------------+----------------+-----------+-----------+--------+---------------------+
| 6.07 | 60430.15036744 | ASO | 17x180s | L | 21.8 |
| 7.19 | 60431.26727265 | OPD | 10x180s | R | 20.8 |
| 7.21 | 60431.28910205 | OPD | 10x200s | R | 21.1 |
| 7.24 | 60431.31329227 | OPD | 12x250s | R | 21.4 |
ASO and OPD data have been calibrated in V and in R, respectively, using the Gaia DR3 Synphot catalog
All the data have been reduced by a single data processing pipeline STDPIPE (Karpov et al., 2022).
GRANDMA is a worldwide coordinated telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/).