right ascension: 343.81 deg | declination: 24.17 deg | galactic latitude: -31.54 deg
On MJD 55355.00 the IceCube Neutrino Observatory reported the detection of the highly-energetic neutrino IceCube-100608A (GCN 9999). Due to the high-energy and the track-like signature the event has a good positional uncertainty and is likely of astrophysical origin. With the goal of contributing to the identification of the corresponding electromagnetic counterpart we report here a brief summary of the results of our multi-wavelength dissection of the region around the event.
The automatic pipeline processing performs a multi-wavelength analysis similar to that presented by Padovani et al. 2017 for IC170922 [1] and consists of a) a search for blazar and other possible candidates counterparts using the VOU-BLazars tool, b) a detailed analysis of the Fermi-LAT gamma-ray emission around the IceCube error region in a temporal window close to the neutrino detection and the full Fermi data set, and c) the production of the broad band SED and of the light-curves of the most promising candidates.
This section provides the results of the search for blazar-like neutrino counterparts using all the publicly available multi-frequency data on the web. While the cross-matching of the neutrino error region with source catalogs provides first insides, it doesn't unfold the full sensitivity and completeness required to get a clear picture of the region. For this reason we are combining here the information from multiple search strategies. First we retrieve information about known sources from the 3HSP, 4FGL and BZCat catalogs. Nevertheless it is not unlikely that there are more, yet undiscovered sources. Hence. in a second step, we then use all the publicly available data via the VOU-Blazar tool to search for spatial coincidences between radio and x-ray sources. Once such an object is identified we get a preliminary classification of the object using the radio to x-ray flux ratio. All this information is combined in the following two plots - radio and x-ray sources (left) and counterpart candidates (right). The description of the different symbols can be found in the caption.
Radio, X-ray and gamma-ray sources in the area including the error region of IC190730. Radio sources appear as red filled circles, X-ray sources as open blue circles, and gamma-ray sources as purple open triangles. Symbol size is proportional to source intensity.
Map of the area around the 90% error region of IC100608A (blue, solid line) showing candidate blazars (based on radio to X-ray flux ratio), objects from selected catalogues (5BZCat, 3HSP, 4FGL), and flat-spectrum radio sources. Blazar types are color coded as follows: orange for HBLs, cyan for IBLs and dark blue for LBLs. Catalogued sources appear as: diamonds for BZCAT blazars, stars for 3HSP blazars, and traingles for 4FGL sources without counterpart in either of the two previously mentioned catalogs.
Astrophysical neutrinos are usually assumed to be produced through the decay of mesons from photo-hadronic or nuclear-hadronic interactions. Along with the neutrinos these processes also produce gamma-rays at similar energies. It is therefore a promising approach to focus on those counterpart candidates with observable gamma-ray emission. In this section we present the analysis of Fermi-LAT data between 100MeV and 800GeV in photon energy. The two plots below show the residual test-statics maps after subtracting known 4FGL sources in a time window of 200 days around the alert (left) and the entire Fermi mission (right). The maps are produced by adding a fictive source with a spectral index of 2 at each position in the region and fitting for the flux normalisation. The subtraction of the known 4FGL source allows us to identify yet unknown gamma-ray sources coincident with the previously identified multi-wavelength candidates. In each of the plots the successive contour lines indicate regions with an excess of 2,3,4,5 sigma respectively.
Fermi-LAT test statistic map between 55255.0 and 55455.0 (200.0 days around the neutrino arrival time) using all photons above 100MeV. 4FGL sources have been substracted to identify new, yet unkown, gamma-ray objects in the region.
Fermi-LAT test statistic map between 54682.7 and 59234.6 (full mission) using all photons above 100MeV. 4FGL sources have been substracted to identify new, yet unkown, gamma-ray objects in the region.
