Probing neutrino emission at GeV energies from compact binary mergers with the IceCube Neutrino Observatory

Abstract

The advent of multi-messenger astronomy has allowed for new types of source searches by neutrino detectors. We present the results of the search for 0.5-100 GeV astrophysical neutrinos detected with IceCube and emitted from compact binary mergers detected by the LIGO, Virgo, and KAGRA interferometers from their first run of observation (O1) to the end of the first part of the fourth (O4a). An innovative approach is used to lower the energy threshold to 0.5 GeV and to search for an excess of GeV neutrinos in time coincidence with astrophysical transient events. Furthermore, we use a statistical combination of all observations, a binomial test, to search for a subpopulation of neutrino emitters. No significant excess was found from the studied mergers, with a best post-trial $p$-value of $40\%$, and there is currently no hint of a population of GeV neutrino emitters found in the IceCube data (post-trial $p$-value = $81\%$).

Figures (4)

• Figure 1: Histogram of the time difference between consecutive ELOWEN events, split between before and after November 28th, 2023. This date corresponds to a change in the online data processing that induced an increase in the ELOWEN rate. The y-axis shows the normalised number of occurrences per time bin and the dashed lines show the corresponding exponential fits.
• Figure 2: Effective areas averaged over the full sky as a function of neutrino energy for ELOWEN IceCube:2021jwt, GRECO IceCube:2022lnv, and GFU IceCube:2016xci samples, summed over neutrinos and anti-neutrinos as well as over all flavours (for GFU, only $\nu_\mu/\bar{\nu}_\mu$ are considered).
• Figure 3: Cumulative distribution of the observed $p$-values for the $\pm 500s$ time window search for O1-O4a GW events (blue line) compared to the background-only expectation, the black line representing the median behaviour with the corresponding $2\sigma$ band.
• Figure 4: Summary of 90% CL upper limits on the all-flavour time-integrated energy-squared flux $E^2 F_{\rm all-flavour}^{\nu+\bar{\nu}}(E)$ assuming a power-law spectrum $F_{\rm all-flavour}^{\nu+\bar{\nu}}(E) = \phi (E/\GeV)^{-2}$. The different colours correspond to different IceCube samples: ELOWEN (this work), GRECO IceCube:2023atb, and GFU IceCube:2022mma. The spans in the horizontal axis correspond to the central 90% sensitive energy range for each GW event and sample. The thicker dashed and dotted lines are the limits corresponding to the two confirmed BNS mergers, GW170817 and GW190425.