Search for spatial coincidence between magnetars and IceCube detected neutrinos

TL;DR

The paper tests whether magnetars contribute to IceCube's diffuse TeV–PeV neutrino flux by searching for spatial coincidences using the IceCube public 10-year muon-track dataset and a catalog of 37 magnetars (galactic and extragalactic). It employs an unbinned maximum-likelihood approach with a data-driven background and a signal PDF based on angular separation, evaluating significance via a test statistic $TS = 2 \log (L(\hat{n}_s)/L(0))$ that follows a half-$\chi^2$ distribution under the null. No significant associations are found; the largest local significance is $TS=3.34$ (≈$1.8\sigma$) for a magnetar, with a post-trial $p$-value of 0.6. Consequently, the study sets 95% confidence level upper limits on magnetar neutrino fluxes and, while stacking across all magnetars yields no excess, it indicates that magnetars do not dominate IceCube's diffuse flux with current data, though next-generation detectors like IceCube-Gen2 could enhance sensitivity.

Abstract

We implement a search for spatial coincidence between high energy neutrinos detected by the IceCube neutrino detector (using the publicly available 10-year muon track data) and 37 magnetars, including six extragalactic sources. We use the unbinned maximum likelihood method for our analysis. We do not find any such spatial association between any of the known magnetars and IceCube-detected neutrinos. Therefore, we conclude that none of the known galactic or extragalactic magnetars contribute to the diffuse neutrino flux observed in IceCube. A stacked analysis also does not show a statistically significant excess.

Figures (2)

• Figure 1: Distribution of TS for null hypothesis using 5000 randomly selected positions uniformly distributed between RA of 0 and $360^{\circ}$, and $\sin(\delta)$ between -1 and 1. The red line curve corresponds to half the PDF of $\chi^2$ distribution with one degree of freedom and provides a good fit to the PDF of TS distribution for TS$>0$.
• Figure 2: Plot of TS as a function of the total differential neutrino flux for 37 magnetars using the IceCube 10-year muon-track data. In this analysis, we considered $\omega_{model}=1$ and $\Gamma=-2.53,-2,-3$. The dashed horizontal line corresponds to TS=-2.7, which can be used to obtain the 95% c.l. upper limit. The stacked 95% c.l. upper limit on the differential neutrino flux is given by $1.2 \times 10^{-6} (\gamma=-3.0), 7.4 \times 10^{-6} (\gamma=-2.53)$, and $2.6 \times 10^{-5} (\gamma=-2.0)$$\rm{GeV^{-1}~cm^{-2}~sec^{-1}}$.