arXiv subjects

Shunhao Ji

Publications and source records attributed to Shunhao Ji.

9 recordsLinked to original sources

arXiv2026

Possible High-Energy Neutrino Emission from Dark Matter Annihilation in the Disrupting Dwarf Galaxy Bo\"{o}tes~III

We report the first search for high-energy neutrino emissions from dark matter (DM) annihilation in stellar-stream cores. Motivated by a recent gamma-ray study that proposed these cores as a new class of indirect DM targets, we analyze three stream cores in the Northern Hemisphere using the public ten-year track-like neutrino data released by IceCube. Under the $\chi\chi\to\nu\bar{\nu}$ annihilation hypothesis, the most significant excess among the three targets is found at the position of the nearby dwarf galaxy Bo\"{o}tes~III, the core of the Styx stream, with a best-fit DM mass of 26.5\,TeV. The excess has a post-trial significance of $3.1\sigma$. Considering the existing IceCube dwarf-galaxy limit for the same channel, we obtain a limit on the J-factor $J_{\rm ann}$, $\log_{10}(J_{\rm ann}/{\rm GeV^2\,cm^{-5}})\gtrsim 19.1^{+0.3}_{-0.5}$. This limit is broadly consistent with empirical estimates of $J_{\rm ann}$ for Bo\"{o}tes~III. The results provide the first candidate target with a possible HE neutrino signal associated with DM annihilation. This neutrino excess and the general existence of DM-induced neutrino signals from other similar sources will be confirmed with the near-future large high-energy neutrino detectors, thus enabling us to probe the nature of DM particles.

astro-ph.HE↗

arXiv2026

High-energy neutrino emission from the Type~IIn supernova SN~2017hcd

Neutrino astronomy provides another window to exploring the Universe, exemplified by the detection of a megaelectronvolt neutrino burst from the core-collapse supernova (CCSN) SN~1987A (refs.~\citenum{hir+87,bio+87}). Commonly discussed theories suggest that some CCSNe could produce neutrinos with energies a thousand times more than those of SN~1987A \cite{tm18}, which has been probed with new-generation facilities \cite{abb+12,aar+15,abb+23}. The interaction of SN ejecta with a dense circumstellar medium (CSM) or a jet, launched in a CCSN, being choked in the stellar envelope of the progenitor or an outside CSM are both well-accepted scenarios for the high-energy neutrino production. Here we report the detection of a high-energy neutrino flare at a 3.9$\sigma$ significance from SN~2017hcd, made by our analysis of the public track-like neutrino data taken by the IceCube Neutrino Observatory \cite{IceCube17}. A Type IIn SN with optical emissions arising from the ejecta--CSM interaction, SN~2017hcd's neutrino flare lasted $\sim$1--2 month, with its central time $\sim$14-day prior to the SN's optical discovery time. Its estimated isotropic neutrino energy (all flavors) is approximately two orders of magnitude higher than the energy ($\sim 10^{50}$\,erg) carried in the SN's ejecta, too high to be explained with the ejecta--CSM scenario. Thus, a choked jet may be the source of the neutrino flare.

astro-ph.HE↗

arXiv2025

An extragalactic gamma-ray binary formed in supernova 2022jli

On May 5 2022, a type Ic supernova (SN) explosion SN~2022jli was discovered. This SN showed additional optical emissions, which were found to exhibit 12.4-day periodic undulations and concordant periodic velocity shifts. These key features likely indicate a compact object in a binary system was formed. A faint $\gamma$-ray source was also detected at the position of the SN and upon checking the $\gamma$-ray photons' arrival times, it was revealed that the same 12.4-day periodicity was likely present. Here we report our detailed analysis results for the $\gamma$-ray source. Not only was the $\gamma$-ray emission detectable for $\sim$1.5\,years since the discovery time, but a strong modulation at period 12.5\,day was also clearly determined. Considering the newly formed compact object to be a neutron star or a stellar-mass black hole, the putative binary, having an orbital period of 12.5\,day, is likely the first extragalactic high-energy system detected. The system may serve as a valuable example for the formation of many such binaries observed in the Milky Way and nearby galaxies.

astro-ph.HE↗

arXiv2025

AT2022sxl: A Candidate Repeating Tidal Disruption Event in Possible Association with Two High-Energy Neutrino Events

We report a candidate repeating tidal disruption event (TDE), AT2022sxl, found from large-field optical survey data. Two flares with a separation time of $\sim$7.2\,yr between the two optical peaks are observed. Related mid-infrared (MIR) flares, with delay times of $\sim$200\,day are also seen. We analyze two optical spectra of the TDE source, onenear the optical peak of the second flare from the Transient Name Server and one at the quiescent flux level after the second flare. The latter was taken by us with the 10.4-m Gran Telescopio Canarias. Comparing the features of the two spectra, we identify that the host is likely a composite galaxy at redshift 0.23 and the TDE event, probably an H+He type, mainly powered broad components in the emission lines of H$\alpha$, H$\beta$, and He~I $\lambda$5876. More interestingly, we find that two Bronze-type neutrino events, detected by the IceCube neutrino observatory, match the TDE in position and the second flare, especially the delayed MIR flare, in time. We discuss the MIR luminosity properties of the currently reported (candidate) neutrino-emitting TDEs and suggest that luminous MIR emission is a prerequisite for neutrino production in TDEs.

astro-ph.HE↗

arXiv2025

Possible Neutrino Emission from the Pulsar Wind Nebula G63.7+1.1

We report on our finding of an excess of $54^{+16}_{-15}$ neutrinos at the location of the pulsar wind nebula (PWN) G63.7+1.1. By analyzing the IceCube track-like neutrino data for a group of 14 PWNe, which are selected as the targets because of their reportedly association with molecular clouds, G63.7+1.1 is found to be the only one detected with neutrino emission and the post-trail significance for the detection is 3.2$\sigma$. Previously, this PWN was estimated to have an age of $\gtrsim$8\,kyr, contain a candidate pulsar detected in X-rays, and have a distance of $\sim$6\,kpc. More importantly and related to the PWN's possible neutrino emission, surrounding molecular materials are seen to interact with the PWN. On the basis of these properties, we examine the proton-proton interactions as the process for the neutrino production. The PWN (or the pulsar) can collectively provide sufficient energy to power the required high-energy (HE) protons. This possibly first neutrino-emitting case in our Galaxy, with problems or other possibilities to be solved or examined, may reveal to us that PWNe are the significant Galactic HE neutrino sources.

astro-ph.HE↗

arXiv2024

PKS~2332$-$017 and PMN J1916$-$1519: Candidate Blazar Counterparts to Two High-energy Neutrino Events

We report our counterpart identification study for two high-energy neutrino events IC-130127A and IC-131204A listed in the IceCube Event Catalog of Alert Tracks. These two events belong to Gold alerts, which have a significant probability of being of astrophysical origin.Within the events' 90\% positional uncertainty regions, we respectively find PKS~2332$-$017 and PMN J1916$-$1519. The first source is a flat-spectrum radio quasar at redshift $z= 1.18$ and the second a blazar of an uncertain type with photometric $z= 0.968$. As they correspondingly had a $γ$-ray flare temporally coincident with the arrival times of IC-130127A and IC-131204A, we identify them as the respective neutrino emitters. Detailed analysis of the $γ$-ray data for the two blazars, obtained with the Large Area Telescope (LAT) onboard {\it the Fermi Gamma-ray Space Telescope (Fermi)}, is conducted. The two flares respectively from PKS~2332$-$017 and PMN~J1916$-$1519 lasted $\sim$4\,yr and $\sim$4\,month, and showed possible emission hardening by containing high-energy $\sim$2--10\,GeV photons in the emissions. Accompanying the flare of PKS~2332$-$017, optical and MIR brightening variations were also observed. We discuss the properties of the two sources and compare the properties with those of the previously reported (candidate) neutrino-emitting blazars.

astro-ph.HE↗

arXiv2024

PKS 2254+074: A Blazar in Likely Association with the Neutrino Event IceCube-190619A

We report our study of the field of a $\simeq$0.2 PeV neutrino event IC-190619A. This neutrino belongs to Gold events, which more likely have an astrophysical origin. Among the two $γ$-ray sources within the neutrino's positional uncertainty region, we find that one of them, the BL-Lac--type blazar PKS~2254+074, had a $γ$-ray flare at the arrival time of the neutrino. The flare is determined to have lasted $\sim$2.5 yr in a 180-day binned light curve, constructed from the data collected with the Large Area Telescope (LAT) onboard {\it the Fermi Gamma-ray Space Telescope (Fermi)}. Accompanying the flare, optical and mid-infrared brightening is also seen. In addition, $\geq$10 GeV high energy photons from the source have been detected, suggesting a hardening of the emission during the flare. Given both the positional and temporal coincidence of PKS~2254+074 with IC-190619A, we suggest that this blazar is likely another member of a few recently identified (candidate) neutrino-emitting blazars.

astro-ph.HE↗

arXiv2024

Identifying Three New AGNs Among Fermi Unidentified Gigaelectronvolt Sources

We report our identification of three gigaelectronvolt $γ$-ray sources, 4FGL J0502.6+0036, 4FGL J1055.9+6507, and 4FGL J1708.2+5519, as Active Galactic Nuclei (AGNs). They are listed in the latest Fermi-LAT source catalog as unidentified ones. We find that the sources all showed $γ$-ray flux variations in recent years. Using different survey catalogs, we are able to find a radio source within the error circle of each source's position. Further analysis of optical sources in the fields allows us to determine the optical counterparts, which showed similar variation patterns to those seen in $γ$-rays. The optical counterparts have reported redshifts of 0.6, 1.5, and 2.3, respectively, estimated from photometric measurements. In addition, we also obtain an X-ray spectrum of 4FGL J0502.6+0036 and a flux upper limit on the X-ray emission of 4FGL J1055.9+6507 by analyzing the archival data. The broadband spectral energy distributions of the three sources from radio to $γ$-rays are constructed. Comparing mainly the $γ$-ray properties of the three sources with those of different sub-classes of AGNs, we tentatively identify them as blazars. Followup optical spectroscopy is highly warranted for obtaining their spectral features and thus verifying the identification.

astro-ph.HE↗

arXiv2023

Dissecting the gamma-ray emissions of the nearby galaxies NGC 1068 and NGC 253

Intrigued by recent high-energy study results for nearby galaxies with gamma-ray emission and in particular NGC~1068 that has been detected as a neutrino-emitting source by the IceCube Neutrino Observatory, we conduct detailed analysis of the $γ$-ray data for the galaxies NGC~1068 and NGC~253, obtained with the Large Area Telescope onboard {\it the Fermi Gamma-ray Space Telescope}. By checking for their possible spectral features and then constructing light curves in corresponding energy ranges, we identify spectral-change activity from NGC ~1068 in $\geq$2\,GeV energy range and long-term detection significance changes for NGC~253 in $\geq$5\,GeV energy range. In the former, the emission appears harder in two half-year time periods than that in the otherwise `quiescent' state. In the latter, a $\sim$2-times detection significance decrease after MJD~57023 is clearly revealed by the test-statistic maps we obtain. Considering studies carried out and models proposed for the $γ$-ray emissions of the two sources, we discuss the implications of our findings. We suspect that the jet (or outflow) in NGC~1068 might contribute to the \gr\ emission. The nature of the long-term detection significance change for NGC~253 is not clear, but since the part of the GeV emission may be connected to the very-high-energy (VHE) emission from the center of the galaxy, it could be further probed with VHE observations.

astro-ph.HE↗