arXiv subjects

Hao-Ning He

Publications and source records attributed to Hao-Ning He.

At least 19 recordsLinked to original sources

arXiv2026

A neutrino flare candidate potentially associated with X-ray emission from tidal disruption event ATLAS17jrp

Tidal disruption events (TDEs), in which stars are disrupted by supermassive black holes, have been proposed as potential sources of high-energy neutrinos through hadronic interactions. X-ray-bright TDEs provide dense photon fields conducive to neutrino production via proton-photon ($pγ$) processes. We conducted a time-dependent unbinned likelihood analysis of ten years (2008-2018) of IceCube muon-track data, focusing on ten TDEs with confirmed X-ray detections during this period. We report a neutrino flare candidate spatially and temporally coincident with the TDE ATLAS17jrp, occurring 19 days after the onset of its X-ray activity and lasting for 56 days, with a post-trial $p$-value of 0.01. This significance is modest, representing a hint of an association. We illustrate the neutrino emission using a simple lepton-hadronic model, where X-ray photons serve as target fields. While this model can account for the neutrino data around 100 TeV, the low-energy neutrinos may imply contributions from an additional component. Although constrained by the sample size of X-ray-detected TDEs, these results underscore the need for high-cadence X-ray monitoring and future neutrino observatories to further explore the connection between TDEs and high-energy neutrinos.

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arXiv2025

Ultrahigh-Energy Gamma-ray Emission Associated with Black Hole-Jet Systems

Black holes (BH), one of the most intriguing objects in the universe, can manifest themselves through electromagnetic radiation initiated by the accretion flow. Some stellar-mass BHs drive relativistic jets when accreting matter from their companion stars, forming microquasars. Non-thermal emission from the radio to tera-electronvolt (TeV) gamma-ray band has been observed from microquasars, indicating the acceleration of relativistic particles. Here we report detection of four microquasars (SS 433, V4641 Sgr, GRS 1915+105, MAXI J1820+070) of spectrum extending to the ultrahigh-energy (UHE; photon energy $E>100$ TeV) band and one microquasar (Cygnus X-1) of spectrum approaching 100 TeV, using the Large High Altitude Air Shower Observatory (LHAASO). Notably, the total emission associated with SS 433 cannot be interpreted with a single leptonic component. In the UHE band, its emission is in spatial coincidence with a giant atomic cloud, which is consistent with a hadronic origin. An elongated source is discovered from V4641 Sgr with the spectrum continuing up to 800 TeV. The detection of UHE gamma rays demonstrates that accreting BHs and their environments can operate as extremely efficient accelerators of particles out of 1 peta-electronvolt (PeV), suggesting microquasars to be important contributors to Galactic cosmic rays especially around the `knee' region.

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arXiv2025

Neutrino and Cascade Gamma-Ray Emission from Magnetized Turbulent Coronae in Seyfert Galaxies

Recent neutrino observations from the IceCube Collaboration suggest that Seyfert galaxies are promising candidate sources of neutrinos. Within the standard disk-corona model, we assume that protons are accelerated by a non-resonant acceleration mechanism driven by magnetized turbulence in the corona. These accelerated protons interact with ambient radiation or matter, producing high-energy neutrinos and gamma rays. In this scenario, gamma rays are largely absorbed within the corona. The neutrino luminosity depends primarily on the properties of the corona (such as the X-ray luminosity and radius) and the spectral energy distribution of the target photons. This study demonstrates the relation between the neutrino luminosity and the X-ray luminosity, and further discusses the contribution of cascade gamma rays to coronal radiation. Notably, MeV gamma rays can effectively escape the source, together with neutrinos, and serve as key observational probes for testing this model. Future MeV gamma-ray telescopes, such as AMEGO-X and e-ASTROGAM, are expected to detect such gamma-ray signatures, providing a critical multi-messenger test of the hadronic corona model.

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arXiv2025

A Giant Peanut-shaped Ultra-High-Energy Gamma-Ray Emitter Off the Galactic Plane

Ultra-high-energy (UHE), exceeding 100 TeV (10^12 electronvolts), γ-rays manifests extreme particle acceleration in astrophysical sources. Recent observations by γ-ray telescopes, particularly by the Large High Altitude Air Shower Observatory (LHAASO), have revealed a few tens of UHE sources, indicating numerous Galactic sources capable of accelerating particles to PeV (10^15 electronvolts) energies. However, discerning the dominant acceleration mechanisms (leptonic versus hadronic), the relative contributions of specific source classes, and the role of particle transport in shaping their observed emission are central goals of modern UHE astrophysics. Here we report the discovery of a giant UHE γ-ray emitter at -17.5° off the Galactic plane - a region where UHE γ-ray sources are rarely found. The emitter exhibits a distinctive asymmetric shape, resembling a giant "Peanut" spanning 0.45° \times 4.6°, indicative of anisotropic particle distribution over a large area. A highly aged millisecond pulsar (MSP) J0218+4232 is the sole candidate accelerator positionally coincident with the Peanut region. Its association with UHE γ-rays extending to 0.7 PeV, if confirmed, would provide the first evidence of a millisecond pulsar powering PeV particles. Such a finding challenges prevailing models, which posit that millisecond pulsars cannot sustain acceleration to PeV energies. The detection reveals fundamental gaps in understanding particle acceleration, cosmic-ray transport, and interstellar magnetic field effects, potentially revealing new PeV accelerator (PeVatron) classes.

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arXiv2025

Search for neutrino emission from LHAASO observed Microquasar with IceCube 10-year data

The Large High Altitude Air Shower Observatory (LHAASO) has detected ultra-high-energy (UHE; E>100 TeV) gamma-ray emission from five microquasars, suggesting their potential as Galactic PeV cosmic-ray accelerators. At these energies, the Klein-Nishima effect strongly suppresses leptonic processes, making neutrinos observation a crucial test for hadronic acceleration. We present a search for neutrino emission from these LHAASO-identified Microquasars using ten years of IceCube muon-track data. No significant neutrino signal was found in either single-source or stacking analyses. Our stacking result further shows that the studied microquasars population can only account for a small fraction of the diffuse neutrino flux along the Galactic Plane. Finally, we demonstrate that new-generation neutrino telescopes, such as HUN, will have the sensitivity to probe harmonic emission from these candidate PeVatrons.

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arXiv2025

Probable evidence for a transient mega-electron volt emission line in the GRB 221023A

Detection of spectral line in gamma-ray bursts (GRBs) is importance for studying GRB physics, as it provides insights into the composition and physical conditions of the GRB environment. However, progress in detecting X-ray or gamma-ray emission and absorption lines in GRB spectra has been relatively slow, only the narrow emission line feature of about 10 MeV found in GRB 221009A has exhibited a significance exceeding $5 σ$. Here, we report the probable evidence of a narrow emission feature at about 2.1 mega-electron volts (MeV) in the spectrum of GRB 221023A. The highest statistical significance of this feature is observed in the time interval between 8 and 30 seconds after Fermi Gamma-Ray Burst Monitor trigger, with the chance probability value $<2.56 \times 10^{-5}$ (after accounting for the look-elsewhere effect), corresponding to a Gaussian-equivalent significance $> 4.20 σ$. We interpret this feature as being generated through the de-excitation of excited electrons in the relativistic hydrogen-like high-atomic-number ions entrained in the GRB jet.

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arXiv2024

Evidence for the Sombrero Galaxy as an Accelerator of the Highest-Energy Cosmic Rays

Ultrahigh-energy cosmic rays (UHECRs) are the highest energy messenger from space, with energies exceeding 1 EeV. Although UHECRs were discovered over 60 years ago, their origin still remains a mystery. Pinpointing sources of UHECRs is crucial for understanding the extreme astrophysical processes that accelerate particles to such extraordinary energies. We searched for UHECR multiplets via analyzing 17 years of data with energies greater than 40 EeV from the Pierre Auger Observatory. A spatial association is found between a multiplet of $25.7^{+6.2}_{-7.0}$ cosmic rays and the Sombrero galaxy with a local (global) significance of $4.5~σ~(3.3~σ)$. The Sombrero galaxy hosts a supermassive central black hole with a mass of $\sim1\times 10^9 M_{\odot}$ and exhibits large-scale radio lobes and jets. Our finding provides critical evidence on active supermassive black holes as the source of the highest-energy cosmic rays.

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arXiv2024

Investigation of Galactic supernova remnants and their environment in 26.6° < l < 30.6°, $\vert b \vert \leq$ 1.25° using radio surveys

The problem of missing Galactic supernova remnants (SNRs) refers to the issue that the currently known Galactic SNRs are significantly incomplete compared to the theoretical prediction. To expand the sample of Galactic SNRs, we use GLEAM and THOR+VGPS data across four wavebands ranging from 118 to 1420 MHz to drive a spectral index map covering the region within 26.6° < l < 30.6°, $\vert b \vert \leq$ 1.25°, where numerous SNR candidates were recently found. By using the spectral index map of the sky region and detailed analysis of the spectral indices of individual sources, we confirmed four SNR candidates, namely G26.75+0.73, G27.06+0.04, G28.36+0.21, and G28.78$-$0.44, as SNRs. Additionally, we discovered an expanding molecular superbubble located in this region, discussed pulsars associated with SNR candidates, and discovered a long H$α$ filament that spatially overlaps with the candidate G29.38+0.10. We suggest that the problem of missing Galactic SNRs not only arises from observation limitations, but also could be due to the low-density environments of some SNRs, and the different SN explosion properties.

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arXiv2024

A Novel Model for the MeV Emission Line in GRB 221009A

Gamma-ray bursts (GRBs) have long been considered potential sources of ultra-high-energy cosmic rays (UHECRs; with energy $\gtrsim 10^{18} {\rm~eV}$). In this work, we propose a novel model generating MeV emission lines in GRB, which can constrain the properties of heavy nuclei that potentially exist in GRB jets. Specifically, we find that relativistic hydrogen-like high-atomic-number ions originating from the $β$ decay of unstable nuclei and/or the recombination entrained in the GRB jet can generate narrow MeV emission lines through the de-excitation of excited-electrons. This model can successfully explain the MeV emission line observed in the most luminous GRB ever recorded, GRB~221009A, with suitable parameters including a Lorentz factor $γ\sim 820-1700$ and a total mass of heavy nuclei $M_{\rm tot} \sim 10^{23} - 10^{26}$~g. Especially, the emission line broadening can be reasonably attributed to both the expansion of the jet shell and the thermal motion of nuclei, naturally resulting in a narrow width ($σ_{\rm line} / E_{\rm line} \lesssim 0.2$) consistent with the observation. Furthermore, we predict that different GRBs can exhibit lines in different bands with various evolving behaviors, which might be confirmed with further observations. Finally, our model provides indirect evidence that GRBs may be one of the sources of UHECRs.

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arXiv2024

A detectable ultra-high-energy cosmic ray outburst from GRB 221009A

Gamma-ray bursts (GRBs) have been proposed as one of promising sources of ultra-high-energy cosmic rays (UHECRs), but observational evidence is still lacking. The nearby B.O.A.T. (brightest of all time) GRB 221009A, an once-in-1000-year event, is able to accelerate protons to $\sim 10^{3}$ EeV. Protons arriving at the Milky Way are dominated by neutron-decay-induced protons. The inter-galactic magnetic fields would not yield a sizable delay of the $\geq 10{\rm~EeV}$ cosmic rays if its strength is $\lesssim 10^{-13}{\rm~G}$, while Galactic magnetic fields would cause a significant time delay. We predict that, an UHECR burst from GRB 221009A would be detectable by the Pierre Auger Observatory and the TA$\times$4, within $\sim$ 10 years. The detection of such an UHECR outburst will provide the direct evidence for UHECR acceleration in GRBs.

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arXiv2021

Investigating the nature of MGRO J1908+06 with multiwavelength observations

The unidentified TeV source MGRO J1908+06, with emission extending from hundreds of GeV to beyond 100TeV, is one of the most intriguing sources in the Galactic plane. MGRO J1908+06 spatially associates with an IceCube hotspot of neutrino emission. Although the hotspot is not significant yet, this suggests a possible hadronic origin of the observed gamma-ray radiation. Here we describe a multiwavelength analysis on MGRO J1908+06 to determine its nature. We identify, for the first time, an extended GeV source as the counterpart of MGRO J1908+06, discovering possibly associated molecular clouds (MCs). The GeV spectrum shows two well-differentiated components: a soft spectral component below $\sim10$ GeV, and a hard one ($Γ\sim1.6$) above these energies. The lower-energy part is likely associated with the dense MCs surrounding the supernova remnant SNR G40.5$-$0.5, whereas the higher-energy component, which connects smoothly with the spectrum observed in TeV range, resembles the inverse Compton emission observed in relic pulsar wind nebulae. This simple scenario seems to describe the data satisfactorily, but raises questions about the interpretation of the emission at hundreds of TeV. In this scenario, no detectable neutrino flux would be expected.

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arXiv2018

Search for GeV flare coincident with the IceCube neutrino flare

Recently the IceCube collaboration and 15 other collaborations reported the spatial and temporal coincidence between the neutrino event IceCube-170922A and the radio-TeV activity of the blazar TXS 0506+056. Their further analysis on 9.5 years of IceCube data discovered neutrino flare between September 2014 and March 2015, when TXS 0506+056 is however in "quiescent" state. We analyze the Fermi-LAT data in that direction, and find another bright GeV source PKS 0502+049, which is at an angle of $1.2^{\circ}$ from TXS 0506+056, with strong activties during the neutrino flare. No other bright GeV source was detected in the region of interest. Though PKS 0502+049 is $1.2^\circ$ separated from TXS 0506+056, it locates within the directional reconstruction uncertainties of 7 neutrinos, out of the 13 neutrino events during the neutrino flare. Together with the observed high flux of the $γ$-ray flare, it may be unreasonable to fully discard the (partial) contribution of PKS 0502+049 to the neutrino flare. The single source assumption used in the neutrino data analysis might need to be revisited.

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arXiv2018

High-energy neutrino flare from cloud-jet interaction in the blazar PKS 0502+049

Following the detection of a $\sim$300 TeV neutrino potentially associated with the flaring blazar TXS 0506+056, an excess of neutrinos around its position in 2014-2015 was revealed by IceCube. However, its contemporaneous quiescence in $γ$-rays is challenging to interpret consistently. Meanwhile, the blazar PKS 0502+049, positioned within the neutrino localization uncertainties, was seen to be flaring in $γ$-rays. We show that dense, line-emitting gas clouds that interact with its jet and induce cosmic ray acceleration and hadronuclear interaction can plausibly explain the 2014-2015 neutrino flare.

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arXiv2018

Active galactic nuclei with GeV activities and the PeV neutrino source candidate TXS 0506+056

On 2017 September 22 the IceCube neutrino observatory detected a track-like, very-high-energy event (IceCube-170922A) that is spatially associated with TXS 0506+056, a quasar at a redshift of $z=0.3365$. This source is characterized by the increased acitivies in a very wide energy range (from radio to TeV) during these days. To investigate the possible connection of the PeV neutrino emission with the GeV activity of blazars, in this work we select 116 bright sources and analyze their lightcurves and spectra. We focus on the sources displaying GeV activities. Among these blazars, TXS 0506+056 seems to be typical in many aspects but is distinguished by the very strong GeV activties. We suggest to search for neutrino outburst in the historical data of IceCube, as recently done for TXS 0506+056, from the directions of these more energetic and harder blazars with strong GeV activities.

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arXiv2018

Neutrinos from Choked Jets Accompanied by Type-II Supernovae

The origin of the IceCube neutrinos is still an open question. Upper limits from diffuse gamma-ray observations suggest that the neutrino sources are either distant or hidden from gamma-ray observations. It is possible that the neutrinos are produced in jets that are formed in the core-collapsing massive stars and fail to break out, the so-called choked jets. We study neutrinos from the jets choked in the hydrogen envelopes of red supergiant stars. Fast photo-meson cooling softens the neutrino spectrum, making it difficult to explain the PeV neutrinos observed by IceCube in a one-component scenario, but a two-component model can explain the spectrum. Furthermore, we predict that a newly born jet-driven type-II supernova may be observed to be associated with a neutrino burst detected by IceCube.

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arXiv2018

Short GRBs: opening angles, local neutron star merger rate and off-axis events for GRB/GW association

The jet breaks in the afterglow lightcurves of short gamma-ray bursts (SGRBs), rarely detected so far, are crucial for estimating the half-opening angles of the ejecta ($θ_{\rm j}$) and hence the neutron star merger rate. In this work we report the detection of jet decline behaviors in GRB 150424A and GRB 160821B and find $θ_{\rm j}\sim 0.1$ rad. Together with five events reported before 2015 and other three "identified" recently (GRB 050709, GRB 060614 and GRB 140903A), we have a sample consisting of nine SGRBs and one long-short GRB with reasonably estimated $θ_{\rm j}$. In particular, three {\it Swift} bursts in the sample have redshifts $z\leq 0.2$, with which we estimate the local neutron star merger rate density {to be $\sim 1109^{+1432}_{-657}~{\rm Gpc^{-3}~yr^{-1}}$ or $162^{+140}_{-83} {\rm Gpc^{-3}yr^{-1}}$ if the narrowly-beamed GRB 061201 is excluded}. Inspired by the typical $θ_{\rm j}\sim 0.1$ rad found currently, we further investigate whether the off-beam GRBs (in the uniform jet model) or the off-axis events (in the structured jet model) can significantly enhance the GRB/GW association or not. For the former the enhancement is at most moderate, while for the latter the enhancement can be much greater and a high GRB/GW association probability of $\sim 10\%$ is possible. We also show that the data of GRB 160821B may contain a macronova/kilonova emission component with a temperature of $\sim 3100$ K at $\sim 3.6$ days after the burst and more data are needed to ultimately clarify.

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arXiv2017

Evaluating the bulk Lorentz factors of outflow material: lessons learned from the extremely-energetic outburst GRB 160625B

GRB 160625B is an extremely-bright outburst with well-monitored afterglow emission. The geometry-corrected energy is high up to $\sim 5.2\times10^{52}$ erg or even $\sim 8\times 10^{52}$ erg, rendering it the most energetic GRB prompt emission recorded so far. We analyzed the time-resolved spectra of the prompt emission and found that in some intervals there were likely thermal-radiation components and the high energy emission were characterized by significant cutoff. The bulk Lorentz factors of the outflow material are estimated accordingly. We found out that the Lorentz factors derived in the thermal-radiation model are consistent with the luminosity-Lorentz factor correlation found in other bursts as well as in GRB 090902B for the time-resolved thermal-radiation components. While the spectral cutoff model yields much lower Lorentz factors that are in tension with the constraints set by the electron pair Compoton scattering process. We then suggest that these spectral cutoffs are more likely related to the particle acceleration process and that one should be careful in estimating the Lorentz factors if the spectrum cuts at a rather low energy (e.g., $\sim$ tens MeV). The nature of the central engine has also been discussed and a stellar-mass black hole is likely favored.

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arXiv2016

HESS J1427-608: an unusual hard unbroken $γ-$ray spectrum in a very wide energy range

We report the detection of a GeV $γ$-ray source which is spatially overlapping and thus very likely associated with the unidentified very-high-energy (VHE) $γ$-ray source HESS J1427-608 with the Pass 8 data recorded by the Fermi Large Area Telescope. The photon spectrum of this source is best described by a power-law with an index of $1.85\pm0.17$ in the energy range of $3-500$ GeV, and the measured flux connects smoothly with that of HESS J1427-608 at a few hundred GeV. This source shows no significant extension and time variation. The broadband GeV-TeV emission over four decades of energies can be well fitted by a single power-law function with an index of 2.0, without obvious indication of spectral cutoff toward high energies. Such a result implies that HESS J1427-608 may be a PeV particle accelerator. We discuss possible nature of HESS J1427-608 according to the multi-wavelength spectral fittings. Given the relatively large errors, either a leptonic or a hadronic model can explain the multi-wavelength data from radio to VHE $γ$-rays. The inferred magnetic field strength is a few $μ$G, which is smaller than typical values of supernova remnants (SNRs), and is consistent with some pulsar wind nebulae (PWNe). On the other hand, the flat $γ$-ray spectrum is slightly different from typical PWNe but similar to that of some known SNRs.

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