Neutrino Emission Research Articles

Astroparticles from X-Ray Binary Coronae

The recent observation of high-energy neutrinos from the Galactic plane implies an abundant population of hadronic cosmic-ray sources in the Milky Way. We explore the role of the coronae of accreting stellar-mass black holes as such astroparticle emitters. We show that the particle acceleration and interaction timescales in the coronal region are tied to the compactness of the X-ray source. Thus, neutrino emission processes may similarly happen in the cores of active galactic nuclei and black hole X-ray binaries (XRBs), despite their drastically different masses and physical sizes. We apply the model to the well-measured XRB Cygnus X-1 and find that the cascaded gamma rays accompanying the neutrino emission naturally explain the GeV emission that only presents during the source’s hard state, while the state-averaged gamma-ray emission explains the LHAASO observation above 20 TeV. We show that XRB coronae could contribute significantly to the Galactic cosmic-ray and Galactic plane neutrino fluxes. Our model predicts variable high-energy neutrino emission from bright Galactic XRBs that may be observed by IceCube and future neutrino observatories.

Neutrino emission in cold neutron stars: Bremsstrahlung and modified urca rates reexamined

Neutrino emission in cold neutron stars is dominated by the modified urca (murca) process and nucleon-nucleon bremsstrahlung. The standard emission rates were provided by Friman and Maxwell in 1979, effectively based on a chiral Lagrangian framework with pion and rho meson exchange, supplemented by Landau parameters to describe short-range interactions. We reevaluate these rates withinthe same framework, correcting several errors and removingunnecessary simplifications, notably the triangular approximation — where the Fermi momenta of protons and leptons negligible compared to that of neutrons — in MURCA, and quantify their importance.The impact of rho meson exchange, previously argued to cancel with interference effects, is actually quite relevant. Altogether, the cooling rates are reduced by as much as a factor 2. We provide comprehensive analytical formulas encompassing all contributions, designed for straightforward numerical implementation. Our results are particularly relevant for studies of physics beyond the standard model, where the emission of new particles — such as axions — is typically computed within the same framework we adopt here.

Chasing the Neutrino Blazar Candidates

In our study of the correlations between IceCube-detected neutrino events and γ-ray properties of blazars, we recognize the inherent challenges posed by the limited detection of neutrinos. In this paper, we explore few-shot learning to deal with the class imbalance and few-shot issues presented in the incremental version of the 12 yr Fermi-LAT γ-ray source catalog (4FGL_ DR3). Specifically, we train a triplet network to transform the blazars with neutrino emission (NBs) and nonblazar samples into an embedding space where their similarities can be measured. With two-way three-shot learning, 199 out of 3708 blazars without neutrino emission (non-NBs) are considered as the potential blazars emitting neutrinos (NB candidates, or NBCs for short), with a similarity score against NBs exceeding 98%. Moreover, the Kolmogorov–Smirnov test supports our identification of NBCs.

Neutrino emission due to pair – annihilation in the neutron star magnetic field

Neutrino emission due to pair – annihilation in the neutron star magnetic field

Search for Joint Multimessenger Signals from Potential Galactic Cosmic-Ray Accelerators with HAWC and IceCube

The origin of high-energy galactic cosmic rays is yet to be understood, but some galactic cosmic-ray accelerators can accelerate cosmic rays up to PeV energies. The high-energy cosmic rays are expected to interact with the surrounding material or radiation, resulting in the production of gamma-rays and neutrinos. To optimize for the detection of such associated production of gamma-rays and neutrinos for a given source morphology and spectrum, a multimessenger analysis that combines gamma-rays and neutrinos is required. In this study, we use the Multi-Mission Maximum Likelihood framework with IceCube Maximum Likelihood Analysis software and HAWC Accelerated Likelihood to search for a correlation between 22 known gamma-ray sources from the third HAWC gamma-ray catalog and 14 yr of IceCube track-like data. No significant neutrino emission from the direction of the HAWC sources was found. We report the best-fit gamma-ray model and 90% CL neutrino flux limit from the 22 sources. From the neutrino flux limit, we conclude that, for five of the sources, the gamma-ray emission observed by HAWC cannot be produced purely from hadronic interactions. We report the limit for the fraction of gamma-rays produced by hadronic interactions for these five sources.

Impacts of Black-hole-forming Supernova Explosions on the Diffuse Neutrino Background

The flux spectrum, event rate, and experimental sensitivity are investigated for the diffuse supernova (SN) neutrino background (DSNB), which originates from past stellar collapses and is also known as a supernova relic neutrino background. For this purpose, the contribution of collapses that lead to successful supernova explosion and black hole (BH) formation simultaneously, which are suggested to be a nonnegligible population from the perspective of Galactic chemical evolution, is taken into account. If the BH-forming SNe involve matter fallback onto the protoneutron star for the long term, their total emitted neutrino energy becomes much larger than that of ordinary SNe and failed SNe (BH formation without explosion). Then, in the case of the normal mass hierarchy in neutrino oscillations and with half of all core-collapse SNe being BH-forming SNe, the expected event rate according to the current DSNB model is enhanced by up to a factor of 2 due to the BH-forming SNe. While substantial uncertainties exist regarding the duration of the matter fallback, which determines the total amount of emitted neutrinos, and the fraction of BH-forming SNe, the operation time required to detect the DSNB at Hyper-Kamiokande would be reduced by such contribution in any case.

AM3: An Open-source Tool for Time-dependent Lepto-hadronic Modeling of Astrophysical Sources

We present the Astrophysical Multimessenger Modeling (AM 3 ) software. AM 3 is a documented open-source software (source code at https://gitlab.desy.de/am3/am3; user guide and documentation at https://am3.readthedocs.io/en/latest/) that efficiently solves the coupled integro-differential equations describing the temporal evolution of the spectral densities of particles interacting in astrophysical environments, including photons, electrons, positrons, protons, neutrons, pions, muons, and neutrinos. The software has been extensively used to simulate the multiwavelength and neutrino emission from active galactic nuclei (including blazars), gamma-ray bursts, and tidal disruption events. The simulations include all relevant nonthermal processes, namely synchrotron emission, inverse Compton scattering, photon–photon annihilation, proton–proton and proton–photon pion production, and photo-pair production. The software self-consistently calculates the full cascade of primary and secondary particles, including nonlinear feedback processes and predictions in the time domain. It also allows the user to track separately the particle densities produced by means of each distinct interaction process, including the different hadronic channels. With its efficient hybrid solver combining analytical and numerical techniques, AM 3 combines efficiency and accuracy at a user-adjustable level. We describe the technical details of the numerical framework and present three examples of applications to different astrophysical environments.

High energy neutrino production in gamma-ray bursts: dependence of the neutrino signal on the jet composition

Heavy nuclei can be synthetized or entrained in gamma-ray bursts (GRBs) with implications on the high-energy neutrino emission. By means of a Monte-Carlo algorithm, we model nuclear cascades and investigate their impact on the neutrino production considering kinetic dominated jets (in the internal shock model, including a dissipative photosphere) as well as Poynting flux dominated jets (for a jet model invoking internal-collision-induced magnetic reconnection and turbulence, ICMART). We find that the ICMART model allows for efficient nuclear cascades leading to an overall larger neutrino fluence than in the other two jet models. The survival of nuclei and inefficient nuclear cascades lead to an overall reduction of the neutrino fluence up to one order of magnitude. However, if nuclei are disintegrated, the neutrino fluence may be comparable to the one emitted from a jet loaded with protons. Exploring the parameter space of jet properties, we conclude that the composition and the bulk Lorentz factor have significant impact on the efficiency of nuclear cascades as well as the spectral shape of the expected neutrino fluence. On the other hand, the neutrino spectral distribution is less sensitive to the power-law index of the accelerated population of protons or heavier nuclei. For what concerns the diffuse emission of neutrinos from GRBs, we find that the uncertainty due to the jet composition can be at most comparable to the one related to the GRB cosmological rate.

Quiescent black hole X-ray binaries as multi-messenger sources

The origin of Galactic cosmic rays (CRs) is unknown even though they have traditionally been connected to supernovae based on energetic arguments. In the past decades, Galactic black holes in X-ray binaries (BHXBs) have been proposed as candidate sources of CRs, which revises the CR paradigm. BHXBs launch two relativistic jets during their outbursts, but recent observations suggested that these jets may be launched even during quiescence. A0620−00 is a well-studied object that shows indications of jet emission. We study the simultaneous radio-to-X-ray spectrum of this source that was detected while the source was in quiescence to better constrain the jet dynamics. Because most BHXBs spend their lifetimes in quiescence (qBHXBs), we used the jet dynamics of A0620−00 to study a population of 105 such sources distributed throughout the Galactic disc, and a further 104 sources that are located in the boxy bulge around the Galactic centre. While the contribution to the CR spectrum is suppressed, we find that the cumulative intrinsic emission of qBHXBs from both the boxy bulge and from the Galactic disc adds to the diffuse emission that various facilities detected from radio to TeV γ rays. We examined the contribution of qBHXBs to the Galactic diffuse emission and investigated the possibility of SKA, INTEGRAL, and CTAO to detect individual sources in the future. Finally, we compare the predicted neutrino flux to the recently presented Galactic diffuse neutrino emission by IceCube.

The shadow and gamma-ray bursts of a Schwarzschild black hole in asymptotic safety

Abstract The effects and rules of the dimensionless parameter $\xi$ on neutrino annihilation $\nu+\bar{\nu}\to e^{-}+e^{+}$ dominated gamma-ray bursts are analysed and investigated within the context of black holes in asymptotic safety. We also computationally model photon orbits around black holes, as photons and neutrinos have the same geodesic equations near black holes. We show that the black hole shadow radius decreases with increasing $\xi$. Calculations are made to determine the temperature of the accretion disk surrounding the black hole and the ratio $\dot{Q}/\dot{Q}_{Newt}$ of energy deposition per unit time to that of the Newtonian scenario. The accretion disk temperature peaks at a higher temperature due to quantum gravity corrections, which increases the probability of neutrino emission from the black hole. It is interesting to note that larger quantum gravity effects cause the ratio value to significantly decline. In the neutrino-antineutrino annihilation process, the energy deposition rate is sufficient even while the energy conversion is inhibited because of quantum corrections. Gamma-ray bursts might originate from the corrected annihilation process. Additionally, we examine the derivative $\mathrm{d}\dot{Q}/\mathrm{d}r$ about the star radius $r$. The findings demonstrate that the ratio is lowered by the black hole's quantum influence. The neutrino pair annihilation grows weaker the more prominent the influence of quantum gravity is.

Berezinsky hidden sources: an emergent tension in the high-energy neutrino sky?

The IceCube Collaboration has recently reported compelling evidence of high-energy neutrino emission from NGC 1068, and also mild excesses for NGC 4151 and CGCG420-015, local Seyfert galaxies. This has increased the interest along neutrino emission from hot-corona surrounding the super massive black holes of Seyfert Galaxies. In this paper, we revisit phenomenological constraints on the neutrino emission from hot-coronae of Seyfert galaxies, using an assumption of sub-equipartition between cosmic-rays and magnetic energy densities. We show that not only these sources are consistent with such an assumption but also that the data point towards low values for the ratio between thermal and magnetic pressure, the so called beta plasma parameters inside Seyfert galaxies. We exploit this finding to constrain the Seyfert diffuse neutrino flux and we obtain that, in order not to overproduce neutrinos, not all the sources can be efficient neutrino emitters. In our approach (along with previous findings), Seyfert galaxies provide a negligible contribution to the diffuse neutrino spectrum above ∼ 100 TeV, allowing space for other astrophysical sources. However, future data from high-energy neutrino telescopes will be crucial to shed more light onto the contribution of this source class to the cosmic neutrino background.

Results of the follow-up of ANTARES neutrino alerts

High-energy neutrinos could be produced in the interaction of charged cosmic rays with matter or radiation surrounding astrophysical sources. To look for transient sources associated with neutrino emission, a follow-up program of neutrino alerts has been operating within the ANTARES collaboration since 2009. This program, named TAToO, has triggered robotic optical telescopes (MASTER, TAROT, ROTSE and the SVOM ground based telescopes) immediately after the detection of any relevant neutrino candidate and scheduled several observations in the weeks following the detection. A subset of ANTARES events with highest probabilities of being of cosmic origin has also been followed by the Swift and the INTEGRAL satellites, the Murchison Widefield Array radio telescope and the H.E.S.S. high-energy gamma-ray telescope. The results of twelve years of observations are reported. In September 2015, ANTARES issued a neutrino alert and during the follow-up, a potential transient counterpart was identified by Swift and MASTER. A multi-wavelength follow-up campaign has allowed to identify the nature of this source and has proven its fortuitous association with the neutrino. No other optical and X-ray counterpart has been significantly associated with an ANTARES candidate neutrino signal. Constraints on transient neutrino emission have been set. The return of experience is particularly important for the design of the alert system of KM3NeT, the next generation neutrino telescope in the Mediterranean Sea.

The Spectra of IceCube Neutrino (SIN) candidate sources

Context. A correlation has been reported between the arrival directions of high-energy IceCube events and γ-ray blazars classified as intermediate- and high-synchrotron-peaked BL Lacs. Subsequent studies have investigated the optical properties of these sources, compiled and analyzed public multiwavelength data, and constrained their individual neutrino emission based on public IceCube point-source data. Aims. We provide a theoretical interpretation of public multiwavelength and neutrino point source data for the 32 BL Lac objects in the sample previously associated with an IceCube alert event. We combined the individual source results to draw conclusions regarding the multimesssenger properties of the sample and the required power in relativistic protons. Methods. We performed particle interaction modeling using open-source numerical simulation software. We constrained the model parameters using a novel and unique approach that simultaneously describes the host galaxy contribution, the observed synchrotron peak properties, the average multiwavelength fluxes, and, where possible, the IceCube point source constraints. Results. We show that a single-zone leptohadronic model can describe the multiwavelength broadband fluxes from all 32 IceCube candidates. In some cases, the model suggests that hadronic emission may contribute a considerable fraction of the γ-ray flux. The required power in relativistic protons ranges from a few percent to a factor of ten of the Eddington luminosity, which is energetically less demanding compared to other leptohadronic blazar models in recent literature. The model can describe the 68% confidence level IceCube flux for a large fraction of the masquerading BL Lacs in the sample, including TXS 0506+056; whereas, for true BL Lacs, the model predicts a low neutrino flux in the IceCube sensitivity range. Physically, this distinction is due to the presence of photons from broad line emission in masquerading BL Lacs, which increase the efficiency of hadronic interactions. The predicted neutrino flux peaks between a few petaelectronvolt and 100 PeV and scales positively with the flux in the gigaelectronvolt, megaelectronvolt, X-ray, and optical bands. Based on these results, we provide a list of the brightest neutrino emitters, which can be used for future searches targeting the 10–100 PeV regime.

Revealing the Production Mechanism of High-energy Neutrinos from NGC 1068

The detection of high-energy neutrino signals from the nearby Seyfert galaxy NGC 1068 provides us with an opportunity to study nonthermal processes near the center of supermassive black holes. Using the IceCube and latest Fermi-LAT data, we present general multimessenger constraints on the energetics of cosmic rays and the size of neutrino emission regions. In the photohadronic scenario, the required cosmic-ray luminosity should be larger than ∼1%−10% of the Eddington luminosity and the emission radius should be ≲15R S in low-β plasma and ≲3R S in high-β plasma. The leptonic scenario overshoots the NuSTAR or Fermi-LAT data for any emission radii we consider, and the required gamma-ray luminosity is much larger than the Eddington luminosity. The beta-decay scenario also violates not only the energetics requirement but also gamma-ray constraints, especially when the Bethe–Heitler and photomeson production processes are consistently considered. Our results rule out the leptonic and beta-decay scenarios in a nearly model-independent manner and support hadronic mechanisms in magnetically powered coronae if NGC 1068 is a source of high-energy neutrinos.

High-energy neutrino emission from tidal disruption event outflow-cloud interactions

High-energy neutrino emission from tidal disruption event outflow-cloud interactions

Enhanced muonization by active-sterile neutrino mixing in protoneutron stars

We study νμ−νs and ν¯μ−ν¯s mixing in the protoneutron star (PNS) created in a core-collapse supernova (CCSN). We point out the importance of the feedback on the general composition of the PNS in addition to the obvious feedback on the νμ lepton number. We show that for our adopted mixing parameters δm2∼102 keV2 and sin22θ consistent with the current constraints, sterile neutrino production is dominated by the Mikheyev–Smirnov–Wolfenstein conversion of ν¯μ into ν¯s and that the subsequent escape of ν¯s increases the νμ lepton number, which in turn enhances muonization of the PNS primarily through νμ+n→p+μ−. While these results are qualitatively robust, their quantitative effects on the dynamics and active neutrino emission of core-collapse supernovae should be evaluated by including νμ−νs and ν¯μ−ν¯s mixing in the simulations. Published by the American Physical Society 2024

Prospects for Time-Domain and Multi-Messenger Science with AXIS

The Advanced X-ray Imaging Satellite (AXIS) promises revolutionary science in the X-ray and multi-messenger time domain. AXIS will leverage excellent spatial resolution (<1.5 arcsec), sensitivity (80× that of Swift), and a large collecting area (5–10× that of Chandra) across a 24-arcmin diameter field of view at soft X-ray energies (0.3–10.0 keV) to discover and characterize a wide range of X-ray transients from supernova-shock breakouts to tidal disruption events to highly variable supermassive black holes. The observatory’s ability to localize and monitor faint X-ray sources opens up new opportunities to hunt for counterparts to distant binary neutron star mergers, fast radio bursts, and exotic phenomena like fast X-ray transients. AXIS will offer a response time of <2 h to community alerts, enabling studies of gravitational wave sources, high-energy neutrino emitters, X-ray binaries, magnetars, and other targets of opportunity. This white paper highlights some of the discovery science that will be driven by AXIS in this burgeoning field of time domain and multi-messenger astrophysics. This White Paper is part of a series commissioned for the AXIS Probe Concept Mission; additional AXIS White Papers can be found at the AXIS website.

Interplay between neutrino kicks and hydrodynamic kicks of neutron stars and black holes

Neutron stars (NSs) are observed with high space velocities and elliptical orbits in binaries. The magnitude of these effects points to natal kicks that originate from asymmetries during the supernova (SN) explosions. Using a growing set of long-time 3D SN simulations with the Prometheus-Vertex code, we explore the interplay of NS kicks that are induced by asymmetric neutrino emission and by asymmetric mass ejection. Anisotropic neutrino emission can arise from a large-amplitude dipolar convection asymmetry inside the proto-NS (PNS) termed LESA (Lepton-number Emission Self-sustained Asymmetry) and from aspherical accretion downflows around the PNS, which can lead to anisotropic neutrino emission (absorption/scattering) with a neutrino-induced NS kick roughly opposite to (aligned with) the kick by asymmetric mass ejection. In massive progenitors, hydrodynamic kicks can reach up to more than 1300 km s−1, whereas our calculated neutrino kicks reach (55–140) km s−1 (estimated upper bounds of (170–265) km s−1) and only ∼(10–50) km s−1, if LESA is the main cause of asymmetric neutrino emission. Therefore, hydrodynamic NS kicks dominate in explosions of high-mass progenitors, whereas LESA-induced neutrino kicks dominate for NSs born in low-energy SNe of the lowest-mass progenitors, when these explode nearly spherically. Our models suggest that the Crab pulsar with its velocity of ∼160 km s−1, if born in the low-energy explosion of a low-mass, single-star progenitor, should have received a hydrodynamic kick in a considerably asymmetric explosion. Black holes, if formed by the collapse of short-lived PNSs and solely kicked by anisotropic neutrino emission, obtain velocities of only some km s−1.

Search for neutrino emission from GRB 221009A using the KM3NeT ARCA and ORCA detectors

Gamma-ray bursts are promising candidate sources of high-energy astrophysical neutrinos. The recent GRB 221009A event, identified as the brightest gamma-ray burst ever detected, provides a unique opportunity to investigate hadronic emissions involving neutrinos. The KM3NeT undersea neutrino detectors participated in the worldwide follow-up effort triggered by the event, searching for neutrino events. In this paper, we summarize subsequent searches, in a wide energy range from MeV up to a few PeVs. No neutrino events are found in any of the searches performed. Upper limits on the neutrino emission associated with GRB 221009A are computed.

Constraining the hadronic properties of star-forming galaxies above 1 GeV with 15-years Fermi-LAT data

Star-forming and starburst galaxies (SFGs and SBGs) are considered to be powerful emitters of non-thermal γ-rays and neutrinos, due to their intense phases of star-formation activity, which should confine high-energy Cosmic-Rays (CRs) inside their environments. On this regard, the Fermi-LAT collaboration has found a correlation between the γ-ray and infrared luminosities for a sample of local sources. Yet, the physics behind these non-thermal emission is still under debate. We provide novel constraints on the tight relation between γ-rays and star formation rate (SFR) exploiting 15 years of public Fermi-LAT data. Thus, we probe the calorimetric fraction Fcal of high-energy protons in SFGs and SBGs, namely, the fraction of high-energy protons actually producing high-energy γ-rays and neutrinos. Further, we extrapolate this information to their diffuse γ-ray and neutrino emissions constraining their contribution to the extra-galactic gamma-ray background (EGB) and the diffuse neutrino flux. Using the publicly-available fermitools, we analyse 15.3 years of γ-ray between 1-1000 GeV data for 70 sources, 56 of which were not previously detected. We relate this emission to a theoretical model for SBGs in order to constrain Fcal for each source and then study its correlation with the star formation rate of the sources. Firstly, we find at 4σ level an indication of γ-ray emission for other two SBGs, namely M 83 and NGC 1365. By contrast, we find that, even with the new description of background, the significance for the γ-ray emission of M 33 (initially reported as discovered) still stands at ~ 4σ (as already reported by previous works).Along with previous findings, the flux of each detected source is consistent with a ~ E -2.3/2.4 spectrum, compatible with the injected CR flux inferred in the Milky-Way. We also notice that the correlation between Fcal and the SFR is in accordance with the expected scaling relation for CR escape dominated by advection. We remark that undiscovered sources strongly constrain Fcal at 95% CL, providing fundamental information when we interpret the results as common properties of SFGs and SBGs. Finally, we find that these sources might contribute (12 ± 3)% to the EGB, while the corresponding diffuse neutrino flux strongly depends on the spectral index distribution along the source class.