Since the start of the gravitational wave observation era, no joint high energy neutrino and gravitational wave event has been found. These non-detections could be used for setting an upper bound on the neutrino emission properties for gravitational wave events individually or for a set of them. Although in the previous joint high energy neutrino and gravitational wave event searches upper limits have been found, there is a lack of consistent method for the calculation. The problem addressed in this paper is finding those limits for astrophysical events which are localized poorly in the sky where the sensitivities of the neutrino detectors change significantly and can also emit neutrinos, for example the gravitational wave detections. Here we describe methods for assigning limits for expected neutrino count, emission fluence and isotropically equivalent emission based on maximum likelihood estimators. Then we apply described methods on the three GW detections from aLIGO's first observing run (O1) and find upper limits for them.
A brief white paper is provided, discussing how the particle acceleration mechanisms taking place within astrophysical sources may mimic or mask signatures of new physics and the role that will be played by next-generation gamma-ray observatories, such as the Cherenkov Telescope Array, in improving our understanding of these phenomena.
IceCube, a cubic-kilometer sized neutrino detector at the Geographic South Pole, has recently discovered a diffuse all-flavor flux of astrophysical neutrinos. However, the corresponding astrophysical sources have not yet been identified in current IceCube analyses. We present a method to interpret the results of a recently published angular correlation analysis in IceCube searching for spatial clustering of muon neutrino events in terms of astrophysical models (given by an arbitrary source count distribution). We exemplarily show the resulting limits on the parameters of a class of source coun…
The IceCube Neutrino Observatory is a cubic kilometer-sized detector designed to detect neutrinos of astrophysical origin. However, muons created by cosmic rays interacting in the atmosphere pose a significant background for these astrophysical neutrinos particularly in the southern equatorial sky. Identifying neutrino events that start in the detector allows us to reduce the atmospheric muon component while retaining a high rate of starting neutrino events. The method presented today also rejects atmospheric neutrinos if they are accompanied by muons from the same cosmic ray shower, lowering …
Understanding cosmic acceleration mechanisms, such as jet formation in black holes, star collapses or binary mergers, and the propagation of accelerated particles in the universe is still a `work in progress' and requires a multi-messenger approach, exploiting the complementarities across all possible probes: ultra-high energy cosmic rays (UHECR), gamma-rays and neutrinos. In this report I will summarize some of the IceCube results concerning searches for astrophysical neutrino point sources and diffuse fluxes from populations of sources widely distributed in the sky or from the interactions o…
Spectral and anisotropy properties of IceCube astrophysical neutrino signal reveal an evidence for a significant Galactic contribution to the neutrino flux in Southern hemisphere. We check if the Galactic contribution is detectable in the astrophysical muon neutrino flux observed from a low positive declinations region of the Northern sky. Estimating the Galactic neutrino flux in this part of the sky from gamma-ray and Southern sky neutrino data, we find that the Northern sky astrophysical muon neutrino signal shows an excess over the Galactic flux. This points to the presence of an additional…
The IceCube Neutrino Observatory has discovered a diffuse all-flavor flux of high-energy astrophysical neutrinos. However, the corresponding astrophysical sources have not yet been identified. Neither significant point sources nor significant angular correlations of event directions have been observed by IceCube or other instruments to date. We present a new method to interpret the non-observation of angular correlations in terms of exclusions on the strength and number of point-like sources in generic astrophysical scenarios. Additionally, we constrain the presence of these sources taking int…
DeepCore, as a densely instrumented sub-detector of IceCube, extends IceCube's energy reach down to about 10 GeV, enabling the search for astrophysical transient sources, e.g., choked gamma-ray bursts. While many other past and on-going studies focus on triggered time-dependent analyses, we aim to utilize a newly developed event selection and dataset for an untriggered all-sky time-dependent search for transients. In this work, all-flavor neutrinos are used, where neutrino types are determined based on the topology of the events. We extend the previous DeepCore transient half-sky search to an …
All sky neutrino searches: Atmospheric neutrinos; Astrophysical neutrinos; Cosmegenic neutrinos; Submitted papers to the 32nd International Cosmic Ray Conference, Beijing 2011.
We present the results of time-integrated searches for astrophysical neutrino sources in both the northern and southern skies. Data were collected using the partially-completed IceCube detector in the 40-string configuration between 2008 April 5 and 2009 May 20, totaling 375.5 days livetime. An unbinned maximum likelihood ratio method is used to search for astrophysical signals. The data sample contains 36,900 events: 14,121 from the northern sky, mostly muons induced by atmospheric neutrinos and 22,779 from the southern sky, mostly high energy atmospheric muons. The analysis includes searches…
A multi-messenger approach with gravitational-wave transients and high-energy neutrinos is expected to open new perspectives in the study of the most violent astrophysical processes in the Universe. In particular, gamma-ray bursts are of special interest as they are associated with astrophysical scenarios predicting significant joint emission of gravitational waves and high-energy neutrinos. Several experiments (e.g. ANTARES, IceCube, LIGO and Virgo) are currently recording data and searching for those astrophysical sources. In this report, we present the first joint analysis effort using data…
IceCube analyses which look for an astrophysical neutrino signal in the southern sky face a large background of atmospheric muons and neutrinos created by cosmic ray air showers. By selecting starting events in the southern sky, atmospheric muons and neutrinos with accompanying muons are rejected, producing a sample with high astrophysical neutrino purity at lower energies than northern sky samples. Our new selection method looks for muon tracks from a neutrino interaction with a vertex contained inside the detector volume by using the good pointing resolution of the track morphology to create…
Astrophysical observations are a powerful tool to constrain effects of Lorentz-invariance violation in the photon sector. Objects at high redshifts provide the longest possible baselines, and gamma-ray telescopes allow us to observe some of the highest energy photons. Observations include polarization measurements and time-of-flight measurements of transient or variable objects to constrain vacuum birefringence and dispersion. Observing multiple sources covering the entire sky allows the extraction of constraints on anisotropy. In this paper, I review methods and recent results on Lorentz- and…
These proceedings present the results of point-like neutrino source searches using ~10 yrs of IceCube data from Apr.~6, 2008 to Jul.~10, 2018. We evaluate the significance of an astrophysical signal from a point-like source looking for an excess of clustered neutrino events with energies above ~1 TeV among the background of atmospheric muons and neutrinos. We perform a full sky scan, a search based on a selected source catalog, and a catalog population study. The most significant location in the Northern hemisphere from the full-sky scan is compatible with the Seyfert galaxy NGC 1068. This obj…
Recent results from IceCube regarding TXS 0506+056 suggest the presence of neutrino flares that are not temporally coincident with a significant corresponding gamma ray flare. Such flares are particularly difficult to identify, as their presence must be inferred from the temporal distribution of neutrino data alone. Here we present the results of using a novel method to search for all such flares across the entire neutrino sky in 10 years of IceCube data, using both Gaussian and box-shaped flare hypotheses. Unlike for past searches, that looked for only the most significant neutrino flare in t…
Although IceCube has discovered a diffuse astrophysical neutrino flux, the underlying sources of these neutrinos remain unknown. Transient astrophysical objects, such as fast radio bursts (FRBs), could explain a large percentage of the measured flux. We present the analysis techniques of IceCube searches for MeV to TeV neutrinos from FRBs. As no significant correlation between IceCube neutrinos and FRBs has been found, we present the first limit on MeV neutrino emission from FRBs and the most constraining limits for neutrinos with GeV to TeV energies. We also describe the prospects for future …
The arrival directions of ultra-high-energy cosmic rays appear to be approximately isotropically distributed over the whole sky, but the last-generation UHECR detector arrays, the Pierre Auger Observatory (Auger) and the Telescope Array (TA), have detected thousands of events, allowing us to study small deviations from isotropy. So far, Auger has detected a large-scale anisotropy consistent with a $\sim 6.5\%$ dipole moment in the distribution of cosmic rays with $E > 8$~EeV, and both collaborations have reported indications for smaller-scale anisotropies at higher energies. On the other hand,…
Searches for unknown physics and decisions between competing astrophysical models to explain data both rely on statistical hypothesis testing. The usual approach in searches for new physical phenomena is based on the statistical Likelihood Ratio Test (LRT) and its asymptotic properties. In the common situation, when neither of the two models under comparison is a special case of the other i.e., when the hypotheses are non-nested, this test is not applicable. In astrophysics, this problem occurs when two models that reside in different parameter spaces are to be compared. An important example i…
Fermi-LAT observations have strongly constrained dark matter annihilation through the joint-likelihood analysis of dwarf spheroidal galaxies (dSphs). These constraints are expected to be robust because dSphs have measurable dark matter content and produce negligible astrophysical emission. However, each dSph is dim, with a predicted flux that typically falls below the accuracy of the background model. We show that this significantly diminishes the reliability of previous joint-likelihood algorithms, and develop an improved analysis that directly accounts for the effect of background mismodelin…
We present the results of archival coincidence analyses using public neutrino data from the 40-string configuration of IceCube (IC40) and contemporaneous public gamma-ray data from Fermi LAT. Our analyses have the potential to discover statistically significant coincidences between high-energy neutrino and gamma-ray signals, and hence, possible jointly-emitting neutrino/gamma-ray transients. This work is an example of more general multimessenger studies that the Astrophysical Multimessenger Observatory Network (AMON) aims to perform. AMON is currently under development and will link multiple r…
The absence of a neutrino flux from self-annihilating dark matter captured in the Sun has tightly constrained some leading particle dark matter scenarios. The impact of astrophysical uncertainties on the capture process of dark matter in the Sun and hence also the derived constraints by neutrino telescopes need to be taken into account. In this review we have explored relevant uncertainties in solar WIMP searches, summarized results from leading experiments, and provided an outlook into upcoming searches and future experiments. We have created an interactive plotting tool that allows the user …
A leading candidate for astrophysical dark matter (DM) is a massive particle with a mass in the range from 50 GeV to greater than 10 TeV and an interaction cross section on the weak scale. The self-annihilation of such particles in astrophysical regions of high DM density can generate stable secondary particles including very high energy gamma-rays with energies up to the DM particle mass. Dwarf spheroidal galaxies of the Local Group are attractive targets to search for the annihilation signature of DM due to their proximity and large DM content. We report on gamma-ray observations taken with …
High-energetic gamma rays from astrophysical targets constitute a unique probe for annihilation or decay of heavy particle dark matter (DM). After several decades, diverse null detections have resulted in strong constraints for DM particle masses up to the TeV scale. While the gamma-ray signature is expected to be universal from various targets, uncertainties of astrophysical origin strongly affect and weaken the limits. At the same time, spurious signals may originate from non-DM related processes. The many gamma-ray targets in the extragalactic sky being searched for DM play a crucial role t…
KM3NeT, a new generation of neutrino telescope, is currently being deployed in the Mediterranean Sea. While its two sites, ORCA and ARCA, were respectively designed for the determination of neutrino mass hierarchy and high-energy neutrino astronomy, this contribution presents a study of the detection potential of KM3NeT in the MeV-GeV energy range. At these low energies, the data rate is dominated by low-energy atmospheric muons and environmental noise due to bioluminescence and K-40 decay. The goal of this study is to characterize the environmental noise in order to optimize the selection of …
This paper is a brief review of the status of the search for astrophysical neutrinos of high energy. Its emphasis is on the search for a hard spectrum of neutrinos from the whole Northern sky above the steeply falling background of atmospheric neutrinos. Current limits are so low that they are beginning to constrain models of the origin of extragalactic cosmic rays. Systematic effects stemming from incomplete knowledge of the background of atmospheric neutrinos are discussed.
Searches for point sources of astrophysical neutrinos and related measurements: Searches for steady and time-variable sources; Follow-up programs; AGNs; GRBs; Moon shadow; Submitted papers to the 32nd International Cosmic Ray Conference, Beijing 2011.
Continuous gravitational-wave (CW) signals such as emitted by spinning neutron stars are an important target class for current detectors. However, the enormous computational demand prohibits fully coherent broadband all-sky searches for prior unknown CW sources over wide ranges of parameter space and for yearlong observation times. More efficient hierarchical "semicoherent" search strategies divide the data into segments much shorter than one year, which are analyzed coherently; then detection statistics from different segments are combined incoherently. To optimally perform the incoherent com…
This whitepaper focuses on the astrophysical systematics which are encountered in dark matter searches. Oftentimes in indirect and also in direct dark matter searches, astrophysical systematics are a major limiting factor to sensitivity to dark matter. Just as there are many forms of dark matter searches, there are many forms of backgrounds. We attempt to cover the major systematics arising in dark matter searches using photons -- radio and gamma rays -- to cosmic rays, neutrinos and gravitational waves. Examples include astrophysical sources of cosmic messengers and their interactions which c…
While large neutrino telescopes have so far mainly focused on the detection of TeV-PeV astrophysical neutrinos, several efforts are ongoing to extend the sensitivity down to the GeV level for transient sources. Only a handful of neutrino searches have been carried out at the moment leaving the signature of astrophysical transients poorly known in this energy range. In this contribution, we discuss the motivations for high-energy neutrino telescopes to explore the GeV energy range and summarize the current limitations of detectors, such as IceCube and KM3NeT. We then present and compare differe…
The realization of multimessenger astrophysics will open new vistas upon the most energetic events in the universe. Messenger particles of all four of nature's fundamental forces, recorded by detectors on the ground and satellites in space, enable coincidence searches for multimessenger phenomena that will allow us to discover, observe, and explore these sources. The Astrophysical Multimessenger Observatory Network (AMON) links multiple high-energy neutrino, cosmic ray, and gamma-ray observatories as well as gravitational wave facilities into a single virtual system, enabling near real-time co…
Indirect searches for products of dark matter annihilation and decay face the challenge of identifying an uncertain and subdominant signal in the presence of uncertain backgrounds. Two valuable approaches to this problem are (1) using analysis methods which take advantage of different features in the energy spectrum and angular distribution of the signal and backgrounds, and (2) more accurate characterization of backgrounds, which allows for more robust identification of possible signals. These two approaches are complementary and can be significantly strengthened when used together. I review …
The frequencies and phases of emission from extra-solar sources measured by Earth-bound observers are modulated by the motions of the observer with respect to the source, and through relativistic effects. These modulations depend critically on the source's sky-location. Precise knowledge of the modulations are required to coherently track the source's phase over long observations, for example, in pulsar timing, or searches for continuous gravitational waves. The modulations can be modelled as sky-location and time-dependent time delays that convert arrival times at the observer to the inertial…
Lorentz invariance, the fundamental symmetry of Einstein's theory of Special Relativity, has been established and tested by many classical and modern experiments. However, many theories that unify the Standard Model of particle physics and General Relativity predict a violation of Lorentz invariance at the Planck scale. While this energy range cannot be reached by current experiments, minute deviations from Lorentz symmetry may be present at lower energies. Astrophysical experiments are very suitable to search for these deviations, since their effects accumulate as photons travel across large …
Are neutrinos Majorana? Fixed-target and high-energy astrophysical searches decide
Universitat de València-CSIC（瓦伦西亚大学-西班牙国家研究委员会）；University of Copenhagen（哥本哈根大学）；Simon Fraser University（西蒙菲莎大学）；Arthur B. McDonald Canadian Astroparticle Physics Research Institute（阿瑟·B·麦克唐纳加拿大高能天体粒子物理研究所）
Short, hard gamma-ray bursts (GRBs) are believed to originate from the coalescence of two neutron stars (NSs) or a NS and a black hole (BH). If this scenario is correct, then short GRBs will be accompanied by the emission of strong gravitational waves (GWs), detectable by GW observatories such as LIGO, Virgo, KAGRA, and LIGO-India. As compared with blind, all-sky, all-time GW searches, externally triggered searches for GW counterparts to short GRBs have the advantages of both significantly reduced detection threshold due to known time and sky location and enhanced GW amplitude because of face-…
We study the implications of dark matter searches, together with collider constraints, on the phenomenological MSSM with neutralino dark matter and focus on the consequences of the related uncertainties in some detail. We consider, inter alia, the latest results from AMS-02, Fermi-LAT and XENON1T. In particular, we examine the impact of the choice of the dark matter halo profile, as well as the propagation model for cosmic rays, for dark matter indirect detection and show that the constraints on the MSSM differ by one to two orders of magnitude depending on the astrophysical hypotheses. On the…
Astrophysical searches for new long-range interactions complement collider searches for new short-range interactions. Conveniently, neutrino flavor oscillations are keenly sensitive to the existence of long-ranged flavored interactions between neutrinos and electrons, motivated by lepton-number symmetries of the Standard Model. For the first time, we probe them using TeV-PeV astrophysical neutrinos and accounting for all large electron repositories in the local and distant Universe. The high energies and colossal number of electrons grant us unprecedented sensitivity to the new interaction, ev…
We investigate for the first time the potential of angular auto- and cross-correlation power spectra in identifying sterile neutrino dark matter in the cosmic X-ray background. We take as reference the performance of the soon-to-be-launched eROSITA satellite. The main astrophysical background sources against sterile neutrino decays are active galactic nuclei, galaxies powered by X-ray binaries, and clusters of galaxies. While sterile neutrino decays are always subdominant in the auto-correlation power spectra, they can be efficiently enhanced when cross-correlating with tracers of the dark mat…
In ten years of observations, the IceCube neutrino observatory has revealed a neutrino sky in tension with previous expectations for neutrino point source emissions. Astrophysical objects associated with hadronic processes might act as production sites for neutrinos, observed as point sources at Earth. Instead, a nearly isotropic flux of astrophysical neutrinos is observed up to PeV energies, prompting a reassessment of the assumed transport and production physics. This work applies a new physical explanation for neutrino production from populations of active galactic nuclei (AGN) and starburs…
Antimatter nuclei in cosmic rays (CR) represent a promising discovery channel for the indirect search of dark matter. We present astrophysical background calculations of CR antideuteron ($\overline{d}$) and antihelium ($\overline{He}$). These particles are produced by high-energy collisions of CR protons and nuclei with the gas nuclei of the interstellar medium. In our calculations, we also consider production and shock acceleration of antinuclei in the shells of supernova remnants (SNRs). The total flux of $\overline{d}$ and $\overline{He}$ particles is constrained using new AMS measurements …
While dark matter (DM) is the key ingredient for a successful theory of structure formation, its microscopic nature remains elusive. Indirect detection may provide a powerful test for some strongly motivated DM particle models. Nevertheless, astrophysical backgrounds are usually expected with amplitudes and spectral features similar to the chased signals. On galactic scales, these backgrounds arise from interactions of cosmic rays (CRs) with the interstellar gas, both being difficult to infer and model in detail from observations. Moreover, the associated predictions unavoidably come with theo…
The cumulative (anti)neutrino production from all core-collapse supernovae within our cosmic horizon gives rise to the diffuse supernova neutrino background (DSNB), which is on the verge of detectability. The observed flux depends on supernova physics, but also on the cosmic history of supernova explosions; currently, the cosmic supernova rate introduces a substantial (+/-40%) uncertainty, largely through its absolute normalization. However, a new class of wide-field, repeated-scan (synoptic) optical sky surveys is coming online, and will map the sky in the time domain with unprecedented depth…
Can we learn about New Physics with astronomical and astro-particle data? Since its launch in 2008, the Large Area Telescope, onboard of the Fermi Gamma-ray Space Telescope, has detected the largest amount of gamma rays in the 20 MeV - 300 GeV energy range and electrons + positrons in the 7 GeV- 1 TeV range. These impressive statistics allow one to perform a very sensitive indirect experimental search for dark matter. We will present the latest results on these searches and the comparison with LHC searches.
We discuss the astrophysical science case for a decihertz gravitational-wave mission. We focus on unique opportunities for scientific discovery in this frequency range, including probes of type IA supernova progenitors, mergers in the presence of third bodies, intermediate mass black holes, seeds of massive black holes, improved sky localization, and tracking the population of merging compact binaries.
The quest for the elusive dark matter (DM) that permeates the Universe (and in general the search for signatures of Physics beyond the Standard Model at astronomical scales) provides a unique opportunity and a tough challenge to the high-energy astrophysics community. In particular, the so-called DM indirect searches - mostly focused on a class of theoretically well-motivated DM candidates such as the weakly-interacting massive particles - are affected by a complex astrophysical background of cosmic radiation. The understanding and modeling of such background requires a deep comprehension of a…
The study of anomalous electromagnetic emission in the sky is the basis of indirect searches for dark matter. It is also a powerful tool to constrain the radiative decay of active neutrinos. Until now, quantitative analyses have focused on the flux and energy spectrum of such an emission; polarisation has never been considered. Here we show that we could be missing out on an essential piece of information. The radiative decay of neutrinos, as well as the interactions of dark matter and neutrinos with Standard Model particles can generate a circular polarisation signal in X-rays or γ-rays. If o…
Instrumental and environmental transient noise bursts in gravitational-wave detectors, or glitches, may impair astrophysical observations by adversely affecting the sky localization and the parameter estimation of gravitational-wave signals. Denoising of detector data is especially relevant during low-latency operations because electromagnetic follow-up of candidate detections requires accurate, rapid sky localization and inference of astrophysical sources. NNETFIX is a machine learning-based algorithm designed to remove glitches detected in coincidence with transient gravitational-wave signal…
