Detection of gamma rays and cosmic rays from the annihilation or decay of dark matter particles is a promising method for identifying dark matter, understanding its intrinsic properties, and mapping its distribution in the universe. I will review rthe current status and discuss the prospects for indirect searches to robustly identify or exclude a dark matter signal using upcoming experiments...
The Milky Way (MW) dwarf spheroidal satellite galaxies (dSphs) are particularly intriguing targets to search for gamma rays from dark matter (DM) annihilation or decay. They are nearby, DM-dominated, and lack significant emission from standard astrophysical processes. Previous studies using the Fermi Large Area Telescope (LAT) of DM-induced emission from dSphs provide some of the most...
The nature and characteristics of dark matter (DM) have long been a mystery in cosmology and astrophysics. Various DM theories propose that weakly interacting massive particles (WIMPs; mass ~ 1 TeV) can decay or annihilate into standard model particles, producing electromagnetic radiation, specifically very-high-energy (VHE) gamma rays exceeding 100 GeV. Additionally, ultra-heavy DM (mass >...
Dwarf spheroidal galaxies (dSphs) are among the most dark matter (DM) dominated objects, with negligible expected astrophysical gamma-ray emission. This makes nearby dSphs ideal targets for indirect searches of a DM particle signal. The accurate knowledge of their DM content makes it possible to derive robust constraints on the velocity-weighted cross section of DM annihilation. We report on a...
Observations of very high-energy (>1 TeV) cosmic gamma rays are a powerful, unique tool to explore new physics beyond the Standard Model. The Southern Wide-field Gamma-Ray Observatory (SWGO), a next-generation experiment looking for cosmic gamma rays, will be situated in the Southern hemisphere with gamma-ray sensitivity up to the PeV range. This observatory will have an order of magnitude...
One of the most elusive unknowns in particle physics and astrophysics today is the fundamental nature of dark matter. It is theoretically well-motivated that dark matter is a weakly interacting massive particle (WIMP) -- a particle lying within the GeV to TeV energy ranges that interacts very weakly with Standard Model particles. Such behavior makes dark matter extremely difficult to detect...
The X-ray and $\gamma$-ray emission of globular clusters (GCs) is attributed to their large fraction of compact binary systems, especially those with millisecond pulsars (MSPs). We analyze a population of 124 Galactic GCs to investigate how their dynamical properties affect the formation and evolution of compact binary systems and how this can be translated into the clusters' observed X-ray...
Dark Matter (DM) existence is a milestone of the cosmological standard model and, yet, its discovery still remains a complete conundrum. In this contribution, we investigate a unique and original way to probe properties of light-particle dark matter candidates, exploiting the nature of the cosmic-ray (CR) transport inside starburst nuclei (SBNs). Indeed, SBNs are considered CR reservoirs,...
Primordial Black Holes (PBHs) may exist and constitute a portion of the Dark Matter. Their discovery would have profound consequences on fundamental physics and possibly solve some outstanding puzzles in cosmology, such as the existence of high-redshift supermassive black holes.
Baryonic matter would be inevitably attracted towards these objects and form structures such as accretion disks,...
This contribution presents our approach to identify potential exotic objects in the gamma-ray sky using the Fermi-LAT 4FGL-DR3 catalog. We employ both supervised and unsupervised classification techniques to analyze the gamma-ray spectra of sources in the catalog.
For the supervised approach, we simulate realistic gamma-ray spectra and utilize them to train a classifier specifically designed...
A key strategy for constraining the properties of particle dark matter is the search for the gamma-rays produced by its annihilation or decay in dwarf spheroidal galaxies. The Model-Agnostic Dark Halo Analysis Tool (MADHAT) is a publicly-available computational tool that uses data from the Fermi-LAT to constrain gamma ray emission from dwarf satellite galaxies and dwarf galaxy candidates due...
In this talk, I will present updated constraints on 'light' dark matter (DM) particles with masses between 1 MeV and 5 GeV. In this range, we can expect DM-produced $e^\pm$ pairs to upscatter ambient photons in the Milky Way via Inverse Compton, and produce a flux of X-rays that can be probed by a range of space observatories. Using diffuse X-ray data from XMM-Newton, INTEGRAL, NuSTAR and...
Dark matter is one of the ingredients of the standard cosmological model although we do not know its fundamental nature. Huge effort has been made in order to perform a direct detection of this dark matter component but up to now we have only seen it interacting gravitationally. In this regard the indirect detection is a promising method to search for dark matter, where we try to look at...
Upcoming neutrino telescopes will have an unprecedented sensitivity to ultra-high-energy (UHE) neutrinos, above 10 PeV. This achievement will allow to test physics beyond the Standard Model at a very high energy scale, including the decay of heavy dark matter particles. Previous works acknowledged this possibility, showing that the total number of detected events will allow to set competitive...
Monopoles are inevitable predictions of GUT theories. They are produced during phase transitions in the early universe, but also mechanisms like Schwinger effect in strong magnetic fields could give relevant contributions to the monopole number density. I will show that from the detection of intergalactic magnetic fields we can infer additional bounds on the magnetic monopole flux. I will also...
Hot white dwarfs lose energy mainly in the form of neutrinos through plasmon decay from the inner part of the star. Dark sectors, which are being studied to explain a broad collection of anomalies and unknown physics, do have an impact in the energy lost by this mechanism. I will focus on a Three Portal model that connects dark sectors to the Standard Model through a dark scalar (Higgs), a...
The creation of anti-nuclei in the Galaxy has been has been discussed as a possible signal of exotic production mechanisms such as primordial black hole evaporation or dark matter decay/annihilation, in addition to the conventional production from cosmic-ray (CR) interactions. Tentative observations of CR antihelium by the AMS-02 collaboration have re-energized the quest to use antinuclei to...
Cosmic-ray antiprotons from AMS-02 offer valuable information about the nature of dark matter, but their interpretation is complicated by large uncertainties in the modeling of cosmic ray propagation. In this talk, I intend to present a novel framework to efficiently marginalize over various uncertainties in order to obtain robust AMS-02 likelihoods for arbitrary dark matter models. The three...
The cosmic-ray experiment AMS-02 has reported the possible detection of $\sim 10$ anti-helium events. Conventional production mechanisms struggle to explain the similar fluxes observed for both isotopes ${}^4\overline{\text{He}}$ and ${}^3\overline{\text{He}}$. In this talk, I discuss how these species could be created through "anti-nucleosynthesis" occurring in fireballs of standard model...
Neutron stars (NSs) are promising cosmic laboratories to test the nature of dark matter (DM). DM captured by the strong gravitational field of these stellar remnants transfers kinetic energy to the star during the collision. This can produce anomalous heating of old neutron stars. Further thermalization and DM annihilation can add an extra source of heating. We improve former calculations of...
Heavy inelastic dark matter can substantially annihilate outside neutron stars for inelastic inter-state mass splittings $\sim$MeV and produce standard model particles. Such inelastic dark matter annihilations can happen during the long timescale of the dark matter thermalization, i.e. losing enough kinetic energy to enter an orbit fully contained inside the neutron star. In this talk, I will...
Neutron stars can host strong electromagnetic fields deep in their magnetospheres capable of sourcing axions. Low mass axions are produced relativistically and can resonantly convert into radio photons as they escape the magnetosphere. For heavier axions an increasing fraction will instead end up populating a cloud of bound states around the parent neutron star. In this talk I will discuss the...
Axion-like particles (ALPs) are a well-motivated candidate for constituting a significant fraction of dark matter in the Universe. They are produced in high-energy environments of core-collapse supernovae (CCSNe) or binary neutron star (BNS) mergers via Primakoff process. As they enter the Milky Way's magnetic field, ALPs could undergo conversion into gamma rays, resulting in a characteristic...
Axion-like particles (ALPs) are a class of pseudo-Nambu-Goldstone bosons that have been proposed as potential candidates for dark matter. When propagating through astronomical environments embedded with magnetic fields, very high-energy gamma rays can convert to ALPs, modifying the spectral energy distribution of the observed target. Our study employs around 40 hours of data from the MAGIC...
In the hunt for new physics phenomena, such as dark matter, it is
crucial to compare experimental data to theoretical models. During this
step, the most likely values of the model’s parameters — such as particle
masses and cross sections — are inferred. However, a rigorous statistical
treatment of such an inference is oftentimes not practically feasible with-
out making significant...
TeV blazars dominate the extragalactic gamma-ray sky and highly energetic pair beams arising from such blazar jets underproduce gamma rays in the GeV band while inverse-Compton scattering off the cosmic microwave background. Isotropic gamma ray background measurements strongly suggest that when the intergalactic magnetic field is feeble, space plasma instabilities can play a crucial role in...
Coherently oscillating axion clumps can in an external magnetic field emit electromagnetic radiation which causes them to decay. In the presence of plasma, such radiation can become resonant if the clump frequency matches the plasma frequency. In this talk, I discuss how backreaction affects the clump frequency over time enabling clumps with a range of different initial frequencies to become...
Photon-ALP oscillation results in the survival of gamma-rays from distant sources above TeV energies. Studies of CAST, Fermi-LAT, and IACT observed events that constrain the ALP parameters. We investigate the effect of photon-ALP oscillations on the gamma-ray spectra of the first extragalactic neutrino source, TXS 0506+056, for the observations of Fermi-LAT and MAGIC around the IC170922-A...
If dark matter is composed of axions, then axion stars form in the cores of dark matter halos. These stars are unstable above a critical mass, decaying to radio photons that heat the intergalactic medium, offering a new channel for axion indirect detection. Axion star decays lead to efficient reionization of the intergalactic medium during the dark ages. By comparing this non-standard...
Dark matter energy injection in the early universe modifies both the ionization history and the temperature of the intergalactic medium. In this work, we improve the CMB bounds on sub-keV dark matter and extend previous bounds from Lyman-$\alpha$ observations to the same mass range, resulting in new and competitive constraints on axion-like particles (ALPs) decaying into two photons. The...
The Galactic Center Gamma-Ray Excess has a spectrum, angular distribution, and overall intensity that agree remarkably well with that expected from annihilating dark matter particles in the form of a ~50 GeV thermal relic. Previous claims that these photons are clustered on small angular scales or trace the distribution of known stellar populations once appeared to favor interpretations in...
The nature of the GeV gamma-ray Galactic center excess (GCE) in the data of Fermi-Large Area Telescope (LAT) is still to be unveiled. While the GCE photon flux is peaked at about few GeV, a high energy tail extending up to tens of GeV has been reported by various studies. If confirmed, such high-energy photons are naturally explained by the inverse Compton emission of electrons and positrons...
The nature of Dark Matter is one of the important unresolved questions in fundamental physics. It is assumed in many Beyond Standard Model theories that dark matter candidates can have weak coupling to Standard Model (SM) particles. In heavy cosmological objects, like galaxies, the Sun, or the Earth, dark matter can be gravitationally accumulated to a high abundance such that it can decay or...
Some candidates for the theory of quantum gravity allow for Lorentz invariance violation (LIV). If Lorentz's invariance is violated, it may cause an observable effect on the very high energy (VHE, E > 100 GeV) light curves and spectra of cosmic sources emitting gamma-ray photons. One of the possible consequences of the LIV is in-vacuo dispersion which implies that the photon group velocity is...
Historically, dark matter searches have primarily focused on hunting for effects from two-to-two scattering. However, given that the visible universe is primarily composed of plasmas governed by collective effects, there is great potential to explore similar effects in the dark sector. Recent semi-analytic work has shown that new areas of parameter space for dark U(1) and millicharged models...
Milli-charged particles (MCP) can be produced through the decay of plasmon in stellar interiors and escape stars without interactions. This extra cooling could alter the brightness of low mass stars at the tip of the red giant branch (RGB). While the current stellar cooling bounds were obtained by estimating the total expected heat loss given the current stellar properties, we improve the...
Instantons can give rise to decay of particles otherwise forbidden. Using data collected at the Pierre Auger Observatory, we present a search for signatures of such instanton-induced decay processes that could be at work for super-heavy particles produced sufficiently during the post-inflationary epoch to match the relic abundance of dark matter inferred today. The non-observation of these...
