arXiv subjects

Andrei E. Egorov

Publications and source records attributed to Andrei E. Egorov.

7 recordsLinked to original sources

arXiv2026

Detection prospects for heavy WIMP dark matter around M31* in microwave band

This work analyzes the detection prospects for weakly interacting massive particles (WIMPs) in dark matter (DM) density spike around the supermassive black hole (SMBH) in Andromeda galaxy M31 in microwave band. WIMP annihilation produces relativistic electrons and positrons, which generate the synchrotron emission in strong magnetic field of the accretion flow medium at microwave frequencies. Properties of this emission, as well as their dependence on DM and medium parameters, were modeled. Atacama Large Millimeter Array (ALMA) sensitivity to this emission and underlying WIMP parameters was estimated. It was obtained that M31* in microwave band represents the unique target, where DM spike signal can be detected in case of realistic spike and halo density profiles. In such case ALMA may reach the thermal s-wave annihilating WIMPs with masses up to around 1 TeV with just 10--100 hours exposure. Optimistic parameter configurations may allow probing all possible WIMP masses up to 100 TeV. Related systematic uncertainties are discussed.

astro-ph.GA↗

arXiv2025

Detection prospects for heavy WIMP dark matter near supermassive black holes, particularly in M31

This work analyzes the detection prospects for weakly interacting massive particles (WIMPs) in dark matter (DM) density spikes around nearby supermassive black holes (SMBHs) by observations in very high energy gamma-ray band. Such spikes are unique targets, which provide a possibility to discover the basic thermal s-wave annihilating WIMP with any mass up to the theoretical unitarity limit ~ 100 TeV. All relevant SMBHs were checked, and only MW* and M31* were identified as worthwhile objects. Cherenkov Telescope Array (CTA) sensitivity to heavy WIMPs in M31* was estimated. It was obtained that CTA will be able to probe a major part of TeV-scale WIMP parameter space in case of optimistic spike density configuration in M31*. In certain scenarios, M31* may yield even stronger constraints than MW*. Relevant systematic uncertainties were explored.

astro-ph.HE↗

arXiv2025

Independent check of sporadic beta decay anomalies reported earlier by Parkhomov

A. Parkhomov reported in the past the detection of strong, short, sporadic, nearly everyday decay rate increases in $β$-isotopes placed at the focus of a concave mirror directed at a clear sky. He interpreted this effect as neutrino-induced decay. These neutrinos were assumed to be slow and arrive from space in the form of gravitationally collimated beams. We precisely replicated this experiment for the purpose of independent verification. We recorded about 50 days of data employing Geiger-counter-based signal and control detectors, $^{40}$K and $^{90}$Sr/$^{90}$Y isotopes as $β$-sources. We did not detect any significant difference between the data from signal and control detectors, both datasets obeyed the standard Poissonian process. Thus, we robustly excluded the hypothesized new effect. We suspect that A. Parkhomov was just misled by a trivial electromagnetic instability of his setup.

nucl-ex↗

arXiv2023

Nature of M31 gamma-ray halo in relation to dark matter annihilation

The present work analyzes various aspects of M31 gamma-ray halo emission in its relation to annihilating dark matter (DM). The main aspect is the predicted effect of asymmetry of the intensity of emission due to inverse Compton scattering (ICS) of a possible population of relativistic electrons and positrons ($e^\pm$) in the galactic halo on starlight photons. This asymmetry is expected to exist around the major galactic axis, and arises due to anisotropy of the interstellar radiation field and the inclination of M31. ICS emission and its asymmetry were modeled by GALPROP code for the trial case of $e^\pm$ generated by annihilating weakly interacting massive particles (WIMPs) with various properties. The asymmetry was obtained to appear at photon energies above $\sim$ 0.1 MeV. Morphological and spectral properties of the asymmetry were studied in detail. Potential observational detection of the asymmetry may allow to infer the leptonic fraction in the emission generation mechanism, thus providing valuable inferences for understanding the nature of M31 gamma-ray halo emission. Specific asymmetry predictions were made for the recently claimed DM interpretation of the outer halo emission. The paper also studied the role of secondary -- ICS and bremsstrahlung -- emissions due to DM annihilation for that interpretation. And, finally, the latter was shown to be somewhat restricted by the recently derived WIMP constraints from radio data on M31.

astro-ph.HE↗

arXiv2023

Updated constraints on WIMP dark matter by radio observations of M31 -- all annihilation channels

The present work derived the robust constraints on annihilating WIMP parameters utilizing new radio observations of M31, as well as new studies of its DM distribution and other properties. The characteristics of emission due to DM annihilation were computed in the frame of 2D galactic model employing GALPROP code adapted specifically for M31. This enabled us to refine various inaccuracies of previous studies on the subject. DM constraints were obtained for all possible annihilation channels except $χχ\rightarrow γγ,ν\barν$. A wide variety of radio data was utilized in the frequency range $\approx$(0.1--10) GHz. As the result the thermal WIMP lighter than fiducially $\approx$(40--70) GeV was excluded in the case of light primary annihilation products $χχ\rightarrow τ^+τ^-,μ^+μ^-,gg,c\overline{c},u\overline{u},d\overline{d},s\overline{s},e^+e^-,b\overline{b}$ (and an arbitrary combination of them). Heavier WIMP, which can annihilate to $W^+W^-,Z^0Z^0,t\overline{t},hh$; can not be probed at the level of thermal cross section, unless one assumes the optimistic cases of DM density and magnetic field distributions in M31. In summary, $m_x \gtrsim 40$ GeV represents the fiducial channel-independent mass limit for the thermal WIMP with the full uncertainty range estimated to be $\approx$(20--90) GeV. The obtained exclusions are competitive to those from Fermi-LAT observations of dwarfs and AMS-02 measurements of antiprotons. Our constraints significantly restrict the opportunity to explain the gamma-ray outer halo of M31 by annihilating DM. And, finally, we questioned the possibility claimed in other studies to robustly constrain heavy thermal WIMP with $m_x > 100$ GeV by radio data on M31.

hep-ph↗

arXiv2022

Updated constraints on WIMP dark matter annihilation by radio observations of M31

The present work derived the robust constraints on annihilating WIMP parameters utilizing new radio observations of M31, as well as new studies of its dark matter distribution and other properties. The characteristics of emission due to DM annihilation were computed in the frame of 2D galactic model employing GALPROP code adapted specifically for M31. This enabled us to refine various inaccuracies of previous studies on the subject. DM constraints were obtained for two representative annihilation channels: $χχ\rightarrow b\overline{b}$ and $χχ\rightarrow τ^+τ^-$. A wide variety of radio data was utilized in the frequency range $\approx$(0.1--10) GHz. As the result the thermal WIMP lighter than fiducially $\approx$ 70 GeV for $b\overline{b}$ channel and $\approx$ 40 GeV for $τ^+τ^-$ was excluded. The corresponding mass threshold uncertainty ranges were estimated to be 20--210 GeV and 18--89 GeV. The obtained exclusions are competitive to those from Fermi-LAT observations of dwarfs and AMS-02 measurements of antiprotons. Our constraints do not exclude the explanation of the gamma-ray outer halo of M31 and the Galactic center excess by annihilating DM. The thermal WIMP with $m_x \approx 70$ GeV, which explains the outer halo, would make a significant contribution to the non-thermal radio flux in M31 nucleus, fitting well both the spectrum and morphology. And, finally, we questioned the possibility claimed in other studies to robustly constrain heavy thermal WIMP with $m_x > 100$ GeV by radio data on M31.

astro-ph.CO↗

arXiv2021

On a possible origin of the gamma-ray excess around the Galactic Center

Recent observations of gamma-rays with the Fermi Large Area Telescope (LAT) in the direction of the inner Galaxy revealed a mysterious GeV excess. Its intensity is significantly above predictions of the standard model of cosmic rays (CRs) generation and propagation with a peak in the spectrum around a few GeV. Popular interpretations of this excess are due to either spherically distributed annihilating dark matter (DM) or abnormal population of millisecond pulsars. We suggested an alternative explanation of the excess through the CR interactions with molecular clouds in the Galactic Center (GC) region. We assumed that the excess could be imitated by the emission of molecular clouds with depleted density of CRs with energies below ~ 10 GeV inside. A novelty of our work is in detailed elaboration of the depletion mechanism of CRs with the mentioned energies through the "barrier" near the cloud edge formed by the self-excited MHD turbulence. Such depletion of CRs inside the clouds may be a reason of deficit of gamma rays from the Central Molecular Zone (CMZ) at energies below few GeV. This in turn changes the ratio between various emission components at those energies, and may potentially absorb the GeV excess by simple renormalization of key components.

astro-ph.HE↗