Article
Astronomy & Astrophysics
Margot Fitz Axen, Julia Speicher, Aimee Hungerford, Chris L. Fryer
Summary: An increasing amount of observational data indicates small-scale anisotropies in cosmic rays, with various models proposed to explain them. The standard diffusion transport methods do not account for transport physics in mediums with finite-scale magnetic field structures. This study introduces a Monte Carlo transport method to investigate the effects of finite-scale magnetic field structures on observed small-scale anisotropies in cosmic rays.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Jiacheng Ding, Yunlei Huang, Xiao-Dong Li, Xin Wang, Yang Wang, Lili Yang
Summary: Since the discovery of neutrinos, their origin has remained a mystery until their association with TXS 0506+056. The recent publication of the fourth catalogue of active galactic nuclei (4LAC) has provided useful data to study these phenomena, particularly the blazars, which constitute the majority of the objects in the catalogue. By utilizing machine learning algorithms and deep learning techniques, researchers have achieved impressive success in classifying blazars, including the challenging task of classifying blazars of uncertain type (BCUs). The study also reveals a potential association between blazars and neutrinos, suggesting the possibility of using neutrinos as a feature for object classification in the future.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
F. Calore, A. Dekker, P. D. Serpico, T. Siegert
Summary: Using the analysis method of INTEGRAL/SPI data and a dark matter spatial template, we investigate the constraints on dark matter candidates lighter than weakly interacting massive particles decaying into line or continuum electromagnetic final state channels. The obtained bounds are the strongest to date for dark matter masses between approximately 60 keV and 16 MeV, experiencing two-body decays producing photon lines.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
D. Allard, J. Aublin, B. Baret, E. Parizot
Summary: This study investigates the anisotropic distribution of ultra-high-energy cosmic rays (UHECRs). The authors find that reproducing the observed dipole modulation is relatively easy, but it does not provide strong constraints on the source scenarios or individual parameters. They also find that the reconstructed dipole direction from the data appears highly unnatural in all scenarios. Additionally, this study predicts the existence of quadrupolar modulation and anisotropy in the composition of UHECRs.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Pierrick Martin, Alexandre Marcowith, Luigi Tibaldo
Summary: This study compares the observed halos of J0633+1746 and B0656+14 and finds possible solutions with smaller extent of diffusion suppression. The results indicate that if all nearby middle-aged pulsars develop such halos, their combined positron flux would saturate the measurement for injection efficiencies smaller than those inferred for the canonical halos in J0633+1746 and B0656+14.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Pierrick Martin, Luigi Tibaldo, Alexandre Marcowith, Soheila Abdollahi
Summary: Pulsar halos are shown to be a possible explanation for currently unidentified sources, but their occurrence rate may affect the number of observed TeV sources that can be accounted for by young PWNe alone.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Mark R. Krumholz, Roland M. Crocker, Stella S. R. Offner
Summary: Cosmic rays in star-forming galaxies play a dominant role in producing both diffuse gamma-ray emissions and ionization. This study establishes a connection between the cosmic rays and star formation rates, gamma-ray luminosities, and ionization rates in galaxies, providing insight into the maximum ionization rate and gamma-ray luminosity in these systems. The results suggest that ionization rates in the Milky Way may include contributions from local sources or enhanced CR-driven ionization not directly linked to star formation. Additionally, gamma-ray luminosity measurements can be used to constrain galactic ionization budgets in starburst galaxies.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Francesco Lucarelli, Gor Oganesyan, Teresa Montaruli, Marica Branchesi, Alessio Mei, Samuele Ronchini, Francesco Brighenti, Biswajit Banerjee, Georgios Gerasimos Voutsinas
Summary: The study focuses on searching for neutrino emission from the prompt and afterglow phases of gamma-ray bursts (GRBs) using the PSLab open-access code. Empirical correlations among various GRB emission parameters are utilized to infer the luminosity and Lorentz factor when redshift measurements are not available. The results show that there is no significant neutrino excess, and constraints are placed on GRB neutrino fluxes and relevant parameters.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Saikat Das, Soebur Razzaque, Nayantara Gupta
Summary: This study investigates whether the gamma-ray blazars associated with IceCube neutrino events are sources of ultra-high-energy cosmic rays. The results suggest that detecting the neutrino and gamma-ray fluxes from these blazars may provide the first direct evidence of UHECR sources. Among them, TXS 0506+056 and 3HSP J095507.9+355101 are the prime targets.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Saikat Das, Nayantara Gupta, Soebur Razzaque
Summary: The study analyzed multiwavelength data of the blazar TXS 0506+056, exploring the prospects for detecting gamma rays and neutrinos, their origin and energy characteristics, with minimal correlation found between VHE gamma rays and neutrinos.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
B. Medina-Carrillo, Sarira Sahu, G. Sanchez-Colon, Subhash Rajpoot
Summary: This study focuses on extreme high-frequency peaked BL Lacs (EHBLs), and reports the first detection of multi-TeV gamma-rays from the EHBL PGC 2402248 by MAGIC telescopes. The authors compare the observed data with different models, and find that the photohadronic model provides the best fit. They also observe that the source is in a low-emission state and has a relatively low bulk Lorentz factor.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Sarira Sahu, Isabel Abigail Valadez Polanco, Subhash Rajpoot
Summary: This article investigates the characteristics and behavior of the high-energy peaked blazar 1ES 2344+514 and explores the fitting effects of two photohadronic models on its observed spectra. The study finds that the new two-zone photohadronic model plays a central role in explaining these spectra.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Vasundhara Shaw, Arjen van Vliet, Andrew M. Taylor
Summary: By analyzing polarized synchrotron emission maps and comparing them with observational data, researchers have constrained the parameters of the Galactic halo bubble magnetic field model. It is found that the magnetic field in the Galactic halo bubble region can significantly impact the deflection of UHECRs propagating from potential local source locations to Earth.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Saikat Das, Soebur Razzaque
Summary: This research finds that conventional leptonic models cannot explain the observation of gamma rays above 10 TeV detected by the LHAASO detector. An additional component is required in the energy range equal to or greater than 10 TeV. The study further suggests that ultrahigh-energy cosmic rays can be accelerated in the blast wave of gamma-ray bursts, and their propagation induces an electromagnetic cascade in the extragalactic medium, which can explain the emission above 10 TeV detected by LHAASO. This could be an indication of ultrahigh-energy cosmic-ray acceleration in gamma-ray bursts.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Addy J. Evans, Louis E. Strigari, Oskar Svenborn, Andrea Albert, J. Patrick Harding, Dan Hooper, Tim Linden, Andrew B. Pace
Summary: We analyze a faint gamma-ray source in the Sagittarius dwarf spheroidal galaxy using Fermi-LAT data. The source is associated with the globular cluster M54 in the 4FGL-DR3 catalogue. We investigate its spectral energy distribution and spatial extension to test two hypotheses: emission from millisecond pulsars or annihilating dark matter. Our results suggest a point-like morphology at low energies, supporting the pulsar interpretation, and do not show evidence for a higher-energy component. Alternatively, the signal favors a dark matter mass of m(chi)= 29.6 +/- 5.8 GeV and an annihilation cross section of sv = (2. 1 +/- 0.59) x10(-26) cm(3) s(-1) for the b b channel (or m(chi)= 8.3 +/- 3.8 GeV and sv = (0.90 +/- 0.25) x10-26 cm(3) s(-1) for the tau(+) tau(-) channel) for the dark matter interpretation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Review
Astronomy & Astrophysics
J. Biteau, E. Prandini, L. Costamante, M. Lemoine, P. Padovani, E. Pueschel, E. Resconi, F. Tavecchio, A. Taylor, A. Zech
Editorial Material
Physics, Multidisciplinary
Laurent Gremillet, Martin Lemoine
Article
Astronomy & Astrophysics
Martin Lemoine, Mikhail A. Malkov
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2020)
Article
Multidisciplinary Sciences
N. Lazzerini, V Balter, A. Coulon, T. Tacail, C. Marchina, M. Lemoine, N. Bayarkhuu, Ts Turbat, S. Lepetz, A. Zazzo
Summary: Strontium isotopic analysis of tooth enamel has the potential to track high-frequency movements of domestic livestock, with short-term residency of about 45 days being resolvable. This study offers new perspectives in various disciplines.
SCIENTIFIC REPORTS
(2021)
Article
Astronomy & Astrophysics
Andreas Zech, Martin Lemoine
Summary: The multi-wavelength emission from extreme-TeV blazars requires a co-acceleration scenario for protons and electrons to provide additional constraints on standard emission models. This scenario reduces the degeneracy of parameter sets and enables a satisfactory description of observed spectral energy distributions. The shock co-acceleration model results in specific values for magnetic field strength and minimum electron Lorentz factors, providing insights into the characteristics of extreme blazars.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Arno Vanthieghem, Martin Lemoine, Laurent Gremillet
Summary: This paper proposes a theoretical model to describe the mechanism of electron heating, and verifies the model through large-scale particle-in-cell simulations. The study shows that the charge-separation field induced by the difference in inertia between electrons and ions can account for the electron heating process.
ASTROPHYSICAL JOURNAL LETTERS
(2022)
Article
Physics, Multidisciplinary
Martin Lemoine
Summary: This Letter provides a concrete implementation of Fermi's model of particle acceleration in magnetohydrodynamic (MHD) turbulence, connecting the rate of energization to the gradients of the velocity of magnetic field lines, which it characterizes within a multifractal picture of turbulence intermittency. It then derives a transport equation in momentum space for the distribution function. This description is shown to be substantiated by a large-scale numerical simulation of strong MHD turbulence. The present general framework can be used to model particle acceleration in a variety of environments.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Fluids & Plasmas
Mikhail Malkov, Martin Lemoine
Summary: When a shock wave propagates perpendicularly to the ambient magnetic field, particles are accelerated faster, but the acceleration stops when the shock overruns the particle orbit. However, in flows resulting from supersonically colliding plasmas bound by perpendicular shocks, acceleration can continue. Preenergized particles can avoid the premature end of acceleration if their gyroradius exceeds the dominant turbulence scale between the shocks. These particles can bounce between the shocks and gradually increase their energy per cycle.
Article
Astronomy & Astrophysics
Virginia Bresci, Martin Lemoine, Laurent Gremillet, Luca Comisso, Lorenzo Sironi, Camilia Demidem
Summary: By analyzing nonresonant particle acceleration in strongly magnetized turbulence through various simulation methods, it is found that the model can successfully describe the increase in particle energy through Fermi-type processes in strong magnetized turbulence. In the particle-in-cell simulations, the parallel shear contribution is significant, while in the magnetohydrodynamic incompressible simulation, both the parallel shear and the transverse compressive term provide roughly equal contributions.
Article
Physics, Fluids & Plasmas
Virginia Bresci, Laurent Gremillet, Martin Lemoine
Summary: The current filamentation instability is commonly observed in plasma flows and exhibits saturation when the plasma flow is asymmetric. Using large-scale simulations, we find that the appropriate criterion for saturation in interpenetrating electron-positron pair plasmas is the magnetic trapping criterion, where the instability growth rate slows down once the quiver frequency of the particles equals or exceeds the instability growth rate. This criterion also applies to electron-ion plasmas when electrons and ions are close to equipartition in the plasma flow.
Article
Astronomy & Astrophysics
Martin Lemoine
Summary: This article discusses the nonthermal acceleration of particles in magnetohydrodynamic turbulence, highlighting the significant impact of velocity gradient intermittency on the acceleration process and proposing the use of an analytical random walk model to capture momentum distribution.
Article
Astronomy & Astrophysics
Camilia Demidem, Martin Lemoine, Fabien Casse
Review
Astronomy & Astrophysics
Arno Vanthieghem, Martin Lemoine, Illya Plotnikov, Anna Grassi, Mickael Grech, Laurent Gremillet, Guy Pelletier
Article
Physics, Fluids & Plasmas
Martin Lemoine, Arno Vanthieghem, Guy Pelletier, Laurent Gremillet
Article
Physics, Fluids & Plasmas
Martin Lemoine, Guy Pelletier, Arno Vanthieghem, Laurent Gremillet