D. Malyshev
A5027191911- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Dark Matter and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Particle physics theoretical and experimental studies
- Particle Detector Development and Performance
- Radio Astronomy Observations and Technology
- Cosmology and Gravitation Theories
- Neutrino Physics Research
- Solar and Space Plasma Dynamics
- Galaxies: Formation, Evolution, Phenomena
- Stellar, planetary, and galactic studies
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- Atomic and Subatomic Physics Research
- Astro and Planetary Science
- Nuclear Physics and Applications
- Scientific Research and Discoveries
- Radiation Detection and Scintillator Technologies
- Particle Accelerators and Free-Electron Lasers
- Medical Imaging Techniques and Applications
- Black Holes and Theoretical Physics
- History and Developments in Astronomy
- Astrophysics and Star Formation Studies
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2021-2024
University of Tübingen
2016-2024
Friedrich-Alexander-Universität Erlangen-Nürnberg
2017-2024
Institut de Recherche sur les Lois Fondamentales de l'Univers
2021-2024
CEA Paris-Saclay
2021-2024
Université Paris-Saclay
2021-2024
National Research University Higher School of Economics
2024
TH Bingen University of Applied Sciences
2024
ETH Zurich
2023
University of Würzburg
2023
The dwarf spheroidal satellite galaxies (dSphs) of the Milky Way are some most dark matter (DM) dominated objects known. We report on gamma-ray observations dSphs based 6 years Fermi Large Area Telescope data processed with new Pass 8 event-level analysis. None significantly detected in gamma rays, and we present upper limits DM annihilation cross section from a combined analysis 15 dSphs. These constraints among strongest robust to date lie below canonical thermal relic for mass $\lesssim$...
The Fermi Large Area Telescope (LAT) has provided the most detailed view to date of emission towards Galactic centre (GC) in high-energy gamma-rays. This paper describes analysis data taken during first 62 months mission energy range 1-100 GeV from a $15^\circ \times 15^\circ$ region about direction GC, and implications for interstellar emissions produced by cosmic ray (CR) particles interacting with gas radiation fields inner Galaxy point sources detected. Specialised models (IEMs) are...
Dark matter in the Milky Way may annihilate directly into gamma rays, producing a monoenergetic spectral line. Therefore, detecting such signature would be strong evidence for dark annihilation or decay. We search lines Fermi Large Area Telescope observations of halo energy range 200 MeV to 500 GeV using analysis methods from our most recent line searches. The main improvements relative previous works are use 5.8 years data reprocessed with Pass 8 event-level and additional resulting...
Weakly interacting massive particles (WIMPs) are a theoretical class of that excellent dark matter candidates. WIMP annihilation or decay may produce essentially monochromatic γ rays detectable by the Fermi Large Area Telescope (LAT) against astrophysical γ-ray emission Galaxy. We have searched for spectral lines in energy range 5–300 GeV using 3.7 years data, reprocessed with updated instrument calibrations and an improved dispersion model compared to previous Fermi-LAT Collaboration line...
We present a measurement of the cosmic-ray electron+positron spectrum between 7 GeV and 2 TeV performed with almost seven years data collected Fermi Large Area Telescope. find that is well fit by broken power law break energy at about 50 GeV. Above GeV, described single spectral index $3.07 \pm 0.02 \; (\text{stat+syst}) 0.04 (\text{energy measurement})$. An exponential cutoff lower than 1.8 excluded 95\% CL.
SS 433 is a microquasar, stellar binary system that launches collimated relativistic jets. We observed in gamma rays using the High Energy Stereoscopic System (H.E.S.S.) and found an energy-dependent shift apparent position of gamma-ray emission from parsec-scale These observations trace energetic electron population indicate inverse Compton scattering mechanism rays. Our modeling morphology constrains location particle acceleration requires abrupt deceleration jet flow. infer presence...
In the recent paper of Hooper and Goodenough (2010) [10] it was reported that γ-ray emission from Galactic Center region contains an excess compared to contributions large-scale diffuse known point sources. This argued be consistent with a signal annihilation Dark Matter power law density profile. We reanalyze Fermi data find instead is "standard model" The main reason for discrepancy interpretation different (as previous works) spectrum source at assumed by [10]. discuss possible reasons...
Several recent works have reported the detection of an unidentified X-ray line at 3.55~keV, which could possibly be attributed to decay dark matter (DM) particles in halos galaxy clusters and M31 galaxy. We analyze all publicly-available XMM-Newton data dwarf spheroidal galaxies test possible DM origin line. Dwarf high mass-to-light ratios their interstellar medium is not a source diffuse emission, thus they are expected provide cleanest signal. Our analysis shows no evidence for presence...
We search for evidence of dark matter (DM) annihilation in the isotropic gamma-ray background (IGRB) measured with 50 months Fermi Large Area Telescope (LAT) observations. An improved theoretical description cosmological DM signal, based on two complementary techniques and assuming generic weakly interacting massive particle (WIMP) properties, renders more precise predictions compared to previous work. More specifically, we estimate cosmologically-induced intensity have an uncertainty a...
We present results of a search for the 3.5 keV emission line in our recent very long (∼ 1.4 Ms) XMM–Newton observation Draco dwarf spheroidal galaxy. The astrophysical X-ray from such dark matter-dominated galaxies is faint, thus they provide test matter origin previously detected other massive, but bright objects, as and galaxy clusters. do not detect statistically significant Draco; this constrains lifetime decaying particle to τ > (7–9) × 1027 s at 95 per cent CL (combining all three...
The central region of the Milky Way is one foremost locations to look for dark matter (DM) signatures. We report first results on a search DM particle annihilation signals using new observations from an unprecedented gamma-ray survey Galactic Center (GC) region, ${\it i.e.}$, Inner Galaxy Survey, at very high energies ($\gtrsim$ 100 GeV) performed with H.E.S.S. array five ground-based Cherenkov telescopes. No significant excess found in 2014-2020 dataset and profile likelihood ratio analysis...
Recurrent Novae are repeating thermonuclear explosions in the outer layers of white dwarfs, due to accretion fresh material from a binary companion. The shock generated by ejected slamming into companion star's wind, accelerates particles very-high-energies. We report very-high-energy (VHE, $\gtrsim100$\,GeV) gamma rays recurrent nova RS\,Ophiuchi up month after its 2021 outburst, using High Energy Stereoscopic System. VHE emission has similar temporal profile lower-energy GeV emission,...
Magnetic fields in galaxies and galaxy clusters are believed to be the result of amplification intergalactic seed during formation large-scale structures universe. However, origin, strength, morphology this magnetic field (IGMF) remain unknown. Lower limits on (or indirect detection of) IGMF can obtained from observations high-energy gamma rays distant blazars. Gamma interact with extragalactic background light produce electron-positron pairs, which subsequently initiate electromagnetic...
GRB221009A is the brightest gamma-ray burst ever detected. To probe very-high-energy (VHE, $>$\!100 GeV) emission, High Energy Stereoscopic System (H.E.S.S.) began observations 53 hours after triggering event, when brightness of moonlight no longer precluded observations. We derive differential and integral upper limits using H.E.S.S. data from third, fourth, ninth nights initial GRB detection, applying atmospheric corrections. The combined yield an energy flux limit $\Phi_\mathrm{UL}^{95\%}...
Employing data collected during the first 25 months' observations by Fermi-LAT, we describe and subsequently seek to model very high energy (>300 MeV) emission from central few parsecs of our Galaxy. We analyze morphological, spectral temporal characteristics source, 1FGL J1745.6-2900. Remarkably, show a clear, statistically significant signal at energies above 10 GeV, where Fermi-LAT has an excellent angular resolution comparable HESS TeV energies, which makes meaningful joint analysis...
Long-term monitoring of PSR J2021+4026 in the heart Cygnus region with Fermi Large Area Telescope unveiled a sudden decrease flux above 100 MeV over timescale shorter than week. The "jump" was near MJD 55850 (2011 October 16), decreasing from (8.33 ± 0.08) × 10−10 erg cm−2 s−1 to (6.86 0.13) s−1. Simultaneously, frequency spindown rate increased (7.8 0.1) 10−13 Hz (8.1 Significant (>5σ) changes pulse profile and marginal (<3σ) emission spectrum occurred at same time. There is also evidence...
We report evidence for extended gamma-ray emission from the Virgo, Fornax and Coma clusters based on a maximum-likelihood analysis of 3-year Fermi-LAT data. For all three clusters, excess is observed within degrees center, peaking at GeV scale. This cannot be accounted by known Fermi sources or galactic extragalactic backgrounds. If interpreted as annihilation supersymmetric dark matter (DM) particles, data prefer models with particle mass in range 20-60 annihilating into b-bbar channel,...
Galaxy clusters are one of the prime sites to search for dark matter (DM) annihilation signals. Depending on substructure DM halo a galaxy cluster and cross sections channels, these signals might be detectable by latest generation $\gamma$-ray telescopes. Here we use three years Fermi Large Area Telescope (LAT) data, which most suitable searching very extended emission in vicinity nearby Virgo cluster. Our analysis reveals statistically significant can well characterized uniformly emitting...
The Crab Nebula is a unique laboratory for studying the acceleration of electrons and positrons through their non-thermal radiation. Observations very-high-energy γ rays from have provided important constraints modelling its broadband emission. We present first fully self-consistent analysis Nebula’s -ray emission between 1 GeV ∼100 TeV, that is, over five orders magnitude in energy. Using open-source software package G AMMAPY , we combined 11.4 yr data Fermi Large Area Telescope 80 h High...
We have obtained measurements and upper limits on the emission of Cyg X-1 in photon energy range 0.03--300 GeV based observations by Fermi. present results separately for hard soft spectral states, as well all analysed data. In state, we detect a weak steady 0.1--10 with power-law index Gamma=2.6+-0.2 at 4 sigma statistical significance. This measurement, even if considered to be an limit, strongly constrains Compton radio jet, that state. The number relativistic electrons jet has low enough...
We report on broad multi-wavelength observations of the 2010-2011 periastron passage gamma-ray loud binary system PSR B1259-63. High resolution interferometric radio establish extended emission trailing position pulsar. Observations with Fermi Gamma-ray Space Telescope reveal GeV flaring activity system, reaching spin-down luminosity pulsar, around 30 days after periastron. There are no clear signatures variability at radio, X-ray and TeV energies time flare. Variability in H$\alpha$ line,...
We report on the results of extensive multi-wavelength campaign from optical to GeV gamma-rays 2014 periastron passage PSR B1259-63, which is a unique high-mass gamma-ray emitting binary system with young pulsar companion. Observations demonstrate stable nature post-periastron flare and prove coincidence start rapid decay H$\alpha$ equivalent width, usually interpreted as disruption Be stellar disk. Intensive X-ray observations reveal changes in spectral behaviour happening at moment flare....