S. Abdollahi
A5047625404- Astrophysics and Cosmic Phenomena
- Dark Matter and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Neutrino Physics Research
- Gamma-ray bursts and supernovae
- Particle physics theoretical and experimental studies
- Pulsars and Gravitational Waves Research
- Particle Detector Development and Performance
- Particle Accelerators and Free-Electron Lasers
- Astrophysics and Star Formation Studies
- Nuclear Physics and Applications
- Astronomical Observations and Instrumentation
- Radiation Detection and Scintillator Technologies
- Superconducting and THz Device Technology
- Semiconductor Lasers and Optical Devices
- Particle accelerators and beam dynamics
- High-Energy Particle Collisions Research
- Nonlinear Photonic Systems
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Advanced Antenna and Metasurface Technologies
Institut de Recherche en Astrophysique et Planétologie
2022-2024
Université Toulouse III - Paul Sabatier
2021-2023
Centre National de la Recherche Scientifique
2017-2023
Université de Toulouse
2021-2023
Hiroshima University
2016-2020
Max Planck Society
2018
Ibaraki University
2017
Institut National de Physique Nucléaire et de Physique des Particules
2017
Laboratoire de Physique des deux infinis Bordeaux
2017
Sharif University of Technology
2007-2016
We present the fourth Fermi Large Area Telescope catalog (4FGL) of gamma-ray sources. Based on first eight years science data from Gamma-ray Space mission in energy range 50 MeV to 1 TeV, it is deepest yet this range. Relative 3FGL catalog, 4FGL has twice as much exposure well a number analysis improvements, including an updated model for Galactic diffuse emission, and two sets light curves (1-year 2-month intervals). The includes 5064 sources above 4 sigma significance, which we provide...
We present an incremental version (4FGL-DR3, for Data Release 3) of the fourth Fermi-LAT catalog gamma-ray sources. Based on first twelve years science data in energy range from 50 MeV to 1 TeV, it contains 6658 The analysis improves that used 4FGL over eight data: more sources are fit with curved spectra, we introduce a robust spectral parameterization pulsars, and extend points TeV. parameters, distributions, associations updated all Light curves rebuilt yr intervals (not 2 month...
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.
Abstract We present 294 pulsars found in GeV data from the Large Area Telescope (LAT) on Fermi Gamma-ray Space Telescope. Another 33 millisecond (MSPs) discovered deep radio searches of LAT sources will likely reveal pulsations once phase-connected rotation ephemerides are achieved. A further dozen optical and/or X-ray binary systems colocated with also harbor gamma-ray MSPs. This catalog thus reports roughly 340 and candidates, 10% all known pulsars, compared to ≤11 before Fermi. Half...
The Fermi Large Area Telescope (LAT) light curve repository (LCR) is a publicly available, continually updated library of gamma-ray curves variable Fermi-LAT sources generated over multiple timescales. LCR aims to provide publication-quality binned on timescales 3 days, 7 and 30 days for 1525 deemed in the source catalog first 10 years observations. consists through full likelihood analyses that model surrounding region, providing fluxes photon indices each time bin. intended as resource...
Gamma rays reveal the Universe's history How many stars have formed in Universe, and when did they do so? These fundamental questions are difficult to answer because there systematic uncertainties converting light we observe into total mass of galaxies. The Fermi-LAT Collaboration addressed these by exploiting way that gamma from distant blazars propagate through intergalactic space, which depends on amount emitted all collaboration found star formation peaked about 3 billion years after Big...
We present the fourth Fermi Large Area Telescope catalog (4FGL) of gamma-ray sources. Based on first eight years science data from Gamma-ray Space mission in energy range 50 MeV to 1 TeV, it is deepest yet this range. Relative 3FGL catalog, 4FGL has twice as much exposure well a number analysis improvements, including an updated model for Galactic diffuse emission, and two sets light curves (1-year 2-month intervals). The includes 5064 sources above 4 sigma significance, which we provide...
The Large Area Telescope on board the Fermi Gamma-ray Space has collected largest ever sample of high-energy cosmic-ray electron and positron events since beginning its operation. Potential anisotropies in arrival directions electrons or positrons could be a signature presence nearby sources. We use almost seven years data with energies above 42 GeV processed Pass 8 reconstruction. present can probe dipole down to level 10^{-3}. take into account systematic effects that mimic true at this...
We present the second catalog of flaring gamma-ray sources (2FAV) detected with Fermi All-sky Variability Analysis (FAVA), a tool that blindly searches for transients over entire sky observed by Large Area Telescope (LAT) on board \textit{Fermi} Gamma-ray Space Telescope. With respect to first FAVA catalog, this benefits from larger data set, latest LAT release (Pass 8), as well an improved analysis includes likelihood techniques more precise localization transients. Applying 7.4 years...
Context. The discovery of extended gamma-ray emission toward a number middle-aged pulsars suggests the possibility long-lived particle confinement beyond classical pulsar wind nebula (PWN) stage. How this emerging source class can be extrapolated to Galactic population remains unclear. Aims. We aim evaluate how halos fit in existing TeV observations, under assumption that all develop similar those observed J0633+1746 or B0656+14 pulsars. Methods. modeled populations supernova remnants, PWNe,...
Abstract The High Altitude Water Cherenkov (HAWC) collaboration recently published their 2HWC catalog, listing 39 very high energy (VHE; >100 GeV) gamma-ray sources based on 507 days of observation. Among these, 19 are not associated with previously known teraelectronvolt (TeV) sources. We have studied 14 these without counterparts VERITAS and Fermi -LAT. detected weak emission in the 1 TeV–30 TeV band region DA 495, a pulsar wind nebula coinciding J1953+294, confirming discovery source...
ABSTRACT A study of the interstellar medium (ISM) and cosmic rays (CRs) using Fermi Large Area Telescope (LAT) data, in a region encompassing nearby molecular clouds MBM 53, 54, 55 far-infrared loop-like structure Pegasus, is reported. By comparing Planck dust thermal emission model with -LAT γ -ray it was found that neither radiance ( R ) nor opacity at 353 GHz τ proportional to total gas column density N (H tot primarily because )/ depend on temperature T d ). The distribution evaluated...
Abstract Cosmic rays are mostly composed of protons accelerated to relativistic speeds. When those encounter interstellar material, they produce neutral pions, which in turn decay into gamma-rays. This offers a compelling way identify the acceleration sites protons. A characteristic hadronic spectrum, with low-energy break around 200 MeV, was detected gamma-ray spectra four supernova remnants (SNRs), IC 443, W44, W49B, and W51C, Fermi Large Area Telescope. detection provided direct evidence...
A 2.1-year periodic oscillation of the gamma-ray flux from blazar PG 1553+113 has previously been tentatively identified in almost 7 year data Fermi Large Area Telescope. After 15 years sky-survey observations, doubling total time range, we report >7 cycle modulation with an estimated significance 4 sigma against stochastic red noise. Independent determinations period and phase earlier new are close agreement (chance probability <0.01). Pulse timing over full light curve is also consistent a...
The middle-aged supernova remnant (SNR) CTB 37A is known to interact with several dense molecular clouds through the detection of shocked H2 and OH 1720 MHz maser emission. In present work, we use eight years Fermi-LAT Pass 8 data, an improved point-spread function increased acceptance, perform detailed morphological spectral studies γ-ray emission toward from 200 MeV GeV. best fit source extension obtained for a very compact Gaussian model significance 5.75σ 68% containment radius 0116 ±...
The charge ratio of cosmic muons holds important information for both the atmospheric neutrino anomaly and hadronic interaction models. In this paper we measured muon () in ray flux momenta range 0.76–1.60 GeV/c by using a telescope. delayed coincidence method is used based on reduced mean lifetime negative due to nuclear capture matter. systematic time-dependent effects are considered grouping decay data into different time intervals. We compared experimental with predictions CORSIKA...
Supernova remnants (SNRs) are believed to be one of the major sources Galactic cosmic rays. SNR CTB 37A is known interact with several dense molecular clouds as traced by OH 1720 MHz maser. Radio and X-ray observations confirm a mixed-morphology classification remnant. The TeV γ-ray source HESS J1714-385 positionally coincident SNR, though it still not clear whether emission originates in or plausible pulsar wind nebula (PWN). In present work, we use 8 years Pass Fermi-LAT data, high...
Abstract An accurate estimate of the interstellar gas density distribution is crucial to understanding medium (ISM) and Galactic cosmic rays (CRs). To comprehend ISM CRs in a local environment, study diffuse γ -ray emission midlatitude region third quadrant was performed. The data 0.1–25.6 GeV energy range Fermi Large Area Telescope (LAT) other tracers such as HI4PI survey Planck dust thermal model were used, northern southern regions analyzed separately. variation <?CDATA...
The recent detection of extended $\gamma$-ray emission around middle-aged pulsars is interpreted as inverse-Compton scattering ambient photons by electron-positron pairs escaping the pulsar wind nebula, which are confined near system unclear mechanisms. This emerging population sources was first discovered at TeV energies and remains underexplored in GeV range. To address this, we conducted a systematic search for along Galactic plane using 14 years Fermi-LAT data above 10 GeV, aiming to...
Alborz-I as the first phase of Alborz Observatory Array supposed to study cosmic ray spectrum around knee at Sharif University Technology campus, Tehran (1200 m a.s.l
The first phase of the Alborz Observatory Array (Alborz-I) is designed to have 20 scintillation detectors study cosmic ray spectrum in energy range 10 12 eV 16 eV.In order collect data under stable environmental conditions, a sub-array consists 5 plastic on pentagon with side m similar central cluster Alborz-I been operationalized since February 2014.This paper studies angular distribution detected showers and resolution compares it simulation result.
The first phase of the Alborz Observatory Array (Alborz-I) consists 20 plastic scintillation detectors each one with surface area 0.25 $m^{2}$ spread over an 40$\times$40 realized to study Extensive Air Showers around $\it knee$ at Sharif University Technology campus. stage project including construction and operation a prototype system has now been completed electronics that will be used in array instrument tested under field conditions. In order achieve realistic estimate performance,...