D. Costantin
A5045946144- Astrophysics and Cosmic Phenomena
- Dark Matter and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Radio Astronomy Observations and Technology
- Pulsars and Gravitational Waves Research
- Particle physics theoretical and experimental studies
- Solar and Space Plasma Dynamics
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Neutrino Physics Research
- Galaxies: Formation, Evolution, Phenomena
- Particle Accelerators and Free-Electron Lasers
- Particle Detector Development and Performance
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Cosmology and Gravitation Theories
- History and Developments in Astronomy
- Bayesian Methods and Mixture Models
- Geophysics and Gravity Measurements
- Gaussian Processes and Bayesian Inference
- Particle accelerators and beam dynamics
- Crystallography and Radiation Phenomena
- Multidisciplinary Science and Engineering Research
- Atomic and Subatomic Physics Research
- Radioactivity and Radon Measurements
University of Padua
2017-2021
Guangzhou University
2017-2020
Department of Education of Guangdong Province
2017-2020
Max Planck Society
2018
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 a catalog of sources detected above 10 GeV by the Fermi Large Area Telescope (LAT) in first 7 years data using Pass 8 event-level analysis. This is Third Catalog Hard Fermi-LAT Sources (3FHL), containing 1556 objects characterized - 2 TeV energy range. The sensitivity and angular resolution are improved factors 3 relative to previous LAT at same energies (1FHL). vast majority (79%) associated with extragalactic counterparts other wavelengths, including 16 located very high...
The fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Gamma-ray Space Telescope Large Area (4LAC) between 2008 August 4 and 2016 2 contains 2863 objects located at high Galactic latitudes (|b|>10{\deg}). It includes 85% more sources than previous 3LAC based on years data. AGNs represent least 79% high-latitude in Fermi-Large Source Catalog (4FGL), which covers energy range from 50 MeV to 1 TeV. In addition, 344 gamma-ray are found low latitudes. Most 4LAC blazars (98%),...
Abstract The Large Area Telescope (LAT) aboard the Fermi spacecraft routinely observes high-energy emission from gamma-ray bursts (GRBs). Here we present second catalog of LAT-detected GRBs, covering first 10 yr operations, 2008 to 2018 August 4. A total 186 GRBs are found; these, 91 show in range 30–100 MeV (17 which seen only this band) and 169 detected above 100 MeV. Most these sources were discovered by other instruments ( /GBM, Swift /BAT, AGILE, INTEGRAL ) or reported Interplanetary...
Abstract We present a search for spatial extension in high-latitude ( ) sources recent Fermi point source catalogs. The result is the High-Latitude Extended Sources Catalog, which provides extensions (or upper limits thereof) and likelihood profiles suite of tested morphologies. find 24 extended sources, 19 were not previously characterized as extended. These include that are potentially associated with supernova remnants star-forming regions. also found γ -ray emission vicinity Cen A radio...
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 detection of high-redshift ($z>$3) blazars enables the study evolution most luminous relativistic jets over cosmic time. More importantly, tend to host massive black holes and can be used constrain space density heavy in early Universe. Here, we report first with \fermi-Large Area Telescope five \gm-ray emitting beyond $z=3.1$, more distant than any previously detected $\gamma$-rays. Among these objects, NVSS J151002+570243 is now known blazar at $z=4.31$. These objects have steeply...
Abstract We report on the observations of gamma-ray burst (GRB) 190114C by Fermi Gamma-ray Space Telescope and Neil Gehrels Swift Observatory . The prompt emission was detected GRB Monitor (GBM), Large Area (LAT), Burst Alert (BAT) long-lived afterglow subsequently observed GBM, LAT, X-ray (XRT), UV Optical Telescope. early-time reveal multiple components that evolve independently, with a delayed power-law component exhibits significant spectral attenuation above 40 MeV in first few seconds...
We present the first Fermi - Large Area Telescope (LAT) solar flare catalog covering 24 th cycle. This contains 45 -LAT flares (FLSFs) with emission in gamma-ray energy band (30 MeV 10 GeV) detected a significance greater than 5 sigma over years 2010-2018. A subsample containing 37 of these exhibit delayed beyond prompt-impulsive hard X-ray phase 21 showing lasting more two hours. No is four flares. also this observations GeV from 3 originating Active Regions located behind limb (BTL)...
The spatial extension of a gamma-ray source is an essential ingredient to determine its spectral properties as well potential multi-wavelength counterpart. capability spatially resolve sources greatly improved by the newly delivered Fermi-Large Area Telescope (LAT) Pass 8 event-level analysis which provides greater acceptance and point spread function, two crucial factors for detection extended sources. Here, we present complete search located within 7 degrees from Galactic plane, using 6...
A citizen science project discovers a new type of gamma-ray millisecond pulsar with no detectable radio pulsations.
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...
Abstract We present the Fermi Large Area Telescope (LAT) observations of binary neutron star merger event GW170817 and associated short gamma-ray burst (SGRB) GRB 170817A detected by Gamma-ray Burst Monitor. The LAT was entering South Atlantic Anomaly at time LIGO/Virgo trigger ( t GW ) therefore cannot place constraints on existence high-energy E > 100 MeV) emission with moment coalescence. focus instead constraining longer timescales. No candidate electromagnetic counterpart timescales...
An excess of $γ$-ray emission from the Galactic Center (GC) region with respect to predictions based on a variety interstellar models and source catalogs has been found by many groups using data {\it Fermi} Large Area Telescope (LAT). Several interpretations this have invoked. In paper we search for members an unresolved population pulsars located in inner Galaxy that are predicted interpretation GC as being due such sources. We use cataloged LAT sources derive criteria efficiently select...
Black holes with masses below approximately $10^{15}$ g are expected to emit gamma rays energies above a few tens of MeV, which can be detected by the Fermi Large Area Telescope (LAT). Although black these cannot formed as result stellar evolution, they may have in early Universe and therefore called Primordial Holes (PBHs). Previous searches for PBHs focused on either short timescale bursts or contribution isotropic gamma-ray emission. We show that, case individual PBHs, LAT is most...
Massive black holes at the centers of galaxies can launch powerful wide-angle winds that, if sustained over time, unbind gas from stellar bulges galaxies. These may be responsible for observed scaling relation between masses central and velocity dispersion stars in galactic bulges. Propagating through galaxy, wind should interact with interstellar medium creating a strong shock, similar to those supernovae explosions, which is able accelerate charged particles high energies. In this work we...
The gamma-ray sky has been observed with unprecedented accuracy in the last decade by Fermi -large area telescope (LAT), allowing us to resolve and understand high-energy Universe. nature of remaining unresolved emission [unresolved background (UGRB)] below LAT source detection threshold can be uncovered characterizing amplitude angular scale UGRB fluctuation field. This Letter presents a measurement autocorrelation power spectrum based on eight years Fermi-LAT Pass 8 data products. analysis...
Using the 1.56m telescope at Shanghai Observatory (ShAO), China, we monitored two sources, BL Lac object S5 0716+714 and Flat Spectrum Radio Quasar (FSRQ) 3C 273. For 0716+714, report 4969 sets of CCD (Charge-coupled Device) photometrical optical observations (1369 for V band, 1861 R band 1739 I band) in monitoring time from Dec.4, 2000 to Apr.5, 2014. 273, 460 (138 146 176 Mar. 28, 2006 Apr. 9, The provide us with a large amount data analyze short-term long-term variabilities. Based on...
We present the \emph{Fermi} Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) observations of LIGO binary black hole merger (BBH) event GW170104. No candidate electromagnetic counterparts was detected by either GBM or LAT. A detailed analysis LAT data over timescales from seconds to days covering localization region is presented. The resulting flux upper bound (5.2--9.4)$\times$10$^{-7}$ erg cm$^{-2}$ s$^{-1}$ in 10-1000 keV range (0.2--13)$\times$10$^{-9}$ 0.1--1 GeV range. also...
We use joint observations by the Neil Gehrels Swift X-ray Telescope (XRT) and Fermi Large Area (LAT) of gamma-ray burst (GRB) afterglows to investigate nature long-lived high-energy emission observed LAT. Joint broadband spectral modeling XRT LAT data reveal that non-detections bright are consistent with a cooling break in inferred electron synchrotron spectrum below and/or energy ranges. Such is sufficient suppress so as be detection threshold. By contrast, LAT-detected bursts best fit lies...
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...