scholarly journals Detection of Gamma Ray Emission from the Sagittarius Dwarf Spheroidal Galaxy

2021 ◽  
Author(s):  
Roland Crocker ◽  
Oscar Macias ◽  
Dougal Mackey ◽  
Mark Krumholz ◽  
Shin'ichiro Ando ◽  
...  
Keyword(s):  
Milky Way ◽  
Gamma Ray ◽  
High Energy ◽  
Galactic Centre ◽  
Large Area ◽  
Massive Black Hole ◽  
Inverse Compton Scattering ◽  
Electron Positron ◽  
Back Ground ◽  
Γ Ray

Abstract The Fermi Bubbles are giant, γ-ray emitting lobes emanating from the nucleus of the Milky Way [1, 2] discovered in ∼1-100 GeV data collected by the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope [3]. Previous work [4] has revealed substructure within the Fermi Bubbles that has been interpreted as a signature of collimated outflows from the Galaxy’s super-massive black hole. Here we show that much of the γ-ray emission associated to the brightest region of substructure – the so-called cocoon – is actually due to the Sagittarius dwarf spheroidal (Sgr dSph) galaxy. This large Milky Way satellite is viewed through the Fermi Bubbles from the position of the Solar System. As a tidally and ram-pressure stripped remnant, the Sgr dSph has no on-going star formation, but we demonstrate that its γ-ray signal is naturally explained by inverse Compton scattering of cosmic microwave back-ground photons by high-energy electron-positron pairs injected by the dwarf’s millisecond pulsar (MSP) population, combined with these objects’ magnetospheric emission. This finding suggests that MSPs likely produce significant γ-ray emission amongst old stellar populations, potentially confounding indirect dark matter searches in regions such as the Galactic Centre, the Andromeda galaxy, and other massive Milky Way dwarf spheroidals.

scholarly journals Fermi-LAT and WMAP observations of the supernova remnant Puppis A

2013 ◽  
Vol 9 (S296) ◽  
pp. 295-299
Author(s):  
Marie-Hélène Grondin ◽  
John W. Hewitt ◽  
Marianne Lemoine-Goumard ◽  
Thierry Reposeur ◽  
Keyword(s):  
Supernova Remnants ◽  
Supernova Remnant ◽  
Gamma Ray ◽  
High Energy ◽  
Radio Spectrum ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Large Area ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Γ Ray

AbstractThe supernova remnant (SNR) Puppis A (aka G260.4-3.4) is a middle-aged supernova remnant, which displays increasing X-ray surface brightness from West to East corresponding to an increasing density of the ambient interstellar medium at the Eastern and Northern shell. The dense IR photon field and the high ambient density around the remnant make it an ideal case to study in γ-rays. Gamma-ray studies based on three years of observations with the Large Area Telescope (LAT) aboard Fermi have revealed the high energy gamma-ray emission from SNR Puppis A. The γ-ray emission from the remnant is spatially extended, and nicely matches the radio and X-ray morphologies. Its γ-ray spectrum is well described by a simple power law with an index of ~2.1, and it is among the faintest supernova remnants yet detected at GeV energies. To constrain the relativistic electron population, seven years of Wilkinson Microwave Anisotropy Probe (WMAP) data were also analyzed, and enabled to extend the radio spectrum up to 93 GHz. The results obtained in the radio and γ-ray domains are described in detail, as well as the possible origins of the high energy γ-ray emission (Bremsstrahlung, Inverse Compton scattering by electrons or decay of neutral pions produced by proton interactions).

scholarly journals A Possible Discovery of a Flaring 1012 eV Gamma-Ray Source near the Red Dwarf EV Lac

1995 ◽  
Vol 151 ◽  
pp. 78-79
Author(s):  
I.Yu. Alekseev ◽  
N.N. Chalenko ◽  
V.P. Fomin ◽  
R.E. Gershberg ◽  
O.R. Kalekin ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Electronic Device ◽  
Angular Size ◽  
High Energy ◽  
Optical Systems ◽  
Relativistic Electrons ◽  
Large Area ◽  
Γ Rays ◽  
Γ Ray ◽  
Ev Lac

During the 1994 coordinated observations of the red dwarf flare star EV Lac, the star was monitored in the very high energy (VHE) γ-ray range around 1012 eV with the Crimean ground-based γ-ray telescope GT-48. This telescope consists of two identical optical systems (Vladimirsky et al. 1994) which were directed in parallel on EV Lac.The detection principle of the VHE γ-rays is based on the Čerenkov radiation emitted by relativistic electrons and positrons. The latter are generated in the interaction of the γ-rays with nuclei in the Earth’s atmosphere that leads to an appearance of a shower of charged particles and γ-quanta. The duration of the Cherenkov radiation flash is very short, just about a few nanoseconds. The angular size of the shower is ∼ 1°. To detect such flashes we use an optical system with large area mirrors and a set of 37 photomultipliers (PMs) in the focal plane. Using the information from these PMs which are spaced hexagonally and correspond to a field of view of 2°.6 on the sky, we can obtain the image of an optical flash. The electronic device permits us to detect nanosecond flashes (40 ns exposure time and 12 μs readout dead-time).

scholarly journals What can Fermi LAT observation of the Galactic Centre tell us about its active past?

2016 ◽  
Vol 12 (S324) ◽  
pp. 115-118
Author(s):  
Gabrijela Zaharijas ◽  
Jovana Petrović ◽  
Pasquale Serpico
Keyword(s):  
Black Hole ◽  
Gamma Ray ◽  
Galactic Center ◽  
High Energy ◽  
Galactic Centre ◽  
Massive Black Hole ◽  
The Past ◽  
High Energy Electrons ◽  
Inverse Compton ◽  
Past Activity

AbstractThe Fermi-LAT gamma-ray data in the inner Galaxy region show several prominent features possibly related to the past activity of the Milky Way’s super massive black hole. At a large, 50 deg scale, the Fermi LAT revealed symmetric hour glass structures with hard energy spectra extending up to 100 GeV (and dubbed ‘the Fermi bubbles’). More recently and closer to the Galactic centre, at the 10 deg scale, several groups have claimed evidence for excess gamma-ray emission that appears symmetric around the Galactic center and has an energy spectrum peaking at few GeVs. We explore here the possibility that this emission originates in inverse Compton emission from high-energy electrons produced in a short duration, burst-like event injecting 1052 − 1053 erg, roughly 106 yrs ago. Several lines of evidence suggest that a series of ‘burst like’ events happened in the vicinity of our black hole in the past and gamma-ray observations may offer a new view of that scenario.

scholarly journals Extreme and high synchrotron peak blazars beyond 4FGL: The 2BIGB γ-ray catalogue

2020 ◽  
Vol 493 (2) ◽  
pp. 2438-2451
Author(s):  
B Arsioli ◽  
Y-L Chang ◽  
B Musiimenta
Keyword(s):  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
High Energy ◽  
Spectral Energy ◽  
Large Area ◽  
Data Repositories ◽  
Total Contribution ◽  
Public Data ◽  
Γ Ray

ABSTRACT This paper presents the results of a γ-ray likelihood analysis over all the extreme and high synchrotron peak blazars (EHSP and HSP) from the 3HSP catalogue. We investigate 2013 multifrequency positions under the eyes of Fermi Large Area Telescope, considering 11 yr of observations in the energy range between 500 MeV and 500 GeV, which results in 1160 γ-ray signatures detected down to the TS=9 threshold. The detections include 235 additional sources concerning the Fermi Large Area Telescope Fourth Source Catalog (4FGL), all confirmed via high-energy TS (Test Statistic) maps, and represent an improvement of ∼25 per cent for the number of EHSP and HSP currently described in γ-rays. We build the γ-ray spectral energy distribution (SED) for all the 1160 2BIGB sources, plot the corresponding γ-ray logN−logS, and measure their total contribution to the extragalactic gamma-ray background, which reaches up to ∼33 per cent at 100 GeV. Also, we show that the γ-ray detectability improves according to the synchrotron peak flux as represented by the figure of merit parameter, and note that the search for TeV peaked blazars may benefit from considering HSP and EHSP as a whole, instead of EHSPs only. The 2BIGB acronym stands for ‘Second Brazil-ICRANet Gamma-ray Blazars’ catalogue, and all the broad-band models and SED data points will be available on public data repositories (OpenUniverse, GitHub, and Brazilian Science Data Center-BSDC).

scholarly journals Fermi-LAT Observations of the Gamma-Ray Burst GRB 130427A

Science ◽  
2013 ◽  
Vol 343 (6166) ◽  
pp. 42-47 ◽  
Author(s):  
M. Ackermann ◽  
M. Ajello ◽  
K. Asano ◽  
W. B. Atwood ◽  
M. Axelsson ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Synchrotron Emission ◽  
Large Area ◽  
Energy Photon ◽  
Isotropic Energy ◽  
Spectral Analyses ◽  
Gamma Ray Burst ◽  
Γ Ray ◽  
High Energy Emission

The observations of the exceptionally bright gamma-ray burst (GRB) 130427A by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope provide constraints on the nature of these unique astrophysical sources. GRB 130427A had the largest fluence, highest-energy photon (95 GeV), longest γ-ray duration (20 hours), and one of the largest isotropic energy releases ever observed from a GRB. Temporal and spectral analyses of GRB 130427A challenge the widely accepted model that the nonthermal high-energy emission in the afterglow phase of GRBs is synchrotron emission radiated by electrons accelerated at an external shock.

scholarly journals The emission of γ-Ray beams with orbital angular momentum in laser-driven micro-channel plasma target

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
B. Feng ◽  
C. Y. Qin ◽  
X. S. Geng ◽  
Q. Yu ◽  
W. Q. Wang ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Orbital Angular Momentum ◽  
Gamma Ray ◽  
Three Dimensional ◽  
High Energy ◽  
Micro Channel ◽  
Inverse Compton Scattering ◽  
Direct Laser ◽  
Plasma Target ◽  
Γ Ray

AbstractWe investigated the emission of multi-MeV γ-Ray beams with orbital angular momentum (OAM) from the interaction of an intense circularly polarized (CP) laser with a micro-channel plasma target. The driving laser can generate high energy electrons via direct laser acceleration within the channel. By attaching a plasma foil as the reflecting mirror, the CP laser is reflected and automatically colliding with the electrons. High energy gamma-photons are emitted through inverse Compton scattering (ICS) during collision. Three-dimensional particle-in-cell simulations reveal that the spin angular momentum (SAM) of the CP laser can be transferred to the OAM of accelerated electrons and further to the emitted gamma-ray beam. These results may guide future experiments in laser-driven gamma-ray sources using micro-structures.

scholarly journals Gamma-ray burst detection prospects for next generation ground-based VHE facilities

2021 ◽  
Author(s):  
G La Mura ◽  
U Barres de Almeida ◽  
R Conceição ◽  
A De Angelis ◽  
F Longo ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Large Area ◽  
Gamma Ray Burst ◽  
Cherenkov Telescopes ◽  
200 Gev ◽  
Energy Domain ◽  
Very High Energy ◽  
Γ Ray ◽  
Very High

Abstract Gamma-ray Bursts (GRB) were discovered by satellite-based detectors as powerful sources of transient γ-ray emission. The Fermi satellite detected an increasing number of these events with its dedicated Gamma-ray Burst Monitor (GBM), some of which were associated with high energy photons (E > 10 GeV), by the Large Area Telescope (LAT). More recently, follow-up observations by Cherenkov telescopes detected very high energy emission (E > 100 GeV) from GRBs, opening up a new observational window with implications on the interpretation of their central engines and on the propagation of very energetic photons across the Universe. Here, we use the data published in the 2nd Fermi-LAT Gamma Ray Burst Catalogue to characterise the duration, luminosity, redshift and light curve of the high energy GRB emission. We extrapolate these properties to the very high energy domain, comparing the results with available observations and with the potential of future instruments. We use observed and simulated GRB populations to estimate the chances of detection with wide-eld ground-based γ-ray instruments. Our analysis aims to evaluate the opportunities of the Southern Wide-eld-of-view Gamma-ray Observatory (SWGO), to be installed in the Southern Hemisphere, to complement CTA. We show that a low-energy observing threshold (Elow < 200 GeV), with good point source sensitivity (Flim ≈ 10−11erg cm−2 s−1 in 1 yr), are optimal requirements to work as a GRB trigger facility and to probe the burst spectral properties down to time scales as short as 10 s, accessing a time domain that will not be available to IACT instruments.

scholarly journals THE 2010 M 87 VHE FLARE AND ITS ORIGIN: THE MULTI-WAVELENGTH PICTURE

2012 ◽  
Vol 08 ◽  
pp. 184-189 ◽  
Author(s):  
◽  
M. RAUE ◽  
L. STAWARZ ◽  
D. MAZIN ◽  
P. COLIN ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Galactic Nuclei ◽  
High Energy ◽  
Massive Black Hole ◽  
Long Baseline ◽  
Multi Wavelength ◽  
Very High Energy ◽  
Γ Ray ◽  
Very Long Baseline Array ◽  
Innermost Region

The giant radio galaxy M 87, with its proximity (16 Mpc) and its very massive black hole ((3-6) × 109 M⊙), provides a unique laboratory to investigate very high energy (E>100 GeV; VHE) gamma-ray emission from active galactic nuclei and, thereby, probe particle acceleration to relativistic energies near supermassive black holes (SMBH) and in relativistic jets. M 87 has been established as a VHE γ-ray emitter since 2005. The VHE γ-ray emission displays strong variability on timescales as short as a day. In 2008, a rise in the 43 GHz Very Long Baseline Array (VLBA) radio emission of the innermost region (core; extension of < 100 R s ; Schwarzschild radii) was found to coincide with a flaring activity at VHE. This had been interpreted as a strong indication that the VHE emission is produced in the direct vicinity of the SMBH. In 2010 a flare at VHE was again detected triggering further multi-wavelength (MWL) observations with the VLBA, Chandra, and other instruments. At the same time, M 87 was also observed with the Fermi-LAT telescope at MeV/GeV energies, the European VLBI Network (EVN), and the Liverpool Telescope (LT). Here, preliminary results from the 2010 campaign will be reported.

scholarly journals 7.8. Particle cascades in Sgr A∗: the possibility of observing their γ-ray signature

1998 ◽  
Vol 184 ◽  
pp. 307-308
Author(s):  
Sera Markoff ◽  
Fulvio Melia ◽  
Ina Sarcevic
Keyword(s):  
Black Hole ◽  
Particle Physics ◽  
Galactic Center ◽  
Theoretical Models ◽  
High Energy ◽  
Massive Black Hole ◽  
Inverse Compton Scattering ◽  
Black Hole Candidate ◽  
Γ Ray ◽  
Sgr A

The recent detection of a γ-ray flux from the direction of the Galactic center by EGRET on the Compton GRO raises the question of whether this is a point source (possibly coincident with the massive black hole candidate Sgr A∗) or a diffuse emitter. Using the latest experimental particle physics data and theoretical models, we have examined in detail the γ-ray spectrum produced by synchrotron, inverse Compton scattering and mesonic decay resulting from the interaction of relativistic protons with hydrogen accreting onto a point-like object. Such a distribution of high-energy baryons may be expected to form within an accretion shock as the inflowing gas becomes supersonic. This scenario is motivated by hydrodynamic studies of Bondi-Hoyle accretion onto Sgr A∗, which indicate that many of its radiative characteristics may ultimately be associated with energy liberated as this plasma descends down into the deep potential well. Earlier attempts at analyzing this process concluded that the EGRET data are inconsistent with a massive point-like object (Mastichiadis & Ozernoy, 1994). Our results demonstrate that a more careful treatment of the physics of p-p scattering suggests that a ~ 106M⊙ black hole may be contributing to this high-energy emission.

Modelling pulsed gamma-ray emissions from millisecond pulsars with double peaks

2019 ◽  
Vol 488 (3) ◽  
pp. 4288-4306
Author(s):  
Shan Chang ◽  
Li Zhang ◽  
Xiang Li ◽  
Zejun Jiang
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Model Parameters ◽  
Large Area ◽  
Radiation Mechanisms ◽  
Millisecond Pulsars ◽  
Double Peaks ◽  
Magnetic Inclination ◽  
Γ Ray ◽  
Energy Emissions

ABSTRACT Pulsed γ-ray properties of 22 millisecond pulsars (MSPs) with double peaks are studied in the revised versions of the outer gap (OG) and the stripped wind (SW) models. The major differences between these two models are magnetic field structures, γ-ray production sites, and radiation mechanisms. In the models, γ-ray light curves of these MSPs are calculated through a Markov chain Monte Carlo (MCMC) method to pick best-fitting model parameters. Our results indicate that (1) both models can reproduce observed double-peak structures of the MSPs well, for most MSPs, a relatively large magnetic inclination angle (α ∼ 50°–90°) and small viewing angle (ζ ∼ 30°–90°) are obtained in the OG model, but a relatively small α ∈ (20°, 60°) and large ζ ∈ (70°, 150°) in the SW model; (2) phase-averaged spectra, cut-off energy, and γ-ray luminosity calculated in both models are consistent with observed those by Fermi-Large Area Telescope (LAT). Therefore, it may be concluded that the OG and the SW models for describing high-energy emissions of MSPs cannot be ruled out at present, and further studies are required.

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