Gamma-ray binaries detected by AGILE

The AGILE satellite is observing the -ray sky since its launch on April 23, 2007. Several important discoveries have been made in Galactic and extragalactic astrophysics starting from its observations above 50 MeV. In this work, I reviewed the most important findings in the study of -ray emitting Galactic binary systems: the first detection above 100 MeV of Cygnus X-1, the discovery of -ray transient emission from Cygnus X-3, the first observation of a colliding wind binary in rays. The AGILE continuous monitoring of the -ray sky is a fundamental ingredient to investigate the non-thermal emission from these sources, the disk-jet coupling, the limit of relativistic particle acceleration in the jet, the origin of the high-energy -ray radiation

The Orion Region: Evidence of enhanced cosmic-ray density in a stellar wind forward shock interaction with a high density shell

Context. In recent years, an in-depth gamma-ray analysis of the Orion region has been carried out by the AGILE and Fermi-LAT (Large Area Telescope) teams with the aim of estimating the H2-CO conversion factor, XCO. The comparison of the data from both satellites with models of diffuse gamma-ray Galactic emission unveiled an excess at (l,b)=[213.9, -19.5], in a region at a short angular distance from the OB star k-Ori. Possible explanations of this excess are scattering of the so-called "dark gas", non-linearity in the H2-CO relation, or Cosmic-Ray (CR) energization at the k-Ori wind shock. Aims. Concerning this last hypothesis, we want to verify whether cosmic-ray acceleration or re-acceleration could be triggered at the k-Ori forward shock, which we suppose to be interacting with a star-forming shell detected in several wavebands and probably triggered by high energy particles. Methods. Starting from the AGILE spectrum of the detected gamma-ray excess, showed here for the first time, we developed a valid physical model for cosmic-ray energization, taking into account re-acceleration, acceleration, energy losses, and secondary electron contribution. Results. Despite the characteristic low velocity of an OB star forward shock during its "snowplow" expansion phase, we find that the Orion gamma-ray excess could be explained by re-acceleration of pre-existing cosmic rays in the interaction between the forward shock of k-Ori and the CO-detected, star-forming shell swept-up by the star expansion. According to our calculations, a possible contribution from freshly accelerated particles is sub-dominant with respect the re-acceleration contribution. However, a simple adiabatic compression of the shell could also explain the detected gamma-ray emission. Futher GeV and TeV observations of this region are highly recommended in order to correctly identify the real physical scenario.Comment: 8 pages, 5 figures, accepted by A&

Correlation between Specific Bacterial Groups in the Oral Cavity and the Severity of Halitosis: Any Possible Beneficial Role for Selected Lactobacilli?

Objective: Halitosis is a widespread problem, normally attributable to specific volatile sulphur compounds (VSC) in the breath. The aim of this study was to first relate halitosis with possible gastric infection by Helicobacter pylori and secondly to quantify specific bacterial groups in the oral cavity flora, thus correlating them with VSC concentrations and Proton Pump Inhibitors (PPIs) intake. Four selected lactobacilli were then assessed in the possible reduction of halitosis in subjects with a total salivary bacterial concentration higher than 105 CFU/ml. Methods: Specific bacterial groups, namely total bacteria, total coliforms, sulphite-reducing bacteria (SRB) and lactobacilli, were quantified in samples of saliva from 29 subjects taking PPIs compared with 36 control subjects. The amount of the three VSC hydrogen sulfide (H2S), methyl mercaptan (CH3SH) and dimethyl sulfide (CH3)2S in the breath and the presence of H. pylori were determined. Results: No significant correlation was found between H. pylori and halitosis as well as with PPIs intake. The baseline bacterial groups quantification (log10 CFU/ml of saliva, PPI group vs. control) showed: total bacteria 8.44 vs. 4.47 (p=0.001); total coliforms 4.95 vs. 2.82 (p=0.001); sulfite-reducing bacteria 5.47 vs. 2.58 (p=0.052); total lactobacilli 4.00 vs. 2.36 (p=0.016). After 15 days of lactobacilli supplementation, the same parameters (d15 vs baseline) gave: total bacteria 7.92 vs. 8.44 (p=0.019); total coliforms 3.13 vs. 4.95 (p=0.001); sulfite-reducing bacteria 4.69 vs. 5.47 (p=0.047); total lactobacilli 7.86 vs. 4.00 (p=0.048). No statistically significant differences were noted in VSC concentrations at any time. Conclusions: The intake of PPIs directly correlated with the overgrowth of specific bacterial groups in the oral cavity, but there was no correlation with H. pylori or with VSC concentration. The significant reduction in all the bacterial groups analysed after two weeks suggested the improvement of the overall oral flora in subjects chronically treated with PPIs

AGILE as a particle detector: Magnetospheric measurements of 10-100 MeV electrons in L shells less than 1.2

We study the capability of the AGILE gamma ray space mission in detecting magnetospheric particles (mostly electrons) in the energy range 10-100 MeV. Our measurements focus on the inner magnetic shells with L ≲ 1.2 in the magnetic equator. The instrument characteristics and a quasi-equatorial orbit of ∼500 km altitude make it possible to address several important properties of the particle populations in the inner magnetosphere. We review the on board trigger logic and study the acceptance of the AGILE instrument for particle detection. We find that the AGILE effective geometric factor (acceptance) is R≃50 cm2 sr for particle energies in the range 10-100 MeV. Particle event reconstruction allows to determine the particle pitch angle with the local magnetic field with good accuracy. We obtain the pitch angle distributions for both the AGILE "pointing" phase (July 2007 to October 2009) and the "spinning" phase (November 2009 to present). In spinning mode, the whole range (0-180 degrees) is accessible every 7 min. We find a pitch angle distribution of the "dumbbell" type with a prominent depression near α = 90° which is typical of wave-particle resonant scattering and precipitation in the inner magnetosphere. Most importantly, we show that AGILE is not affected by solar particle precipitation events in the magnetosphere. The satellite trajectory intersects magnetic shells in a quite narrow range (1.0 ≲ L ≲ 1.2); AGILE then has a high exposure to a magnetospheric region potentially rich of interesting phenomena. The large particle acceptance in the 10-100 MeV range, the pitch angle determination capability, the L shell exposure, and the solar-free background make AGILE a unique instrument for measuring steady and transient particle events in the inner magnetosphere

Retinal defects in mice lacking the autism-associated gene Engrailed-2

Defective cortical processing of visual stimuli and altered retinal function have been described in autism spectrum disorder (ASD)patients. In keeping with these findings, anatomical and functional defects have been found in the visual cortex and retina of mice bearing mutations for ASD-associated genes. Here we sought to investigate the anatomy and function of the adult retina of Engrailed 2 knockout (En2 −/− )mice, a model for ASD. Our results showed that En2 is expressed in all three nuclear layers of the adult retina. When compared to age-matched En2 +/+ controls, En2 −/− adult retinas showed a significant decrease in the number of calbindin + horizontal cells, and a significant increase in calbindin + amacrine/ganglion cells. The total number of ganglion cells was not altered in the adult En2 −/− retina, as shown by Brn3a + cell counts. In addition, En2 −/− adult mice showed a significant reduction of photoreceptor (rhodopsin)and bipolar cell (Pcp2, PKCα)markers. Functional defects were also present in the retina of En2 mutants, as indicated by electroretinogram recordings showing a significant reduction in both a-wave and b-wave amplitude in En2 −/− mice as compared to controls. These data show for the first time that anatomical and functional defects are present in the retina of the En2 ASD mouse model

High-energy Gamma-Ray Activity from V404 Cygni Detected by AGILE during the 2015 June Outburst

The AGILE satellite detected transient high-energy γ-ray emission from the X-ray binary V404 Cygni, during the 2015 June outburst observed in radio, optical, X-ray, and soft γ-ray frequencies. The activity was observed by AGILE in the 50-400 MeV energy band, between 2015 June 24 UT 06:00:00 and 2015 June 26 UT 06:00:00 (MJD 57197.25-57199.25), with a detection significance of ∼4.3σ. The γ-ray detection, consistent with a contemporaneous observation by Fermi-LAT, is correlated with a bright flare observed at radio and hard X-ray frequencies, and with a strong enhancement of the 511 keV line emission, possibly indicating plasmoid ejections in a lepton-dominated transient jet. The AGILE observations of this binary system are compatible with a microquasar scenario in which transient jets are responsible for the high-energy γ-ray emission

Detection methods for the Cherenkov Telescope Array at very-short exposure times

The Cherenkov Telescope Array (CTA) will be the next generation ground-based observatory for very-high-energy (VHE) gamma-ray astronomy, with the deployment of tens of highly sensitive and fast-reacting Cherenkov telescopes. It will cover a wide energy range (20 GeV - 300 TeV) with unprecedented sensitivity. To maximize the scientific return, the observatory will be provided with an online software system that will perform the first analysis of scientific data in real-time. This study investigates the precision and accuracy of available science tools and analysis techniques for the short-term detection of gamma-ray sources, in terms of sky localization, detection significance and, if significant detection is achieved, a first estimation of the integral photon flux. The scope is to evaluate the feasibility of the algorithms' implementation in the real-time analysis of CTA. In this contribution we present a general overview of the methods and some of the results for the test case of the short-term detection of a gamma-ray burst afterglow, as the VHE counterpart of a gravitational wave event.Comment: Proceedings of the 37th International Cosmic Ray Conference (ICRC 2021), PoS(ICRC2021)69, 8 pages + full author list, 5 figure

AGILE Study of the Gamma-Ray Emission from the SNR G78.2+2.1 (Gamma Cygni)

We present a study of the γ-ray emission detected by the Astrorivelatore Gamma ad Immagini LEggero-Gamma Ray Imaging Detector (AGILE-GRID) from the region of the SNR G78.2+2.1 (Gamma Cygni). In order to investigate the possible presence of γ rays associated with the SNR below 1 GeV, it is necessary to analyze the γ-ray radiation underlying the strong emission from the pulsar PSR J2021+4026, which totally dominates the field. An “off-pulse” analysis has been carried out, by considering only the emission related to the pulsar off-pulse phase of the AGILE-GRID light curve. We found that the resulting off-pulsed emission in the region of the SNR—detected by the AGILE-GRID above 400 MeV—partially overlaps the radio shell boundary. By analyzing the averaged emission on the whole angular extent of the SNR, we found that a lepton-dominated double-population scenario can account for the radio and γ-ray emission from the source. In particular, the MeV-GeV averaged emission can be explained mostly by Bremsstrahlung processes in a high density medium, whereas the GeV-TeV radiation can be explained by both Bremsstrahlung (E ≲ 250 GeV) and inverse Compton processes (E ≳ 250 GeV) in a lower density medium