Gamma-ray observations of Supernova Remnants with Fermi -LAT data

After 8 years of data taking, the Large Area Telescope (LAT) onboard the Fermi satellite has shown an excellent capability to detect and observe Supernova Remnants (SNRs) from few hundred MeV up to few hundred GeV. It provides crucial information on physical processes happening at the source, involving both accelerated leptons and hadrons, in order to understand the mechanisms responsible for the acceleration of primary Cosmic Rays. We interpreted the multiwavelength Spectral Energy Distribution (SED) of a sample of different types of SNRs, which have been observed by the Fermi-LAT. We show how the environment in which the supernova shock is propagating affects the interpretation of its SED. We evaluated the spectral features of the accelerated particle spectra and estimated the acceleration efficiency, as well as the maximum energy of accelerated particles

Galactic science with Fermi -LAT

High energy γ-rays reveal extreme, non-thermal processes in the Universe. The Fermi Large Area Telescope (LAT) has been exploring the γ-ray sky for almost eight years, enabling the observation of many powerful events happening in our Galaxy. The wide energy range and field of view make the LAT a unique instrument to monitor the sky and study both powerful transient events and longterm phenomena. We present a review of the latest results obtained by the FermiLAT observation of Galactic object

Hunting the gamma-ray emission from Fast Radio Burst with Fermi-LAT

Fast radio bursts (FRBs) are one of the most exciting new mysteries of astrophysics. Their origin is still unknown, but recent observations seems to link them to Soft Gamma Repeaters and, in particular, to magnetar giant flares (MGFs). The recent detection of a MGF at GeV energies by the \textit{Fermi} Large Area Telescope (LAT) motivated the search for GeV counterparts to the >100 currently known FRBs. Taking advantage of more than 12 years of \textit{Fermi}-LAT data, we perform a search for gamma-ray emission from all the reported repeating and non-repeating FRBs. We analyse on different-time scales the \textit{Fermi}-LAT data of each individual source separately, including a cumulative analysis on the repeating ones. In addition, we perform the first stacking analysis at GeV energies of this class of sources in order to constrain the gamma-ray properties of the FRBs that are undetected at high energies. The stacking analysis is a powerful method that allow a possible detection from below-threshold FRBs providing important information on these objects. In this talk we present the preliminary results of our study and we discuss their implications for the predictions of gamma-ray emission from this class of source

Direct femtosecond laser fabrication of superhydrophobic aluminum alloy surfaces with anti-icing properties

Ice formation is a serious issue in many fields, from energy to aerospace, compromising the devices' efficiency and security. Superhydrophobicity has been demonstrated to be correlated to the anti-icing properties of surfaces. However, fabricating surfaces with robust water repellence properties also at subzero temperature is still a great challenge. In this work, femtosecond laser (fs-laser) texturing is exploited to produce superhydrophobic surfaces with anti-icing properties on Al2024, an aluminum alloy of great interest in cold environments, in particular for aircraft production. Our textured substrates present self-cleaning properties and robust water repellency at subzero temperatures. Moreover, outstanding anti-icing properties are achieved on the textured surfaces at-20 °C, with water droplets bouncing off the surface before freezing

Minimally invasive (flapless) crown lengthening by erbium: YAG laser in aesthetic zone

Crown lengthening is a surgical procedure aimed at exposure of a larger tooth surface by gingivectomy alone or with cortical bone remodelling for aesthetic purposes in the anterior zone of the maxilla or for reconstruction of teeth affected by subgingival caries. We report two cases of crown lengthening in the anterior maxilla for aesthetic purposes by gingival and bone re-contouring performed by erbium-doped yttrium aluminium garnet (erbium:YAG) laser. As highlighted in this report, the erbium:YAG laser-assisted crown lengthening is less invasive and also leads to faster clinical outcomes in contrast to the conventional surgical technique by scalpel incision, flap elevation and osteoplastic

Hunting for gamma-ray emission from fast radio bursts

Context. Fast radio bursts (FRBs) are a recently discovered class of GHz-band, ms-duration, Jansky-level-flux astrophysical transients. Although hundreds of models have been proposed so far for FRB progenitors (the most popular ones involve magnetars), their physical origin and emission mechanism are still a mystery, making them one of the most compelling problems in astrophysics. Aims. FRBs are caused by astrophysical processes that are not yet understood. Exploring their high-energy counterpart is crucial for constraining their origin and emission mechanism. Methods. Thanks to more than 13 years of gamma-ray data collected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope, and to more than 1000 FRB events (from 561 non-repeating and 22 repeating sources), one of the largest samples created thus far, we performed the largest and deepest search for high-energy emission from FRB sources to date (between 100 MeV and 1 TeV). In addition to the analysis involving individual FRB events on different timescales (from a few seconds up to several years), we performed, for the first time, a stacking analysis on the full sample of FRB events as well as a search for triplet photons in coincidence with the radio event. Results. We do not detect significant emission, reporting the most stringent constraints, on short timescales, for the FRB-like emission from SGR 1935+2154 with Eγ < 1041 erg, corresponding to a factor η < 107 with respect to the emitted radio energy. Similarly, for the stacked signal of steady emission from all repeaters, the obtained upper limit (UL) on the FRBs luminosity (Lγ < 1.6×1043 erg s-1) is more than two orders of magnitude lower than those derived from the individual sources. Finally, no individual or triplet photons have been significantly associated with FRB events. We derived the LAT ms-sensitivity to be ~0.3 ph cm-2 s-1 and constrained the gamma-ray energy Eγ,δT = 1 ms ≲ 1047(DL/150 Mpc)2 erg, ruling out a gamma-ray-to-radio energy ratio greater than 109 on ms timescales. Conclusions. The results reported here represent the most stringent UL reported so far on the high-energy emission from FRBs on short and long time scales, as well as on cumulative emission and individual photon searches. While the origin of FRBs is still unclear, our work provides important constraints for FRB modelling, which might shed light on their emission mechanism

Gamma-ray emission from young radio galaxies and quasars: the flaring episode of the peculiar galaxy PKS B1413+135

According to radiative models, radio galaxies are predicted to produce gamma rays from the earliest stages of their evolution onwards.The study of the high-energy emission from young radio sources is crucial for providing information on the most energetic processes associated with these sources, the actual region responsible for this emission, as well as the structure of the newly born radio jets. Despite systematic searches for young radio sources at gamma-ray energies, only a handful of detections have been reported so far. Taking advantage of more than 11 years of \textit{Fermi}-LAT data, we investigate the gamma-ray emission of 162 young radio sources (103 galaxies and 59 quasars), the largest sample of young radio sources used so far for a gamma-ray study. We analyse the \textit{Fermi}-LAT data of each individual source separately to search for a significant detection. In addition, we perform the first stacking analysis of this class of sources in order to investigate the gamma-ray emission of the young radio sources that are undetected at high energies. We report the detection of significant gamma-ray emission from 11 young radio sources, including the discovery of significant gamma-ray emission from the compact radio galaxy PKS 1007+142. Although the stacking analysis of below-threshold young radio sources does not result in a significant detection, it provides stringent upper limits to constrain the gamma-ray emission from these objects. In this talk we present the results of our study and we discuss their implications for the predictions of gamma-ray emission from this class of sources

Search for Early Gamma-ray Production in Supernovae Located in a Dense Circumstellar Medium with the Fermi LAT

Supernovae (SNe) exploding in a dense circumstellar medium (CSM) are hypothesized to accelerate cosmic rays in collisionless shocks and emit GeV gamma rays and TeV neutrinos on a time scale of several months. We perform the first systematic search for gamma-ray emission in Fermi LAT data in the energy range from 100 MeV to 300 GeV from the ensemble of 147 SNe Type IIn exploding in dense CSM. We search for a gamma-ray excess at each SNe location in a one year time window. In order to enhance a possible weak signal, we simultaneously study the closest and optically brightest sources of our sample in a joint-likelihood analysis in three different time windows (1 year, 6 months and 3 months). For the most promising source of the sample, SN 2010jl (PTF10aaxf), we repeat the analysis with an extended time window lasting 4.5 years. We do not find a significant excess in gamma rays for any individual source nor for the combined sources and provide model-independent flux upper limits for both cases. In addition, we derive limits on the gamma-ray luminosity and the ratio of gamma-ray-to-optical luminosity ratio as a function of the index of the proton injection spectrum assuming a generic gamma-ray production model. Furthermore, we present detailed flux predictions based on multi-wavelength observations and the corresponding flux upper limit at 95% confidence level (CL) for the source SN 2010jl (PTF10aaxf).Comment: Accepted for publication in ApJ. Corresponding author: A. Franckowiak ([email protected]), updated author list and acknowledgement

Multiwavelength Evidence for Quasi-periodic Modulation in the Gamma-ray Blazar PG 1553+113

We report for the first time a gamma-ray and multi-wavelength nearly-periodic oscillation in an active galactic nucleus. Using the Fermi Large Area Telescope (LAT) we have discovered an apparent quasi-periodicity in the gamma-ray flux (E >100 MeV) from the GeV/TeV BL Lac object PG 1553+113. The marginal significance of the 2.18 +/-0.08 year-period gamma-ray cycle is strengthened by correlated oscillations observed in radio and optical fluxes, through data collected in the OVRO, Tuorla, KAIT, and CSS monitoring programs and Swift UVOT. The optical cycle appearing in ~10 years of data has a similar period, while the 15 GHz oscillation is less regular than seen in the other bands. Further long-term multi-wavelength monitoring of this blazar may discriminate among the possible explanations for this quasi-periodicity.Comment: 8 pages, 5 figures. Accepted to The Astrophysical Journal Letters. Corresponding authors: S. Ciprini (ASDC/INFN), S. Cutini (ASDC/INFN), S. Larsson (Stockholm Univ/KTH), A. Stamerra (INAF/SNS), D. J. Thompson (NASA GSFC

A fast muon tagger method for imaging atmospheric cherenkov telescopes

The Cherenkov Telescope Array (CTA) will be the next major observatory for Very High Energy gamma-ray astronomy. Its optical throughput calibration relies on muon Cherenkov rings. This work is aimed at developing a fast and efficient muon tagger at the camera level for the CTA telescopes. A novel technique to tag muons using the capabilities of silicon photomultiplier Compact High-Energy Camera CHEC-S, one of the design options for the camera of the small size telescopes, has been developed, studying and comparing different algorithms such as circle fitting with the Taubin method, machine learning using a neural network and simple pixel counting. Their performance in terms of efficiency and computation speed was investigated using simulations with varying levels of night sky background light. The application of the best performing method to the large size telescope camera has also been studied, to improve the speed of the muon preselection