Solar gamma rays and modulation of cosmic rays in the inner heliosphere

The first evidence of the gamma-ray emission from the quiescent Sun was found in the archival EGRET data that was later confirmed by Fermi-LAT observations with high significance. This emission is produced by Galactic cosmic rays (CRs) penetrating the inner heliosphere and inter- acting with the solar atmosphere and optical photons. The solar emission is characterized by two spatially and spectrally distinct components: (i) disk emission due to the CR cascades in the solar atmosphere, and (ii) spatially extended inverse Compton (IC) emission due to the CR electrons scattering off of solar photons. The intensity of both components associated with Galactic CRs anti-correlate with the level of the solar activity being the brightest during solar minimum. In this paper we discuss updates of the models of the IC component of the emission based on CR measurements made at different levels of solar activity, and we make predictions for e- ASTROGAM and AMEGO, proposed low-energy gamma-ray missions.Comment: 7 pages, 3 figures, Proceedings of the 35th International Cosmic Ray Conference, ICRC201

The Third Fermi Large Area Telescope Catalog of Gamma-ray Pulsars

We present 294 pulsars found in GeV data from the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope. Another 33 millisecond pulsars (MSPs) discovered in 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 co-located with LAT sources also likely harbor gamma-ray MSPs. This catalog thus reports roughly 340 gamma-ray pulsars and candidates, 10% of all known pulsars, compared to $\leq 11$ known before Fermi. Half of the gamma-ray pulsars are young. Of these, the half that are undetected in radio have a broader Galactic latitude distribution than the young radio-loud pulsars. The others are MSPs, with 6 undetected in radio. Overall, >235 are bright enough above 50 MeV to fit the pulse profile, the energy spectrum, or both. For the common two-peaked profiles, the gamma-ray peak closest to the magnetic pole crossing generally has a softer spectrum. The spectral energy distributions tend to narrow as the spindown power $\dot E$ decreases to its observed minimum near $10^{33}$ erg s$^{-1}$, approaching the shape for synchrotron radiation from monoenergetic electrons. We calculate gamma-ray luminosities when distances are available. Our all-sky gamma-ray sensitivity map is useful for population syntheses. The electronic catalog version provides gamma-ray pulsar ephemerides, properties and fit results to guide and be compared with modeling results.Comment: 142 pages. Accepted by the Astrophysical Journal Supplemen

Space instrumentation environmental verification: Dynamic tests on GLAST LAT tracker trays

The GLAST satellite is a mission for the detection of gamma rays of both galactic and extra-galactic origin in the energy range 20 keV-300 GeV. The satellite is planned to be launched in 2007 by NASA. Gamma rays detection is based on the pair conversion mechanism achieved by a multilayer silicon strip detector interleaved with a tungsten target for photon conversion and e(+)-e(-) pairs tracking. The GLAST program did foresee a wide use of vibration tests both in development and in qualification phases. The acceptance phase in aerospace environment is usually demanding in terms of vibration tests. Furthermore in this program the trays' design and manufacturing procedure might have been highly vibration sensitive, and experimental validation was considered highly recommendable. This paper aims to give evidence of the performed tests. A critical analysis of the tests is proposed and some results will be also presented. (c) 2006 Published by Elsevier B.V

Cosmic rays and their modulation in the heliosphere by studying gamma rays from the Sun with Fermi-LAT: updated models

The Sun is a known quiescent gamma-ray source. Its gamma-ray steady-state, characterized by two distinct emissions, is unique for its spatially and spectrally distinct components: 1) disc emission due by pion decay of CR hadrons interacting with the solar atmosphere; 2) spatially extended emission from inverse Compton (IC) scattering of CR electrons on the solar photons of the heliosphere. Being produced by CRs, which are affected by solar modulation, the intensity of both emissions is expected to be inversely proportional to the solar activity. After the discovery of the quiet solar emission with EGRET, thanks to the high sensitivity of Fermi-LAT we can now monitor the solar steady-state in the various periods of solar activity. The release of Pass 8 data, with its improved event reconstruction and larger effective area, provides a unique opportunity to refine the study and extend it to different solar activities and also to lower and higher energies. In fact a first study was conducted using 18 month of data during low solar activity, where the best model for IC emission was investigated. Now the recent CR electron and positron measurements by Pamela, AMS-02, Fermi, and the changed solar activity call for a more extended analysis. We present here updates on solar IC models based on available CR measurements for different solar activity

Perspectives on the performance of a multilayer Silicon TRD (SiTRD)

The Silicon TRD (SiTRD) is a transition radiation detector consisting of multiple modules, each composed by a radiator followed by a silicon strip detector (SSD), inserted inside a magnetic field region. A full Monte-Carlo simulation of the SiTRD has been developed in order to study the performance of the detector for particle identification and momentum measurement. The simulation code, that describes the TR production and the processes of charges deposition and generation of electric signals inside the SSDs, has been tailored using the data taken with a 3-5 GeV/c momentum electron-pion beam. The pion rejection power and the momentum resolution have been studied as a function of the detector parameters. (C) 2004 Elsevier B.V. All rights reserved

Fermi-LAT observations of the gamma-ray emission from the quiescent sun - first 6 years in orbit

The quiescent sun is a steady source of high energy gamma-ray emission due to the interactions of cosmic ray (CR) protons and electrons with matter and photons in the solar environment. Such interactions lead to two components of the emission with distinctly different spatial distributions and spectra: a point-like emission from the solar disk due to the CR cascades in the solar atmosphere, and the extended emission from the inverse Compton (IC) scattering of CR electrons off solar photons that is coming from the whole heliosphere. The Fermi-LAT Collaboration has reported the detection of the gamma-ray emission from the quiescent sun in a previous publication, based on the first 18 months of observations. In this paper we present the results of the first 6 years of observations. The new Pass 8 event-level analysis was applied to the data set. Significantly larger photon statistics and better instrument performance allow us to explore both components of the emission in greater details and let us better comparisons of data with current models of the IC component. Moreover, the longer period of observations allows us to study the variations of the emission over the solar cycle