43 research outputs found
Fermi LAT observations of cosmic-ray electrons from 7 GeV to 1 TeV
We present the results of our analysis of cosmic-ray electrons using about 8
million electron candidates detected in the first 12 months on-orbit by the
Fermi Large Area Telescope. This work extends our previously-published
cosmic-ray electron spectrum down to 7 GeV, giving a spectral range of
approximately 2.5 decades up to 1 TeV. We describe in detail the analysis and
its validation using beam-test and on-orbit data. In addition, we describe the
spectrum measured via a subset of events selected for the best energy
resolution as a cross-check on the measurement using the full event sample. Our
electron spectrum can be described with a power law with no prominent spectral features within systematic uncertainties.
Within the limits of our uncertainties, we can accommodate a slight spectral
hardening at around 100 GeV and a slight softening above 500 GeV.Comment: 20 pages, 23 figures, 2 tables, published in Physical Review D 82,
092004 (2010) - contact authors: C. Sgro', A. Moisee
The On-orbit Calibrations for the Fermi Large Area Telescope
The Large Area Telescope (LAT) on--board the Fermi Gamma ray Space Telescope
began its on--orbit operations on June 23, 2008. Calibrations, defined in a
generic sense, correspond to synchronization of trigger signals, optimization
of delays for latching data, determination of detector thresholds, gains and
responses, evaluation of the perimeter of the South Atlantic Anomaly (SAA),
measurements of live time, of absolute time, and internal and spacecraft
boresight alignments. Here we describe on orbit calibration results obtained
using known astrophysical sources, galactic cosmic rays, and charge injection
into the front-end electronics of each detector. Instrument response functions
will be described in a separate publication. This paper demonstrates the
stability of calibrations and describes minor changes observed since launch.
These results have been used to calibrate the LAT datasets to be publicly
released in August 2009.Comment: 60 pages, 34 figures, submitted to Astroparticle Physic
Fermi Large Area Telescope Performance after 10 Years of Operation
The Large Area Telescope (LAT), the primary instrument for the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy gamma-ray telescope, covering the energy range from 30 MeV to more than 300 GeV. We describe the performance of the instrument at the 10 yr milestone. LAT performance remains well within the specifications defined during the planning phase, validating the design choices and supporting the compelling case to extend the duration of the Fermi mission. The details provided here will be useful when designing the next generation of high-energy gamma-ray observatories