[en] Context. Since the launch of the Fermi satellite, the number of known gamma-ray pulsars has increased tenfold. Most gamma-ray detected pulsars are young and energetic, and many are associated with TeV sources. PSR J1357-6429 is a high spin-down power pulsar (È = 3.1 × 1036 erg s"-"1), discovered during the Parkes multibeam survey of the Galactic plane, with significant timing noise typical of very young pulsars. In the very-high-energy domain (E > 100 GeV), H.E.S.S. has reported the detection of the extended source HESS J1356-645 (intrinsic Gaussian width of 12') whose centroid lies 7' from PSR J1357-6429. Aims. We search for gamma- and X-ray pulsations from this pulsar, characterize the neutron star emission and explore the environment of PSR J1357-6429. Methods. Using a rotational ephemeris obtained with 74 observations made with the Parkes telescope at 1.4 GHz, we phase-fold more than two years of gamma-ray data acquired by the Large Area Telescope on-board Fermi as well as those collected with XMM-Newton, and perform gamma-ray spectral modeling. Results. Significant gamma- and X-ray pulsations are detected from PSR J1357-6429. The light curve in both bands shows one broad peak. Gamma-ray spectral analysis of the pulsed emission suggests that it is well described by a simple power-law of index 1.5 ± 0.3_s_t_a_t ± 0.3_s_y_s_t with an exponential cut-off at 0.8 ± 0.3_s_t_a_t ± 0.3_s_y_s_t GeV and an integral photon flux above 100 MeV of (6.5 ± 1.6_s_t_a_t ± 2.3_s_y_s_t) × 10"-"8 cm"-"2 s"-"1. The X-ray spectra obtained from the new data provide results consistent with previous work. Upper limits on the gamma-ray emission from its potential pulsar wind nebula (PWN) are also reported. Conclusions. Assuming a distance of 2.4 kpc, the Fermi LAT energy flux yields a gamma-ray luminosity for PSR J1357-6429 of L_γ = (2.13 ± 0.25_s_t_a_t ± 0.83_s_y_s_t) × 1034 erg s"-"1, consistent with an relationship. The Fermi non-detection of the pulsar wind nebula associated with HESS J1356-645 provides new constraints on the electron population responsible for the extended TeV emission.

[en] We report on γ-ray analysis of the region containing the bright TeV source HESS J1640–465 and the close-by TeV source HESS J1641–463 using 64 months of observations with the Fermi Large Area Telescope (LAT). Previously only one GeV source was reported in this region and was associated with HESS J1640–465. With an increased data set and the improved sensitivity afforded by the reprocessed data (P7REP) of the LAT, we now report the detection, morphological study, and spectral analysis of two distinct sources above 100 MeV. The softest emission in this region comes from the TeV source HESS J1641–463 which is well fitted with a power law of index Γ = 2.47 ± 0.05 ± 0.06 and presents no significant γ-ray signal above 10 GeV, which contrasts with its hard spectrum at TeV energies. The Fermi-LAT spectrum of the second TeV source, HESS J1640–465 is well described by a power-law shape of index Γ = 1.99 ± 0.04 ± 0.07 that links up naturally with the spectral data points obtained by the High Energy Stereoscopic System (H.E.S.S.). These new results provide new constraints concerning the identification of these two puzzling γ-ray sources

[en] Since its launch, the Fermi satellite has firmly identified 5 pulsar wind nebulae plus a large number of candidates, all powered by young and energetic pulsars. HESS J1857 + 026 is a spatially extended γ-ray source detected by H.E.S.S. and classified as a possible pulsar wind nebula candidate powered by PSR J1856 + 0245. Here, we search for γ-ray pulsations from PSR J1856+0245 and explore the characteristics of its associated pulsar wind nebula. Using a rotational ephemeris obtained from the Lovell telescope at Jodrell Bank Observatory at 1.5 GHz, we phase-fold 36 months of γ-ray data acquired by the Large Area Telescope (LAT) aboard Fermi. We also perform a complete γ-ray spectral and morphological analysis. No γ-ray pulsations were detected from PSR J1856+0245. But, significant emission is detected at a position coincident with the TeV source HESS J1857 + 026. The γ-ray spectrum is well described by a simple power-law with a spectral index of Γ = 1.53 ± 0.11_s_t_a_t ± 0.55_s_y_s_t and an energy flux of G(0.1–100 GeV) = (2.71 ± 0.52_s_t_a_t ± 1.51_s_y_s_t) × 10"-"1"1 erg cm"-"2 s"-"1. The γ-ray luminosity is L_P_W_N"γ (0.1–100 GeV)=(2.5 ± 0.5_s_t_a_t ± 1.5_s_y_s_t) × 10"3"5 (d/9 kpc)"2 erg s"-"1, assuming a distance of 9 kpc. This implies a γ-ray efficiency of ~5% for E-dot = 4.6 × 10"3"6 erg s"-1, in the range expected for pulsar wind nebulae. This detailed multi-wavelength modeling provides new constraints on its pulsar wind nebula nature.

[en] The Crab Pulsar and Nebula are the remnants of the explosion of the supernova SN1054, which was observed by Chinese astronomers. Previously detected by EGRET, the Crab Pulsar and Nebula have been extensively observed in the gamma-ray energy band by the Large Area Telescope (LAT) onboard the Fermi satellite. The data collected by the LAT during its early operation stage have allowed a detailed measurement of the fluxes and of the energy spectra of both sources. The pulsar spectrum is consistent with the EGRET measurement in the region below 1 GeV and is well described by a power law with exponential cutoff at a few GeV. The nebula spectrum is well modeled by a sum of two power laws, identified respectively as the falling edge of the synchrotron and the rising edge of the inverse Compton components, and is in agreement with the observations from Earth-based telescopes.

[en] The Vela supernova remnant (SNR) is the closest SNR to Earth containing an active pulsar, the Vela pulsar (PSR B0833–45). This pulsar is an archetype of the middle-aged pulsar class and powers a bright pulsar wind nebula (PWN), Vela-X, spanning a region of 2° × 3° south of the pulsar and observed in the radio, X-ray, and very high energy γ-ray domains. The detection of the Vela-X PWN by the Fermi Large Area Telescope (LAT) was reported in the first year of the mission. Subsequently, we have reinvestigated this complex region and performed a detailed morphological and spectral analysis of this source using 4 yr of Fermi-LAT observations. This study lowers the threshold for morphological analysis of the nebula from 0.8 GeV to 0.3 GeV, allowing for the inspection of distinct energy bands by the LAT for the first time. We describe the recent results obtained on this PWN and discuss the origin of the newly detected spatial features

[en] There are only a few very-high-energy sources in our Galaxy that might accelerate particles up to the knee of the cosmic-ray spectrum. To understand the mechanisms of particle acceleration in these PeVatron candidates, Fermi-Large Area Telescope (LAT) and High-Energy Stereoscopic System (H.E.S.S.) observations are essential to characterize their γ-ray emission. HESS J1640–465 and the PeVatron candidate HESS J1641–463 are two neighboring (0.25°) γ-ray sources, spatially coincident with the radio supernova remnants (SNRs) G338.3–0.0 and G338.5+0.1. Detected both by H.E.S.S. and the Fermi-LAT, we present here a morphological and spectral analysis of these two sources using 8 yr of Fermi-LAT data between 200 MeV and 1 TeV with multiwavelength observations to assess their nature. The morphology of HESS J1640–465 is described by a 2D Gaussian (σ = 0.053° ± 0.011°_stat ± 0.03°_syst) and its spectrum is modeled by a power law with a spectral index Γ = 1.8 ± 0.1_stat ± 0.2_syst. HESS J1641–463 is detected as a point-like source and its GeV emission is described by a logarithmic-parabola spectrum with α = 2.7 ± 0.1_stat ± 0.2_syst and significant curvature of β = 0.11 ± 0.03_stat ± 0.05_syst. Radio and X-ray flux upper limits were derived. We investigated scenarios to explain their emission, namely, the emission from accelerated particles within the SNRs spatially coincident with each source, molecular clouds illuminated by cosmic rays from the close-by SNRs, and a pulsar/pulsar wind nebula origin. Our new Fermi-LAT results and the radio and flux X-ray upper limits pose severe constraints on some of these models.

[en] We report the detection of GeV γ-ray emission from the supernova remnant (SNR) Puppis A with the Fermi Gamma-Ray Space Telescope. Puppis A is among the faintest SNRs yet detected at GeV energies, with a luminosity of only 2.7 × 10³⁴ (D/2.2 kpc)² erg s^–1 between 1 and 100 GeV. The γ-ray emission from the remnant is spatially extended, with a morphology matching that of the radio and X-ray emission, and is well described by a simple power law with an index of 2.1. We attempt to model the broadband spectral energy distribution (SED), from radio to γ-rays, using standard nonthermal emission mechanisms. To constrain the relativistic electron population we use 7 years of Wilkinson Microwave Anisotropy Probe data to extend the radio spectrum up to 93 GHz. Both leptonic- and hadronic-dominated models can reproduce the nonthermal SED, requiring a total content of cosmic-ray electrons and protons accelerated in Puppis A of at least W _CR ≈ (1-5) × 10⁴⁹ erg.

[en] We report the discovery of extended gamma-ray emission measured by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope in the region of the supernova remnant (SNR) HB 3 (G132.7+1.3) and the W3 II complex adjacent to the southeast of the remnant. W3 is spatially associated with bright "1"2CO (J = 1–0) emission. The gamma-ray emission is spatially correlated with this gas and the SNR. We discuss the possibility that gamma rays originate in interactions between particles accelerated in the SNR and interstellar gas or radiation fields. The decay of neutral pions produced in nucleon–nucleon interactions between accelerated hadrons and interstellar gas provides a reasonable explanation for the gamma-ray emission. The emission from W3 is consistent with irradiation of the CO clouds by the cosmic rays accelerated in HB 3

[en] We announce the discovery of 1-100 GeV gamma-ray emission from the archetypal TeV pulsar wind nebula (PWN) HESS J1825-137 using 20 months of survey data from the Fermi-Large Area Telescope (LAT). The gamma-ray emission detected by the LAT is significantly spatially extended, with a best-fit rms extension of σ = 0.⁰56 ± 0.⁰07 for an assumed Gaussian model. The 1-100 GeV LAT spectrum of this source is well described by a power law with a spectral index of 1.38 ± 0.12 ± 0.16 and an integral flux above 1 GeV of (6.50 ± 0.21 ± 3.90) x 10^-9 cm^-2 s^-1. The first errors represent the statistical errors on the fit parameters, while the second ones are the systematic uncertainties. Detailed morphological and spectral analyses bring new constraints on the energetics and magnetic field of the PWN system. The spatial extent and hard spectrum of the GeV emission are consistent with the picture of an inverse Compton origin of the GeV-TeV emission in a cooling-limited nebula powered by the pulsar PSR J1826-1334.