We present an analysis of 123 Gamma-ray bursts (GRBs) with known redshifts possessing an afterglow plateau phase. We reveal that $L_a-T^{*}_a$ correlation between the X-ray luminosity $L_a$ at the end of the plateau phase and the plateau duration, $T
^*_a$, in the GRB rest frame has a power law slope different, within more than 2 $sigma$, from the slope of the prompt $L_{f}-T^{*}_{f}$ correlation between the isotropic pulse peak luminosity, $L_{f}$, and the pulse duration, $T^{*}_{f}$, from the time since the GRB ejection. Analogously, we show differences between the prompt and plateau phases in the energy-duration distributions with the afterglow emitted energy being on average $10%$ of the prompt emission. Moreover, the distribution of prompt pulse versus afterglow spectral indexes do not show any correlation. In the further analysis we demonstrate that the $L_{peak}-L_a$ distribution, where $L_{peak}$ is the peak luminosity from the start of the burst, is characterized with a considerably higher Spearman correlation coefficient, $rho=0.79$, than the one involving the averaged prompt luminosity, $L_{prompt}-L_a$, for the same GRB sample, yielding $rho=0.60$. Since some of this correlation could result from the redshift dependences of the luminosities, namely from their cosmological evolution we use the Efron-Petrosian method to reveal the intrinsic nature of this correlation. We find that a substantial part of the correlation is intrinsic. We apply a partial correlation coefficient to the new de-evolved luminosities showing that the intrinsic correlation exists.
During its first six years of operation, the Fermi Large Area Telescope (LAT) has detected >30 MeV gamma-ray emission from more than 40 solar flares, nearly a factor of 10 more than those detected by EGRET. These include detections of impulsive and s
ustained emissions, extending up to 20 hours in the case of the 2012 March 7 X-class flares. We will present an overview of solar flare detections with LAT, highlighting recent results and surprising features, including the detection of >100 MeV emission associated with flares located behind the limb. Such flares may shed new light on the relationship between the sites of particle acceleration and gamma-ray emission.
The Fermi Large Area Telescope (LAT) is the most sensitive instrument ever deployed in space for observing gamma-ray emission >100 MeV. This sensitivity has enabled the LAT to detect gamma-ray emission from the Sun during quiescent periods from pions
produced by cosmic-ray protons interacting in the solar atmosphere and from cosmic-ray electrons interacting with solar optical photons. The LAT has detected high-energy gamma-ray emission associated with GOES M-class and X-class X-ray flares accompanied by coronal mass ejections and solar energetic particle events. In a number of cases, LAT has detected gamma rays with energies up to several hundreds of MeV during the impulsive phase and gamma rays up to GeV energies sustained for several hours after the impulsive phase. This presentation focuses on observations in the impulsive emission phase in solar flares, including the modest GOES M2-class flare at SOL2010-06-12T0057 and more recent detections, such as the bright X-class flares of March 2012.
