Ludovic Guillemot

Learn More
We report the detection of pulsed gamma-rays from the young, spin-powered radio pulsar PSR J2021+3651 using data acquired with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (formerly GLAST). The light curve consists of two narrow peaks of similar amplitude separated by 0.468 ± 0.002 in phase. The first peak lags the maximum of the 2(More)
We report the detection of high energy γ-ray emission from the young and energetic pul-sar PSR B1509−58 and its pulsar wind nebula (PWN) in the composite supernova remnant SNR G320.4−1.2 (aka MSH 15−52). Using 1 year of survey data with the Fermi-Large Area Telescope (LAT), we detected pulsations from PSR B1509−58 up to 1 GeV and extended γ-ray emission(More)
Dark matter (DM) particle annihilation or decay can produce monochromatic γ-rays readily distinguishable from astrophysical sources. γ-ray line limits from 30 GeV to 200 GeV obtained from 11 months of Fermi Large Area Space Telescope data from 20-300 GeV are presented using a selection based on requirements for a γ-ray line analysis, and integrated over(More)
In this paper, we present a new bit allocation procedure based on the approximation of the rate distortion (R-D) functions provided by our efficient lattice vector quantizer with pyramidal dead zone (DZLVQ). Here, we show that DZLVQ R-D functions can be efficiently fitted by an exponential model. This property leads to an analytical solution to the bit(More)
Following its launch in June 2008, the Fermi Gamma-ray Space Telescope (Fermi) began a sky survey in August. The Large Area Telescope (LAT) on Fermi in 3 months produced a deeper and better-resolved map of the γ-ray sky than any previous space mission. We present here initial results for energies above 100 MeV for the 205 most significant (statistical(More)
The problem of the design of a joint watermarking and compression (JWC) scheme allowing an efficient variable rate coding is addressed here. We have proposed in previous works a method, called modulated lattice vector quantization (MLVQ), based on dither modulation and lattice vector quantization (LVQ) and have shown experimentally its good performances. In(More)
Here we propose a new blockwise Rate-Distortion (R-D) model dedicated to lattice vector quantization (LVQ) of sparse and structured signals. We first show that the clustering properties leads to a distribution of the norm L<sup>&#x03B1;</sup> of source vectors close to a mixture of Gamma density. From this issue, we derive the joint distribution of vectors(More)