Ref HAL: in2p3-00148471_v1
Ref Arxiv: 0705.1605
DOI: 10.1051/0004-6361:20077280
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
54 citations
Résumé:

We present the discovery of two very-high-energy gamma-ray sources in an ongoing systematic search for emission above 100 GeV from pulsar wind nebulae in survey data from the H.E.S.S. telescope array. Imaging Atmospheric Cherenkov Telescopes are ideal tools for searching for extended emission from pulsar wind nebulae in the very-high-energy regime. H.E.S.S., with its large field of view of 5 degrees and high sensitivity, gives new prospects for the search for these objects. An ongoing systematic search for very-high-energy emission from energetic pulsars over the region of the Galactic plane between -60 degrees < l < 30 degrees, -2 degrees < b < 2 degrees is performed. For the resulting candidates, the standard H.E.S.S. analysis was applied and a search for multi-wavelength counterparts was performed. We present the discovery of two new candidate gamma-ray pulsar wind nebulae, HESS J1718-385 and HESS J1809-193. H.E.S.S. has proven to be a suitable instrument for pulsar wind nebula searches.

Ref HAL: in2p3-00147240_v1
Ref Arxiv: 0704.0171
DOI: 10.1051/0004-6361:20077299
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
87 citations
Résumé:

The complex Monoceros Loop SNR/Rosette Nebula region contains several potential sources of very-high-energy (VHE) gamma-ray emission and two as yet unidentified high-energy EGRET sources. Sensitive VHE observations are required to probe acceleration processes in this region. The H.E.S.S. telescope array has been used to search for very high-energy gamma-ray sources in this region. CO data from the NANTEN telescope were used to map the molecular clouds in the region, which could act as target material for gamma-ray production via hadronic interactions. We announce the discovery of a new gamma-ray source, HESS J0632+058, located close to the rim of the Monoceros SNR. This source is unresolved by H.E.S.S. and has no clear counterpart at other wavelengths but is possibly associated with the weak X-ray source 1RXS J063258.3+054857, the Be-star MWC 148 and/or the lower energy gamma-ray source 3EG J0634+0521. No evidence for an associated molecular cloud was found in the CO data.

Commentaires: 5 pages, 4 figures, to appear in A&A

Ref HAL: in2p3-00142313_v1
Ref Arxiv: astro-ph/0703427
DOI: 10.1051/0004-6361:20066950
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
99 citations
Résumé:

Results from gamma-ray observations by the H.E.S.S. telescope array in the direction of the young stellar cluster Westerlund 2 are presented. Stereoscopic imaging of Cherenkov light emission of gamma-ray induced showers in the atmosphere is used to study the celestial region around the massive Wolf-Rayet (WR) binary WR 20a. Spectral and positional analysis is performed using standard event reconstruction techniques and parameter cuts. The detection of a new gamma-ray source is reported from H.E.S.S. observations in 2006. HESS J1023-575 is found to be coincident with the young stellar cluster Westerlund 2 in the well-known HII complex RCW 49. The source is detected with a statistical significance of more than 9 sigma, and shows extension beyond a point-like object within the H.E.S.S. point-spread function. The differential gamma-ray spectrum of the emission region is measured over approximately two orders of magnitude in flux. The spatial coincidence between HESS J1023-575 and the young open cluster Westerlund 2, hosting e.g. the massive WR binary WR 20a, requires a look into a variety of potential models to account for the observed very-high-energy (VHE) gamma-ray emission. Considered emission scenarios include emission from the colliding wind zone of WR 20a, collective stellar winds from the extraordinary ensemble of hot and massive stars in the stellar cluster Westerlund 2, diffusive shock acceleration in the wind-blown bubble itself, and supersonic winds breaking out into the interstellar medium (ISM). The observed source extension argues against a single star origin of the observed VHE emission.

Commentaires: 7 pages, 5 figures, accepted for publication in A&A

Ref HAL: in2p3-00130812_v1
Ref Arxiv: astro-ph/0702336
DOI: 10.1051/0004-6361:20066737
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
20 citations
Résumé:

We present the results of a search for pulsed very-high-energy (VHE) gamma-ray emission from young pulsars using data taken with the H.E.S.S. imaging atmospheric Cherenkov telescope system. Data on eleven pulsars, selected according to their spin-down luminosity relative to distance, are searched for gamma-ray signals with periodicity at the respective pulsar spin period. Special analysis efforts were made to improve the sensitivity in the 100 GeV gamma-ray energy domain in an attempt to reduce the gap between satellite and ground-based gamma-ray instruments. No significant evidence for pulsed emission is found in any data set. Differential upper limits on pulsed energy flux are determined for all selected pulsars in the approximate gamma-ray energy range between 100 GeV and 50 TeV, using different limit determination methods, testing a wide range of possible pulsar light curves and energy spectra. The limits derived here imply that the magnetospheric VHE gamma-ray production efficiency in young pulsars is less than 10^-4 of the pulsar spin-down luminosity, requiring spectral turnovers for the high-energy emission of four established gamma-ray pulsars, and constrain the inverse Compton radiation component predicted by several outer gap models.

Commentaires: 13 pages, 11 figures, accepted for publication in A&A