Ref HAL: in2p3-00274380_v1
Ref Arxiv: 0803.2844
DOI: 10.1051/0004-6361:20079230
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
67 citations
Résumé:

HESS J1745-303 is an extended, unidentified VHE (very high energy) gamma-ray source discovered using HESS in the Galactic Plane Survey. Since no obvious counterpart has previously been found in longer-wavelength data, the processes that power the VHE emission are not well understood. Combining the latest VHE data with recent XMM-Newton observations and a variety of source catalogs and lower-energy survey data, we attempt to match (from an energetic and positional standpoint) the various parts of the emission of HESS J1745-303 with possible candidates. Though no single counterpart is found to fully explain the VHE emission, we postulate that at least a fraction of the VHE source may be explained by a supernova-remnant/molecular-cloud association and/or a high-spin-down-flux pulsar.

Commentaires: 11 pages, 4 figures, Accepted for publication in Astronomy & Astrophysics

Ref HAL: in2p3-00263434_v1
Ref Arxiv: 0802.4021
DOI: 10.1051/0004-6361:200809603
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
46 citations
Résumé:

Aims: The BL Lac object RGB J0152+017 (z=0.080) was predicted to be a very high-energy (VHE; > 100 GeV) gamma-ray source, due to its high X-ray and radio fluxes. Our aim is to understand the radiative processes by investigating the observed emission and its production mechanism using the High Energy Stereoscopic System (H.E.S.S.) experiment. Methods: We report recent observations of the BL Lac source RGB J0152+017 made in late October and November 2007 with the H.E.S.S. array consisting of four imaging atmospheric Cherenkov telescopes. Contemporaneous observations were made in X-rays by the Swift and RXTE satellites, in the optical band with the ATOM telescope, and in the radio band with the Nancay Radio Telescope. Results: A signal of 173 gamma-ray photons corresponding to a statistical significance of 6.6 sigma was found in the data. The energy spectrum of the source can be described by a powerlaw with a spectral index of 2.95+/-0.36stat+/-0.20syst. The integral flux above 300 GeV corresponds to ~2% of the flux of the Crab nebula. The source spectral energy distribution (SED) can be described using a two-component non-thermal synchrotron self-Compton (SSC) leptonic model, except in the optical band, which is dominated by a thermal host galaxy component. The parameters that are found are very close to those found in similar SSC studies in TeV blazars. Conclusions: RGB J0152+017 is discovered as a source of VHE gamma-rays by H.E.S.S. The location of its synchrotron peak, as derived from the SED in Swift data, allows clearly classification it as a high-frequency-peaked BL Lac (HBL).

Commentaires: 6 pages, 2 figures; Accepted for publication in A&A on February 20, 2008

Ref HAL: in2p3-00263525_v1
Ref Arxiv: 0803.0682
DOI: 10.1051/0004-6361:200809655
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
35 citations
Résumé:

The >100 GeV gamma-ray source, HESS J1713-381, apparently associated with the shell-type supernova remnant (SNR) CTB 37B, was discovered using H.E.S.S. in 2006. X-ray follow-up observations with Chandra were performed in 2007 with the aim of identifying a synchrotron counterpart to the TeV source and/or thermal emission from the SNR shell. These new Chandra data, together with additional TeV data, allow us to investigate the nature of this object in much greater detail than was previously possible. The new X-ray data reveal thermal emission from a ~4' region in close proximity to the radio shell of CTB 37B. The temperature of this emission implies an age for the remnant of ~5000 years (assuming a spherical Sedov expansion), disfavouring a suggested association with the supernova of AD 373. A bright (approx 7 x10^-13erg cm^-2 s^-1) and unresolved (<1'') source (CXOU J171405.7-381031) with a soft (Gamma ~ 3.3) non -thermal spectrum is also detected in coincidence with the radio shell. Absorption indicates a column density consistent with the thermal emission from the shell suggesting a genuine association rather than a chance alignment. The observed TeV morphology is consistent with an origin in the complete shell of CTB 37B. The relatively high apparent gas density of the CTB 37B environment (n < 1 cm^-3) and the lack of diffuse non-thermal X-ray emission, are suggestive of an origin of the gamma-ray emission via the decay of neutral pions produced in interactions of protons and nuclei rather than inverse Compton (IC) emission from relativistic electrons.

Commentaires: Submitted to Astronomy and Astrophysics (8 pages, 6 figures)

Ref HAL: in2p3-00013575_v1
Ref Arxiv: astro-ph/0106210
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé:

To date, only three objects have been firmly established as very high-energy gamma-ray sources in the Northern sky: the Crab nebula, which is a plerion, and the two blazars Markarian 501 and Markarian 421. This paper reviews the most striking results obtained for these sources by the CAT atmospheric Cherenkov imaging telescope.

Ref HAL: in2p3-00087398_v1
Ref Arxiv: astro-ph/0109286
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé:

To date, only two extragalactic objects have been firmly established as very high-energy gamma-ray sources in the Northern sky: these are the two blazars Markarian 501 and Markarian 421. This paper reviews the most striking results obtained from these sources by the CAT atmospheric Cherenkov imaging telescope, with a particular emphasis on the 1999-2000 and 2000-2001 observation campaigns of Markarian 421.

Commentaires: 4 pages, 5 figures, to appear in Proc. of the SF2A conference "Semaine de l'Astrophysique Francaise", May 28 - June 1st, 2001 (Lyon, France) - GAM

Ref HAL: in2p3-00025670_v1
DOI: 10.1140/epjc/s2006-02569-7
Exporter : BibTex | endNote
576 citations
Résumé:

The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for the neutral Higgs bosons which are predicted by the Minimal Supersymmetric Standard Model (MSSM). The data of the four collaborations are statistically combined and examined for their consistency with the background hypothesis and with a possible Higgs boson signal. The combined LEP data show no significant excess of events which would indicate the production of Higgs bosons. The search results are used to set upper bounds on the cross-sections of various Higgs-like event topologies. The results are interpreted within the MSSM in a number of ``benchmark" models, including CP-conserving and CP-violating scenarios. These interpretations lead in all cases to large exclusions in the MSSM parameter space. Absolute limits are set on the parameter tanb and, in some scenarios, on the masses of neutral Higgs bosons.

Commentaires: Submitted to Eur. Phys. J. C

Ref HAL: in2p3-00260702_v1
Ref Arxiv: 0802.3841
DOI: 10.1051/0004-6361:20078715
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
22 citations
Résumé:

The H.E.S.S. experiment, an array of four Imaging Atmospheric Cherenkov Telescopes with high sensitivity and large field-of-view, has been used to search for emitters of very-high-energy (VHE, >100 GeV) gamma-rays along the Galactic plane, covering the region 30 deg < l < 60 deg, 280 deg < l < 330 deg, and -3 deg < b < 3 deg. In this continuation of the H.E.S.S. Galactic Plane Scan, a new extended VHE gamma-ray source was discovered at alpha(2000)=19h12m49s, delta(2000)=+10d09'06'' (HESS J1912+101). Its integral flux between 1-10 TeV is ~10% of the Crab Nebula flux in the same energy range. The measured energy spectrum can be described by a power law with a photon index Gamma = 2.7+-0.2(stat)+-0.3(sys). HESS J1912+101 is plausibly associated with the high spin-down luminosity pulsar PSR J1913+1011. We also discuss associations with an as yet unconfirmed SNR candidate proposed from low frequency radio observation and/or with molecular clouds found in 13CO data.

Commentaires: 6 pages, 2 figures; Accepted for publication in A&A on February 20, 2008