Institut für Physik und Astronomie
Refine
Has Fulltext
- no (64)
Language
- English (64)
Is part of the Bibliography
- yes (64)
Keywords
- gamma rays: general (21)
- radiation mechanisms: non-thermal (17)
- ISM: supernova remnants (12)
- gamma rays: galaxies (11)
- cosmic rays (10)
- galaxies: active (10)
- acceleration of particles (8)
- astroparticle physics (6)
- gamma rays: stars (6)
- galaxies: jets (5)
- gamma rays: ISM (5)
- gamma-rays: galaxies (5)
- ISM: clouds (4)
- X-rays: binaries (4)
- BL Lacertae objects: individual: PKS 2155-304 (3)
- ISM: individual objects: G338.3-0.0 (2)
- binaries: general (2)
- galaxies: nuclei (2)
- infrared: diffuse background (2)
- pulsars: general (2)
- pulsars: individual: PSR B0833-45 (2)
- relativistic processes (2)
- stars: massive (2)
- surveys (2)
- BL Lacertae objects: general (1)
- BL Lacertae objects: individual (Mrk 501) (1)
- BL Lacertae objects: individual (PG 1553+113) (1)
- BL Lacertae objects: individual: 1ES 1312-423 (1)
- BL Lacertae objects: individual: 1ES 2322-409 (1)
- BL Lacertae objects: individual: AP Librae (1)
- BL Lacertae objects: individual: SHBL J001355.9-185406 (1)
- BL Lacertae objects: individual: lES 0229+200 (1)
- BL Lacertae objects: individual: lES 1101-232 (1)
- Galaxy: center (1)
- Galaxy: general (1)
- ISM: individual objects (SNR G338.3-0.0, SNR G338.5+0.1) (1)
- ISM: individual objects: Crab nebula (1)
- ISM: individual objects: HESS J1832-093 (1)
- ISM: individual objects: Puppis A (1)
- ISM: individual objects: SNR G1.9+0.3 (1)
- ISM: individual objects: SNR G22.7-0.2 (1)
- ISM: individual objects: SNR G330.2+1.0 (1)
- ISM: jets and outflows (1)
- ISM: magnetic fields (1)
- X-rays: general (1)
- X-rays: individuals: Circinus X-1 (1)
- X-rays: individuals: G15.4+0.1 (1)
- X-rays: individuals: GRS 1915+105 (1)
- X-rays: individuals: V4641 Sgr (1)
- X-rays: stars (1)
- astroparticle physic (1)
- black hole physics (1)
- catalogs (1)
- convection (1)
- cosmic background radiation (1)
- dark matter detectors (1)
- dark matter experiments (1)
- diffuse radiation (1)
- diffusion (1)
- dwarfs galaxies (1)
- errata, addenda (1)
- galaxies: distances and redshifts (1)
- galaxies: individual (M 87) (1)
- galaxies: individual: PKS 0625-354 (1)
- galaxies: magnetic fields (1)
- galaxies: starburst (1)
- gamma ray detectors (1)
- gamma rays: general(HESS J0632+057, VER J0633+057) (1)
- gamma-ray burst: individual (GRB 170817A) (1)
- gamma-ray burst: individual: GRB 100621A (1)
- gamma-rays: ISM (1)
- gamma-rays: general (1)
- gravitational lensing: strong (1)
- gravitational waves (1)
- intergalactic medium (1)
- methods: observational (1)
- pulsars: individual: PSR B1259-63 (1)
- quasars: individual: 3C 279 (1)
- quasars: individual: PKS 1510-089 (1)
- stars: black holes (1)
- stars: early-type (1)
- stars: individual: 1FGL J1018.6-5856 (1)
- stars: individual: LS 2883 (1)
- stars: magnetars (1)
- stars: winds, outflows (1)
- supernovae: general (1)
- supernovae: individual: HESS J1818-154 (1)
Institute
The quasar PKS 1510-089 (z = 0.361) was observed with the H.E.S.S. array of imaging atmospheric Cherenkov telescopes during high states in the optical and GeV bands, to search for very high energy (VHE, defined as E >= 0.1 TeV) emission. VHE gamma-rays were detected with a statistical significance of 9.2 standard deviations in 15.8 h of H. E. S. S. data taken during March and April 2009. A VHE integral flux of I(0.15 TeV < E < 1.0TeV) = (1.0 +/- 0.2(stat) +/- 0.2(sys)) x 10(-11) cm(-2) s(-1) is measured. The best-fit power law to the VHE data has a photon index of G = 5.4 +/- 0.7(stat) +/- 0.3(sys). The GeV and optical light curves show pronounced variability during the period of H.E.S.S. observations. However, there is insufficient evidence to claim statistically significant variability in the VHE data. Because of its relatively high redshift, the VHE flux from PKS 1510-089 should suffer considerable attenuation in the intergalactic space due to the extragalactic background light (EBL). Hence, the measured gamma-ray spectrum is used to derive upper limits on the opacity due to EBL, which are found to be comparable with the previously derived limits from relatively-nearby BL Lac objects. Unlike typical VHE-detected blazars where the broadband spectrum is dominated by nonthermal radiation at all wavelengths, the quasar PKS 1510-089 has a bright thermal component in the optical to UV frequency band. Among all VHE detected blazars, PKS 1510-089 has the most luminous broad line region. The detection of VHE emission from this quasar indicates a low level of gamma - gamma absorption on the internal optical to UV photon field.
Discovery of high and very high-energy emission from the BL Lacertae object SHBL J001355.9-185406
(2013)
The detection of the high-frequency peaked BL Lac object (HBL) SHBL J001355.9-185406 (z = 0.095) at high (HE; 100 MeV < E < 300 GeV) and very high-energy (VHE; E > 100 GeV) with the Fermi Large Area Telescope (LAT) and the High Energy Stereoscopic System (H.E.S.S.) is reported. Dedicated observations were performed with the H. E. S. S. telescopes, leading to a detection at the 5.5 sigma significance level. The measured flux above 310 GeV is (8.3 +/- 1.7(stat) +/- 1.7(sys)) x 10(-13) photons cm(-2) s(-1) (about 0.6% of that of the Crab Nebula), and the power-law spectrum has a photon index of Gamma = 3.4 +/- 0.5(stat) +/- 0.2(sys). Using 3.5 years of publicly available Fermi-LAT data, a faint counterpart has been detected in the LAT data at the 5.5 sigma significance level, with an integrated flux above 300 MeV of (9.3 +/- 3.4(stat) +/- 0.8(sys)) x 10(-10) photons cm(-2) s(-1) and a photon index of Gamma = 1.96 +/- 0.20(stat) +/- 0.08(sys). X-ray observations with Swift-XRT allow the synchrotron peak energy in vF(v) representation to be located at similar to 1.0 keV. The broadband spectral energy distribution is modelled with a one-zone synchrotron self-Compton (SSC) model and the optical data by a black-body emission describing the thermal emission of the host galaxy. The derived parameters are typical of HBLs detected at VHE, with a particle-dominated jet.
A deep observation campaign carried out by the High Energy Stereoscopic System (HESS) on Centaurus A enabled the discovery of gamma-rays from the blazar 1ES 1312-423, 2 degrees away from the radio galaxy. With a differential flux at 1 TeV of phi(1 TeV) = (1.9 +/- 0.6(stat) +/- 0.4(sys)) x 10(-13) cm(-2) s(-1) TeV-1 corresponding to 0.5 per cent of the Crab nebula differential flux and a spectral index Gamma = 2.9 +/- 0.5(stat) +/- 0.2(sys), 1ES 1312-423 is one of the faintest sources ever detected in the very high energy (E > 100 GeV) extragalactic sky. A careful analysis using three and a half years of Fermi Large Area Telescope (Fermi-LAT) data allows the discovery at high energies (E > 100 MeV) of a hard spectrum (Gamma = 1.4 +/- 0.4(stat) +/- 0.2(sys)) source coincident with 1ES 1312-423. Radio, optical, UV and X-ray observations complete the spectral energy distribution of this blazar, now covering 16 decades in energy. The emission is successfully fitted with a synchrotron self-Compton model for the non-thermal component, combined with a blackbody spectrum for the optical emission from the host galaxy.
Axionlike particles (ALPs) are hypothetical light (sub-eV) bosons predicted in some extensions of the Standard Model of particle physics. In astrophysical environments comprising high-energy gamma rays and turbulent magnetic fields, the existence of ALPs can modify the energy spectrum of the gamma rays for a sufficiently large coupling between ALPs and photons. This modification would take the form of an irregular behavior of the energy spectrum in a limited energy range. Data from the H. E. S. S. observations of the distant BL Lac object PKS 2155 - 304 (z = 0.116) are used to derive upper limits at the 95% C. L. on the strength of the ALP coupling to photons, g(gamma a) < 2.1 x 10(-11) GeV-1 for an ALP mass between 15 and 60 neV. The results depend on assumptions on the magnetic field around the source, which are chosen conservatively. The derived constraints apply to both light pseudoscalar and scalar bosons that couple to the electromagnetic field.