Discovery of the Binary Pulsar PSR B1259-63 in Very-High-Energy Gamma Rays around Periastron with H.E.S.S

We report the discovery of very-high-energy (VHE) gamma-ray emission of the binary system PSR B1259-63/SS 2883 of a radio pulsar orbiting a massive, luminous Be star in a highly eccentric orbit. The observations around the 2004 periastron passage of the pulsar were performed with the four 13 m Cherenkov telescopes of the H.E.S.S. experiment, recently installed in Namibia and in full operation since December 2003. Between February and June 2004, a gamma-ray signal from the binary system was detected with a total significance above 13 sigma. The flux was found to vary significantly on timescales of days which makes PSR B1259-63 the first variable galactic source of VHE gamma-rays observed so far. Strong emission signals were observed in pre- and post-periastron phases with a flux minimum around periastron, followed by a gradual flux decrease in the months after. The measured time-averaged energy spectrum above a mean threshold energy of 380 GeV can be fitted by a simple power law F_0(E/1 TeV)^-Gamma with a photon index Gamma = 2.7+-0.2_stat+-0.2_sys and flux normalisation F_0 = (1.3+-0.1_stat+-0.3_sys) 10^-12 TeV^-1 cm^-2 s^-1. This detection of VHE gamma-rays provides unambiguous evidence for particle acceleration to multi-TeV energies in the binary system. In combination with coeval observations of the X-ray synchrotron emission by the RXTE and INTEGRAL instruments, and assuming the VHE gamma-ray emission to be produced by the inverse Compton mechanism, the magnetic field strength can be directly estimated to be of the order of 1 G.Comment: 10 pages, 8 figures, accepted in Astronomy and Astrophysics on 2 June 2005, replace: document unchanged, replaced author field in astro-ph entry - authors are all members of the H.E.S.S. collaboration and three additional authors (99+3, see document

The breeding system of Ornithopus sativus Brot. subsp. sativus

Genetic traits within Ornithopus sativus Brot. make it suitable for breeding as a forage legume in agriculture. The breeding system of O. sativus must be understood to stabilize valuable traits once developed. Hybridization between white‐flowered and pink‐flowered genotypes of O. sativus revealed the white flower colour to be inherited recessively to pink, while early flowering showed genetic dominance over late flowering (d = 0.5). The pink flower colour was always associated with red pigmentation on seedling hypocotyls, which provided a pragmatic aid in the selection process. Pollination of O. sativus is largely autogamous, but examination of hypocotyl colour of seedlings from white‐flowered trap plants placed among pink‐flowered plants in a sward indicated a xenogamic cross‐pollination rate of 25% is possible. This significant level of cross‐pollination revealed opportunities for breeding desirable traits within the species, while providing a warning that shifts in population structure could occur in response to selection pressure

Immune response in deep cervical lymph nodes and spleen in the mouse after antigen deposition in different intracerebral sites

Brain interstitial and cerebrospinal fluid drainage into the lymphatics was studied by injections of 5 microliters of packed sheep red blood cells (SRBC) injected into the caudate nucleus, the occipital lobe, and the lateral ventricle of the brain in mice. The number of plaque-forming cells (PFC) was determined in the deep cervical lymph nodes, the axillary lymph nodes, and the spleen, and the number of PFC was compared with the response in the same tissues after intravenous immunization with 0.1 ml 10% SRBC. The weight of the deep cervical lymph nodes increased 3.0 times on day 3 after injection in the brain parenchyma compared with the weight of these nodes after intravenous immunization. The antigen-specific response peaked on day 5, 392 +/- 37 PFC/10(6) for IgG in the deep cervical lymph nodes after antigen deposition in the caudate nucleus, whereas only a minor peak in the antigen-specific response was obtained after intraventricular antigen deposition, 127 +/- 79 PFC x 10(6) for IgG on day 6. There were no increased PFC in any of the lymph nodes after intravenous immunization. The experiments show an antigen-specific response in the deep cervical lymph nodes after intracerebral antigen deposition, whereas antigens deposited in the lateral ventricles drain preferentially to the blood, with a high response in the spleen