Microquasars are binary star systems with relativistic radio-emitting jets. They are potential sources of cosmic rays and can be used to elucidate the physics of relativistic jets. We report the detection of variable gamma-ray emission above 100 gigaelectron volts from the microquasar LS I 61 + 303. Six orbital cycles were recorded. Several detections occur at a similar orbital phase, which suggests that the emission is periodic. The strongest gamma-ray emission is not observed when the two stars are closest to one another, implying a strong orbital modulation of the emission or absorption processes.

The superheavy element with atomic number $Z=117$ was produced as an evaporation residue in the ${}^{48}\mathrm{Ca}+{}^{249}\mathrm{Bk}$ fusion reaction at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. The radioactive decay of evaporation residues and their $\alpha$-decay products was studied using a detection setup that allowed measuring decays of single atomic nuclei with half-lives between sub-$\mu \mathrm{s}$ and a few days. Two decay chains comprising seven $\alpha$ decays and a spontaneous fission each were identified and are assigned to the isotope ${}^{294}117$ and its decay products. A hitherto unknown $\alpha$-decay branch in ${}^{270}\mathrm{Db}$ ($Z=105$) was observed, which populated the new isotope ${}^{266}\mathrm{Lr}$ ($Z=103$). The identification of the long-lived ($T_{1/2}={1.0}_{-0.4}^{+1.9}\mathrm{h}$) $\alpha$-emitter ${}^{270}\mathrm{Db}$ marks an important step towards the observation of even more long-lived nuclei of superheavy elements located on an “island of stability.”

The MAGIC telescope took data of very high energy ?-ray emission from the blazar Markarian 421 (Mrk 421) between 2004 November and 2005 April. We present a combined analysis of data samples recorded under different observational conditions, down to ?-ray energies of 100 GeV. The flux was found to vary between 0.5 and 2 crab (integrated above 200 GeV), considered a low state when compared to known data. Although the flux varied day by day, no short-term variability was observed, although there is some indication that not all nights show an equally quiescent state. The results at higher energies were found to be consistent with previous observations. A clear correlation is observed between ?-ray and X-ray fluxes, whereas no significant correlation between ?-ray and optical data is seen. The spectral energy distribution between 100 GeV and 3 TeV shows a clear deviation from a power law, more clearly and at lower flux than previous observations at higher energies. The deviation persists after correcting for the effect of attenuation by the extragalactic background light, and most likely is source-inherent. There is a rather clear indication of an inverse Compton peak around 100 GeV. The spectral energy distribution of Mrk 421 can be fitted by a one-zone synchrotron self-Compton model, suggesting once again a leptonic origin of the very high energy ?-ray emission from this blazar.status: publishe

Resonant laser ionization and spectroscopy are widely used techniques at radioactive ion beam facilities to produce pure beams of exotic nuclei and measure the shape, size, spin and electromagnetic multipole moments of these nuclei. However, in such measurements it is difficult to combine a high efficiency with a high spectral resolution. Here we demonstrate the on-line application of atomic laser ionization spectroscopy in a supersonic gas jet, a technique suited for high-precision studies of the ground- and isomeric-state properties of nuclei located at the extremes of stability. The technique is characterized in a measurement on actinium isotopes around theN=126 neutron shell closure. A significant improvement in the spectral resolution by more than one order of magnitude is achieved in these experiments without loss in efficiency.