Borexino calibrations: Hardware, Methods, and Results

Borexino was the first experiment to detect solar neutrinos in real-time in the sub-MeV region. In order to achieve high precision in the determination of neutrino rates, the detector design includes an internal and an external calibration system. This paper describes both calibration systems and the calibration campaigns that were carried out in the period between 2008 and 2011. We discuss some of the results and show that the calibration procedures preserved the radiopurity of the scintillator. The calibrations provided a detailed understanding of the detector response and led to a significant reduction of the systematic uncertainties in the Borexino measurements

A Revised Parallax and its Implications for RX J185635-3754

New astrometric analysis of four WFPC2 images of the isolated neutron star RX J185635-3754 show that its distance is 117 +/- 12 pc, nearly double the originally published distance. At the revised distance, the star's age is 5 x 10^5 years, its space velocity is about 185 km/s, and its radiation radius inferred from thermal emission is approximately 15 km, in the range of many equations of state both with and without exotic matter. These measurements remove observational support for an extremely soft equation of state. The star's birthplace is still likely to be in the Upper Sco association, but a connection with zeta Oph is now unlikely.Comment: submitted to ApJ Letter

Investigation of high energy radiation from a plasma focus

Included are seventeen topics covering the experimental setup, diagnostics, analyses and various applications of the plasma focus. An invention, a hypocycloidal-pinch apparatus, is also included

A Black Hole Nova Obscured by an Inner Disk Torus

Stellar-mass black holes (BHs) are mostly found in X-ray transients, a subclass of X-ray binaries that exhibit violent outbursts. None of the 50 Galactic BHs known show eclipses, which is surprising for a random distribution of inclinations. Swift J1357.2-0933 is a very faint X-ray transient detected in 2011. On the basis of spectroscopic evidence, we show that it contains a BH in a 2.8 h orbital period. Further, high-time resolution optical light curves display profound dips without X-ray counterparts. The observed properties are best explained by the presence of an obscuring toroidal structure moving outwards in the inner disk seen at very high inclination. This observational feature should play a key role in models of inner accretion flows and jet collimation mechanisms in stellar-mass BHs.Comment: 23 pages (9 in the supplementary material), 6 figures (3 are supplementary figures). This is the author's version of the work. It is posted here by permission of the AAAS for personal use, not for redistribution. The definitive version was published in Science on Vol. 339 no. 6123 on 1 March 201