The 1998 outburst of the X-ray transient XTE J2012+381 as observed with BeppoSAX

We report on the results of a series of X-ray observations of the transient black hole candidate XTE J2012+381 during the 1998 outburst performed with the BeppoSAX satellite. The observed broad-band energy spectrum can be described with the superposition of an absorbed disk black body, an iron line plus a high energy component, modelled with either a power law or a Comptonisation tail. The source showed pronounced spectral variability between our five observations. While the soft component in the spectrum remained almost unchanged throughout our campaign, we detected a hard spectral tail which extended to 200 keV in the first two observations, but became barely detectable up to 50 keV in the following two. A further re-hardening is observed in the final observation. The transition from a hard to a soft and then back to a hard state occurred around an unabsorbed 0.1-200 keV luminosity of 10^38 erg/s (at 10 kpc). This indicates that state transitions in XTE 2012+281 are probably not driven only by mass accretion rate, but additional physical parameters must play a role in the evolution of the outburst.Comment: Paper accepted for publication on A&A (macro included, 9 pages, 5 figures

Human herpesvirus 6: An emerging pathogen.

Infections with human herpesvirus 6 (HHV-6), a beta-herpesvirus of which two variant groups (A and B) are recognized, is very common, approaching 100% in seroprevalence. Primary infection with HHV-6B causes roseola infantum or exanthem subitum, a common childhood disease that resolves spontaneously. After primary infection, the virus replicates in the salivary glands and is shed in saliva, the recognized route of transmission for variant B strains; it remains latent in lymphocytes and monocytes and persists at low levels in cells and tissues. Not usually associated with disease in the immunocompetent, HHV-6 infection is a major cause of opportunistic viral infections in the immunosuppressed, typically AIDS patients and transplant recipients, in whom HHV-6 infection/reactivation may culminate in rejection of transplanted organs and death. Other opportunistic viruses, human cytomegalovirus and HHV-7, also infect or reactivate in persons at risk. Another disease whose pathogenesis may be correlated with HHV-6 is multiple sclerosis. Data in favor of and against the correlation are discussed

BeppoSAX observations of the black hole candidates LMC X-1 and LMC X-3

We describe BeppoSAX observations of the black hole candidates LMC X--1 and LMC X--3 performed in Oct. 1997. Both sources can be modelled by a multicolor accretion disk spectrum, with temperature $\sim 1$ keV. However, there is some evidence that a thin emitting component coexists with the thick disk at these temperatures. In the direction of LMC X--1, we detected a significant emission above 10 keV, which we suspect originates from the nearby source PSR 0540-69. For LMC X--1, we estimate an absorbing column density of $\simeq 6\times 10^{21}$ cm$^{-2}$, which is almost ten times larger than that found for LMC X--3. In both sources, we find no indication of emission or absorption features whatsoever.Comment: 4 pages, 2 figures. Accepted for pubblication in the Proc. of 32nd Cospar scientific assembly, Nagoya, 13-15 July 199