X-Ray Spectral and Timing Observations of Cygnus X-2

We report on a joint BeppoSAX/RXTE observation of the Z-type low-mass X-ray binary Cyg X-2. The source was in the so-called high overall intensity state and in less than 24 hr went through all three branches of the Z track. The continuum X-ray spectrum could be described by the absorbed sum of a soft thermal component, modeled as either a blackbody or a multicolor disk blackbody, and a Comptonized component. The timing power spectrum showed several components, including quasi-periodic oscillations in the range 28-50 Hz while the source was on the horizontal branch (horizontal branch oscillation; HBO). We found that the HBO frequency was well correlated with the parameters of the soft thermal component in the X-ray spectrum. We discuss implications of this correlation for models of the HBO

A Chronological History of X-Ray Astronomy Missions

In this chapter, we briefly review the history of X-ray astronomy through its missions. We follow a temporal development, from the first instruments onboard rockets and balloons to the most recent and complex space missions. We intend to provide the reader with detailed information and references on the many missions and instruments that have contributed to the success of the exploration of the X-ray universe. We have not included missions that are still operating, providing the worldwide community with high-quality observations. Specific chapters for these missions are included in a dedicated section of the handbook

Discovery of Microsecond Soft Lags in the X-Ray Emission of the Atoll Source 4U1636-536

Exploiting the presence of kilohertz quasi-periodic oscillations (QPOs) in the timing power spectrum, we find that the soft x-ray emission of the neutron-star X-ray binary and atoll source 4U1636-536 modulated at the QPO frequency lags behind that of the hard x-ray emission. Emission in the 3.8-6.4 keV band is delayed by 25.0 +/- 3.3 microseconds relative to the 9.3-69 keV band. The delay increases in magnitude with increasing energy. Our results are consistent with those of Vaughan et al. (1997), when the sign is corrected (Vaughan et al. 1998), for the atoll source 4U1608-52. The soft lag could be produced by Comptonization of hard photons injected into a cooler electron cloud or by intrinsic spectral softening of the emission during each oscillation cycle.Comment: Accepted to the Astrophysical Journal Letters, 4 page

Discovery of a Hard X-Ray Source, SAX J0635+0533, in the Error Box of the Gamma-Ray Source 2EG 0635+0521

We have discovered an x-ray source, SAX J0635+0533, with a hard spectrum within the error box of the GeV gamma-ray source in Monoceros, 2EG J0635+0521. The unabsorbed x-ray flux is 1.2*10^-11 erg cm^-2 s^-1 in the 2-10 keV band. The x-ray spectrum is consistent with a simple powerlaw model with absorption. The photon index is 1.50 +/- 0.08 and we detect emission out to 40 keV. Optical observations identify a counterpart with a V-magnitude of 12.8. The counterpart has broad emission lines and the colors of an early B type star. If the identification of the x-ray/optical source with the gamma-ray source is correct, then the source would be a gamma-ray emitting x-ray binary.Comment: Accepted to the Astrophysical Journal, 8 page

Cosmic ray oriented performance studies for the JEM-EUSO first level trigger

JEM-EUSO is a space mission designed to investigate Ultra-High Energy Cosmic Rays and Neutrinos (E > 5 ⋅ 1019 eV) from the International Space Station (ISS). Looking down from above its wide angle telescope is able to observe their air showers and collect such data from a very wide area. Highly specific trigger algorithms are needed to drastically reduce the data load in the presence of both atmospheric and human activity related background light, yet retain the rare cosmic ray events recorded in the telescope. We report the performance in offline testing of the first level trigger algorithm on data from JEM-EUSO prototypes and laboratory measurements observing different light sources: data taken during a high altitude balloon flight over Canada, laser pulses observed from the ground traversing the real atmosphere, and model landscapes reproducing realistic aspect ratios and light conditions as would be seen from the ISS itself. The first level trigger logic successfully kept the trigger rate within the permissible bounds when challenged with artificially produced as well as naturally encountered night sky background fluctuations and while retaining events with general air-shower characteristics

Low mass X-ray binaries: studio simultaneo spettro-temporale a larga banda

Dottorato di ricerca in fisica. 12. ciclo. Supervisore Natale RobbaConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - Piazza Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Renal haemodynamics and coronary atherosclerotic burden are associated in patients with hypertension and mild coronary artery disease

Intrarenal hemodynamic alterations are independent predictors of cardiovascular events in different populations. It has been hypothesized that there is an association between renal hemodynamics and coronary atherosclerotic burden in patients with hypertension. Therefore, the present study examined the associations between renal hemodynamics, coronary atherosclerotic burden and carotid atherosclerotic disease. A total of 130 patients with hypertension aged between 30-80 years who had been referred for an elective coronary angiography were enrolled in the present study. A duplex ultrasound of the intrarenal vasculature was performed to evaluate the resistive index (RI), pulsatility index (PI) and acceleration time (AT). The carotid intima-media thickness was additionally assessed. A coronary angiography was performed to detect the atherosclerotic burden using the Gensini Score (GS). Based on the GS values, subjects were divided into quintiles (I: ≤9; II: 9-17; III: 17-30; IV: 30-44; and V: GS >44) as well as in subjects with mild (GS ≤30) or severe coronary disease (GS >30). A weak significant difference in PI was identified among quintiles (P=0.041), whereas, RI and AT did not differ significantly. PI was associated with GS in the group with low coronary atherosclerotic burden (GS ≤30; P=0.047), whereas, no association was detected in subjects with GS >30. This association remained following adjustment for age and left ventricular ejection fraction (P=0.025). In conclusion, renal vascular alterations were associated with coronary atherosclerotic burden in patients with hypertension with mild coronary disease