We present absolute parallaxes and relative proper motions for five AM CVn stars, which we obtained using the Fine Guidance Sensors on board the Hubble Space Telescope. Our parallax measurements translate into distances dAMCVn = 606 +135 −93 pc; dHPLib = 197 +14 −12 pc; dCRBoo = 337 +44 −35 pc; dV803Cen = 347 +32 −27 pc; and dGPCom = 75 +2 −2 pc. From these distances we estimate the space densi...

Context. The IUE database provides a large number of UV high and low-resolution spectra of RS CVn-type stars from 1978 to 1996. In particular, many of these stars were monitored continuously during several seasons by IUE. Aims. Our main purpose is to study the short and long-term chromospheric activity of the RS CVn systems most observed by IUE: HD 22468 (V711 Tau, HR 1099, K1IV+G5V), HD 21242 ...

Vehicular Ad hoc Networks (VANETs) is an essential part of Intelligent Transportation System (ITS), which aims to improve the road safety. However, the main challenge in VANET is the spectrum scarcity which is more severe especially in the urban environment. In this view using Cognitive Radio (CR) technology in VANET has emerged as a promising solution providing additional resources and allowin...

Coherent radio emission from stars can be used to constrain fundamental coronal plasma parameters, such as density and magnetic field strength. It is also a probe of chromospheric magnetospheric acceleration mechanisms. Close stellar binaries, RS Canum Venaticorum (RS CVn) systems, are particularly interesting their heightened level activity possible direct interaction make them unique laborato...

PURPOSE Although rare, children and young adults can suffer from significant cardiac arrhythmia, especially in the context of congenital malformations and after cardiac surgery. METHODS A total of 62 patients (32 female, median age 20 years) underwent an invasive electrophysiology study between 2008-2011: half had normal cardiac anatomy, whereas the remaining patients had various types of con...

In this elementary paper we establish a few novel results in set theory; their interest is wholly foundational-philosophical in motivation. We show that in Cantor-Von Neumann Set-Theory, which is a reformulation of Von Neumann’s original theory of functions and things that does not introduce ‘classes’ (let alone ‘proper classes’), developed in the 1920ies, both the Pairing Axiom and ‘half’ the ...

We present an X-ray analysis of a 4 Gyr old open cluster, M67, using archival XMM–Newton data. The aim of this study was to find new X-ray members of M67, and to use the updated member list for studying X-ray variability, and derive the X-ray luminosity functions (XLFs) of different stellar types and compare them with other star clusters of similar age. We report the detection of X-ray emission...

We study the effect of short term variations of the evolution of AM CVn systems on their gravitational wave emissions and in particular LISA observations. We model the systems according to their equilibrium mass-transfer evolution as driven by gravitational wave emission and tidal interaction, and determine their reaction to a sudden perturbation of the system. This is inspired by the suggestio...