ﻻ يوجد ملخص باللغة العربية
We apply the Deloye & Bildsten (2003) isentropic models for donors in ultracompact low-mass X-ray binaries to the AM CVn population of ultracompact, interacting binaries. The mass-radius relations of these systems donors in the mass range of interest ($M_2<0.1 msun$) are not single-valued, but parameterized by the donors specific entropy. This produces a range in the relationships between system observables, such as orbital period, $Porb$, and mass transfer rate, $Mdot$. For a reasonable range in donor specific entropy, $Mdot$ can range over several orders of magnitude at fixed $Porb$. We determine the unique relation between $Mdot$ and $M_2$ in the AM CVn systems with known donor to accretor mass ratios, $q=M_2/M_1$. We use structural arguments, as well as each systems photometric behavior, to place limits on $Mdot$ and $M_2$ in each. Most systems allow a factor of about 3 variation in $Mdot$, although V803 Cen, if the current estimates of its $q$ are accurate, is an exception and must have $M_2 approx 0.02 msun$ and $Mdot approx 10^{-10} msun$ yr$^{-1}$. Our donor models also constrain each donors core temperature, $T_c$, range and correlate $T_c$ with $M_2$. We examine how variations in donor specific entropy across the white dwarf family citep{nele01a} of AM CVn systems affects this populations current galactic distribution. Allowing for donors that are not fully degenerate produces a shift in systems towards longer $Porb$ and higher $Mdot$ increasing the parameter space in which these systems can be found. This shift increases the fraction of systems whose $Porb$ is long enough that their gravity wave (GW) signal is obscured by the background of detached double white dwarf binaries that dominate the GW spectrum below a frequency $approx 2$ mHz.
We present Chandra and Swift X-ray observations of four extremely low-mass (ELM) white dwarfs with massive companions. We place stringent limits on X-ray emission from all four systems, indicating that neutron star companions are extremely unlikely a
We discuss results of our study on AM CVn binaries formed with donors that never ignited He before contact. For the first time, we treat the donors in these systems in the context of a full stellar structure evolution theory and find that the binarys
We present the results of a two and a half year optical photometric monitoring programme covering 16 AM CVn binaries using the Liverpool Telescope on La Palma. We detected outbursts in seven systems, one of which (SDSS J0129) was seen in outburst for
We present the results of some recent research on AM CVn systems. We present: X-ray/UV observations made using XMM-Newton; the X-ray grating spectrum of RX J1914+24; preliminary results of a search for radio emission from AM CVn binaries, and discuss
We present the results of XMM-Newton observations of four AM CVn systems -- AM CVn, CR Boo, HP Lib and GP Com. Their light curves show very different characteristics. The X-ray light curves show no coherent pulsations, suggesting the accreting white