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Classical nova outbursts are powered by thermonuclear runaways that take place in the H-rich accreted envelopes of white dwarfs in close binary systems. Extensive numerical simulations of nova outbursts have shown that the accreted envelopes attain peak temperatures ranging between 108 and 4×108 K, for about several hundred seconds, and therefore, their ejecta is expected to show signatures of a significant nuclear activity. Indeed, it has been claimed that novae can play a certain role in the enrichment of the interstellar medium through a number of intermediate-mass elements. This includes 17O, 15N, and 13C, systematically overproduced in huge amounts with respect to solar abundances, with a lower contribution in a number of other species with A<40, such as 7Li, 19F, or 26Al. X-ray bursts, in turn, constitute the most frequent source of stellar explosions in the Galaxy (and the third most energetic events after supernovae and nova outbursts). They take place in the H/He-rich envelopes accreted onto neutron stars in binary systems. In this paper, we will present new hydrodynamic models (1D) of both classical nova outbursts and X-ray bursts, from the onset of accretion up to the explosion phase, with special emphasis on their gross observational properties and on their associated nucleosynthesis. Two-dimensional models of mixing at the core-envelope interface during nova outbursts will also be presented. The impact of nuclear uncertainties on the final nucleosynthetic yields will be discussed in detail for the two astrophysical scenarios. [ABSTRACT FROM AUTHOR]

In this paper we want to discuss the status of Astroparticle Physics, which is now in its golden age. Astroparticle physics—the new branch of physics born roughly at the end of the 1980-ies—takes into account results obtained from the observations of cosmic sources via photonic experiments and particle experiments, and try to detect their global behaviour in order to understand the physical processes giving rise to them. All this for a better knowledge of the physics governing the whole Universe. Because of a limited length of the paper we will discuss only a selection of arguments, which are biased by our knowledge, as follows: 1. Introduction 2. Few Remarkable Notes 3. Background in the Universe 4. A Round-the-Universe Cruise 5. Prospects Conclusions [ABSTRACT FROM AUTHOR]

In this study, a spectral analysis of the dwarf nova WX Hyi (which is a Cataclysmic Variables (CV)) is presented. The system was observed during the normal ourburst with the XMM-Newton observatory. X-ray bolometric flux value (EX<=12 keV) is estimated to be ∼2.98×10-12 erg cm-2 s-1 and X-ray luminosity LX = 5×1031 erg/s. Elemental abundance was founded 3 factor of solar abundances. If the gas temperature is higher than 107 K, it is optically thin. Therefore, they are radiated as thermal bremsstrahlung X-ray emission. PN+MOS detector measurements indicate that X-ray emitting maximum plasma temperature is kTMax = 31.3 keV (3.6322×108 K). Hence, the X-ray spectrum analysis during the normal outburst of WX Hyi is indicated a hot and optically thin plasma in the boundary layer that cools via an isobaric cooling flow while settling onto the white dwarf. For this temperature, the mass accretion rate is estimated to be MBL = 4×1014 gr/s (6.3×10-12 M⊙/yr). The ratio of the Boundary Layer (BL) (X-ray) luminosity to the disc luminosity was estimated to be LBL/Ldisc∼0.3. We calculated the mass accretion ratio of BL to the accretion disc (MBL/Mdisc) to be ∼0.74 and ∼0.27 during the rise to the outburst and outburst, respectively. A great quantity of the accreting gas from the rise to the outburst is lost in a wind. Fe XXV line at 6.7 keV is originated from a plasma having temperature of 107–108 K. The obtained temperature value from this study is compatible with this plasma structure. [ABSTRACT FROM AUTHOR]

Cataclysmic variables are the nearest and most easily studied laboratories for understanding accretion onto compact objects. FUSE has provided the first significant sample of high resolution, high S/N spectra of such objects in the wavelength range 900–1183 Å. As expected, the FUSE spectra of most nova-like variables and dwarf novae in outburst show broad features associated with emission from the inner accretion disk. Detailed modeling has proven difficult, however, because the flux near the Lyman limit is higher than expected, indicating that the vertical structure of the disk differs significantly from that of normal stellar atmospheres of similar temperature and gravity. Wind features, due to OVI and CIII, are also evident in many systems, and in most cases are accompanied by fairly narrow lower ionization-state lines that are blue shifted by no more than a few 100 km s-1. These narrower features and the small number of systems with P-Cygni-like profiles suggest that most of the wind features observed with FUSE arise in material fairly near the disk surface, a picture quite different from that inferred from analyses of longer wavelength HST data. Dwarf nova systems in optical quiescence show FUV emission from the WD, which is heated by and cools after outbursts, and from the disk, and, surprisingly, at least in some cases, the hot spot. Here I will briefly illustrate the contributions FUSE has made to our understanding of cataclysmic variables, describe the quantitative state of the modeling, and suggest where we might go from here. [ABSTRACT FROM AUTHOR]

Globular clusters harbour an excess of X-ray sources compared to the number of X-ray sources in the Galactic plane. It has been proposed that many of these X-ray sources are cataclysmic variables that have an intermediate magnetic field, i.e. intermediate polars, which remains to be confirmed and understood. We present here several methods to identify intermediate polars in globular clusters from multiwavelength analysis. First, we report on XMM-Newton, Chandra and HST observations of the very dense Galactic globular cluster NGC 2808. By comparing UV and X-ray properties of the cataclysmic variable candidates, the fraction of intermediate polars in this cluster can be estimated. We also present the optical spectra of two cataclysmic variables in the globular cluster M 22. The HeII (4868 Å) emission line in these spectra could be related to the presence of a magnetic field in these objects. Simulations of Simbol-X observations indicate that the angular resolution is sufficient to study X-ray sources in the core of close, less dense globular clusters, such as M 22. The sensitivity of Simbol-X in an extended energy band up to 80 keV will allow us to discriminate between hard X-ray sources (such as magnetic cataclysmic variables) and soft X-ray sources (such as chromospherically active binaries). [ABSTRACT FROM AUTHOR]

Low-mass X-ray binary (LMXB) systems are comprised of a low-mass, K or M dwarflike star orbiting a compact object. Stellar black hole masses and their distributions are important inputs for binary evolution and supernova models. Currently, the main limiting factor in determining accurate black hole masses in LMXBs is the uncertainty of the orbital inclination angle due to an unknown amount of contaminating light in the near infrared. If present, this light dilutes the ellipsoidal variations of the low-mass secondary star, and thus gives the appearance of a lower orbital inclination system. It has been generally thought that the near infrared ellipsoidal light curves of these systems were relatively uncontaminated and represented primarily the light from the low-mass secondary star; however, recent disk and jet models have thrust this thinking into question. We combine our data from the Spitzer Space Telescope with our ground-based optical and near infrared data for several LMXBs to characterize and derive the amount of light contaminating the near-infrared ellipsoidal variations of the low-mass secondary star. [ABSTRACT FROM AUTHOR]

An overview is given of the properties of the various kinds of quasi-periodic luminosity modulations observed in cataclysmic variables (CVs). The two principal types, known in the CV literature as dwarf nova oscillations and quasi-periodic oscillations, have similarities to the high and low frequency quasi-periodic oscillations in X-Ray binaries. There is a further well observed class known as longer period dwarf nova oscillations. In CVs the observed interrelations between these oscillations suggests a model of magnetically controlled accretion onto a rapidly rotating equatorial belt of accreted gas. Non-radial oscillations of the central white dwarf are observed in some systems. [ABSTRACT FROM AUTHOR]

We present system parameters for a small sample of short period, eclipsing CVs taken from the Sloan Digital Sky Survey. Three out of seven of the systems possess brown dwarf donor stars and have thus evolved past the orbital period minimum. This is broadly consistent with predictions that 40–70 per cent of CVs should have evolved past the orbital period minimum. The donor star masses themselves are inconsistent with model predictions, unless enhanced angular momentum loss (e.g. from circumbinary discs) is invoked. However, the mass transfer rates as deduced from white dwarf effective temperatures are not consistent with enhanced mass transfer rates. Solution of this conundrum will require independent estimates of the mass transfer rates in short period CVs. The white dwarfs show a strong tendency towards high masses. This may in part be due to selection effects. There is one Iron core white dwarf, and no Helium core white dwarfs in our sample, despite predictions that 30–80 per cent of short period CVs should contain Helium core white dwarfs. [ABSTRACT FROM AUTHOR]

The high-speed photometer ‘OPTIMA’, short for Optical Pulsar Timing Analyzer, was used to record optical (450–950 nm) light curves of selected cataclysmic variables of type AM Her (Polars) with sub-second temporal resolution. The objects RX J0704+62, RX J0953+14, and EK UMa were re-observed several years after their discovery to provide up to date light curves with good statistics. The eclipsing binary DP Leo, which had been observed during 20 years previous to the OPTIMA measurements, was shown to have an orbital ephemeris with a quadratic term. For HU Aqr we have collected data over the years 1999 to 2007. HU Aqr evolved in luminosity from a high state in 2000 to a low state that persists since 2001. We detected variability in HU Aqr in the form of optical flashes with timescales of seconds. [ABSTRACT FROM AUTHOR]

Dwarf novae (DNe) are a subclass of Cataclysmic Variables (CVs) with outbursts powered by a disk instability leading to a sudden increase in the accretion rate. The Digital Access to a Sky Century at Harvard (DASCH) Collaboration is preparing to digitize over 500,000 Harvard plates from the 1880s to the 1980s with limiting magnitudes ranging from B∼14–19. As a demonstration project, we have scanned more than 500 plates in the fields centered on the galactic open cluster M44. There are 21 CVs in the fields within 10 degrees of M44 covered by the scans. Here we present the preliminary results of DN outbursts of the known CVs to derive long-term DN outburst duty cycles. In addition, a 100y lightcurve for a XMM–Newton source is also presented to demonstrate DASCH capabilities. [ABSTRACT FROM AUTHOR]

Large differences between the properties of the known sample of cataclysmic variable stars (CVs) and the predictions of the theory of binary star evolution have long been recognised. However, because all existing CV samples suffer from strong selection effects, observational bias must be considered before it is possible to tell whether there is an inconsistency, which would imply a failure of the evolutionary model. We have modelled common selection effects and illustrate their influence on observed CV samples. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Classical novae participate in the cycle of Galactic chemical evolution in which grains and metal enriched gas in their ejecta, supplementing those of supernovae, AGB stars, and Wolf-Rayet stars, are a source of heavy elements for the ISM. Once in the diffuse gas, this material is mixed with the existing gases and then incorporated into young stars and planetary systems during star formation. Infrared observations have confirmed the presence of carbon, SiC, hydrocarbons, and oxygen-rich silicate grains in nova ejecta, suggesting that some fraction of the pre-solar grains identified in meteoritic material come from novae. The mean mass returned by a nova outburst to the ISM probably exceeds ∼ 2 × 10-4 M⊙. Using the observed nova rate of 35±11 per year in our Galaxy, it follows that novae introduce more than ∼ 7 × 10-3 M⊙ yr-1 of processed matter into the ISM. Novae are expected to be the major source of 15N and 17O in the Galaxy and to contribute to the abundances of other isotopes in this atomic mass range. Here, we report on how changes in the nuclear reaction rates affect the properties of the outburst and alter the predictions of the contributions of novae to Galactic chemical evolution. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

We report the identification of RXJ0636 as a new intermediate polar. The system’s light curves and spectral analysis, together with a variety of its physical parameters are presented. A brief description of the observations leading to the above mentioned identification is also given. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The influence of the magnetic field on process of the accretion onto White Dwarfs in Cataclysmic Variables (CVs) is discussed. Except for the Polars or AM Her objects, the strength of magnetic field can not be measured directly in CVs by modern techniques. But there is growing evidence that most of the types of Cataclysmic Variables classified on the basis of their observational characteristics are behaving in one or the other way under the influence of the magnetic field of the accreting White Dwarf, among other things. Here, we discuss the bulk of CVs that are traditionally considered as non magnetic and review the properties that could be best explained by the magnetic governed accretion process. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

RX J0806.3-1527 is thought to be a 321s orbital period (the shortest known) double white dwarf binary system. According to the double degenerate binary (DDB) scenario this source is expected to be one of the strongest Gravitational Wave (GW) emitter candidates. In the last years RX J0806.3-1527 has been studied in great details, through multiwavelength observational campaigns. We present here the timing results obtained thanks to a 3.5-year long optical monitoring campaign carried out by the Very Large Telescope (VLT) and the Telescopio Nazionale Galileo (TNG) which allowed us to unambiguously detect and study the orbital period derivative (spin-up at a rate of ∼10-3s yr-1) of the 321s modulation based on phase coherent techniques, to detect the linear polarisation (at a level of about 2%), and to study the broad band energy spectrum. The VLT/TNG observational strategy we used allowed us, for the first time, to infer a P-P coherent solution for the archival X-ray observations over a 9.5 years baseline. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The theory of classical nova outbursts is reviewed. It shows that the different nova characteristics can be reproduced by varying the values of three basic and independent parameters: the white dwarf mass MWD, the temperature of its isothermal core TWD and the mass transfer rate M. The parameter space is shown to be constrained by several analytical considerations. We present a grid of multicycle nova evolution models that spans the entire grid of parameter combinations for C-O white dwarfs. The full grid covers the entire range of observed nova characteristics, even those of peculiar objects, which have not been numerically reproduced until now. Most remarkably, runs for very low M lead to very high values for some characteristics, such as outburst amplitude A >= 20, high super-Eddington luminosities at maximum, heavy element abundance of the ejecta Zej ≈ 0.63 and high ejected masses mej ≈ 7 × 10-4 M⊙. Some hitherto unpublished results of the long term evolution of a low mass accreting white dwarf are also presented. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

A deep (R ∼ 19.5) photographic Hα Survey of the southern Galactic Plane was recently completed using the UK Schmidt Telescope at the AAO. In addition, we have recently started a similar, CCD-based survey of the northern Galactic Plane using the Wide Field Camera on the INT. Both surveys aim to provide information on many types of emission line objects, such as planetary nebulae, luminous blue variables and interacting binaries. Here, we focus specifically on the ability of Hα emission line surveys to discover cataclysmic variables (CVs). Follow-up observations have already begun, and we present initial spectra of a candidate CV discovered by these surveys. We also present results from analyzing the properties of known CVs in the Southern Survey. By calculating the recovery rate of these objects, we estimate the efficiency of Hα-based searches in finding CVs. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

J-MAPS and Gaia are two asterometry missions to be launched in 2012. The positions of stars brighter than 15 magnitude will be measured to accuracies of better than one milli-arcsecond and 25 micro-arcseconds, respectively. Accurate distances (eff of the white dwarf, the long-term accretion rate of the binary can be estimated and compared with the expected accretion rate of magnetic braking for CVs above the period gap (>3 hr) and gravitational braking for those below the gap (<2 hr). For nova-like systems, whose luminosity is dominated by the accretion disk and affected by interstellar extinction and reddening, accurate distances can help constrain the temperature profile of the disk. [ABSTRACT FROM AUTHOR]

Classical novae occur in close binary systems (main-sequence star + white dwarf). V4743 Sgr is a very fast nova exhibiting a X-ray spectrum which is consistent with a view on the optically thick atmosphere of an extremely hot white dwarf (WD). It exhibits strong absorption features of the C V, C VI, N VI, N VII, and O VII resonance lines indicating an effective temperature of about 610kK. We present preliminary results of a spectral analysis by means of line-blanketed non-LTE atmosphere models of a XMM-Newton RGS-1 spectrum of V4743 Sgr, taken about half a year after its outburst. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

We describe work-in-progress to analyse the available HETG spectra on sixteen spectra from ten cataclysmic variables. We approach the analysis from dual directions, using globally-fit, multi-temperature components and via a line-by-line delineation of emission line properties. As an ultimate science goal, we intend to compare the results of the two approaches for consistency. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

We present for the first orbital phase resolved spectra of intermediate polar (IP), EX Hya, during two different states with a factor of 3 difference between the X-ray count rates. We find definite spectral variations between different states of the source. The adopted model is composed of two MEKAL plus a VMCFLOW components to account for the continuum which is partially absorbed. Additional Gaussian lines at energies ∼6, 4, 6.7 and 6.9 keV were also included to fit the residuals. The soft component of the spectrum is found to be harder during orbital minimum, suggesting the presence of extra ionized absorbing column. Moreover, the presence of cold emission Fekα line points toward the presence of a reflection component probably due to an accretion disk and/or a bulge at the impact zone. [ABSTRACT FROM AUTHOR]

I report the preliminary results of two recent Chandra surveys which together resulted in new observations of 30 Galactic globular clusters. The aim of these observations is to probe in detail the overabundance of various classes of X-ray sources—low-mass X-ray binaries (LMXBs), cataclysmic variables (CVs), millisecond pulsars (MSPs), and active main-sequence binaries (ABs)—in globular clusters. The overabundance of low-mass X-ray binaries in outburst has long been known and is the result of the dynamical interactions unique to the dense stellar environs in globular clusters. Results from the early Chandra observations of globular clusters established that the entire low-mass X-ray binary population (including the low-luminosity quiescent systems) is overabundant, as is the cataclysmic variable population. When combined with previous Chandra observations, these two recent surveys have uncovered over 90% of the dynamically formed X-ray source population in all Galactic globular clusters. These sources are a powerful probe of the internal dynamics of globular clusters. In addition, these data test the recent suggestion (Fregeau 2008) that we have misunderstood the dynamical states of globular clusters. [ABSTRACT FROM AUTHOR]

We analyze the cycles in the possible intermediate polar V795 Her, the optical counterpart of 2RXP J171256.0+333121, using the photometric V band CCD observations obtained within 5 days in 2008. We find that the times of the minimum intensity of the known cycle of ∼2.8028 hours are more stable than those of the peak intensity. We show that while the smoothed profile of the folded intensity curve is single-peaked, the profile of its residuals is double-peaked. We resolve the variations of the superimposed cycle of ∼0.01 d during a single night; this cycle is thus not caused by spin modulation of the white dwarf. We discuss our observations in terms of superhumps. [ABSTRACT FROM AUTHOR]