The Ritter-Kolb Catalogue and its Impact on Research into CVs, LMXBs and related Objects

In the first part of this paper, the Ritter-Kolb catalogue (RKcat for short), its history and a few examples of its application to research in the field of cataclysmic variables are briefly described. In a second part we look forward to possible future applications of RKcat for the study of cataclysmic variables, low-mass X-ray binaries and related objects. Last but not least we also briefly comment on the future of the RKcat service itself

Catalogue of cataclysmic binaries, low-mass X-ray binaries and related objects (Seventh edition)

The catalogue lists coordinates, apparent magnitudes, orbital parameters, and stellar parameters of the components and other characteristc properties of 472 cataclysmic binaries, 71 low-mass X-ray binaries and 113 related objects with known or suspected orbital periods together with a comprehensive selection of the relevant recent literature. In addition, the catalogue contains a list of references to published finding charts for 635 of the 656 objects, and a cross-reference list of alias object designations. Literature published before 1 January 2003 has, as far as possible, been taken into account. All data can be accessed via the dedicated catalogue webpage at http://www.mpa-garching.mpg.de/RKcat/ and http://physics.open.ac.uk/RKcat/ and at CDS via anonymous ftp to cdsarc.u-strasbg.fr (30.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/404/301. We will update the information given on the catalogue webpage regularly, initially every six months

Properties of discontinuous and nova-amplified mass transfer in cataclysmic variables

We investigate the effects of discontinuous mass loss in recurrent outburst events on the long-term evolution of cataclysmic variables (CVs). Similarly we consider the effects of frictional angular momentum loss (FAML), i.e. interaction of the expanding nova envelope with the secondary. The Bondi-Hoyle accretion model is used to parametrize FAML in terms of the expansion velocity vexp of the nova envelope at the location of the secondary; we find that small vexp causes strong FAML. Numerical calculations of CV evolution over a wide range of parameters demonstrate the equivalence of a discontinuous sequence of nova cycles and the corresponding mean evolution (replacing envelope ejection by a continuous wind), even close to the mass-transfer instability. A formal stability analysis of discontinuous mass transfer confirms this, independent of details of the FAML model. FAML is a consequential angular momentum loss that amplifies the mass-transfer rate driven by systemic angular momentum losses such as magnetic braking. We show that for a given vexp and white dwarf mass the amplification increases with secondary mass and is significant only close to the largest secondary mass consistent with mass-transfer stability. The amplification factor is independent of the envelope mass ejected during the outburst, whereas the mass-transfer amplitude induced by individual nova outbursts is proportional to it. In sequences calculated with nova model parameters taken from Prialnik & Kovetz, FAML amplification is negligible, but the outburst amplitude in systems below the period gap with a white dwarf mass ≃ 0.6 M⊙ is larger than a factor of 10. The mass-transfer rate in such systems is smaller than 10−11 M⊙ yr−1 for ≃ 0.5 Myr (≃ 10 per cent of the nova cycle) after the outburst. This offers an explanation for intrinsically unusually faint CVs below the period ga

The minimum period problem in cataclysmic variables

We investigate if consequential angular momentum losses (CAML) or an intrinsic deformation of the donor star in CVs could increase the CV bounce period from the canonical theoretical value ~65 min to the observed value $P_{min} \approx77$ min, and if a variation of these effects in a CV population could wash out the theoretically predicted accumulation of systems near the minimum period (the period spike). We are able to construct suitably mixed CV model populations that a statisticial test cannot rule out as the parent population of the observed CV sample. However, the goodness of fit is never convincing, and always slightly worse than for a simple, flat period distribution. Generally, the goodness of fit is much improved if all CVs are assumed to form at long orbital periods. The weighting suggested by King, Schenker & Hameury (2002) does not constitute an improvment if a realistically shaped input period distribution is used. Put your abstract here.Comment: 10 pages, Latex, 13 postscript figures, Accepted for publication in MNRA

Monitoring of Extracellular TCA Cycle Intermediates in Mammalian Cell Culture

In recent years, monitoring of metabolites such as glucose, lactate, ammonia, glutamine, glutamate, and other amino acids has been introduced for many cell cultivations. Assaying intracellular metabolites might reveal further insights into metabolism. However, some of the mainly intracellular or even mitochondrial appearing metabolites can also be found in the medium supernatant at micromolar concentrations. Since no active transport mechanisms for excretion of these intermediates are known for most mammalian production cell lines, they might leak out of the cells and thus could be correlated to intracellular concentrations. In this work, we are investigating extracellular concentrations of five organic acids (succinic, malic, fumaric, citric, isocitric acid) during growth looking at different media and cell lines. Moreover, clear influences on concentrations were also expected to occur after viral infection of MDCK cells. The analysis is performed using an anion-exchange chromatography system (DX-320, Dionex, Idstein, Germany) with a conductivity detector. Due to high protein content of the medium, sample preparation posed some problems. Several strategies have been investigated for an optimal recovery of the abovementioned organic acids. Experiments showed that certain amounts of these organic acids already occurred in fresh medium, coming from both serum and peptone being supplements for the culture medium. Nevertheless, first results indicate significant changes of concentrations during the course of cultivation, probably not correlated to dead cells. In batch cultivation, malic, fumaric and citric acid show an almost linear increase after the lag phase, whereas isocitric and succinic acid seem to reach a constant level during stationary phase

Mass transfer cycles in close binaries with evolved companions

We give a global analysis of mass transfer variations in low-mass X-ray binaries and cataclysmic variables whose evolution is driven by the nuclear expansion of the secondary star. We show that limit cycles caused by irradiation of the secondary by the accreting primary are possible in a large class of these binaries. In the high state, the companion transfers a large fraction of its envelope mass on a thermal timescale. In most cases this implies super-Eddington transfer rates and would thus probably lead to common-envelope evolution and the formation of an ultrashort-period binary. Observed systems with (sub)giant secondaries stabilize themselves against this possibility either by being transient or by shielding the secondary from irradiation in some way. © 1997. The American Astronomical Society. All rights reserved