We present the analysis of photometric and spectroscopic data of two classical Cepheids, FN Aquilae and V1344 Aquilae. Based on the joint treatment of the new and earlier radial velocity data, both Galactic Cepheids have been found to be a member in a spectroscopic binary system. To match the phases of the earlier radial velocity data correctly with the new ones, we also determined the temporal...

We report recent XMM-Newton investigations of PSR J1836+5925, the “next Geminga,” which determined an X-ray pulsation of ∼173.3 ms. Its X-ray periodicity is consistent with the γ -ray ephemeris at the same epoch. The X-ray folded light curve has a sinusoidal structure that is different from the double-peaked γ -ray pulse profile. We have also analyzed the X-ray phase-averaged spectra which show...

Near the edges of the instability strip the rate of stellar evolution is larger than the growth-rate of the pulsation amplitude, and the same holds whenever the star is engaged in pulsational mode switching. Stellar evolution therefore controls both the onset of pulsation at the edges of the instability strip and of mode switching inside it. Two types of switchings (bifurcations) occur. In a so...

Observations of the southern Cepheid ℓ Car to yield the mean angular diameter and angular pulsation amplitude have been made with the Sydney University Stellar In-terferometer (SUSI) at a wavelength of 696 nm. The resulting mean limb-darkened angular diameter is 2.990±0.017 mas (i.e. ±0.6 per cent) with a maximum-to-minimum amplitude of 0.560±0.018 mas corresponding to 18.7±0.6 per cent in the ...

A short analysis is presented of the effects on the cepheid light curve shape, i.e. on the Fourier parameters usually adopted for its description, of the blending of the stellar image with other close stars. The conclusion is that, within reasonable error, the effects are in general small and the Fourier decomposition is confirmed to be a useful tool for pulsation mode discrimination. A large e...

Pulsation modes have recently been observed in a handful of white dwarf (WD) primaries of cataclysmic variables, allowing an interesting new probe into the structure of accreting WD's. We briefly discuss the seismology of these objects, how stellar properties may be inferred from the observed mode frequencies, and mode driving mechanisms. For one pulsator, GW Lib, we have shown that a WD mass M...