Related papers: Pulsations in the atmosphere of the rapidly oscill…

Some Ap stars with strong magnetic fields pulsate in high order p-modes; they are called roAp (rapidly oscillating Ap) stars. The p-mode frequencies are modified by the magnetic fields. Although the large frequency separations are hardly…

Rapidly oscillating Ap (roAp) stars have rarely been found in binary or higher order multiple systems. This might have implications for their origin. We intend to study the multiplicity of this type of chemically peculiar stars, looking for…

Prior to the last decade, most observations of roAp stars have concerned the light variations. Recently some new, striking results of spectroscopic observations with high time resolution, high spectral dispersion, and a high signal-to-noise…

It is shown for the first time that the stripped helium stars with masses 2 to 7 solar mass which are formed in close binary systems in the so-called case B of mass-exchange and retained low-mass hydrogen-helium envelopes, experience…

Photometry from the All-Sky Automated Survey for Supernovae (ASAS-SN), along with the AAVSO VSTAR time-series analysis package has been used to study the pulsational properties of 31 R Coronae Borealis (RCB) stars. Periods have been derived…

Aims. Despite photometry and spectroscopy of its oscillations obtained over the past 25 years, the pulsation frequency spectrum of the rapidly oscillating Ap (roAp) star gamma Equ has remained poorly understood. Better time-series…

Regular intrinsic brightness variations observed in many stars are caused by pulsations. These pulsations provide information on the global and structural parameters of the star. The pulsation periods range from seconds to years, depending…

We report on a comprehensive analysis of the kilo-Hz (>~600 Hz) quasi-periodic oscillations (kHz QPOs) detected from the neutron star X-ray transient Aquila X-1 (Aql X-1) with the Rossi X-ray Timing Explorer, between 1997 and 2007. Among…

S-type AGB stars have a C/O ratio which suggests that they are transition objects between oxygen-rich M-type stars and carbon-rich C-type stars. As such, their circumstellar compositions of gas and dust are thought to be sensitive to their…

Spectroscopy is a powerful tool for detecting variability in the rapidly oscillating Ap (roAp) stars. The technique requires short integrations times and high resolution, and so is limited to only a few telescopes and instruments. To test…

Quasi-periodic pulsations (QPPs), which carry time features and plasma characteristics of flare emissions, are frequently observed in light curves of solar/stellar flares. In this paper, we investigated non-stationary QPPs associated with…

Aims: We present accurate photometric time series of two Be stars: NW Ser and V1446 Aql. Both stars were observed at the Observatorio de Sierra Nevada (Granada) in July 2003 with an automatic four-channel Str\"omgren photometer. We also…

We study the influence of Stark broadening and stratification effects on Si\i lines in the rapidly oscillating (roAp) star 10 Aql, where the Si\i 6142.48 \AA and 6155.13 \AA lines are asymmetrical and shifted. First we have calculated Stark…

We present results of the radial velocity (RV) analysis of spectroscopic time-series observations of the roAp star HD24712 (HR1217) which were carried out simultaneously with the Canadian MOST mini-satellite photometry. Only lines of the…

Chemically peculiar A stars (Ap) are extreme examples of the interaction of atomic element diffusion processes with magnetic fields in stellar atmospheres. The rapidly oscillating Ap stars provide a means for studying these processes in 3D…

We have obtained time-resolved spectroscopic observations for a sample of 10 cool Ap stars using the ultra-stable spectrograph HARPS at the ESO 3.6-m telescope. The aim of our study was to search for low-amplitude oscillations in Ap stars…

The recent discovery of large-amplitude pulsations in faint blue stars (BLAPs) provides both challenges for stellar pulsation theory and opportunities to explore the late evolution of low-mass stars. This paper explores the radial-mode…

We introduce a model for pulsars in which non-radial oscillations of high spherical degree (l) aligned to the magnetic axis of a spinning neutron star reproduce the morphological features of pulsar beams. In our model, rotation of the…

We present a new analysis of the rapidly oscillating Ap (roAp) star, 2MASS J$19400781-4420093$ (J1940; $V=13.1$). The star was discovered using SuperWASP broadband photometry to have a frequency of 176.39 d$^{-1}$ (2041.55 $\mu$Hz; $P =…

With FORS1 at the VLT we have tried for the first time to measure the magnetic field variation over the pulsation cycle in six roAp stars to begin the study of how the magnetic field and pulsation interact. For the star HD101065, which has…