Related papers: Pulsations in the atmosphere of the rapidly oscill…
Three topics are discussed: 1) Photometric observations of the rapidly oscillating Ap stars have shown that the pulsation amplitude drops dramatically as a function of wavelength from the blue to the red. A theoretical derivation, plus…
Rapidly oscillating Ap stars exhibit an astrophysically interesting combination of strong, dipolar-like magnetic fields and high-overtone p-mode pulsations similar to the Sun. Recent time-resolved spectroscopy of these stars unravelled a…
Non pulsating neutron stars in low mass X-ray binaries largely outnumber those that show pulsations. The lack of detectable pulses represents a big open problem for two important reasons. The first is that the structure of the accretion…
Precise time-series photometry with the MOST satellite has led to identification of 10 pulsation frequencies in the rapidly oscillating Ap (roAp) star HD 134214. We have fitted the observed frequencies with theoretical frequencies of…
We present time-series spectroscopy of the rapidly oscillating Ap star HR 3831. This star has a dominant pulsation period of 11.7 minutes and a rotation period of 2.85 days. We have analysed 1400 intermediate-resolution spectra of the…
We present the analysis of K2 short cadence data of the rapidly oscillating Ap (roAp) star, 33 Librae (HD 137949). The precision afforded to the K2 data allow us to identify at least 11 pulsation modes in this star, compared to the three…
The 60 known rapidly oscillating Ap (roAp) stars are excellent laboratories to test pulsation models in the presence of stellar magnetic fields. Our survey is dedicated to search for new group members in the Northern Hemisphere. We attempt…
We report the discovery of an episode of coherent millisecond X-ray pulsation in the neutron star low-mass X-ray binary Aql X-1. The episode lasts for slightly more than 150 seconds, during which the pulse frequency is consistent with being…
RRab stars are large amplitude pulsating stars in which the pulsation is associated with strong shock wake propagating in the atmosphere. The objective of this study is to provide a general overview of the dynamical structure of the…
Pulsational variability is observed in several types of main sequence stars with anomalous chemical abundances. In this contribution I summarize the relationship between pulsations and chemical peculiarities, giving special emphasis to…
High-resolution spectroscopic time series of rapidly oscillating Ap stars show evidence for a co-existence of standing and running waves in their atmospheric layers. With the purpose of understanding these observations we have carried out a…
We present an analysis of the pulsation behaviour of the Delta Scuti stars 7 Aql (HD 174532) and 8 Aql (HD 174589) -- a new variable star -- observed in the framework of STEPHI XII campaign during 2003 June--July. 183 hours of high…
Due to the strong magnetic field and related abnormal surface layers existing in rapidly oscillating Ap stars, systematic errors are likely to be present when determining their effective temperatures, which potentially compromises…
We present an analysis of high time resolution spectra of the chemically peculiar Ap star HD 213637. The star shows rapid radial velocity variations with a period close to the photometric pulsation period. Radial velocity pulsation…
Observations of the A5p star KIC 8677585 obtained during the Kepler 10-d commissioning run with 1-min time resolution show that it is a roAp star with several frequencies with periods near 10 min. In addition, a low frequency at 3.142…
An interesting asteroseismic target is the G9.5 IV solar-like star beta Aql. This is an ideal target for asteroseismic investigations, because precise astrometric measurements are available from Hipparcos that greatly help in constraining…
We discuss pulsations of the rapidly oscillating Ap (roAp) star HD 24712 (HR 1217) based on nonadiabatic analyses taking into account the effect of dipole magnetic fields. We have found that all the pulsation modes appropriate for HD 24712…
We present recent results from our radial velocity (RV) studies of rapidly oscillating Ap (roAp) stars. Our measurements reveal that the pulsational amplitude of these stars depends on the spectral region that is examined. For one star,…
We present bisector measurements of the H-alpha line of the rapidly oscillating Ap (roAp) star, Alpha-Cir, obtained from dual-site observations with medium-dispersion spectrographs. The velocity amplitude and phase of the principal…
HR 1217 is one of the best-studied rapidly oscillating Ap (roAp) stars, with eight known oscillation modes that are distorted by a strong, global magnetic field. We have reanalysed the multisite observations of HR 1217 taken in 1986 and…