相关论文: Amplitude Modulation in the ZZ Ceti Star GD 244

The lightcurves of variable DA stars are usually multi-periodic and non-sinusoidal, so that their Fourier transforms show peaks at eigenfrequencies of the pulsation modes and at sums and differences of these frequencies. These combination…

New V-band CCD observations of variable star V2455 Cyg were performed during two nights in September 2017. According to all times of maximum light and new maxima, the O-C curve was analyzed. The period changes of V2455 Cyg were investigated…

We report a time-series analysis of satellite photometry of the non-radially pulsating Oe star zeta Oph, principally using data from SMEI obtained 2003--2008, but augmented with MOST and WIRE results. Amplitudes of the strongest photometric…

We combine all the reliably-measured eigenperiods for hot, short-period ZZ Ceti stars onto one diagram and show that it has the features expected from evolutionary and pulsation theory. To make a more detailed comparison with theory we…

We report on the discovery of variable circular polarization in the SW Sex star LS Pegasi. The observed modulation has an amplitude of ~0.3 % and a period of 29.6 minutes, which we assume as the spin period of the magnetic white dwarf. We…

Numerical simulations of light curves of variable DA white dwarfs (ZZ Ceti stars) predict flux amplitudes with surface distributions different from the spherical harmonics of the pulsation mode in deeper layers. In contrast to the results…

Magnetic chemically peculiar stars of the main sequence can present rotational periods as long as many decades. Here we report the results of an observational campaign started in 2001 aimed at establishing these very long periods from the…

Context. We present our findings on 18 formerly known ZZ Ceti stars observed by the TESS space telescope in 120s cadence mode during the survey observation of the southern ecliptic hemisphere. Aims. We focus on the frequency analysis of the…

Ultra-massive hydrogen-rich (DA) white dwarfs (WD) are expected to have a substantial portion of their cores in a crystalline state at the effective temperatures characterizing the ZZ Ceti instability strip, as a result of Coulomb…

We present time-series photometry of 31 massive DA white dwarfs with $M\gtrsim 0.9~M_\odot$ within the ZZ Ceti instability strip from the Montreal White Dwarf Database 100 pc sample. The majority of the targets had no previous time-series…

We have used long-term AAVSO visual observations and Fourier and wavelet analysis to identify periods and study long-term amplitude variations in 44 red supergiants. Of these, 12 stars had data which were too sparse and/or had low amplitude…

The Kepler spacecraft provides new opportunities to search for long term frequency and amplitude modulations of oscillation modes in pulsating stars. We ana- lyzed nearly two years of uninterrupted data obtained with this instrument on the…

We report on the analysis of 436.1 hrs of nearly continuous high-speed photometry on the pulsating DB white dwarf GD358 acquired with the Whole Earth Telescope (WET) during the 2006 international observing run, designated XCOV25. The…

LSI +61 303 is an exotic binary system consisting of a ~10 Msun B star and a compact object which is probably a neutron star. The system is associated with the interesting radio source GT0236+610 that exhibits bright radio outbursts with a…

We report on numerical calculations of nonadiabatic eigenvalues and eigenfunctions for g-modes in ZZ Ceti variables. The spectrum of overstable $l=1$ modes delineates the instability strip. Its blue edge occurs where $\omega \tau_c \approx…

We present the first asteroseismological study for 42 massive ZZ Ceti stars based on a large set of fully evolutionary carbon$-$oxygen core DA white dwarf models characterized by a detailed and consistent chemical inner profile for the core…

Extensive photometric multisite campaigns of the Delta Scuti variable FG Vir are presented. For the years 2003 and 2004, 926 hours of photometry at the millimag precision level were obtained. The combinations with earlier campaigns lead to…

The Tsinghua University-Ma Huateng Telescope for Survey (TMTS) has been constantly monitoring the northern sky since 2020 in search of rapidly variable stars. To find variable white dwarfs (WDs), the TMTS catalog is cross-matched with the…

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…

It is well known that in the Sun, the frequencies and amplitudes of acoustic modes vary throughout the solar cycle. Indeed, while the magnetic activity goes towards its maximum, the frequencies of the modes increase and their amplitudes…