Related papers: Pulsations in M dwarf stars
Pulsars are stars that emit electromagnetic radiation in well-defined time intervals. The frequency of such pulses decays with time as is quantified by the {\it braking index} ($n$). In the canonical model $n = 3$ for all pulsars, but…
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…
The study is devoted to radial pulsations in Population I Cepheids with masses from 5.4 to 6 Msun. Solution of the equations of radiation hydrodynamics and turbulent convection for nonlinear stellar pulsations was obtained with initial…
Stars which are rapidly rotating are expected to show high levels of activity according to the activity-rotation relation. However, previous TESS studies have found Ultra Fast Rotating (UFR) M dwarfs with periods less than one day…
The collection of high-quality photometric data by space telescopes is revolutionizing the area of white-dwarf asteroseismology. Among the different kinds of pulsating white dwarfs, there are those that have He-rich atmospheres, and they…
A spectroscopic analysis of SDSS J160043.6+074802.9, a binary system containing a pulsating subdwarf-O (sdO) star with a late-type companion, yields Teff = 70 000 +/- 5000 K and log g = 5.25 +/- 0.30, together with a most likely type of K3V…
We have analysed 10 months of public data from the Kepler space mission to measure rotation periods of main-sequence stars with masses between 0.3 and 0.55 M_sun. To derive the rotational period we introduce the autocorrelation function and…
This paper introduces a new empirical model for the rotational evolution of Sun-like stars -- those with surface convection zones and non-convective interior regions. Previous models do not match the morphology of observed (rotation…
We have measured v sin i with high precision for a sample of dM3 stars (86 targets). We detected rotation in 82 stars (73 dM3 stars, and 9 dM3e stars). We compare our measurements of v sin i for all the stars in our dM0, dM2, dM3 and dM4…
In the course of conducting a deep (14.5 ~< r ~< 23), 20 night survey for transiting planets in the rich ~550 Myr old open cluster M37 we have measured the rotation periods of 575 stars which lie near the cluster main sequence, with masses…
In order to understand the periodic and semi-periodic variations of luminous O- B- A-type stars, linear nonadiabatic stability analyses for radial and nonradial oscillations have been performed for massive evolutionary models ($8M_\odot -…
We study a nonlinear development of radial pulsation instability to a resonant excitation of nonradial modes. Our theory covers the cases of axisymmetric (m=0) modes as well as (m,-m) pairs. Adopting a simplified treatment of the radial and…
We report the detection of periodic variations on the T_eff ~32 000 K DA white dwarf star HE 1017-1352. We obtained time series photometry using the 4.1 m SOAR telescope on three separate nights for a total of 16.8 h. From the frequency…
Models of M-type Miras with masses of 1 $M_\odot$ and 1.2 $M_\odot$, i.e. with envelope masses of about 0.4 $M_\odot$ and 0.6 $M_\odot$, have been constructed, and a comparison has been made of their observable properties. Geometric…
To improve the understanding of the pulsational instabilities of some of the PG1159-type pre-white dwarfs we performed detailed stability analyses on helium star evolutionary models. With the canonical chemical compositions, pulsational…
We present time-series VLT spectroscopy and NTT photometry of the cataclysmic variable SDSS J220553.98+115553.7, which contains a pulsating white dwarf. We determine a spectroscopic orbital period of 82.825 +/- 0.089 min from velocity…
The time scales of variability in active M dwarfs can be related to their various physical parameters. Thus, it is important to understand such variability to decipher the physics of these objects. In this study, we have performed the low…
All single stars that are born with masses up to 8.5 - 10 $M_\odot$ will end their lives as a white dwarf (WD) star. In this evolutionary stage, WDs enter the cooling sequence, where the stars radiate away their thermal energy, and are…
We describe a new mechanism for pulsations in evolved stars: relaxation oscillations driven by a coupling between the luminosity-dependent mass-loss rate and the H fuel abundance in a nuclear-burning shell. When mass loss is included, the…
Space photometry has revealed rich pulsation spectra in classical Be stars. Often frequency pairs can be found that differ by nearly the frequency of a third genuine stellar variability. The lowest currently known of these so-called…