Related papers: Staying star gamma Equ
The present work explores the theoretical effects of rotation in calculating the period ratios of double-mode radial pulsating stars with special emphasis on high-amplitude delta Scuti stars (HADS). Diagrams showing these period ratios vs.…
We have matched the astrometric data from Gaia Data Release 2 to the sample of stars with measured rotation periods from Kepler. Using 30,305 stars with good distance estimates, we select 16,248 as being likely main sequence single stars…
Recent observations suggest the existence of two characteristic cycle times for early-type M stars dependent on the rotation period. They are of order one year for the fast rotators ($P_{\rm rot}<1$ day) and of order 4 years for the slower…
According to two estimated relations between the initial period and the dynamo-generated magnetic dipole field of pulsars, we calculate the statistical distributions of pulsar initial periods. It is found that proto-pulsars are very likely…
The rotation-mass-age relationship offers a promising avenue for measuring the ages of field stars, assuming the attendant uncertainties to this technique can be well characterized. We model stellar angular momentum evolution starting with…
Power spectra of the light curves of semiregular variables, based on visual magnitude estimates spanning many decades, show clear evidence for stochastic excitation. This supports the suggestion by Christensen-Dalsgaard et al. (2001) that…
We present the first short time scale observations of the roAp star gamma Equ in linear polarized light obtained with the PEPSI polarimeter installed at the LBT. These observations are used to search for pulsation variability in Stokes Q…
Accretion of interstellar material by a magnetized, slowly rotating isolated neutron star is discussed. We show that the average persistent X-ray luminosity of these objects is unlikely to exceed 4x10^26 erg/s. They can also appear as X-ray…
We study the dynamical instability against bar-mode deformation of differentially rotating stars. We performed numerical simulation and linear perturbation analysis adopting polytropic equations of state with the polytropic index $n=1$. It…
The Kepler space telescope leaves a legacy of tens of thousands of stellar rotation period measurements. While many of these stars show strong periodicity, there exists an even bigger fraction of stars with irregular variability for which…
Period changes of Delta Scuti stars have been collected or redetermined from the available observations and are compared with values computed from evolutionary models with and without convective core overshooting. For the radial pulsators…
Duration and period of transits in extrasolar planetary systems can exhibit long-term variations for a variety of reasons. Here we investigate how systemic proper motion, which steadily re-orients planetary orbit with respect to our line of…
For the non-rotating gaseous stars modeled by the compressible Euler-Poisson system with general pressure law, Lin and Zeng [18] proved a turning point principle, which gives the sharp linear stability/instability criteria for the…
(abridged) Context: Main-sequence late-type stars with masses less than $0.35 M_\odot$ are fully convective. Aims: The goal is to study convection, differential rotation, and dynamos as functions of rotation in fully convective stars.…
Context. The rotation period of stars is an important parameter along with mass, radius, effective temperature. It is an essential parameter for any radial velocity monitoring, as stellar activity can mimic the presence of a planet at the…
We report rotation periods for 20 cool (FGK) main sequence member stars of the 4 Gyr-old open cluster M 67 (= NGC 2682), obtained by analysing data from Campaign 5 of the K2 mission with the Kepler Space Telescope. The rotation periods…
Context: Rotation plays a key role in the life cycles of stars with masses above 8 Msun. Hence, accurate knowledge of the rotation rates of such massive stars is critical for understanding their properties and for constraining models of…
B-type stars are known to rotate at various velocities, including very fast rotators near the critical velocity as the Be stars. In this paper, we provide stellar models covering the mass range between 1.7 to 15 Msun, which includes the…
We present the discovery of a long-period, rapidly oscillating Ap star, HD177765. Using high-resolution time-series observations obtained with UVES at the ESO VLT telescope, we found radial velocity variations with amplitudes 7-150 m/s and…
Galactic field Be stars were studied by taking into account the effects induced by the fast rotation on their fundamental parameters. Fractional ages $\tau/\tau\_{\rm MS}$ ($\tau\_{\rm MS}$ = time spent in the MS) against stellar mass…