相关论文: The influence of chromospheric activity on line fo…
Magnetic fields and stellar spots can alter the equivalent widths of absorption lines in stellar spectra, varying during the activity cycle. This also influences the information that we derive through spectroscopic analysis. In this study…
Studying chromospheric activity of contact binaries is an important way of revealing the magnetic activity processes of these systems. An efficient but somewhat neglected method for that is to follow the changes of the H$\alpha$ line…
By using the LAMOST time-domain survey data, we study stellar activities based on the $\rm{H_{\alpha}}$ lines for about 2000 stars in four $K$2 plates. Two indices, $R_{\rm{H\alpha}}^{'}$ and $R_{\rm{H\alpha}}^{+}$, are computed from LAMOST…
During solar flares, spectral lines formed in the photosphere have been shown to exhibit changes to their profiles despite the challenges of energy transfer to these depths. Recent work has shown that deep-forming spectral lines are subject…
We study the differences in chromospheric structure induced in K stars by stellar activity, to expand our previous work for G stars, including the Sun as a star. We selected six stars of spectral type K with 0.82$<B-V<$0.90, including the…
Neutral Fe lines are the most abundant in the spectrum of late stars. They are used to obtain different basic stellar parameters such as relative abundances, surface gravity, and effective temperature. However, the centers of many of these…
Because of the complex physics that governs the formation of chromospheric lines, interpretation of solar chromospheric observations is difficult. The origin and characteristics of many chromospheric features are, because of this,…
The main chromospheric activity indicator is the S index, which is esentially the ratio of the flux in the core of the Ca II H and K lines to the continuum nearby, and is well studied basically for stars from F to K. Another usual…
Stellar magnetic activity is a source of noise in the study of the transits of extrasolar planets. It induces flux variations which affect significantly the transit depth determination and the derivations of planetary and stellar…
We present new spectroscopic observations in the Ca~{\sc ii} H \& K line region for a sample of 28 chromospherically active binary systems (RS$~$CVn and BY$~$Dra classes), with different activity levels. By using the spectral subtraction…
Context: Chromospheric activity produces both photometric and spectroscopic variations that can be mistaken as planets. Large spots crossing the stellar disc can produce planet-like periodic variations in the light curve of a star. These…
The O I 135.6 nm spectral line is formed in the chromosphere at the same heights as the Mg II h&k line cores are formed. As the O I line is optically thin, it represents a possibility for measuring the non-thermal velocities in this region…
Spectroscopic equilibrium allows us to obtain precise stellar parameters in Sun-like stars. It relies on the assumption of the iron excitation and ionization equilibrium. However, several works suggest that magnetic activity may affect…
Different approaches have been adopted to study short- and long-term stellar magnetic activity, and although the mechanisms by which low-mass stars generate large-scale magnetic fields are not well understood, it is known that stellar…
Aims. Other stars are known to have magnetic cycles similar to that of the Sun. The relationship between these activity variations and the observed radial-velocity is still not satisfactorily understood. In this first paper our aim is to…
Stellar chromospheric activity serves as a valuable proxy for estimating stellar ages, though its applicable range and accurate functional form are still debated. In this study, utilizing the LAMOST spectra we compiled a catalog of open…
Chromospherically sensitive atomic lines display different spectra in stellar active regions, spots, and the photosphere, raising the possibility that exoplanet transmission spectra are contaminated by the contrast between various portions…
We analyze a 1-hour time series of Ca II H intensity spectra and polarimetric spectra around 630 nm to derive the signature of the chromospheric heating and to investigate its relation to magnetic fields. We derived several characteristic…
Effective temperatures, surface gravities, and iron abundances were derived for 109 stars observed by the K2 mission using equivalent width measurements of Fe I and Fe II lines. Calculations were carried out in LTE using Kurucz model…
Chromospheric heating is an important ingredient in the energy budget of the solar atmosphere, which is challenging to quantify from observations. By using 3D radiative magnetohydrodynamic simulations of the solar atmosphere combined with…