Related papers: A representative sample of Be stars V: H{\alpha} v…
We obtained the first long, homogenous time-series of V2104Cyg, consisting of 679 datapoints, with the uvbybeta photometers of Sierra Nevada and San Pedro Martir Observatories with the aim to detect and subsequently interpret the intrinsic…
We have studied variability of the spectral lines of the OB star $\delta $Ori A--the brightest component of the $\delta $Ori triple system. Forty spectra with signal-to-noise ratios $\approx$500--800 and a time resolution of four minutes…
We present H band (1.53 - 1.69 micron) spectra of 57 isolated Be stars of spectral types O9-B9 and luminosity classes III,IV & V. The HI Brackett (n-4) series is seen in emission from Br 11-18, and FeII emission is also apparent for a…
The combination of photometry, spectroscopy and spectropolarimetry of the chemically peculiar stars often aims to study the complex physical phenomena such as stellar pulsation, chemical inhomogeneity, magnetic field and their interplay…
Be stars possess gaseous circumstellar disks that modify in many ways the spectrum of the central B star. Furthermore, they exhibit variability at several timescales and for a large number of observables. Putting the pieces together of this…
In this paper we present results of the spectroscopic analysis of H$\alpha$ line profile of the Be star 60 Cygni. We present time evolution of the equivalent width of the H$\alpha$ line profiles during years 1992 - 2016 and $V/R$ variation…
13\,Tau is a rarely studied bright B9V type star ({\sl V} = 5.68 mag), which shows a weak and double-peaked H{$\alpha$} emission profile in its spectra. In this study, we presented high-precision photometric data of 13\,Tau taken by the…
We investigate the line-profile variability (lpv) of H-alpha for a large sample of O-type supergiants. We used the Temporal Variance Spectrum (TVS) analysis, developed by Fullerton et al 1996 and modified by us to take into account the…
An analysis of solid-state features in infrared spectra of 46 Herbig Ae/Be stars is presented. The presence of solid-state emission bands is compared to other indicators of circumstellar material, such as Halpha emission, optical…
Massive stars show a variety of spectral variability: presence of discrete absorption components in UV P-Cygni profiles, optical line profile variability, X-ray variability, radial velocity modulations. Our goal is to study the spectral…
We use ~12,000 spectra of ~3,500 magnetically active M0-M9 dwarfs from the Sloan Digital Sky Survey taken at 10-15 minute intervals, together with ~300 spectra of ~60 M0-M8 stars obtained hourly with the Hydra multi-object spectrometer, to…
We study the time variations of the cycles of 20 active stars based on decades-long photometric or spectroscopic observations. A method of time-frequency analysis, as discussed in a companion paper, is applied to the data. Fifteen stars…
The long-term variation of the H$\alpha$ line in $\alpha$ Eri has 14-15 years cyclic \bbe phase transitions. The disc formation time scales, interpreted as the periods during which the H$\alpha$ line emission increases from zero to its…
We report on optical high-dispersion spectroscopic monitoring observations of the Be/X-ray binary A0535+26/V725 Tau, carried out from November 2005 to March 2009. The main aim of these monitoring observations is to study spectral…
The line profile variability and photometric variability of the O9.5 Vp star HD93521 are examined in order to establish the properties of the non-radial pulsations in this star. Fourier techniques are used to characterize the modulations of…
Observations from the Heliospheric Imagers (HI-1) on both the STEREO spacecraft have been analysed to search for very long period large amplitude stellar variability, finding 6 new candidates. A total of 85 objects, mostly previously known…
High-dispersion IUE data encode significant information about aggregate line absorptions that cannot be conveniently extracted from individual spectra. We apply a new technique in which fluxes from each echelle order of a short wavelength…
We present the results of spectropolarimetric observations of 12 Herbig Ae/Be objects. Our data have the largest spectropolarimetric wavelength coverage, 4560 {\AA} to 9480 {\AA}, published to date. A change in linear polarisation across…
Context. Plaskett's star (HD47129) is a very massive O-star binary in a post Roche-lobe overflow stage. CoRoT observations of this system revealed photometric variability with a number of frequencies. Aims. The aim of this paper is to…
A reliable determination of the basic physical properties and variability patterns of hot emission-line stars is important for understanding the Be phenomenon and ultimately, the evolutionary stage of Be stars. This study is devoted to one…