Related papers: On the H$\alpha$ emission from the $\beta$ Cephei …
The spin-down of Be stars due to angular momentum transport from star to disc has been considered. This has been prompted by empirical studies of observed optical and IR line profile studies indicating that the disc is rotating in a…
We performed a systematic search for Chandra archival observations of Herbig Ae/Be stars. These stars are fully radiative and not expected to support dynamo action analogous to their convective lower-mass counterparts, the T Tauri stars.…
Because many classical Be stars may owe their nature to mass and angular-momentum transfer in a close binary, the present masses, temperatures, and radii of their components are of high interest for comparison to stellar evolution models.…
We analyzed the star HD 171219, one of the relatively bright Be stars observed in the seismo field of the CoRoT satellite, in order to determine its physical and pulsation characteristics. Classical Be stars are main-sequence objects of…
PSR B1259-63/LS 2883 is a very high energy (VHE; E > 100 GeV) gamma-ray emitting binary consisting of a 48 ms pulsar orbiting around a Be star with a period of 3.4 years. The Be star features a circumstellar disk which is inclined with…
The intriguing binary LS V +22 25 (LB-1) has drawn much attention following claims of it being a single-lined spectroscopic binary with a 79-day orbit comprising a B-type star and a ~70 Msun black hole. Recent analyses have implied that the…
Recently published Spitzer observations of the classical Cepheid archetype delta Cephei revealed an extended dusty nebula surrounding this star and its hot companion. The infrared emission resembles a bow shock aligned with the direction of…
The light elements, Li, Be, and B, provide tracers for many aspects of astronomy including stellar structure, Galactic evolution, and cosmology. We have taken spectra of Be in 117 metal-poor stars ranging in metallicity from [Fe/H] = -0.5…
Classical Be stars are fast rotating, near main sequence B-type stars. The rotation and the presence of circumstellar discs profoundly modify the observables of active Be stars. Our goal is to infer stellar and disc parameters, as well as…
The Halpha line emission formation region in the circumstellar disc of alpha Eri is: a) extended with a steep outward matter density decline during low H$\alpha$ emission phases; b) less extended with rather constant density distribution…
H$\alpha$ is a powerful tracer of accretion and chromospheric activity, which has been detected in the case of young brown dwarfs and even recently in planetary mass companions (e.g. PDS70 b and c). H$\alpha$ detections and characterisation…
Binary systems consisting of an early type star and a black hole (BH) are crucial for understanding various astrophysical phenomena, particularly the origins of detected gravitational wave sources. Be binary systems are expected to…
HR 7409 (7 Vul) is a newly identified Be star possibly part of the Gould Belt and is the massive component of a 69-day spectroscopic binary. The binary parameters and properties of the Be star measured using high-dispersion spectra obtained…
Context. HD 110432 was classified as a "\gamma Cas X-ray analog" since it has similar peculiar X-ray and optical characteristics, i.e. a hard-thermal X-ray variable emission and an optical spectrum affected by an extensive disk. Lopes de…
The majority of massive classical Be stars are thought to be binary interactions products. Their rapid rotation and often strong, variable, and emission-line dominated spectrum, make spectroscopic analysis challenging. Hence, robust binary…
The presence of three more Herbig Ae/Be (HAeBe) stars in the Cepheus Flare within a 1.5$^{\circ}$ radius centered on HD 200775 suggests that star formation is prevalent in a wider region of the LDN 1147/1158, LDN 1172/1174, and LDN 1177…
We present a detailed visible and near-IR spectro-interferometric analysis of the Be-shell star $\omicron$ Aquarii from quasi-contemporaneous CHARA/VEGA and VLTI/AMBER observations. We measured the stellar radius of $\omicron$ Aquarii as…
We present a systematic investigation of $\beta$ Cephei (BCEP) stars by integrating photometric data from the Transiting Exoplanet Survey Satellite (TESS) with astrometric parameters from Gaia Data Release 3. Utilizing TESS's short-cadence…
The light curves of 252 B-star candidates in the Kepler data base are analyzed in a similar fashion to that done by Balona et al. (2011) to further characterize B star variability, increase the sample of variable B stars for future study,…
Only 3-4 per cent of galactic O stars are observed to display the emission features representative of the OBe phenomenon, compared to galactic B stars, which display these characteristics in 25-35 per cent of B0 and B1 stars. We present new…