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We examine high-cadence space photometry taken by the Transiting Exoplanet Survey Satellite (TESS) of a sample of evolved massive stars (26 Wolf-Rayet stars and 8 Luminous Blue Variables or candidate LBVs). To avoid confusion problems, only…

The Milky Way's central parsec is a highly extinguished region with a population of high-proper-motion stars. We have tracked 145 stars for $\sim$10 years at wavelengths between 1 and 4 microns to analyze extinction effects in…

HD 189733 is an exoplanetary system consisting of a transiting hot Jupiter and an active K2V-type main sequence star. We aim to use VLT/UVES high resolution echelle spectra to study a stellar flare. We have performed simultaneous analyses…

The B0.5IVe star gam Cas is of great interest because it is the prototype of a small group of classical Be stars having hard X-ray emission of unknown origin. We discuss results from ongoing B and V observations of the gam Cas star-disk…

V909 Cas is a little-studied example of a \b{eta} Cep pulsating variable located in the OB association Cas OB8 in the Perseus spiral arm of the Milky Way. Photometric observations in 2016-7 provided 30 new times of pulsation extrema and…

Two observations of V959 Mon, done using the Chandra X-ray gratings during the late outburst phases (2012 September and December), offer extraordinary insight into the physics and chemistry of this Galactic ONe nova. the X-ray flux was 1.7…

Repeated spectroscopic observations made with the 6m telescope of yielded new data on the radial-velocity variability of the anomalous yellow supergiant QYSge. The strongest and most peculiar feature in its spectrum is the complex profile…

SAO244567, the exciting star of the Stingray nebula, is rapidly evolving. Previous analyses suggested that it has heated up from an effective temperature of about 21kK in 1971 to over 50kK in the 1990s. Canonical post-asymptotic giant…

Betelgeuse is a pulsating red supergiant whose brightness is semi periodically variable and in February 2020 reached a historical minimum, the Great Dimming. The aims of this study are to characterize Betelgeuse's variability based on…

Over the five years of high-resolution spectroscopy of the cool star identified with the IR source IRAS20508+2011, the photospheric radial velocity variability Vr=15-30km/s is detected. In the same time, the Halpha profile varied from an…

Young stars exhibit variability due to changes in the gas accretion rate onto them, an effect that should be quite significant in the early stages of their formation. As protostars are embedded within their natal cloud, this variability may…

In this paper we present high resolution 4.7micron spectra of the isolated Herbig Be star HD100546. HD100546 has been the subject of intense scrutiny because it is a young nearby star with a transitional disk. We observe the Delta v=1…

We present a new luminous star in M33 located in the nuclear region. The star shows strong FeII and [FeII] forest, hydrogen emissions in the spectrum, as well as nebular lines. TiII and SiII lines were detected in absorption, their radial…

We present near infrared spectroscopy of the recurrent nova RS Oph obtained on several occasions after its latest outburst in 2006 February. The 1-5 mircon spectra are dominated by the red giant, but the H I, He I, and coronal lines present…

We have obtained FUSE and HST/STIS time-resolved spectroscopy of the polar AM Herculis during a deep low state. The spectra are entirely dominated by the emission of the white dwarf. Both the far-ultraviolet (FUV) flux as well as the…

EK Draconis, a nearby young solar-type star (G1.5V, 50-120 Myr), is known as one of the best proxies for inferring the environmental conditions of the young Sun. The star frequently produces superflares and Paper I presented the first…

We have made a serendipitous discovery of an enigmatic outflow source, IRAS 05506+2414 (hereafter IRAS 05506), as part of a multi-wavelength survey of pre-planetary nebulae (PPNs). The HST optical and near-infrared images show a bright…

Abriged version for astroph: The young late-type star V1118 Orionis was in outburst from 2005 to 2006. We followed the outburst with optical and near-infrared photometry; the X-ray emission was further probed with observations taken with…

We use new studies of the cosmic evolution of star-forming galaxies to estimate the production rate of ionizing photons from hot, massive stars at low and intermediate redshifts. The luminosity function of blue galaxies in the Canada-France…

While performing a survey to detect recoiling supermassive black holes, we have identified an unusual source having a projected offset of 800 pc from a nearby dwarf galaxy. The object, SDSS J113323.97+550415.8, exhibits broad emission lines…