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AX J0049.4-7323 is a Be/X-ray binary that shows an unusual and poorly understood optical variability that consists of periodic and bright optical outbursts, simultaneous with X-ray outbursts, characterised by a highly asymmetric profile.…

Emission-line stars are typically surrounded by dense circumstellar material, often in form of rings or disc-like structures. Line emission from forbidden transitions trace a diversity of density and temperature regimes. Of particular…

We present the results of optical and near-IR spectroscopic and near-IR photometric observations of the emission-line stars Hen3-298 and Hen3-303. Strong emission in the H-alpha line is found in both objects. The presence of Fe II and [O I]…

The hierarchical multiple system XY Leo, despite nearly 90 yr of observations, remains enigmatic. It offers a unique testbed for close binary evolution, involving processes such as mass transfer, angular momentum loss, and the von…

Flares and coronal mass ejections (CMEs) are important for the evolution of the atmospheres of planets and their potential habitability, particularly for planets orbiting M stars at a distance < 0.4 AU. Detections of CMEs on these stars…

Study the ionized gas in metal-poor environments is key to understanding the mechanisms regulating galaxy evolution. However, most of the previous studies of extragalactic HII regions rely on unresolved observations of gaseous structures.…

BRITE-Constellation has observed the exoplanet host star $\beta$ Pictoris for 225 days from November 2016 to June 2017. These data allow for an accurate description of the pulsational properties and an asteroseismic interpretation. They…

An object with a very peculiar light-curve was discovered recently using Kepler data. Authors argue that this object may be a transiting disintegrating planet with a comet like dusty tail. We calculate the light-curves of stars with such…

We have made a clear detection of p-mode oscillations in the nearest solar-like G2V star $\alpha$ Cen A with the CORALIE spectrograph on the 1.2-m Swiss telescope at the ESO La Silla Observatory. We report the 5 nights of observation on…

The unprecedented detail of the WFPC2 colour-magnitude diagrams of the resolved stellar population of Leo A presented here allows us to determine a new distance and an accurate star formation history for this extremely metal-poor Local…

The dust disk around Beta Pic must be produced by collision or by evaporation of orbiting Kuiper belt-like objects. Here we present the Orbiting-Evaporating-Bodies scenario in which the disk is a gigantic multi-cometary tail supplied by…

We present the results of the observations of some roAp stars made at Mount Stromlo Observatory during 17 nights in 2001 September-October. This long observing run permitted us to obtain a good phase-rotation coverage. In chemically…

Radial velocity observations of the F8 V star Upsilon Andromedae taken at Lick and at Whipple Observatories have revealed evidence of three periodicities in the line-of-sight velocity of the star. These periodicities have been interpreted…

Remote investigations of the ancient solar system matter has been traditionally carried out through the observations of long-period (LP) comets that are less affected by solar irradiation than the short-period counterparts orbiting much…

We report the discovery of a new planetary system around the K giant $\eta$ Cet (HIP 5364, HD 6805) based on 118 high-precision optical radial velocities taken at Lick Observatory since July 2000. Since October 2011 an additional nine…

The type-IV bursts, associated with coronal mass ejections (CMEs), occasionally extend to the decameter-hectrometric (DH) range. We present a comprehensive catalog of simultaneous multi-vantage point observations of DH type-IV bursts by…

Aims: We test the technique of spectro-astrometry as a potential method to investigate the close environment of massive young stars. Method: Archival VLT near infrared K band spectra (R=8900) of three massive young stellar objects and one…

The ejecta of thermally-pulsating AGB stars largely control the chemical evolution of galaxies. Yet, both, the mass-loss process and the gas chemical composition remain poorly understood. We present maps of the extended 12CO and 13CO…

TiO plays an important role in determining the atmospheric structure of M-type stars and in shaping the visual part of their spectra. We compute synthetic spectra for late-type M giants and identify systematic discrepancies in the…

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…