Related papers: The hot R Coronae Borealis star DY Centauri is a b…

We confirmed the binary nature of the Be star 7~Vul, derived a~more accurate spectroscopic orbit with an orbital period of (69.4212+/-0.0034) d, and improved the knowledge of the basic physical elements of the system. Analyzing available…

Models based on their binary origin have been very successful in reproducing the properties of field subdwarf-B stars, but the observations of their analogues in globular clusters has posed new problems, while the discovery of multiple…

We present the radial velocity curve of a single-lined spectroscopic binary in the faint Hercules dwarf spheroidal (dSph) galaxy, based on 34 individual spectra covering more than two years of observations. This is the first time that…

I present the results of time-resolved photometry of a selection of central stars of planetary nebulae. The study reveals periodic variability in two of the eight central stars observed, those of NGC 6026 and NGC 6337. The variability…

We are undertaking the first systematic infrared (IR) census of R Coronae Borealis (RCB) stars in the Milky Way, beginning with IR light curves from the Palomar Gattini IR (PGIR) survey. PGIR is a 30 cm $J$-band telescope with a 25…

This study presented a new analysis for the TESS-observed W Ursae Majoris (W UMa) binary star YY Coronea Borealis (YY CrB). The light curve was analyzed by the PHysics Of Eclipsing BinariEs (PHOEBE) Python version together with the Markov…

Short-period binaries represent extreme cases in the generation of stellar coronae via a rotational dynamo. Such stars are important for probing the origin and nature of coronae in the regimes of rapid rotation and activity saturation. VW…

An R Coronae Borealis (RCB) star is a rare type of supergiant star that is increasingly thought to be the evolved merger product of two white dwarfs. Recently, many of them have been found distributed in a thin disk structure embedded…

The star R Corona Borealis (R CrB) shows forbidden lines of [O II], [N II], and [S II] during the deep minimum when the star is fainter by about 8 to 9 magnitudes from normal brightness, suggesting the presence of nebular material around…

We report the discovery of an extremely close, eclipsing binary system. A white dwarf is orbited by a core He-burning compact hot subdwarf star with a period as short as $\simeq0.04987 {\rm d}$ making this system the most compact hot…

In this paper we present a spectroscopic study of six double-lined binaries, five of which were recently discovered in a high-resolution spectroscopic survey of optical counterparts of stellar X-ray sources. Thanks to high-resolution…

LoTr 5 is a planetary nebula with an unusual long-period binary central star. As far as we know, the pair consists of a rapidly rotating G-type star and a hot star, which is responsible for the ionization of the nebula. The rotation period…

In 2007, R Coronae Borealis (R CrB) went into an historically deep and long decline. In this state, the dust acts like a natural coronagraph at visible wavelengths, allowing faint nebulosity around the star to be seen. Imaging has been…

Abell 70 is a planetary nebula (PN) whose nucleus at optical wavelengths is a G8 star with enhanced carbon and s-process abundances--a "barium star." The cool star is a binary companion of the true, hot central star. In several other…

Context: R Coronae Borealis (RCB) variables and their non-variable counterparts, the dustless Hydrogen-Deficient Carbon (dLHdC) stars have been known to exhibit enhanced s-processed material on their surfaces, especially Sr, Y, and Ba. No…

The results of long-term surveys of radial velocities of cool Ap and Am stars are presented. There are two samples, one of about 100 Ap stars and the other of 86 Am stars. Both have been observed with the CORAVEL scanner from Observatoire…

We are investigating the formation and evolution of dust around the hydrogen-deficient supergiants known as R Coronae Borealis (RCB) stars. We aim to determine the connection between the probable merger past of these stars and their current…

We have identified a binary companion to (42355) 2002 CR46 in our ongoing deep survey using the Hubble Space Telescope's High Resolution Camera. It is the first companion to be found around an object in a non-resonant orbit that crosses the…

Spitzer/IRS spectra from 5 to 37 um for a complete sample of 31 R Coronae Borealis stars (RCBs) are presented. These spectra are combined with optical and near-infrared photometry of each RCB at maximum light to compile a spectral energy…

Decades after their discovery, only four hydrogen-deficient carbon (HdC) stars were known to have no circumstellar dust shell. This is in complete contrast to the $\sim$130 known Galactic HdC stars that are notorious for being heavy dust…