Related papers: The carbon star DY Persei may be a cool R Coronae …

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…

Rare types of variable star may give unique insight into short-lived stages of stellar evolution. The systematic monitoring of millions of stars and advanced light curve analysis techniques of microlensing surveys make them ideal for…

We have observed P-Cygni and asymmetric, blue-shifted absorption profiles in the He I 10830 lines of twelve R Coronae Borealis (RCB) stars over short (1 month) and long (3 year) timescales to look for variations linked to their…

We report the discovery of 19 new R Coronae Borealis (RCB) star and DY Per candidates with light curves from the All-Sky Automated Survey for Supernovae (ASAS-SN). We examined both an existing set of 1602 near/mid-IR selected candidates and…

Atmospheric parameters for hot DB (helium atmosphere) white dwarfs near effective temperatures of 25000K are extremely difficult to determine from optical spectroscopy. This is particularly unfortunate, because this is the range of variable…

We report the most comprehensive UBV(RI)_C observations of the bright, radially pulsating field stars SW And, DH Peg, CU Com, DY Peg. Long term variation has been found in the ultraviolet colour curves of SW And and DH Peg. We apply our…

EROS 2 (Experience de Recherche d'Objets Sombres) conducted a survey of the SMC between July 1996 and February 2003 in two EROS broad-band colours, V_E and R_E. The photometric data of 4.2 million stars have been searched for behaviour…

We analyze H-alpha observations of the recurrent nova T CrB obtained during the last decade. For the first time the H-alpha emission profile is analyzed after subtraction of the red giant contribution. Based on our new radial velocity…

NSV 11154 has been confirmed as a new member of the rare hydrogen deficient R Coronae Borealis (RCB) stars based on new photometric and spectroscopic data. Using new photometry, as well as archival plates from the Harvard archive, we have…

The set of orbital elements available for chemically-peculiar red giant (PRG) stars has been considerably enlarged thanks to a decade-long CORAVEL radial-velocity monitoring of about 70 barium stars and 50 S stars. This paper presents a…

Upon its release the Gaia DR3 catalogue has led to tremendous progress in multiple fields of astronomy by providing the complete astrometric solution for nearly 1.5 billion sources. We analysed the photometric and astrometric results for…

We present H- and K-band spectra for late-type Kepler Objects of Interest (the "Cool KOIs"): low-mass stars with transiting-planet candidates discovered by NASA's Kepler Mission that are listed on the NASA Exoplanet Archive. We acquired…

A ROSAT survey of the Alpha Per open cluster in 1993 detected its brightest star, mid-F supergiant Alpha Persei: the X-ray luminosity and spectral hardness were similar to coronally active late-type dwarf members. Later, in 2010, a Hubble…

Mid-infrared photometry of R Coronae Borealis stars obtained from various satellites from IRAS to WISE has been utilized in studying the variations of the circumstellar dust's contributions to the spectral energy distribution of these…

Measurements of [C/Fe], [Ca/H], and [Fe/H] have been derived from Keck I LRISb spectra of 35 giants in the Draco dwarf spheroidal galaxy. The iron abundances are derived by a spectrum synthesis modeling of the wavelength region from 4850 to…

A radial-velocity monitoring of the Carbon-Enhanced Metal-Poor (CEMP) star HE 0017+0055 over 8 years with the Nordic Optical Telescope and Mercator telescopes reveals variability with a period of 384 d and amplitude of 540$\pm27$ m…

During a search for previously unknown Galactic emission nebulae, we discovered a faint 36' diameter Halpha emission nebula centered around the periodic variable YY Hya. Although this star has been classified as RR-Lyr variable, such a…

Taking advantage of the Gaia Data Release 2, recent studies have revisited the evolution of carbon-polluted white dwarfs (DQs) across a large range of effective temperatures. These analyses have clearly confirmed the existence of two…

Carbon stars (with C/O> 1) were long assumed to all be giants, because only AGB stars dredge up significant carbon into their atmospheres. The case is nearly iron-clad now that the formerly mysterious dwarf carbon (dC) stars are actually…

Orbital decay by gravitational-wave radiation will cause some close-binary white dwarfs (WDs) to merge within a Hubble time. The results from previous hydrodynamical WD-merger simulations have been used to guide calculations of the…