Related papers: R Coronae Borealis Stars at Minimum Light -- UW Ce…
Surface abundances of 14 (11 majority class and 3 minority class) R Coronae Borealis stars (RCBs) along with the final flash object, V4334 Sgr (Sakurai's object) are revised based on their carbon abundances measured from the observed C2…
In this paper we present for the first time, the study of low resolution $H$- and $K$- band spectra of 7 DY\,Per type and suspects stars as well as DY\,Persei itself. We also observed $H$- and $K$- band spectra of 3 R Coronae Borealis (RCB)…
RW Aurigae is a young stellar system containing a classical T Tauri star as the primary component. It shows deep, irregular dimmings, first detected in 2010. At the University Observatory Jena, we carried out optical follow-up observations.…
Some of the observational aspects related to the evolutionary status and dust production in R Cor Bor stars are discussed. Recent work regarding the surface abundances, stellar winds and evidence for dust production in these high luminosty…
The R Coronae Borealis (RCB) stars are extremely hydrogen-deficient carbon stars which produce large amounts of dust, causing sudden deep declines in brightness. They are believed to be formed primarily through white dwarf mergers. In this…
V348 Sgr is simultaneously an active hot R Coronae Borealis (RCB) variable, a peculiar extreme helium star, and the hydrogen-deficient central star of a planetary nebula. Explaining the RCB-type variability has been difficult since the star…
It is increasingly suspected that the rare R Coronae Borealis (RCB) stars - hydrogen-deficient and carbon-rich supergiant stars - are the products of mergers of CO/He white-dwarf binary systems in the intermediate mass regime…
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…
We report the discovery of R Coronae Borealis (RCB) stars in the Andromeda galaxy (M31) using the Palomar Transient Factory (PTF). RCB stars are rare hydrogen-deficient, carbon-rich supergiant variables, most likely the merger products of…
The remarkable hot R Coronae Borealis star DY Cen is revealed to be the first and only binary system to be found among the R Coronae Borealis (RCB) stars and their likely relatives, including the Extreme Helium stars and the…
We present high resolution spectra of the five known hydrogen-deficient carbon (HdC) stars in the vicinity of the 10830 Angstrom line of neutral helium. In R Coronae Borealis (RCB) stars the He I line is known to be strong and broad, often…
Since its discovery in 1990, UW CrB (also known as MS1603+2600) has remained a peculiar source without firm classification. Our current understanding is that it is an Accretion Disc Corona (ADC) low mass X-ray binary. In this paper we…
Abundance analyses of the two newly discovered R Coronae Borealis (RCB) stars ASAS-RCB-8 and ASAS-RCB-10 were conducted using high-resolution optical spectra and model atmospheres. Their chemical compositions place the pair among the…
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…
R Coronae Borealis (RCB) stars are rare hydrogen-deficient carbon-rich variable supergiants thought to be the result of dynamically unstable white dwarf mergers. We attempt to model RCBs through all the relevant timescales by simulating a…
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…
We present the first speckle interferometric observations of R CrB, the prototype of a class of peculiar stars which undergo irregular declines in their visible light curves. The observations were carried out with the 6m telescope at the…
The globular cluster X-ray source CXO J033831.8-352604 in NGC 1399 has recently been found to show strong emission lines of [O III] and [N II] in its optical spectrum in addition to ultraluminous X-ray emission with a soft X-ray spectrum.…
UX Orionis stars are the most active young stars; they undergo sporadic fadings of 2 - 4 magnitudes in the V-band, due to variable circumstellar extinction caused by a nearly edge-on star-disc system. The long-lasting monitoring of a number…
The current $super-active$ state of the recurrent nova T CrB has been observed with unprecedented detail. Previously published observations provide strong evidence that this state is due to an enhancement of the flow of material through the…