Related papers: Mid-Infrared Variations of R Coronae Borealis Star…

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…

R Coronae Borealis variable stars are suspected to sporadically eject optically thick dust clouds causing, when one of them lies on the line-of-sight, a huge brightness decline in visible light. Mid-infrared interferometric observations of…

We present optical and infrared imaging and spectroscopy of the R Coronae Borealis-type (R Cor Bor) star IRAS 00450+7401. Optical spectra further confirm its classification as a cool R Cor Bor system, having a hydrogen-deficient carbon star…

The study of extended, cold dust envelopes surrounding R Coronae Borealis (RCB) stars began with their discovery by IRAS. RCB stars are carbon-rich supergiants characterized by their extreme hydrogen deficiency and for their irregular and…

We present mid-infrared spectra of T Tauri stars in the Taurus star-forming region obtained with the Spitzer Infrared Spectrograph (IRS). For the first time, the 5-36 micron spectra of a large sample of T Tauri stars belonging to the same…

R Coronae Borealis stars (RCBs) are the best candidates to be the products of white dwarf mergers in the intermediate mass range ($0.4<M_{tot}<1.1$ M$_{\odot}$). After a merger, a He envelope surrounds a CO core, and a short-lived…

We present recent polarimetric images of the highly variable star R CrB using ExPo and archival WFPC2 images from the HST. We observed R CrB during its current dramatic minimum where it decreased more than 9 mag due to the formation of an…

Dust emission is an important tool in studies of star-forming clouds, as a tracer of column density and indirectly via the dust evolution that is connected to the history and physical conditions of the clouds. We examine radiative transfer…

We obtained 13 epochs of mid-infrared interferometry with the MIDI instrument at the VLTI between April 2004 and July 2007, covering pulsation phases 0.45-0.85 within four cycles. The data are modeled with a radiative transfer model of the…

The R Coronae Borealis (RCB) variables are rare, hydrogen-deficient, carbon-rich supergiants known for large, erratic declines in brightness due to dust formation. Recently, the number of known RCB stars in the Milky Way and Magellanic…

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 present the results of UBVJHKLM photometry of R CrB spanning the period from 1976 to 2001. Studies of the optical light curve have shown no evidence of any stable harmonics in the variations of the stellar emission. In the L band we…

Interstellar dust grains are responsible for modifying the spectral energy distribution (SED) of galaxies, both absorbing starlight at UV and optical wavelengths and converting this energy into thermal emission in the infrared. The detailed…

Residual Spitzer/IRS spectra for a sample of 31 R Coronae Borealis (RCB) stars are presented and discussed in terms of narrow emission features superimposed on the quasi-blackbody continuous infrared emission. A broad ~6-10 um dust emission…

From VLT/NACO diffraction-limited images of RY~Sgr, we report the first direct detection of heterogeneities in the circumstellar envelope of a R Coronae Borealis variable star. Several bright and very large dust clouds are seen in various…

Mid-infrared arcs of dust emission are often seen near ionizing stars within HII regions. A possible explanations for these arcs is that they could show the outer edges of asymmetric stellar wind bubbles. We use two-dimensional,…

R Coronae Borealis stars (RCBs) are hydrogen-deficient and carbon-rich supergiant stars. They are very rare, as only $\sim50$ are actually known in our Galaxy. Interestingly, RCBs are strongly suspected to be the evolved merger product of…

Spectral energy distribution (SED) in protostellar disks is determined by the disks'internal dissipation and reprocessing of irradiation from their host stars. Around T Tauri stars, most mid-infrared (MIR) radiation (in a few to a few ten…

This paper presents the initial results of a multi-site photometric programme to examine the extraordinary behaviour displayed by 18 R Coronae Borealis (RCB) stars in the Magellanic Clouds (MCs). RCB stars exhibit a unique variability…

We present results from a systematic infrared (IR) census of R Coronae Borealis (RCB) stars in the Milky Way, using data from the Palomar Gattini IR (PGIR) survey. R Coronae Borealis stars are dusty, erratic variable stars presumably formed…