New R Coronae Borealis stars discovered in OGLE-III Galactic Bulge fields from their mid- and near- infrared properties

Abstract

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 inside the Galactic Bulge. This unexpected high density can give us more insight into the nature and age of RCB stars. We applied and tested successfully a new technique to find RCB stars based on the particular infrared emission. We demonstrated that RCB stars can now be found without the need of a light curve analysis, and therefore outside optically monitored fields. The selection of RCB candidates was based on their near-infrared excess and on particular mid-infrared emission of RCB shells, using photometric data from the 2MASS and Spitzer/GLIMPSE surveys. The OGLE light curves of all RCB candidates were then inspected visually and the ones presenting large and fast declines were followed-up spectroscopically . We discovered two new R Coronae Borealis stars, but also propose four new candidates. We stress that all of the 7 known RCB stars located in both Spitzer/GLIMPSE and OGLE-III fields were re-discovered, which indicates the high efficiency of our analysis. The proposed new technique to find RCB stars has been successful. It can now be extented to larger area, specially where the instellar extinction is too high to have been monitored by microlensing surveys, i.e the inner part of the Galactic Bulge.

10 pages, 7 figures, Accepted for publication in A&A . V2: Published version - Spectra figure replaced to eliminate previous artefacts due to the reduction process

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Cited by in corpus (11)

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• A plethora of new R Coronae Borealis stars discovered from a dedicated spectroscopic follow-up survey
• The dawn of a new era for dustless HdC stars with GAIA eDR3
• Modeling R Coronae Borealis Stars: Effects of He-Burning Shell Temperature and Metallicity
• Discovery of Bright Galactic R Coronae Borealis and DY Persei Variables: Rare Gems Mined from ACVS
• A Spectral Classification System for Hydrogen-deficient Carbon Stars
• An All-Sky Search For R Coronae Borealis Stars in ASAS-SN
• Mid-Infrared Variations of R Coronae Borealis Stars
• High-resolution optical spectroscopy of the R Coronae Borealis star V532 Ophiuchi at maximum light