R Coronae Borealis stars in the Galactic Bulge discovered by EROS-2

Abstract

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 discovering also such rare variable stars. One example is the R Coronae Borealis (RCB) stars, a rare type of evolved carbon-rich supergiant. We have conducted a systematic search of the EROS-2 database for the Galactic catalogue Bulge and spiral arms to find Galactic RCB stars. The light curves of $\sim$100 million stars, monitored for 6.7 years (from July 1996 to February 2003), have been analysed to search for the main signature of RCB stars, large and rapid drops in luminosity. Follow-up spectroscopy has been used to confirm the photometric candidates. We have discovered 14 new RCB stars, all in the direction of the Galactic Bulge, bringing the total number of confirmed Galactic RCB stars to about 51. After reddening correction, the colours and absolute magnitudes of at least 9 of the stars are similar to those of Magellanic RCB stars. This suggests that these stars are in fact located in the Galactic Bulge, making them the first RCB stars discovered in the Bulge. The localisation of the 5 remaining RCBs is more uncertain: 4 are either located behind the Bulge at an estimated maximum distance of 14 kpc or have an unusual thick circumstellar shell; the other is a DY Per RCB which may be located in the Bulge, even if it is fainter than the known Magellanic DY Per. From the small scale height found using the 9 new Bulge RCBs, $61<h_{Bulge}^{RCB}<246$ pc (95% C.L.), we conclude that the RCB stars follow a disk-like distribution inside the Bulge.

arXiv comment20 pages, 26 figures, Accepted in A&A

References in corpus (21)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Limits on the Macho Content of the Galactic Halo from the EROS-2 Survey of the Magellanic Clouds
• SINFONI in the Galactic Center: young stars and IR flares in the central light month
• The Magellanic Clouds Photometric Survey: The Small Magellanic Cloud Stellar Catalog and Extinction Map
• New Period-Luminosity and Period-Color Relations of Classical Cepheids: I. Cepheids in the Galaxy
• Measuring Galactic Extinction: A Test
• Very Large Excesses of 18O in Hydrogen-Deficient Carbon and R Coronae Borealis Stars: Evidence for White Dwarf Mergers
• Extinction Map of the Galactic center: OGLE-II Galactic bulge fields
• Galactic Bulge Microlensing Optical Depth from EROS-2
• Extinction within 10 degrees of the Galactic Centre using 2MASS
• The MACHO Project LMC Variable Star Inventory: X. The R Coronae Borealis Stars
• V605 Aql: The Older Twin of Sakurai's Object
• New constraints on SN Ia progenitor models
• Something about the structure of the Galaxy
• Observation of Microlensing towards the Galactic Spiral Arms. EROS II 3 year survey
• R CrB Candidates in the Small Magellanic Cloud: Observations of Cold, Featureless Dust with the Spitzer Infrared Spectrograph
• Discovery of Five New R Coronae Borealis Stars in the MACHO Galactic Bulge Database
• EROS 2 photometry of probable R Coronae Borealis stars in the Small Magellanic Cloud
• First detection of dust clouds around R CrB variable stars
• A snapshot of the inner dusty regions of a RCrB-type variable
• The Newly Active R Coronae Borealis Star, V2552 Oph

Cited by in corpus (23)

• Post-merger evolution of carbon-oxygen + helium white dwarf binaries and the origin of R Coronae Borealis and extreme helium stars
• The optically bright post-AGB population of the LMC
• New Magellanic Cloud R Coronae Borealis and DY Per type stars from the EROS-2 database: the connection between RCBs, DYPers and ordinary carbon stars
• The ongoing pursuit of R Coronae Borealis stars: ASAS-3 survey strikes again
• Reproducing the observed abundances in RCB and HdC stars with post-double degenerate merger models - constraints on merger and post-merger simulations and physics processes
• Tracking down R Coronae Borealis stars from their mid-infrared WISE colours
• A plethora of new R Coronae Borealis stars discovered from a dedicated spectroscopic follow-up survey
• The influence of binarity on dust obscuration events in the planetary nebula M 2-29 and its analogues
• The dawn of a new era for dustless HdC stars with GAIA eDR3
• Discovery of Bright Galactic R Coronae Borealis and DY Persei Variables: Rare Gems Mined from ACVS
• Searching transients in large-scale surveys. A method based on the Abbe value
• New R Coronae Borealis stars discovered in OGLE-III Galactic Bulge fields from their mid- and near- infrared properties
• Census of R Coronae Borealis stars I: Infrared light curves from Palomar Gattini IR
• A Spectral Classification System for Hydrogen-deficient Carbon Stars
• An All-Sky Search For R Coronae Borealis Stars in ASAS-SN
• Abundance analyses of the new R Coronae Borealis stars: ASAS-RCB-8 and ASAS-RCB-10
• Are DY\,Persei stars cooler cousins of R Coronae Borealis stars?
• Do Hydrogen-deficient Carbon Stars have Winds?
• HE 1015-2050: Discovery of a Hydrogen-deficient carbon star at high galactic latitude
• NSV 11154 Is a New R Coronae Borealis Star
• High-resolution optical spectroscopy of the R Coronae Borealis star V532 Ophiuchi at maximum light
• RR Lyrae stars with variable mean magnitudes
• EROS light curve data base