The MACHO Project LMC Variable Star Inventory. X. The R Coronae Borealis Stars

Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Clayton, Geoffrey C.; Cook, K. H.; Dalal, Neal; Drake, A. J.; Freeman, K. C.; Geha, Marla; Gordon, K. D.; Griest, K.; Kilkenny, D.; Lehner, M. J.; Marshall, Stuart; Minniti, D.; Misselt, K. A.; Nelson, C A; Peterson, B. A.; Popowski, Piotr; Pratt, M. R.; Quinn, Peter J.; Stubbs, C. W.; Sutherland, William J.; Tomaney, A.; Vandehei, T.; Welch, D. L.

doi:10.1086/321369

Cited by 85 publications

(178 citation statements)

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“…They were all obtained in 2008; individual epochs are listed in Table 2. Alcock et al 2001 and 5 in the SMC 2 , Tisserand et al 2004) as well as 5 RCB candidates selected either from their optical spectra (Morgan et al 2003) 3 or their mid-infrared featureless spectra (Kraemer et al 2005;Buchanan et al 2006). The EROS-2 light curves of all these objects, if catalogued, are available at the following URL: http://eros.in2p3.fr/ Variables/RCB/RCB-LMC.html…”

Section: Observational Datamentioning

confidence: 99%

“…We catalogued and obtained photometric time-series for 16 of the 17 confirmed LMC RCB and DYPer stars presented by Alcock et al (2001); only HV 12842, located in the extreme north part of the LMC (outside our fields) is missing. Large declines are observed during the 6.7 years of our monitoring in 11 cases.…”

Section: Previously Known Rcb Starsmentioning

confidence: 99%

“…A detailed review of their characteristics has been written by Clayton (1996). RCB stars are also rare: only 51 have been discovered in our Galaxy (Tisserand et al 2008, and references therein), including 9 that are likely located inside the Galactic Bulge, 17 in the Large Magellanic Cloud (Alcock et al 2001), and 5 in the Small Magellanic Cloud (Tisserand et al 2004). This rarity suggests that RCBs may correspond to a brief phase of stellar evolution or an uncommon evolutionary path.…”

Section: Introductionmentioning

confidence: 99%

“…The MACHO and EROS-2 collaborations have thus discovered half of the known sample of RCB stars (Alcock et al 2001;Tisserand et al 2004;Zaniewski et al 2005;Tisserand et al 2008). Note also that the OGLE-3 collaboration presents a useful real-time monitoring of known RCBs on their web site (Udalski 2008).…”

Section: Introductionmentioning

confidence: 99%

“…Only 8 examples are currently known: 4 in the LMC (Alcock et al 2001), 2 in the SMC (Tisserand et al 2004), and 2 others in our Galaxy (Tisserand et al 2008), including the prototype DY Persei (Alksnis & Jumike 1990). They are recognised among typical RCB stars by their slower declines in brightness and symmetric recoveries.…”

Section: Introductionmentioning

confidence: 99%

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New Magellanic Cloud R Coronae Borealis and DY Persei type stars from the EROS-2 database: the connection between RCBs, DYPers, and ordinary carbon stars

Tisserand

Wood²,

Marquette

et al. 2009

A&A

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Context. R Coronae Borealis stars (RCB) are a rare type of evolved carbon-rich supergiant stars that are increasingly thought to result from the merger of two white dwarfs, called the Double degenerate scenario. This scenario is also studied as a source, at higher mass, of type Ia Supernovae (SnIa) explosions. Therefore a better understanding of RCBs composition would help to constrain simulations of such events. Aims. We searched for and studied RCB stars in the EROS Magellanic Clouds database. We also extended our research to DY Per type stars (DYPers) that are expected to be cooler RCBs (T ∼ 3500 K) and much more numerous than their hotter counterparts. With the aim of studying possible evolutionary connections between RCBs and DYPers, and also ordinary carbon stars, we compared their publically available broad band photometry in the optical, near, and mid-infrared. Methods. The light curves of ∼70 millions stars, monitored for 6.7 years (from July 1996 to February 2003), have been analysed to search for the main signature of RCBs and DYPers: a large (up to 9 mag) drop in luminosity. Carbon stars with fading episodes were also found by inspecting numerous light curves of objects that presented an infrared excess in the 2MASS and Spitzer-SAGE and S 3 MC databases. Follow-up optical spectroscopy was used to confirm each photometric candidate found. Results. We have discovered and confirmed 6 new Magellanic Cloud RCB stars and 7 new DYPers, but also listed new candidates: 3 RCBs and 14 DYPers. Optical and infrared colour magnitude diagrams that give new insights into these two sets of stars are discussed. We estimated a range of Magellanic RCB shell temperatures between 360 and 600 K. Conclusions. We confirm the wide range of absolute luminosity known for RCB stars, M V ∼ −5.2 to -2.6. Our study further shows that mid-infrared surveys are ideal to search for RCB stars, since they have thinner and cooler circumstellar shells than classical post-AGB stars. In addition, by increasing the number of known DYPers by ∼400%, we have been able to shed light on the similarities in the spectral energy distribution between DYPers and ordinary carbon stars. We also observed that DYPer circumstellar shells are fainter and hotter than those of RCBs. This suggests that DYPers may simply be ordinary carbon stars with ejection events, but more abundance analysis is necessary to give a status on a possible evolutionnary connexion between RCBs and DYPers.Key words. stars: AGB and post-AGB -stars: carbon -supergiants -Magellanic Clouds Based on observations made with the CNRS/INSU MARLY telescope at the European Southern Observatory, La Silla, Chile.Figures 7-13 are only available in electronic form at

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