What Is the Shell Around R Coronae Borealis?

Montiel, Edward; Clayton, Geoffrey C.; Marcello, Dominic; Lockman, Felix J.

doi:10.1088/0004-6256/150/1/14

Cited by 14 publications

(12 citation statements)

References 56 publications

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“…Mass loss plays an important role in R CrB evolution. Dusty shells, with dust masses up to 10 −3 M , exist in the surroundings of R CrB stars and are interpreted to have formed during the R CrB phase (Montiel et al 2015(Montiel et al , 2018. The terminal velocities of R CrB star winds are v ∞ ≈ 300 km s −1 (Clayton et al 2003(Clayton et al , 2013.…”

Section: Effects Of Mass Lossmentioning

confidence: 99%

Evolutionary Models for R Coronae Borealis Stars

Schwab

2019

ApJ

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We use Modules for Experiments in Stellar Astrophysics (MESA) to construct stellar evolution models that reach a hydrogen-deficient, carbon-rich giant phase like the R Coronae Borealis (R CrB) stars. These models use opacities from OPAL and AESOPUS that cover the conditions in the cool, H-deficient, CNO-enhanced envelopes of these stars. We compare models that begin from homogeneous He stars with models constructed to reproduce the remnant structure shortly after the merger of a He and a CO white dwarf (WD). We emphasize that models originating from merger scenarios have a thermal reconfiguration phase that can last up to ≈ 1 kyr post merger, suggesting some galactic objects should be in this phase. We illustrate the important role of mass loss in setting the lifetimes of the R CrB stars. Using AGB-like mass loss prescriptions, models with CO WD primaries 0.7 M typically leave the R CrB phase with total masses ≈ 0.6 − 0.7 M , roughly independent of their total mass immediately post-merger. This implies that the descendants of the R CrB stars may have a relatively narrow range in mass and luminosity as extreme He stars and a relatively narrow range in mass as single WDs.

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Section: Effects Of Mass Lossmentioning

confidence: 99%

Evolutionary Models for R Coronae Borealis Stars

Schwab

2019

ApJ

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“…The AMR simulations presented here use 8 levels of refinement. These simulations were also presented in Montiel et al (2015) in order to study mass loss from WD mergers.…”

Section: Amr Codementioning

confidence: 99%

The Role of Dredge-up in Double White Dwarf Mergers

Staff¹,

Wiggins²,

Marcello³

et al. 2018

ApJ

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“…These brightness variations are due to clouds of carbon dust ejected by the stars along the line of sight that obscure the photosphere. In doing so continuously, amorphous carbon dust grains (García-Hernández et al 2011) build up around the stars and circumstellar dust shells form (Tisserand 2012;Montiel et al 2015). Five members of the HdC stars formed a small subclass for decades as Send offprint requests to: Patrick Tisserand; e-mail: tisserand@iap.fr…”

Section: Introductionmentioning

confidence: 99%

The dawn of a new era for dustless HdC stars withGaiaeDR3

Tisserand

Crawford

Clayton

et al. 2022

A&A

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Context. Decades after their discovery, only four hydrogen-deficient carbon (HdC) stars were known to have no circumstellar dust shell. This is in complete contrast to the ∼130 known Galactic HdC stars that are notorious for being heavy dust producers, i.e. the R Coronae Borealis (RCB) stars. Together they form a rare class of supergiant stars that are thought to originate from the merger of CO/He white dwarf (WD) binary systems, otherwise known as the double degenerate scenario. Aims. We searched for new dustless HdC (dLHdC) stars to understand their Galactic distribution, to estimate their total number in the Milky Way and to study their evolutionary link with RCB stars and extreme Helium stars, the final phase of HdC stars. Methods. We used primarily the 2MASS and GAIA eDR3 all-sky catalogues to select candidates that were then followed up spectroscopically. We studied the distribution of known and newly discovered stars in the HR diagram. Results. We discovered 27 new dLHdC stars, one new RCB star, and two new EHe stars. Surprisingly, 20 of the new dLHdC stars share a characteristic of the known dLHdC star HD 148839, having lower atmospheric hydrogen deficiencies. The uncovered population of dLHdC stars exhibit a Bulge-like distribution, like the RCB stars, but show multiple differences from those that indicate they are a different population of HdC stars following its own evolutionary sequence with a fainter luminosity and also a narrow range of effective temperatures, between 5000 and 8000 K. Not all the new dLHdC stars belong to that new population, as we found indication of a current low dust production activity around four of them: the warm F75, F152, C526 and the cold A166. Those could in fact be typical RCB stars passing through a transition time, going in or out of the RCB phase. Conclusions. For the first time we have evidence of a large range of absolute magnitude in the overall population of HdC stars, spanning more than 3 mag. In the favoured formation framework, this is explained by a large range in the initial total WD binary mass which leads to a series of evolutionary sequences with distinct maximum brightness and initial temperature. The cold Galactic RCB stars are also noticeably fainter than the Magellanic ones, possibly due to a difference in metallicity between the original population of stars resulting in different WD mass ratio. The unveiled population of dLHdC stars indicates that the ability to create dust could be linked to the initial total mass. In our Galaxy, there could be as many dLHdC stars as RCB stars.

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What Is the Shell Around R Coronae Borealis?

Cited by 14 publications

References 56 publications

Evolutionary Models for R Coronae Borealis Stars

Evolutionary Models for R Coronae Borealis Stars

The Role of Dredge-up in Double White Dwarf Mergers

The dawn of a new era for dustless HdC stars withGaiaeDR3

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