Evolution of low-mass star and brown dwarf eclipsing binaries

By G. Chabrier, J. Gallardo, Isabelle Baraffe. 2007

305 citations recorded by the source corpus.

Context. We examine the evolution of low-mass star and brown dwarf eclipsing binaries. These objects are rapid rotators and are believed to shelter large magnetic fields. Aims. We suggest that reduced convective efficiency, due to fast rotation and large field strengths, and/or to magnetic spot coverage of the radiating surface significantly affect their evolution, leading to a reduced heat flux and thus larger radii and cooler effective temperatures than for regular objects. Methods. We have considered such processes in our evolutionary calculations, using a phenomenological approach. Results. This yields mass–radius and effective temperature–radius relationships in agreement with the observations. We also reproduce the effective temperature ratio and the radii of the two components of the recently discovered puzzling eclipsing brown dwarf system. Conclusions. These calculations show that fast rotation and/or magnetic activity may significantly affect the evolution of eclipsing binaries and that the mechanical and thermal properties of these objects depart from the ones of non-active low-mass objects. We find that, for internal field strengths compatible with the observed surface value of a few kiloGauss, convection can be severely inhibited.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/d2aadb98720bff714021066e9e8fea3e0c114481

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In Astronomy and Astrophysics

1. Timothy Morton
2. D. Charbonneau
3. J. Johnson
4. A. Mann
5. E. Gaidos
6. A. Kraus
7. L. Hillenbrand
8. K. Luhman

Citations in the corpus

• PLANET HUNTERS: A TRANSITING CIRCUMBINARY PLANET IN A QUADRUPLE STAR SYSTEM (2012, background): “This enhances their activity, which is usually manifested by modulations in the light curve produced by spots, X-ray emission, and other phenomena, and leads to the observed effects (e.g., Mullan & MacDonald 2001; Chabrier et al. 2007).”
• AN EMPIRICAL CALIBRATION TO ESTIMATE COOL DWARF FUNDAMENTAL PARAMETERS FROM H-BAND SPECTRA (2014, background): “This was first noted for binary stars (e.g. Popper 1997; Torres & Ribas 2002; Berger et al. 2006; Lopez Morales 2007; Chabrier et al. 2007), but has been demonstrated in stars with interferometric radii measurements (e.g. Berger et al. 2006; Boyajian et al. 2012).”
• EPISODIC ACCRETION AT EARLY STAGES OF EVOLUTION OF LOW-MASS STARS AND BROWN DWARFS: A SOLUTION FOR THE OBSERVED LUMINOSITY SPREAD IN H–R DIAGRAMS? (2009, background): “Another explanation, as discussed in Chabrier et al. (2007), is that fast rotation and/or the presence of a magnetic field yields a smaller heat flux output, thus (i) a larger radius and (ii) a cooler Teff , while barely affecting the luminosity, for a given mass.”
• THE EVOLUTION OF CATACLYSMIC VARIABLES AS REVEALED BY THEIR DONOR STARS (2011, background): “Chabrier et al. (2007) explored both of these possibilities, with findings that may be relevant to CV donors (cf. L08).”
• THE MASS–RADIUS(–ROTATION?) RELATION FOR LOW-MASS STARS (2010, background): “These radii are a crucial component in testing stellar models because small changes in opacities and convective efficiencies can significantly change the interior structure, leading to significance changes in the expected radius at a given mass (e.g. Chabrier et al. 2007).”
• New Models of Jupiter in the Context of Juno and Galileo (2019, methodology): “This ”mixed” (Chabrier et al./MH13) pure hydrogen EOS is then combined with the new pure helium one (Chabrier et al. (2018), Soubiran et al. (in prep)) to obtain a complete EOS for the H/He mixture at any given helium mass fraction Y . Figure 1 displays the relative error on the density between our ”
• Large-scale magnetic topologies of late M dwarfs⋆ (2008, background): “Chabrier et al. (2007) proposed in a phenomenological approach that a strong magnetic field may inhibit convection and produce the observed trends.”
• A PHOTOMETRIC VARIABILITY SURVEY OF FIELD K AND M DWARF STARS WITH HATNet (2009, unknown): “(Ribas 2006; Torres et al. 2006; López-Morales 2007; Chabrier et al. 2007).”
• Detection of carbon monoxide in the high-resolution day-side spectrum of the exoplanet HD 189733b (2013, background): “Strong magnetic fields in the short-period low-mass DLEBs are thought to be responsible for the radius inflation (see e.g. Chabrier et al. 2007; Morales et al. 2010).”
• THE NIRSPEC ULTRACOOL DWARF RADIAL VELOCITY SURVEY (2010, background): “%) discrepancies between models and mass and radius measurements of low-mass stars in eclipsing binary systems (Chabrier et al. 2007).”
• Large-scale magnetic topologies of early M dwarfs (2008, background): “Effects of rotation and magnetic fields on the stellar structure and on the evolution (e.g., Chabrier et al. 2007, not taken into account in existing studies) are however likely to affect model predictions significantly.”
• A new vision of giant planet interiors: Impact of double diffusive convection (2012, background): “At last, rapid rotation and/or strong magnetic fields, necessarily present in Jupiter and Saturn interiors, are known to hamper large-scale convection (Chabrier et al. 2007), possibly leading to imperfect mixing of heavy elements in part of the envelope.”
• HOW TO CONSTRAIN YOUR M DWARF: MEASURING EFFECTIVE TEMPERATURE, BOLOMETRIC LUMINOSITY, MASS, AND RADIUS (2015, result): “…results, with some studies suggesting magnetic fields are adequate to reconcile models and observations (e.g., MacDonald & Mullan 2012; Feiden & Chaboyer 2013; Torres et al. 2014), while others question the validity of the magnetic hypothesis (e.g., Chabrier et al. 2007; Feiden & Chaboyer 2014a).”
• CHARACTERIZING THE COOL KOIs. III. KOI 961: A SMALL STAR WITH LARGE PROPER MOTION AND THREE SMALL PLANETS (2012, result): “…been suggested that mutual magnetic interactions in short-period M dwarf binaries introduce discrepancies in the mass-radius-effective temperature relationships as compared to single field M dwarfs (Chabrier et al. 2007), and recent observational evidence supports this scenario (Kraus et al. 2011).”
• The relation between the most-massive star and its parental star cluster mass (2009, background): “Very young low-mass PMS stars and brown dwarfs are still difficult to model because they are dominated by the unknown accretion history, and magnetic fields and fast rotation have a strong influence (Chabrier et al. 2007; Ribas et al. 2008).”