Hämatometrokolpos

Deeg, K. H.; Mitsiouli, O.

doi:10.1007/s00112-002-0483-2

Cited by 11 publications

(16 citation statements)

References 15 publications

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“…Indeed, flares have been reported on CM Dra since 1966 (Eggen & Sandage 1967). Other reports of flares can be found in Lacy (1977), Vilhu et al (1989), Kim et al (1997), Deeg et al (1998), Saar & Bookbinder (1998), Nelson & Caton (2007) and Kozhevnikova et al (2009).…”

Section: Observational Properties Of CM Dra: Flaresmentioning

confidence: 94%

“…The flare data allow one to determine the rates at which flares occur in CM Dra: the rates range from a low of 0.011 per hour (in 1995: Deeg et al 1998) to 0.057 per hour (Nelson & Caton 2007). These flaring rates are quite low compared to Population I flare stars with similar luminosity: there, the flare rates can be ≥2 per hour (Kim et al 1997).…”

Section: Observational Properties Of CM Dra: Flaresmentioning

confidence: 99%

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Precision modelling of M dwarf stars: the magnetic components of CM Draconis

MacDonald

Mullan

2012

Monthly Notices of the Royal Astronomical Society

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The eclipsing binary CM Draconis (CM Dra) contains two nearly identical red dwarfs of spectral class dM4.5. The masses and radii of the two components have been reported with unprecedentedly small statistical errors: for M, these errors are 1 part in 260, while for R, the errors reported by Morales et al. are 1 part in 130. When compared with standard stellar models with appropriate mass and age (≈4 Gyr), the empirical results indicate that both components are discrepant from the models in the following sense: the observed stars are larger in R (‘bloated’), by several standard deviations, than the models predict. The observed luminosities are also lower than the models predict. Here, we attempt at first to model the two components of CM Dra in the context of standard (non‐magnetic) stellar models using a systematic array of different assumptions about helium abundances (Y), heavy element abundances (Z), opacities and mixing length parameter (α). We find no 4‐Gyr‐old models with plausible values of these four parameters that fit the observed L and R within the reported statistical error bars. However, CM Dra is known to contain magnetic fields, as evidenced by the occurrence of star‐spots and flares. Here we ask: can inclusion of magnetic effects into stellar evolution models lead to fits of L and R within the error bars? Morales et al. have reported that the presence of polar spots results in a systematic overestimate of R by a few per cent when eclipses are interpreted with a standard code. In a star where spots cover a fraction f of the surface area, we find that the revised R and L for CM Dra A can be fitted within the error bars by varying the parameter α. The latter is often assumed to be reduced by the presence of magnetic fields, although the reduction in α as a function of B is difficult to quantify. An alternative magnetic effect, namely inhibition of the onset of convection, can be readily quantified in terms of a magnetic parameter δ≈B2/4πγpgas (where B is the strength of the local vertical magnetic field). In the context of δ models in which B is not allowed to exceed a ‘ceiling’ of 106 G, we find that the revised R and L can also be fitted, within the error bars, in a finite region of the f–δ plane. The permitted values of δ near the surface leads us to estimate that the vertical field strength on the surface of CM Dra A is about 500 G, in good agreement with independent observational evidence for similar low‐mass stars. Recent results for another binary with parameters close to those of CM Dra suggest that metallicity differences cannot be the dominant explanation for the bloating of the two components of CM Dra.

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Section: Observational Properties Of CM Dra: Flaresmentioning

confidence: 94%

Section: Observational Properties Of CM Dra: Flaresmentioning

confidence: 99%

Precision modelling of M dwarf stars: the magnetic components of CM Draconis

MacDonald

Mullan

2012

Monthly Notices of the Royal Astronomical Society

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“…For a graphical illustration of the effects of limb darkening, see fig. 1 of Deeg et al (1998). Finally, using the Mandel & Agol formalism prevented us from computing accurately the geometrically complex case of the planet partially transiting both stars simultaneously (see Fig.…”

Section: Simulated Data Generationmentioning

confidence: 99%

“…These short‐period binaries are compact enough to allow for a theoretical planet to have a stable orbit outside and around both components (P‐type orbit) – hereafter circumbinary (CB) planet. These objects are relatively unstudied, and the most serious attempt so far to detect CB planets was the TEP project (Deeg et al 1998, 2000, 2008; Doyle et al 2000) which was focused mainly on CM Dra – but none was found.…”

Section: Introductionmentioning

confidence: 99%

An algorithm for photometric identification of transiting circumbinary planets

Ofir

2008

Monthly Notices of the Royal Astronomical Society

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Transiting planets manifest themselves by a periodic dimming of their host star by a fixed amount. On the other hand, light curves of transiting circumbinary (CB) planets are expected to be neither periodic nor to have a single depth while in transit. These propertied make the popular transit‐finding algorithm Box Least Squares (BLS) almost ineffective so a modified version of BLS for the identification of CB planets was developed – CB‐BLS. We show that using this algorithm it is possible to find CB planets in the residuals of light curves of eclipsing binaries that have noise levels of 1 per cent and more – quality that is routinely achieved by current ground‐based transit surveys. Previous searches for CB planets using variation in eclipse times minima of CM Dra and elsewhere are more closely related to radial velocity than to transit searches and so are quite distinct from CB‐BLS. Detecting CB planets is expected to have significant impact on our understanding of exoplanets in general, and exoplanet formation in particular. Using CB‐BLS will allow to easily harness the massive ground‐ and space‐based photometric surveys in operation to look for these hard‐to‐find objects.

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“…Besides the radial velocity and gravitational microlensing techniques, extrasolar planets may also be found and studied by the transit method. After several early pioneering works (Guinan et al 1997; Deeg et al 1998; Doyle et al 2000), this method was first successfully applied to HD 209458b (Charbonneau et al 2000; Henry et al 2000; Mazeh et al 2000), a planet orbiting a nearby star that was discovered by the radial velocity technique. An advantage of the transit technique is that it is readily applicable to planets orbiting both nearby and distant stars.…”

Section: Introductionmentioning

confidence: 99%

Candidate extrasolar planet transits discovered in the Microlensing Observations in Astrophysics-I Galactic bulge data

Abe

Bond

Furuta

et al. 2005

Monthly Notices of the Royal Astronomical Society

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We present the results of a search for candidate planetary transits using the Microlensing Observations in Astrophysics‐I (MOA‐I) microlensing survey data in the Galactic bulge. To achieve sufficient photometric precision, the analysis was confined to a selected subset of stars on selected images. Periodicities of light curves were found with a Box fitting Least Squares (BLS) procedure. This yielded 12 candidates. The derived radii of the candidates ranged from 1.7 to 3.2 RJ, consistent with interpretations in terms of blended binaries, late M dwarfs or strongly irradiated giant planets. Follow‐up spectroscopic observations would be required to identify actual planets amongst the candidates by radial velocity variations. The results confirm that microlensing surveys provide an effective means for finding candidate planetary transits. It is anticipated that the recently commissioned MOA‐II telescope will provide further candidates in the future.

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Hämatometrokolpos

Cited by 11 publications

References 15 publications

Precision modelling of M dwarf stars: the magnetic components of CM Draconis

Precision modelling of M dwarf stars: the magnetic components of CM Draconis

An algorithm for photometric identification of transiting circumbinary planets

Candidate extrasolar planet transits discovered in the Microlensing Observations in Astrophysics-I Galactic bulge data

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