The Spotted Flare Stars BY Dra and CC Eri: A model for the spots and some Astrophysical Implications

Bopp, B. W.; Evans, David S.

doi:10.1093/mnras/164.4.343

Cited by 89 publications

(46 citation statements)

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“…Both stars in the YY Gem system are of nearly equal spectral type, dM1e, in a synchronous orbit with a period of 0.81 d. YY Gem was the first late-type star on which periodic photometric variability was detected (Kron 1952). Bopp & Evans (1973) have explained similar brightness variations on the flare star BY Dra by rotation of star spots, and stars displaying this phenomenon are since then termed BY Dra variables. Doppler images of YY Gem have revealed spots at mid-latitudes on both stars (Hatzes 1995).…”

Section: Introductionmentioning

confidence: 99%

Simultaneous X-ray spectroscopy of YY Gem withChandraandXMM-Newton

Stelzer

Burwitz

Audard

et al. 2002

A&A

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Abstract.We report on a detailed study of the X-ray spectrum of the nearby eclipsing spectroscopic binary YY Gem. Observations were obtained simultaneously with both large X-ray observatories, XMM-Newton and Chandra. We compare the high-resolution spectra acquired with the Reflection Grating Spectrometer onboard XMM-Newton and with the Low Energy Transmission Grating Spectrometer onboard Chandra, and evidence in direct comparison the good performance of both instruments in terms of wavelength and flux calibration. The strongest lines in the X-ray spectrum of YY Gem are from oxygen. Oxygen line ratios indicate the presence of a low-temperature component (1−4 MK) with density n e ≤ 2 × 10 10 cm −3 . The X-ray lightcurve reveals two flares and a dip corresponding to the secondary eclipse. An increase of the density during phases of high activity is suggested from time-resolved spectroscopy. Time-resolved global fitting of the European Photon Imaging Camera CCD spectrum traces the evolution of temperature and emission measure during the flares. These medium-resolution spectra show that temperatures >10 7 K are relevant in the corona of YY Gem although not as dominant as the lower temperatures represented by the strongest lines in the high-resolution spectrum. Magnetic loops with length on the order of 10 9 cm, i.e., about 5% of the radius of each star, are inferred from a comparison with a one-dimensional hydrodynamic model. This suggests that the flares did not erupt in the (presumably more extended) inter-binary magnetosphere but are related to one of the components of the binary.

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Section: Introductionmentioning

confidence: 99%

Simultaneous X-ray spectroscopy of YY Gem withChandraandXMM-Newton

Stelzer

Burwitz

Audard

et al. 2002

A&A

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“…Such stars were then named 'BY Dra stars' by Kunkel (1975). Based on some rigorous arguments obtained from observations, the variability seen in BY Dra type stars was confirmed in terms of dark regions on the surface of the stars in later works such as those of Bopp & Evans (1973), Torres & Ferraz Mello (1973), Friedemann & Gürtler (1975), Vogt (1975), and Bopp & Fekel (1977). RS Cvn type stars exhibit the same variability as BY Dra stars.…”

Section: Introductionmentioning

confidence: 81%

High-Level Magnetic Activity on a Low-Mass Close Binary: GSC 02038-0293

Dal

Sipahi

Özdarcan

2012

Publ. – Astron. Soc. Aust

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Taking into account results obtained from light-curve analysis and out-of-eclipse analyses, we discuss the nature of GSC 02038-00293 and also its magnetic activity behaviour. We obtained light curves of the system during observing seasons 2007, 2008 and 2011. We obtained its secondary minimum clearly in I-band observations in 2008 for the first time. Analysing this light curve, we found the physical parameters of the components. The light-curve analysis indicates that the possible mass ratio of the system is 0.35. We obtained the remaining V-band light curves, extracting the eclipses. We modelled these remaining curves using the SPOTMODEL program and found possible spot configurations of the magnetically active component for each observing season. The models demonstrated that there are two active longitudes for the active component. The models reveal that both active longitudes migrate in the direction of decreasing longitude. We also examined the light curves in out-of-eclipse phases with respect to minimum and maximum brightness, amplitude, etc. The amplitude of the curves during out-of-eclipse phases varies in a sinusoidal way with a period of ,8.9 yr; the mean brightness of the system is dramatically decreasing. The phases of the deeper minimum during out-of-eclipse periods exhibit a migration toward decreasing phase.

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“…This could imply the appearance of some type of activity center, though the data are too sparse to be very conclusive. Bopp and Evans (1973) have indicated the applicability of the "spot" model to BY Dra in detail based upon previous observations, and there seems to be little doubt that one can account for most of the known behavior of this star by the "spot" model, if some modifications are made.…”

Section: By Draconis (Hd 234677)mentioning

confidence: 96%

Observations of the red-dwarf emission-line objects LP101-15, BY Draconis, GT Pegasi, and FF Andromedae

Martins¹

1975

PASP

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Photoelectric UBVRI photometry of LP101-15, BY Dra, GT Peg, and FF And is presented, and implications with respect to the "center of activity" model are discussed. Apparently the most physically acceptable model to date, facular-like areas and flare activity are included in an attempt to explain all aspects of the behavior of this class of stars. Data for BY Dra and GT Peg are inconclusive at this time, but FF And can be fairly well understood in terms of the "center of activity" model. A slight secondary eclipse may have been detected for LP101-15, but verification is needed.

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The Spotted Flare Stars BY Dra and CC Eri: A model for the spots and some Astrophysical Implications

Cited by 89 publications

References 0 publications

Simultaneous X-ray spectroscopy of YY Gem withChandraandXMM-Newton

Simultaneous X-ray spectroscopy of YY Gem withChandraandXMM-Newton

High-Level Magnetic Activity on a Low-Mass Close Binary: GSC 02038-0293

Observations of the red-dwarf emission-line objects LP101-15, BY Draconis, GT Pegasi, and FF Andromedae

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