The microlensing signatures of starspots

Abstract

Point lens microlensing events with impact parameter close to the source stellar radius allow the observer to study the surface brightness profile of the lensed source. We have examined the effect of photospheric star spots on multicolour microlensing lightcurves and investigated the detectability of such spots in different wavebands as a function of spot temperature, position, radius and lens trajectories. We include the effect of limb darkening and spot projection as a function of position on the stellar disc. In particular we apply the updated, state-of-the-art NEXTGEN stellar atmosphere models of Hauschildt et al which predict very strong limb darkening and which are likely to be applicable to the source stars considered here. Our results indicate that star spots generally give a clear signature for transit events. Moreover, this signature is strongly suppressed by limb darkening for spots close to the limb, although the spots may still be clearly detected for favourable lens trajectories. It is also clear that intensive temporal sampling throughout the duration of the transit is necessary in order for such events to be effective as a tool for imaging stellar photospheres. Nonetheless, with sufficiently well sampled light curves of good photometric precision, microlensing can indeed place useful constraints on the presence or otherwise of photospheric starspots.

12 pages, 10 figures, MNRAS 335, 539 (2002)

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Cited by in corpus (13)

• Detecting stellar spots through polarimetry observations of microlensing events in caustic-crossing
• Characterizing Lenses and Lensed Stars of High-Magnification Single-lens Gravitational Microlensing Events With Lenses Passing Over Source Stars
• Starspots Modelling and Flare Analysis on Selected MV Stars
• The Scales of Gravitational Lensing
• Starspot induced effects in microlensing events with rotating source star
• Resolving Stellar Atmospheres I: The H alpha line and comparisons to microlensing observations
• Characterization of Stellar Spots in Next-Generation Microlensing Surveys
• Timing analysis in microlensing
• Non-radially pulsating stars as microlensing sources
• Measuring Limb Darkening of Stars in high magnification Microlensing Events by the Finite Element Method
• Determination of Stellar Ellipticities in Future Microlensing Surveys
• Variation of the stellar color in high-magnification and caustic-crossing microlensing events
• Microlensing and Photon Bunching: The impact of decoherence