Gravitational microlensing as a test of stellar model atmospheres

Abstract

We present calculations illustrating the potential of gravitational microlensing to discriminate between classical models of stellar surface brightness profiles and the recently computed ``Next Generation'' models of Hauschildt et al. These spherically-symmetric models include a much improved treatment of molecular lines in the outer atmospheres of cool giants -- stars which are very typical sources in Galactic bulge microlensing events. We show that the microlensing signatures of intensively monitored point and fold caustic crossing events are readily able to distinguish between NextGen and the classical models, provided a photometric accuracy of 0.01 magnitudes is reached. This accuracy is now routinely achieved by alert networks, and hence current observations can discriminate between such model atmospheres, providing a unique insight on stellar photospheres.

4 pages, 4 figures, Astronomy & Astrophysics (Letters), vol. 388, L1 (2002)

References in corpus (9)

• The NextGen Model Atmosphere grid for $3000\le \Teff \le 10000\K$
• The NextGen Model Atmosphere grid: II. Spherically symmetric model atmospheres for giant stars with effective temperatures between 3000 and 6800~K
• Finite Source Sizes and the Information Content of MACHO-Type Lens Search Light Curves
• Limb-Darkening of a K Giant in the Galactic Bulge: PLANET Photometry of MACHO 97-BLG-28
• PLANET observations of microlensing event OGLE-1999-BUL-23: limb darkening measurement of the source star
• Probing Red Giant Atmospheres with Gravitational Microlensing
• Direct multi-wavelength limb-darkening measurements of three late-type giants with the Navy Prototype Optical Interferometer
• Applications of Microlensing to Stellar Astrophysics
• Chromatic and spectroscopic signatures of microlensing events as a tool for the gravitational imaging of stars

Cited by in corpus (5)

• Probing the atmosphere of the bulge G5III star OGLE-2002-BUL-069 by analysis of microlense H alpha line
• Characterizing Lenses and Lensed Stars of High-Magnification Single-lens Gravitational Microlensing Events With Lenses Passing Over Source Stars
• Resolving Stellar Atmospheres I: The H alpha line and comparisons to microlensing observations
• Exoplanetary searches with gravitational microlensing: polarization issues
• The color signature of the transit of HD 209458: Discrepancies between stellar atmospheric models and observations