Astron. Astrophys. 343, 41-50 (1999)

Microlens diagnostics of accretion disks in active galactic nuclei

A. Yonehara  ^{*  1}, S. Mineshige ¹, J. Fukue ², M. Umemura ³ and E.L. Turner <sup>4

1</sup> Department of Astronomy, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
² Astronomical Institute, Osaka Kyoiku University, Asahigaoka, Kashiwara, Osaka 582-0026, Japan
³ Center for Computational Physics, Tsukuba University, Tsukuba, Ibaraki 305-0006, Japan
⁴ Princeton University Observatory, Peyton Hall, Princeton, NJ 08544, USA

Received 27 April 1998 / Accepted 20 October 1998

Abstract

The optical-ultraviolet continuum from active galactic nuclei (AGN) seems to originate from optically thick and/or thin disks, and occasionally from associated circumnuclear starburst regions. These different possible origins can, in principle, be distinguished by observations of gravitational microlensing events. We performed numerical simulations of microlensing of an AGN disk by a single lensing star passing in front of the AGN. Calculated spectral variations and light curves show distinct behavior, depending on the nature of the emitting region; time variation over few months with strong wavelength dependence is expected in the case of an optically thick disk (standard disk ), while an optically thin disk (advection-dominated disk ) will produce shorter, nearly wavelength-independent variation. In the case of an associated circumnuclear starburst region much slower variations (over a year) will be superposed on the shorter variations caused by microlensing of the disk.

Key words: accretion, accretion disks galaxies: active galaxies: nuclei galaxies: quasars: general gamma rays: bursts

* Research Fellow of the Japan Society for the Promotion of Science

Send offprint requests to: A. Yonehara

Correspondence to: yonehara@kusastro.kyoto-u.ac.jp

SIMBAD Objects

Contents

• 1. Introduction
• 2. Method of the simulation
  • 2.1. Accretion disk models
    • 2.1.1. Optically thick disk
    • 2.1.2. Optically thin disk
  • 2.2. Microlensing events
• 3. Results of the calculations
  • 3.1. Model parameters
  • 3.2. Spectral variation
  • 3.3. Light curves
  • 3.4. Parameter dependence
• 4. Discussion
• 5. Summary
• Acknowledgements
• References

© European Southern Observatory (ESO) 1999

Online publication: March 1, 1999
helpdesk.link@springer.de