Astron. Astrophys. 327, 145-154 (1997)

Dust around young stars

Photopolarimetric activity of the classical Herbig Ae/Be star RR Tauri ^*

A.N. , Rostopchina ¹, V.P. , Grinin ^{1, 2}, A. , Okazaki ³, P.S. , Thé ⁴, S. , Kikuchi ⁵, D.N. , Shakhovskoy ¹, N.Kh. and Minikhulov <sup>6

1</sup> Crimean Astrophysical Observatory, Crimea, 334413, Nauchny, Ukraine
² Astronomical Institute of the St. Petersburg University, St. Petersburg, Russia
³ Department of Science Education, Gunma University, Aramaki, Maebashi, Gunma 371, Japan
⁴ Astronomical Institute "Anton Pannekoek", University of Amsterdam, The Netherlands
⁵ Dodaira Observatory, National Astronomical Observatory, Tokigawa, Saitama 355-03, Japan
⁶ Astrophysical Institute, Dushanbe, 734042, Tadjikistan

Received 2 January 1997 / Accepted 21 March 1997

Abstract

The classical Herbig Ae/Be (HAeBe) star RR Tau is known as a highly variable young star with an amplitude of variability of about in the V pass-band. In this paper we present the results of coordinated Crimea-Dodaira multi-band photo-polarimetric observations of this star which cover fully the observed interval of its brightness changes. Within the observed interval of its light variations the linear polarization of RR Tau anti-correlates with its brightness changes. The dependence of the linear polarization on the stellar magnitude agrees well with the model according to which the main source of the intrinsic polarization of RR Tau is scattered radiation by the circumstellar (CS) disk-like dust envelope (probably the protoplanetary disk) seen edge-on or under a small inclination to the line-of-sight, and that the brightness variations are caused by variable obscuration of the star by revolving circumstellar dust clouds.

A comparison with previous photo-polarimetric observations of this star shows that the Stokes parameters of its polarized radiation are quite stable on a time scale of about 7 years. By using this fact we have separated the interstellar and intrinsic components of the observed polarization. The numerical modeling of the intrinsic linear polarization together with the colour-magnitude diagrams of RR Tau show that the circumstellar disk-like envelope around this star is strongly flattened and that the characteristic size of the grains is intermediate between that of interstellar dust and dust in the old protoplanetary disk of Pictoris. We assume on the basis of this analysis that RR Tau is surrounded by a young protoplanetary disk and that it can be considered as a young progenitor of Pictoris.

Key words: stars: pre-main sequence stars: variables stars: individual: RR Tau polarization stars: circumstellar matter

* Tables 1 and 2 are only available in electronic form at CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

Send offprint requests to: A.N. Rostopchina

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Contents

• 1. Introduction
• 2. The observations
• 3. Results
  • 3.1. The photometric activity of RR Tau
  • 3.2. The polarimetric activity of RR Tau
• 4. Discussion
  • 4.1. "Flares" of RR Tau
  • 4.2. The energy distribution of RR Tau
  • 4.3. The scattered radiation and the screening effect
  • 4.4. Circumstellar dust modeling
  • 4.5. Comparison with other objects
• 5. Conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: April 8, 1998
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