Volume 481, Number 2, April II 2008
|Page(s)||423 - 432|
|Section||Interstellar and circumstellar matter|
|Published online||07 February 2008|
Accretion properties of T Tauri stars in σ Orionis *
Osservatorio Astrofisico di Arcetri, INAF, Largo E. Fermi 5, 50125 Firenze, Italy e-mail: firstname.lastname@example.org
2 Università di Firenze, Dipartimento di Astronomia, Largo E. Fermi 5, 50125 Firenze, Italy
3 ESO, Karl-Schwarschild Strasse 2, 85748 Garching bei München, Germany
4 Osservatorio Astronomico di Palermo, INAF, Piazza del Parlamento 1, 90134 Palermo, Italy
Accepted: 16 January 2008
Accretion disks around young stars evolve in time with time scales of a few million years. We present here a study of the accretion properties of a sample of 35 stars in the ∼3 million-year-old star-forming region σ Ori. Of these, 31 are objects with evidence of disks, based on their IR excess emission. We use near-IR hydrogen recombination lines (Paγ) to measure their mass accretion rate. We find that the accretion rates are significant lower in σ Ori than in younger regions, such as ρ Oph, consistently with viscous disk evolution. The He I 1.083 μm line is detected (either in absorption or in emission) in 72% of the stars with disks, also providing evidence of accretion-powered activity in very low accretors, where other accretion indicators disappear.
Key words: stars: formation / accretion, accretion disks
© ESO, 2008
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