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Issue A&A
Volume 495, Number 2, February IV 2009
Page(s) L13 - L16
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361/200811535
Published online 09 February 2009

A&A 495, L13-L16 (2009)
DOI: 10.1051/0004-6361/200811535

Letter

Discovery of an old photoevaporating disk in $\sigma$ Orionis

E. Rigliaco1, 2, A. Natta1, S. Randich1, and G. Sacco3

1  Osservatorio Astrofisico di Arcetri, INAF, Largo E. Fermi 5, 50125 Firenze, Italy
    e-mail: erigliaco@arcetri.astro.it
2  Università di Firenze, Dipartimento di Astronomia, Largo E. Fermi 2, 50125 Firenze, Italy

3  Osservatorio Astronomico di Palermo, INAF, Piazza del Parlamento 1, 90134 Palermo, Italy

Received 17 December 2008 / Accepted 2 February 2009

Abstract
The photoevaporation of circumstellar disks is a powerful process in the disk dissipation at the origin of the Orion proplyds. This Letter reports the first detection of a photoevaporating disk in the final but long-lasting phase of its evolution. The disk is associated to a low-mass T Tauri member of the $\sigma$ Ori Cluster. It is characterized by a very low (if any) accretion rate and by a tenuous ( $\dot M_{\rm loss}$  $\sim 10^{-9}$ $M_\odot$/yr) photoevaporation wind, which is unambiguously detected in the optical spectrum of the object. The wind emits strong forbidden lines of [SII] and [NII] because the low-mass star is close to a powerful source of ionizing photons, the O9.5 star $\sigma$ Ori.


Key words: stars: formation -- accretion, accretion disks



© ESO 2009


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