Quanz, S. P. and Henning, T. and Bouwman, J. and van Boekel, R. and Juhász, A. and Linz, H. and Pontoppidan, K. M. and Lahuis, F. (2007) Evolution of dust and ice features around FU Orionis objects. Astrophysical Journal, 668 (1). pp. 359-383. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:QUAapj07
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We present spectra for a sample of 14 FUors and two T Tauri stars observed with Spitzer or ISO. Based on the appearance of the 10 μm silicate feature, we define two categories of FUors. Objects showing the silicate feature in absorption (Category 1) are still embedded in a circumstellar envelope. The shape of the silicate bands is in good agreement with typical dust compositions of the ISM. Only one object appears too rich in amorphous pyroxene dust, but a superposed emission feature can explain the observed shape. We derive optical depths and extinction values from the silicate and additional ice bands. Particularly, the analysis of the CO_2 ice band at 15.2 μm allows us to search for evidence for ice processing and to constrain whether the absorbing material is physically linked to the central object. For objects showing the silicate band in emission (Category 2), we argue that the feature comes from the surface layer of accretion disks. We find evidence that grain growth has already taken place within the disks, but no clear indications for crystallization are present. We discuss how these observations fit into the picture of a young and active accretion disk. Finally, a framework is proposed how the two categories of FUors can be understood in a general paradigm of the evolution of young, low-mass stars. As one object (Parsamian 21) shows PAH emission features typical for evolved stars, we question its status as a FUor. Additionally, two spectra (RNO1B and L1551 IRS 5) show [Fe ii] emission lines that are attributed to hot, dense, or shocked material related to outflows.
|Additional Information:||© 2007 American Astronomical Society. Print publication: Issue 1 (2007 October 10); received 2007 May 11; accepted for publication 2007 June 24. S. P. Q. kindly acknowledges support from the German Friedrich-Ebert-Stiftung. We are grateful to Henrik Beuther and Kees Dullemond for interesting and insightful discussions and thank the referee for a detailed report helping to improve the style and content of this paper. The version of the ISO data presented in this paper corresponds to Highly Processed Data Product (HPDP) sets available for public use in the ISO Data Archive. OSIA is a joint development of theSWS consortium. Contributing institutes are SRON, MPE, KUL, and the ESA Astrophysics Division. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. Facilities: Spitzer, ISO. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands, and the United Kingdom) and with the participation of ISAS and NASA. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA.|
|Subject Keywords:||accretion, accretion disks; circumstellar matter; dust, extinction; stars: formation; stars: individual (FU Ori); stars: pre-main sequence|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||13 Jul 2009 16:14|
|Last Modified:||26 Dec 2012 10:54|
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