MOST photometry of the enigmatic PMS pulsator HD 142666^*

¹ Institut für Astronomie, Universität Wien, Türkenschanzstrasse 17, 1180 Vienna, Austria e-mail: [zwintz;lastname]@astro.univie.ac.at
² Department of Astronomy and Physics, St. Mary's University, Halifax, NS B3H 3C3, Canada e-mail: [guenther;mcasey]@ap.smu.ca
³ Institute of Astronomy, School of Physics, University of Sydney, NSW 2006, Australia e-mail: dhuber@physics.usyd.edu.au
⁴ Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada e-mail: rowe@phas.ubc.ca, [kuschnig;matthews]@astro.ubc.ca, gordonwa@uvic.ca
⁵ NASA-Ames Research Park, MS-244-30, Moffett Field, CA 94035, USA
⁶ Départment de physique, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, QC H3C 3J7, Canada e-mail: moffat@astro.umontreal.ca
⁷ David Dunlap Observatory, University of Toronto, PO Box 360, Richmond Hill, ON L4C 4Y6, Canada e-mail: rucinski@astro.utoronto.ca
⁸ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA e-mail: sasselov@cfa.harvard.edu

Received: 9 October 2008
Accepted: 21 November 2008

Abstract

Context. Modeling of pre-main sequence (PMS) stars through asteroseismology of PMS p-mode pulsators has only recently become possible, and spacebased photometry is one of the important sources of data for these efforts. We present precise photometry of the pulsating Herbig Ae star HD 142666  obtained in two consecutive years with the MOST (Microvariability & Oscilations of STars) satellite.

Aims. Previously, only a single pulsation period was known for HD 142666. The MOST photometry reveals that HD 142666  is multi-periodic. However, the unique identification of pulsation frequencies is complicated by the presence of irregular variability caused by the star's circumstellar dust disk. The two light curves obtained with MOST in 2006 and 2007 provided data of unprecedented quality to study the pulsations in HD 142666  and also to monitor the circumstellar variability.

Methods. Frequency analysis was performed using the routine sigspec  and the results from the 2006 and 2007 campaigns were then compared to each other with the software cinderella  to identify frequencies common to both light curves. The correlated frequencies were then submitted to an asteroseismic analysis.

Results. We attribute 12 frequencies to pulsation. Model fits to the three frequencies with the highest amplitudes lie well outside the uncertainty box for the star's position in the HR diagram based on published values. Some of the frequencies appear to be rotationally split modes.

Conclusions. The models suggest that either (1) the published estimate of the luminosity of HD 142666, based on a relation between circumstellar disk radius and stellar luminosity, is too high and/or (2) additional physics such as mass accretion may be needed in our models to accurately fit both the observed frequencies and HD 142666's position in the HR diagram.