Rotationally Modulated g-modes in the Rapidly Rotating δ Scuti Star Rasalhague (α Ophiuchi)
- Autor(en)
- J. D. Monnier, R. H. D. Townsend, X. Che, M. Zhao, T. Kallinger, J. Matthews, A. F. J. Moffat
- Abstrakt
Despite a century of remarkable progress in understanding stellar interiors, we know surprisingly little about the inner workings of stars spinning near their critical limit. New interferometric imaging of these so-called rapid rotators combined with breakthroughs in asteroseismology promise to lift this veil and probe the strongly latitude-dependent photospheric characteristics and even reveal the internal angular momentum distribution of these luminous objects. Here, we report the first high-precision photometry on the low-amplitude δ Scuti variable star Rasalhague (α Oph, A5IV, 2.18 Msun,{ω}/{ω_c}˜ 0.88) based on 30 continuous days of monitoring using the MOST satellite. We have identified 57 ± 1distinct pulsation modes above a stochastic granulation spectrum with a cutoff of ~26 cycles day-1. Remarkably, we have also discovered that the fast rotation period of 14.5 hr modulates low-frequency modes (1-10 day periods) that we identify as a rich family of g-modes (|m| up to 7). The spacing of the g-modes is surprisingly linear considering Coriolis forces are expected to strongly distort the mode spectrum, suggesting we are seeing prograde "equatorial Kelvin"waves (modes ell = m). We emphasize the unique aspects of Rasalhague motivating future detailed asteroseismic modeling—a source with a precisely measured parallax distance, photospheric oblateness, latitude temperature structure, and whose low-mass companion provides an astrometric orbit for precise mass determinations.Based on data from the MOST satellite, a Canadian Space Agency mission operated by Dynacon, Inc., the University of Toronto Institute of Aerospace Studies, and the University of British Columbia, with assistance from the University of Vienna, Austria.
- Organisation(en)
- Institut für Astrophysik
- Externe Organisation(en)
- University of Michigan, University of Wisconsin, Madison, California Institute of Technology (Caltech), University of British Columbia (UBC), Université de Montréal
- Journal
- The Astrophysical Journal
- Band
- 725
- Seiten
- 1192-1201
- ISSN
- 0004-637X
- DOI
- https://doi.org/10.1088/0004-637X/725/1/1192
- Publikationsdatum
- 2010
- Peer-reviewed
- Ja
- ÖFOS 2012
- 103004 Astrophysik
- Schlagwörter
- Link zum Portal
- https://ucris.univie.ac.at/portal/de/publications/rotationally-modulated-gmodes-in-the-rapidly-rotating--scuti-star-rasalhague--ophiuchi(f9f726a2-e56b-496d-9353-1b508f90698b).html