ROTATIONALLY MODULATED g-MODES IN THE RAPIDLY ROTATING {delta} SCUTI STAR RASALHAGUE ({alpha} OPHIUCHI)
- University of Michigan Astronomy Department, 941 Dennison Bldg, Ann Arbor, MI 48109-1090 (United States)
- Department of Astronomy, University of Wisconsin-Madison, Sterling Hall, 475 N. Charter Street, Madison, WI 53706 (United States)
- Jet Propulsion Laboratory, Pasadena, CA (United States)
- University of British Columbia, Vancouver, BC V6T 1Z1 (Canada)
- Universite de Montreeal, C.P. 6128, Succ. C-V, QC H3C 3J (Canada)
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 {delta} Scuti variable star Rasalhague ({alpha} Oph, A5IV, 2.18 M{sub sun}, {omega}/{omega}{sub c}{approx}0.88) based on 30 continuous days of monitoring using the MOST satellite. We have identified 57 {+-} 1 distinct pulsation modes above a stochastic granulation spectrum with a cutoff of {approx}26 cycles day{sup -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 l = 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.
- OSTI ID:
- 21474374
- Journal Information:
- Astrophysical Journal, Vol. 725, Issue 1; Other Information: DOI: 10.1088/0004-637X/725/1/1192; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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