KOI-54: THE KEPLER DISCOVERY OF TIDALLY EXCITED PULSATIONS AND BRIGHTENINGS IN A HIGHLY ECCENTRIC BINARY

Journal Article · Tue Nov 01 00:00:00 EDT 2011 · Astrophysical Journal, Supplement Series

DOI:https://doi.org/10.1088/0067-0049/197/1/4· OSTI ID:21562420

Welsh, William F; Orosz, Jerome A ^[1]; Aerts, Conny; Zima, Wolfgang ^[2]; Brown, Timothy M ^[3]; Brugamyer, Erik; Cochran, William D ^[4]; Gilliland, Ronald L ^[5]; Guzik, Joyce Ann ^[6]; Kurtz, D W ^[7]; Latham, David W; Quinn, Samuel N ^[8]; Marcy, Geoffrey W ^[9]; Allen, Christopher ^[10]; Batalha, Natalie M ^[11]; Bryson, Steve; Caldwell, Douglas A; Howell, Steve B ^[12]; Buchhave, Lars A ^[13]

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1. Astronomy Department, San Diego State University, San Diego, CA 92182 (United States)
2. Instituut voor Sterrenkunde, K. U. Leuven, B-3001 Leuven (Belgium)
3. Las Cumbres Observatory Global Telescope, Goleta, CA 93117 (United States)
4. McDonald Observatory and Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States)
5. Space Telescope Science Institute, Baltimore, MD 21218 (United States)
6. XTD-2, MS T086, Los Alamos National Laboratory, Los Alamos, NM 87545-2345 (United States)
7. Jeremiah Horrocks Institute of Astrophysics, University of Central Lancashire, Preston PR1 2HE (United Kingdom)
8. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
9. Department of Astronomy, University of California, Berkeley, CA 94720 (United States)
10. Orbital Sciences Corporation/NASA Ames Research Center, Moffett Field, CA 94035 (United States)
11. Department of Physics and Astronomy, San Jose State University, San Jose, CA 95192 (United States)
12. NASA Ames Research Center M/S 244-30, Moffett Field, CA 94035 (United States)
13. Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen (Denmark)

Kepler observations of the star HD 187091 (KIC 8112039, hereafter KOI-54) revealed a remarkable light curve exhibiting sharp periodic brightening events every 41.8 days with a superimposed set of oscillations forming a beating pattern in phase with the brightenings. Spectroscopic observations revealed that this is a binary star with a highly eccentric orbit, e = 0.83. We are able to match the Kepler light curve and radial velocities with a nearly face-on (i = 5.{sup 0}5) binary star model in which the brightening events are caused by tidal distortion and irradiation of nearly identical A stars during their close periastron passage. The two dominant oscillations in the light curve, responsible for the beating pattern, have frequencies that are the 91st and 90th harmonic of the orbital frequency. The power spectrum of the light curve, after removing the binary star brightening component, reveals a large number of pulsations, 30 of which have a signal-to-noise ratio {approx}>7. Nearly all of these pulsations have frequencies that are either integer multiples of the orbital frequency or are tidally split multiples of the orbital frequency. This pattern of frequencies unambiguously establishes the pulsations as resonances between the dynamic tides at periastron and the free oscillation modes of one or both of the stars. KOI-54 is only the fourth star to show such a phenomenon and is by far the richest in terms of excited modes.

• OSTI ID: 21562420
• Journal Information: Astrophysical Journal, Supplement Series, Vol. 197, Issue 1; Other Information: DOI: 10.1088/0067-0049/197/1/4; ISSN 0067-0049
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
BINARY STARS
BRIGHTNESS
DIAGRAMS
ORBITS
OSCILLATION MODES
OSCILLATIONS
PULSATIONS
RADIAL VELOCITY
VISIBLE RADIATION
ELECTROMAGNETIC RADIATION
INFORMATION
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
STARS
VELOCITY