RESUMO
HD 89744 is an F7 V star with a mass of 1.4 M middle dot in circle, an effective temperature of 6166 K, an age of 2.0 Gyr, and metallicity &sqbl0;Fe&solm0;H&sqbr0;=0.18. The radial velocity of the star has been monitored with the Advanced Fiber-Optic Echelle spectrograph at the Whipple Observatory since 1996, and evidence has been found for a low-mass companion. The data were complemented by additional data from the Hamilton spectrograph at Lick Observatory during the companion's periastron passage in the fall of 1999. As a result, we have determined the star's orbital wobble to have a period P=256 days, an orbital amplitude K=257 m s-1, and an eccentricity e=0.7. From the stellar mass, we infer that the companion has a minimum mass m2sini=7.2 MJ in an orbit with a semimajor axis a2=0.88 AU. The eccentricity of the orbit, among the highest known for extrasolar planets, continues the trend that extrasolar planets with semimajor axes greater than about 0.15 AU tend to have much higher eccentricities than are found in our solar system. The high metallicity of the parent star reinforces the trend that parent stars of extrasolar planets tend to have high metallicity.
RESUMO
Helioseismology requires nearly continuous observations of the oscillations of the solar surface for long periods of time in order to obtain precise measurements of the sun's normal modes of oscillation. The GONG project acquires velocity images from a network of six identical instruments distributed around the world. The GONG network began full operation in October 1995. It has achieved a duty cycle of 89 percent and reduced the magnitude of spectral artifacts by a factor of 280 in power, compared with single-site observations. The instrumental noise is less than the observed solar background.
