Abstract
We report a new giant planet orbiting the K giant HD 155233, as well as four stellar-mass companions from the Pan-Pacific Planet Search, a southern hemisphere radial velocity survey for planets orbiting nearby giants and subgiants. We also present updated velocities and a refined orbit for HD 47205b (7 CMa b), the first planet discovered by this survey. HD 155233b has a period of 885$\pm$63 days, eccentricity e=0.03$\pm$0.20, and m sin i=2.0$\pm$0.5 M_jup. The stellar-mass companions range in m sin i from 0.066 M_sun to 0.33 M_sun. Whilst HD 104358B falls slightly below the traditional 0.08 M_sun hydrogen-burning mass limit, and is hence a brown dwarf candidate, we estimate only a 50% a priori probability of a truly substellar mass.
Highlights
Radial velocity planet search efforts have been underway for more than 20 yr, discovering hundreds of new planetary companions
The Pan-Pacific Planet Search (PPPS) used the UCLES echelle spectrograph (Diego et al 1990) at the Australian Telescope (AAT) to obtain high-resolution spectra, with an observing procedure identical to that used by the 16-year Anglo–Australian Planet Search (AAPS)
Precise Doppler velocities are derived using the well-established point spread function (PSF) modelling techniques described in Butler et al (1996)
Summary
Radial velocity planet search efforts have been underway for more than 20 yr, discovering hundreds of new planetary companions. We note that it has recently become possible to modify planet-search Doppler codes to obtain precise velocities for SB2s, by including the secondary star’s spectrum in the modelling process if the flux ratio is known. This novel approach is being applied to the Alpha Centauri binary system (Bergmann et al 2015; Endl et al 2015). A further 31 stars in the PPPS sample show large-amplitude velocity variations or long-term trends, which indicate stellar-mass companions This yields a first-order binary fraction of 48/167 = 29 per cent, for a sample which was initially selected to avoid suspected binaries (Wittenmyer et al 2011).
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