非表示:
キーワード:
techniques: radial velocities
methods: data analysis
planetary
systems
stars: abundances
stars: individual: HD 220197
stars:
individual: HD 233832
Astrophysics - Earth and Planetary Astrophysics
要旨:
Context. Statistical studies of exoplanets have shown that giant planets are more commonly hosted by metal-rich dwarf stars than low-metallicity stars, while no such correlation is evident for lower mass planets. The search for giant planets around metal-poor stars and the estimate of their occurrence fp is an important element in providing support to models of planet formation.
Aims: We present results from the HARPS-N search for giant planets orbiting metal-poor (- 1.0 ≤[Fe/H] ≤-0.5 dex) stars in the northern hemisphere, complementing a previous HARPS survey on southern stars in order to update the estimate of fp.
Methods: High-precision HARPS-N observations of 42 metal-poor stars were used to search for planetary signals to be fitted using differential evolution Markov chain Monte Carlo single- Keplerian models. We then joined our detections to the results of the previous HARPS survey on 88 metal-poor stars to provide a preliminary estimate of the two-hemisphere fp.
Results: We report the detection of two new giant planets around HD 220197 and HD 233832. The first companion has Msin i = 0.20-0.04+0.07 MJup and an orbital period of 1728-80+162 days, and for the second companion, we find two solutions of equal statistical weight with periods of 2058-40+47 and 4047-117+91 days and minimum masses of 1.78-0.06+0.08 and 2.72-0.23+0.23 MJup, respectively. Joining our two detections with the three from the southern survey, we obtain a preliminary and conservative estimate of the global frequency of fp = 3.84 -1.06+2.45% for giant planets around metal-poor stars.
Conclusions: The two new giant planets orbit dwarf stars at the metal-rich end of the HARPS-N metal- poor sample. This corroborates previous results that suggested that giant planet frequency is still a rising function of the host star [Fe/H]. We also note that all detections in the overall sample are giant long-period planets. Based on observations made with the HARPS-N spectrograph on the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma (Spain) by the INAF - Fundación Galileo Galilei (Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias).RV data (Table 5) are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/621/A110">http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/621/A110</A>
