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- Title
The GAPS Programme with HARPS-N at TNG: XVIII. Two new giant planets around the metal-poor stars HD 220197 and HD 233832.
- Authors
Barbato, D.; Sozzetti, A.; Biazzo, K.; Malavolta, L.; Santos, N. C.; Damasso, M.; Lanza, A. F.; Pinamonti, M.; Affer, L.; Benatti, S.; Bignamini, A.; Bonomo, A. S.; Borsa, F.; Carleo, I.; Claudi, R.; Cosentino, R.; Covino, E.; Desidera, S.; Esposito, M.; Giacobbe, P.
- Abstract
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 M sin i = 0.20−0.04+0.07 $\sin{i}=0.20_{-0.04}^{+0.07}$ sin i = 0.20 − 0.04 + 0.07 MJup and an orbital period of 1728−80+162 $1728_{-80}^{+162}$ 1728 − 80 + 162 days, and for the second companion, we find two solutions of equal statistical weight with periods of 2058−40+47 $2058_{-40}^{+47}$ 2058 − 40 + 47 and 4047−117+91 $4047_{-117}^{+91}$ 4047 − 117 + 91 days and minimum masses of 1.78−0.06+0.08 $1.78_{-0.06}^{+0.08}$ 1.78 − 0.06 + 0.08 and 2.72−0.23+0.23 $2.72_{-0.23}^{+0.23}$ 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% $f_p=3.84_{-1.06}^{+2.45}\%$ f p = 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.
- Subjects
METALS; DWARF stars; GAS giants; ORBITS (Astronomy); PHOTOMETRY
- Publication
Astronomy & Astrophysics / Astronomie et Astrophysique, 2019, Vol 621, pN.PAG
- ISSN
0004-6361
- Publication type
Article
- DOI
10.1051/0004-6361/201834305