Investigation of the Key Parameters in the Process of Extrasolar Planet Formation around Intermediate-Mass G-K Giant Stars

• Applicant: Professor Dr. Artie P. Hatzes
• Subject Area: Astrophysics and Astronomy
• Term: from 2011 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 181884489

• Final Report Year: 2017

Final Report Abstract

The main results of our program are summarized as follows: 1. Our program K-giant stars have a median mass of 1.3 M⨀ and a median metallicity of [Fe/H] = -0.1. 2. Approximately 15 % of our samples have stellar companions. 3. One star in our sample has a brown dwarf companion with minimum mass, m sin i = 42 MJup. The frequency of brown dwarfs companions in our sample is ≈ 1 %. 4. Approximately 20 % of our samples have candidate giant planet companions. 5. The planet candidates of our sample have an average mass of about 6 MJup, an average period ≈ 500 d, and a mean eccentricity of 0.20. If these are all planet candidates, then planets around K giant stars tend to be massive and on eccentric orbits. 6. Our program has discovered two giant planets of K giant stars in the shortest period orbits, HD 32518 (P = 157.5) and HD 94084 (P = 111 d). 7. We have discovered long-period RV variations in 3 K giant stars which initially mimicked the variations due to a planet. These were later shown to have amplitude variations suggesting a stellar origin. This is a new phenomenon in K giant stars, most likely caused by stellar oscillations. If true, the occurrence rate for planets around K giant stars may have to be revised downwards.

Publications

• "Exoplanets around G-K Giants" 2011, in Planetary Systems Beyond the Main Sequence: Proceedings of the International Conference. AIP Conference Proceedings, Volume 1331, pp. 79-87
  Döllinger, Michaela P.; Hatzes, Artie P.; Pasquini, Luca; Guenther, Eike W.; Hartmann, Michael; Setiawan, Johny; Girardi, Léo; de Medeiros, Jose R.; da Silva, Licio; Schuh, Sonja; Drechsel, Horst & Heber, Ulrich
  
• "Long-lived, long-period radial velocity variations in Aldebaran: A planetary companion and stellar activity" 2015, Astronomy & Astrophysics, 580, 31
  Hatzes, A. P.; Cochran, W. D.; Endl, M.; Guenther, E. W.; MacQueen, P.; Hartmann, M.; Zechmeister, M.; Han, I.; Lee, B.-C.; Walker, G. A. H.; Yang, S.; Larson, A. M.; Kim, K.-M.; Mkrtichian,, D. E.; Döllinger, M.; Simon,, A. E. & Girardi, L.
  
• "Mass of WASP-33b", 2015, Astronomy & Astrophysics, 578, 4
  Lehmann, H.; Guenther, E.; Sebastian, D.; Döllinger, M.; Hartmann, M. & Mkrtichian, D. E.
  
• "Spectroscopic and Interferometric Measurements of Nine K Giant Stars" 2016, Astronomical Journal, 152, 66
  Baines, Ellyn K.; Döllinger, Michaela P.; Guenther, Eike W.; Hatzes, Artie P.; Hrudkovu, Marie & Belle, Gerard T. van