Journal of The Korean Astronomical Society (천문학회지)

The Korean Astronomical Society (한국천문학회)
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A Search for Exoplanets around Northern Circumpolar Stars. VII. Detection of Planetary Companion Orbiting the Largest Host Star HD 18438

  • Byeong-Cheol Lee (Korea Astronomy and Space Science Institute) ;
  • Jae-Rim Koo (Kongju National University) ;
  • Gwanghui Jeong (Korea Astronomy and Space Science Institute) ;
  • Myeong-Gu Park (Department of Astronomy and Atmospheric Sciences, Kyungpook National University) ;
  • Inwoo Han (Korea Astronomy and Space Science Institute) ;
  • Yeon-Ho Choi (Korea Astronomy and Space Science Institute)
  • Received : 2021.07.26
  • Accepted : 2023.03.15
  • Published : 2023.12.30
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Abstract

We have been conducting a exoplanet search survey using Bohyunsan Observatory Echelle Spectrograph (BOES) for the last 18 years. We present the detection of exoplanet candidate in orbit around HD 18438 from high-precision radial velocity (RV) mesurements. The target was already reported in 2018 (Bang et al. 2018). They conclude that the RV variations with a period of 719 days are likely to be caused by the pulsations because the Lomb-Scargle periodogram of HIPPARCOS photometric and Hα EW variations for HD 18438 show peaks with periods close to that of RV variations and there were no correlations between bisectors and RV measurements. However, the data were not sufficient to reach a firm conclusion. We obtained more RV data for four years. The longer time baseline yields a more accurate determination with a revised period of 803 ± 5 days and the planetary origin of RV variations with a minimum planetary companion mass of 21 ± 1 MJup. Our current estimate of the stellar parameters for HD 18438 makes it currently the largest star with a planetary companion.

Keywords

Acknowledgement

B.C.L acknowledges partial support by the KASI (Korea Astronomy and Space Science Institute) grant 2021-1-830-08 and acknowledge support by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2021283200). M.G.P. was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2019R1I1A3A02062242) and KASI under the R&D program supervised by the Ministry of Science, ICT and Future Planning. This research made use of the SIMBAD database, operated at the CDS, Strasbourg, France.

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