Search for exoplanet around northern circumpolar stars - Four planets around HD 11755, HD 12648, HD 24064, and 8 Ursae Minoris

TL;DR

This study conducted a precise radial velocity survey of northern circumpolar stars, leading to the discovery of four new exoplanets orbiting stars HD 11755, HD 12648, HD 24064, and 8 UMi, expanding knowledge of exoplanets in this region.

Contribution

It is the first to identify multiple exoplanets around northern circumpolar stars using high-resolution RV measurements and comprehensive activity analysis.

Findings

Discovered four new exoplanets with minimum masses between 1.5 and 9.4 M_Jup.

Detected orbital periods ranging from 93 to 535 days.

Confirmed planetary nature by excluding stellar activity as the cause of RV variations.

Abstract

Aims. This program originated as the north pole region extension of the established exoplanet survey using 1.8 m telescope at Bohyunsan Optical Astronomy Observatory (BOAO). The aim of our paper is to find exoplanets in northern circumpolar stars with a precise radial velocity (RV) survey. Methods. We have selected about 200 northern circumpolar stars with the following criteria: Dec. > 70 degree, 0.6 < B-V < 1.6, HIPPARCOS_scat < 0.05 magnitude, and 5.0 < mv < 7.0. The high-resolution, fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) was used for the RV survey. Chromospheric activities, the HIPPARCOS photometry, and line bisectors were analyzed to exclude other causes for the RV variations. Results. In 2010, we started to monitor the candidates and have completed initial screening for all stars for the last five years. We present the detection of four new exoplanets. Stars HD 11755, HD 12648, HD 24064, and 8 UMi all show evidence for giant planets in Keplerian motion. The companion to HD 11755 has a minimum mass of 6.5 M_Jup in a 433-day orbit with an eccentricity of 0.19. HD 12648 is orbited by a companion of minimum mass of 2.9 M_Jup having a period of 133 days and an eccentricity of 0.04. Weak surface activity was suspected in HD 24064. However, no evidence was found to be associated with the RV variations. Its companion has a minimum mass of 9.4 M_Jup, a period of 535 days, and an eccentricity of 0.35. Finally, 8 UMi has a minimum mass of 1.5 M_Jup, a period of 93 days with an eccentricity of 0.06.