Extrasolar planet searches at the TUG: Test observations and capabilities

A small group of collaborators was established at the end of 2007 with the objective of starting an extrasolar planet search at the TÜBİTAK National Observatory of Turkey. High resolution spectra of some radial velocity standards and planet-harbouring stars have since been obtained using an iodine (I2) absorption cell placed in front of the entrance slit of the Coude Echelle Spectrograph (CES) in the 1.5-m Russian-Turkish Telescope (RTT150). To determine precise radial velocity measurements for these stars, a new computer code was developed by one of the collaborators (MY) using an IDL (Interactive Data Language) programing platform specific to the RTT150’s CES + I2-cell data. This paper summarises the technical setup, the new code, the test observation results and the precision achieved in the radial velocity measurements. The results from radial velocity standards and planet-harbouring stars show that a precision of approximately 10 m s−1 was achieved with the CES on the RTT150 during the three years of test observations. In addition, the instrumental profile (IP) characteristics of the CES on the RTT150 in this study were derived by modelling the observed B-star + I2 spectra. The observed instrumental profiles were a typical Gaussian shape and exhibited small variations that depended on the position on the CCD and also varied between exposures, which affected the precision of the radial velocity measurements.

► We started a extrasolar planet search survey at Turkish National Observatory.
► I2-cell was successfully installed to the Coude Echelle Spectrograph at RTT150.
► We achieved a precision about 10 m/s for CES on RTT150.
► A specific computer code was developed to determine radial velocity measurements.
► We continue to follow radial velocity variations of 50 selected G and K giants.