Solar-type Oscillations in Procyon: Test Observations with the Iodine Cell and the HIgh Dispersion Echelle Spectrograph (HIDES)

E. Kambe1, B. Sato2,3, Y. Takeda4, H. Izumiura3, S. Masuda3
1 Department of Earth and Ocean Sciences, National Defense Academy, Yokosuka, Kanagawa 239-8686, Japan
2 Department of Astronomy, School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
3 Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Kamogata-cho, Okayama 719-0232, Japan
4 Komazawa University, Komazawa, Setagaya, Tokyo 154-8525, Japan

 

We made a test observation of a possible solar-type oscillating star, Procyon, with our newly developed iodine cell for the Okayama 1.88 m reflector and its HIgh Dispersion Echelle Spectrograph. About 550 stellar spectra superposed by iodine molecular lines (star+I2 spectra) were obtained during five consecutive nights in December, 2000. We estimated a stellar radial velocity of each spectrum by modeling star+I2 spectrum with our preliminary I2 data analysis computer codes. The method is similar to that by Valenti et al. (1995) and an instrumental profile of each spectrum is corrected for using I2 lines.
Our preliminary results show that the radial velocity of the star was stable within an accuracy of 4 ms-1, with an exception of its hours-to-days variation of an amplitude of about 10 ms-1. The variation is highly artificial due to insufficient modeling of the star+I2 spectra. The result of period analysis of the radial velocity of the star, however, shows power excesses at frequencies around 1 mHz, which may be due to solar-type oscillations in the star. Our periodogram is consistent to those in previous literatures but the highest peak amplitude of 70 cms-1 may be slightly lower than before. From our observations alone, it is difficult to detect possible frequency patterns in the periodogram which are predicted by theories of nonradial pulsations.
We continuously improve our I2 data analysis softwares. One of our aims is to derive consistent radial velocities from multi-site observations. We are going to observe Procyon again next December.

 
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