R Canis Majoris is a bright, short-period (1d.1359) Algol-type eclipsing binary. For a long time, it was considered to be a low-mass binary star with M1 = 1.1M⊙ and M2 = 0.17M⊙ primary and secondary components, respectively (Tomkin, 1985). Glazunova, Yushchenko & Mkrtichian (2009) found new masses for the primary and secondary components of M1=1.81M⊙ and M2=0.23M⊙, respectively and resolved a long-standing problem with the low masses of components for this binary. Budding and Butland (2011) confirmed the results of Glazunova, Yushchenko & Mkrtichian and obtained improved orbits and masses. New spectroscopic observations of R CMa were done during 8 nights on December 2012 with the 2.4-meter telescope of the Thai National Observatory (TNO) and fibre-fed medium resolution echelle spectrograph. We obtained new, accurate orbital radial velocities of the two components of this binary system. Results of these investigations and the new orbital parameters are presented.

ABSTRACT
1. INTRODUCTION
2. OBSERVATIONS AND DATA REDUCTION
3. LSD ANALYSIS AND RV DETERMINATION
4. RADIAL VELOCITY ANALYSIS
5. CONCLUSIONS
REFERENCES

• S. Komonjinda(Department of Physics and Materials Science, Faculty of Science, Chiang Mai University)
• D. E. Mkrtichian(National Astronomical Research Institute of Thailand/Crimean Astrophysical Observatory, Taras Shevchenko National University of Kyiv)
• N. A-thano(Department of Physics and Materials Science, Faculty of Science, Chiang Mai University)