Determination of the radial velocity of two supergiant stars

In the present study, two high-resolution spectra of two supergiant stars, HD 159378 and HD 75276, were analyzed. These spectra were obtained in 2003, using a CCD incorporated into the HERCULES spectrograph, coupled to the 1 m Cassegrain McLellan telescope, from the Mt. John Observatory of the University of Canterbury (New Zealand). Both cover the range lambda lambda similar to 4,500 - 7,080 angstrom, R = 41,000, with a linear dispersion of 2 angstrom/mm, and fractionated into 44 and 46 orders, respectively. For the spectral analysis, the wavelength calibration was performed with a Th-Ar comparison lamp. Using the IRAF (Image Reduction and Analysis Facility) software subroutines and following standard selection criteria, 38 and 146 photospheric lines were identified for HD 159378 and HD 75276, respectively. Applying the Doppler Effect, the average radial velocity was derived for each of the stars with their respective barycentric correction, obtaining the value of (- 14.6 +/- 0.6) km/s and (24.0 +/- 0.4) km /s, for HD 159378 and HD 75276, respectively. In addition to the photospheric lines, it was also possible to identify some of the lines of the Balmer Series; In the case of HD 159378, the H alpha line was identified, , obtaining a radial velocity of- 5.1 km/s. On the other hand, for HD 75276, H beta line could be observed, with a calculated value of the radial velocity of- 24.2 km/s; highlighting the fact that it is the first time that an analysis of any of the lines of the Balmer Series has been carried out for this star and its radial velocity has been calculated. In the range of the two analyzed spectra, no lines in emission or P-Cygni profiles were found.