HD 51844: an eccentric delta Scuti star
Markus Hareter

HD 51844 is a binary system composed of two nearly equal stars, where one component pulsates. The orbital period is 33.5 days and the eccentricity is 0.49. We could identify 115 pulsation frequencies where the dominant four frequencies account for most of the pulsational light variation. The pulsation frequencies show resonances (ratios of 3:2, 3:4 and 3:5), an effect which has not yet been reported for delta Scuti stars. Moreover, the light curve shows a brightening event of 3 mmag, but no eclipses. Thus, HD 51844 is the first "Heartbeat" star reported among the CoRoT targets. A dedicated spectroscopic campaign allowed to derive the radial velocity curves and the chemical composition of the photosperes. Both stars are chemically peculiar of Delta Delphini type, meaning (mild) Am/Fm peculiarities. Both components exhibit strong lines of s-process elements, but the most significant difference is in Sc. While the pulsating star shows weak Sc lines, the nonpulsating star shows a slightly subsolar Sc abundance. When comparing the frequency modulation from photometry to the analysis of the radial velocities from spectroscopy, one finds that for such stars, the spectroscopic analysis is superior to the analysis of light curve alone, even though the CoRoT light curve is of excellent quality. We also searched for the possible "large separation" of the pulsation frequencies and found a good candidate spacing of 1.74 c/d.