Spectroscopic analysis of roAp star HD 60435: Determination of the rotation axis inclination

We present a spectroscopic study of roAp star HD 60435, which ceased pulsating in the last few years. To accurately model a magnetic star’s pulsational behaviour, we need to determine the inclination of the rotational axis to constrain possible geometries. This study contains a detailed vsini analysis based on an extensive spectroscopic data set. HD 60435 was observed with the high-resolution (R=80,000) Veloce spectrograph on four nights across six months. Our observations indicate no evidence of binarity, as there are no double-line profiles, and the radial velocity remains constant. We determined vsini with MCMC profile fitting, including the intrinsic stellar profile (consisting of temperature, micro- and macroturbulence), instrumental broadening and rotational broadening. The fitting process was conducted on a single Fe I line at 543.45 nm, as it is well isolated, insensitive to magnetic broadening, and on a weighted average of LSD profiles. There is no significant difference between the two and no evidence for additional broadening mechanisms in LSD profiles, resulting in a determined value of 11.3 ± 0.5 km/s, with a standard deviation of 0.05 km/s for individual exposures. Further analysis of atmospheric parameters follows with T_eff, logg, and [Fe/H] determined from well-isolated iron lines. These parameters were used to proceed with the determination of individual abundances.