A search for rapid pulsations in the magnetic cool chemically peculiar star HD3980

TL;DR

This study searched for rapid pulsations in the magnetic Ap star HD3980 using high-resolution spectroscopy but found no pulsations above 20-30 m/s, despite its promising parameters for roAp star behavior.

Contribution

The paper provides the first detailed spectroscopic analysis of HD3980, including chemical abundances and magnetic field measurements, and reports a null detection of rapid pulsations.

Findings

No pulsations detected above 20-30 m/s.

Chemical abundances show large overabundances of rare earth elements.

Line profile variability correlates with rotation period.

Abstract

The Ap star HD3980 appears to be a promising roAp candidate based on its fundamental parameters, leading us to search for rapid pulsations with the VLT UV-Visual Echelle Spectrograph (UVES). A precise Hipparcos parallax and estimated temperature of 8100K place HD3980 in the middle of the theoretical instability strip for rapidly oscillating Ap stars, about halfway through its main sequence evolution stage. The star has a strong, variable magnetic field, as is typical of the cool magnetic Ap stars. Dipole model parameters were determined from VLT observations using FORS1. From Doppler shift measurements for individual spectral lines of rare earth elements and the H-alpha line core, we find no pulsations above 20-30 m/s. This result is corroborated by inspection of lines of several other chemical elements, as well as with crosscorrelation for long spectral regions with the average spectrum as a template. Abundances of chemical elements were determined and show larger than solar abundances of rare earth elements. Further, ionisation disequilibria for the first two ionised states of Nd and Pr are detected. We also find that the star has a strong overabundance of manganese, which is typical for much hotter HgMn and other Bp stars. Line profile variability with the rotation period was detected for the majority of chemical species.