Variability of the Ap Star HD9996

TL;DR

This study presents new magnetic field measurements of the binary star HD9996, refining its magnetic period to 21.8 years and linking it to the star's precession, with additional analysis of photometric variations and rotational properties.

Contribution

The paper provides the first refined magnetic period for HD9996 and links it to stellar precession, enhancing understanding of magnetic variability in Ap stars.

Findings

Magnetic period of HD9996 refined to 21.8 years

Long-term photometric variations match magnetic period

Evidence suggests the period is related to stellar precession

Abstract

We present here new measurements of the longitudinal magnetic field (B_e) in the binary system HD9996, where the primary companion is an Ap star. Series of 63 B_e observations was obtained in years 1994-2011 with the 1m optical telescope of the Special Astrophysical Observatory (Russia). New magnetic data allowed us to refine the long-term magnetic period of HD9996 to P_mag=21.8 years. Compilation of archival photometric data showed the existence of long term variations of HD9996 in time scale of 22-23 yr consistent with P_mag}. We identify P_mag with the precession period of the primary Ap star and summarize search for a short-term rotational period and the rotational line broadening in this star.