HD 213637

Lore & Background

HD 213637 was identified as a chemically peculiar star by N. Houk and M. Smith-Moore in 1988. Its spectrum shows strong metallicity and line blocking in the visual band, characteristic of rapidly oscillating Ap stars. The rapid p-mode oscillation was discovered in 1997 by P. Martinez and associates, with a light curve peaking at a pulsation period of 11 minutes. Pulsation amplitudes vary depending on the element measured.

The star possesses a strong surface magnetic field, measured at 740±141 G with a surface field of 5.5 kG. Its effective temperature of 7,030 K is one of the lowest measured for a magnetic chemically peculiar star, including roAp stars. Iron peak elemental abundances are at or below solar, while strontium, yttrium, and zirconium are overabundant.

HD 213637 is estimated to be 570 million years old, with 1.5 times the mass and 1.48 times the radius of the Sun. It radiates 5.5 times the Sun's luminosity. The star rotates slowly, with a projected rotational velocity of 3.5±0.5 km/s. Evolutionary models suggest it is near or past the end of its time on the main sequence.

Reader's Guide

HD 213637 is significant as one of the coolest known rapidly oscillating Ap stars, providing a benchmark for studying magnetic fields and pulsations in chemically peculiar stars at lower effective temperatures. Its strong surface magnetic field and unusual elemental abundances—overabundant in strontium, yttrium, and zirconium while iron peak elements are at or below solar—offer insights into atomic diffusion and magnetic confinement processes. The discovery of its rapid p-mode oscillations in 1997 by P. Martinez and associates added to the small sample of roAp stars with measured pulsation periods, helping refine models of stellar interiors and magnetic field interactions. Its evolutionary status near or past the end of the main sequence, combined with its slow rotation, makes it a valuable case for understanding the late-stage evolution of magnetic Ap stars. The star's distance of about 692 light-years and receding radial velocity of 5.3 km/s place it in a broader Galactic context. As a solitary variable star, it avoids complications from binarity, allowing clearer interpretation of its intrinsic variability and magnetic properties.