Magnetic Fields of CP Stars in the OrionOB1 Association. IV. Stars of Subgroup 1b

TL;DR

This study measures magnetic fields in 15 CP stars of OrionOB1 subgroup 1b, revealing a higher prevalence and strength of magnetic fields compared to subgroup 1a, supporting the fossil origin theory of stellar magnetism.

Contribution

It provides new magnetic field measurements for young CP stars in OrionOB1 subgroup 1b, offering insights into magnetic field evolution and testing theories of stellar magnetism.

Findings

Higher proportion of strong magnetic fields in subgroup 1b

Magnetic fields are significantly stronger in subgroup 1b

Supports fossil origin hypothesis of stellar magnetic fields

Abstract

The paper presents magnetic field measurements for 15 chemically peculiar (CP) stars of subgroup~1b in the OrionOB1 association. We have found that the proportion of stars with strong magnetic fields among these 15 CP stars is almost twice as large as in subgroup 1a. Along with this, the age of subgroup 1b is estimated as 2 Myr, and the age of subgroup~1a is in the order of 10 Myr. The average root-mean-square magnetic field Be for stars in subgroup 1b is 2.3 times higher than that for stars in subgroup 1a. The conclusions obtained fall within the concept of the fossil origin of large-scale magnetic fields in B and A stars, but the rate of field weakening with age appears anomalously high. We present our results as an important observational test for calibrating the theory of stellar magnetic field formation and evolution.