The Initial Magnetic Field Distribution in AB Stars

TL;DR

This study infers the initial magnetic field distribution of AB stars by combining observations and models, revealing a Gaussian distribution with a mean around 770 G, but also highlighting discrepancies with independent measurements.

Contribution

It provides the first detailed inference of initial magnetic field distributions in AB stars, suggesting a possible bimodal or mass-dependent distribution.

Findings

Most consistent distribution is Gaussian with mean 770 G and std 146 G.

Discrepancy between inferred and independent measurements suggests complex field origins.

Initial magnetic fields may be bimodal or vary with stellar mass.

Abstract

Stars are born with magnetic fields, but the distribution of their initial field strengths remains uncertain. We combine observations with theoretical models of magnetic field evolution to infer the initial distribution of magnetic fields for AB stars in the mass range of 1.6 - 3.4 M$_{\odot}$. We tested a variety of distributions with different shapes and found that a distribution with a mean of $\sim$800 G and a full width of $\sim$600 G is most consistent with the observed fraction of strongly magnetized stars as a function of mass. Our most-favored distribution is a Gaussian with a mean of $\mu$ = 770 G and standard deviation of $\sigma$ = 146 G. Independent approaches to measure the typical field strength suggest values closer to 2 - 3 kG, a discrepancy that could suggest a mass-dependent and bimodal initial field distribution, or an alternative theoretical picture for the origin of these magnetic fields.