# Why are magnetic Ap stars slowly rotating?

Source: [Why are magnetic Ap stars slowly rotating?](<https://www.sota2.com/research/paper/68fa1e107a2b558e2931f26c>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2025-10-23T13:33:46.368Z

Authors: K. Stepien

Published: 1998-05-05T11:01:18.000Z

## Abstract

Observational data on rotation of Ap stars suggest that the bulk of their rotation rates form a separate Maxwellian distribution with an average value 3-4 times lower than the normal star distribution. No evidences for a significant angular momentum (AM) loss on the main sequence (MS) have been found. It is thus concluded that Ap stars must lose a large fraction of their initial angular momentum (AM) in the pre-MS phase of evolution, most probably as a result of the interaction of their primordial magnetic fields with accretion disks and stellar winds. The observationally most acceptable values of accretion rate from the disk, 10^(-8) M\_sun/year, of mass loss rate via a magnetized wind, 10^(-8) M\_sun/year, and of the surface magnetic field, 1 kG on the ZAMS, result in the AM loss in full agreement with observations.   There exists a separate group of extremely slowly rotating Ap stars, with periods of the order of 10-100 years. They are too numerous to come from the distribution describing the bulk of Ap stars. It is conjectured that their extremely low rotation rates are the result of additional AM loss on the MS.

## Recorded benchmark results

A research result applies to its stated dataset, split, metric and evaluation configuration. Compare like-for-like settings, preserve the metric's unit and direction, and distinguish paper-reported results from independent reproduction. The best result recorded here is not a claim of exhaustive, current global coverage.

## Original sources and implementation

[Original paper](<https://arxiv.org/abs/astro-ph/9805032>)

[PDF](<https://arxiv.org/pdf/astro-ph/9805032.pdf>)