MOST Observations of sigma Ori E: Challenging the Centrifugal Breakout Narrative

TL;DR

This study used three weeks of photometric data from the MOST satellite to observe sigma Ori E, finding no evidence of centrifugal breakout and suggesting it does not significantly influence the star's magnetospheric mass.

Contribution

The paper provides observational evidence challenging the role of centrifugal breakout in the magnetospheric dynamics of sigma Ori E.

Findings

No evidence of centrifugal breakout in light curves

Discrepancy between observed and predicted magnetospheric mass

Centrifugal breakout likely not dominant in mass regulation

Abstract

We present results from three weeks' photometric monitoring of the magnetic helium-strong star sigma Ori E using the MOST microsatellite. The star's light curve is dominated by twice-per-rotation eclipse-like dimmings arising when magnetospheric clouds transit across and occult the stellar disk. However, no evidence is found for any abrupt centrifugal breakout of plasma from the magnetosphere, either in the residual flux or in the depths of the light minima. Motivated by this finding we compare the observationally inferred magnetospheric mass against that predicted by a breakout analysis. The large discrepancy between the values leads us to argue that centrifugal breakout does not play a significant role in establishing the magnetospheric mass budget of sigma Ori E.