The most rapidly rotating He-strong emission line star: HR7355

TL;DR

This paper reports the discovery and analysis of HR 7355, the fastest rotating He-strong star with Balmer emission, revealing new insights into the properties of magnetically confined circumstellar material in such stars.

Contribution

It identifies HR 7355 as the most rapidly rotating He-strong star known, with detailed spectroscopic and photometric analysis of its emission and rotation characteristics.

Findings

HR 7355 is the fastest rotating He-strong star known.

It exhibits Balmer emission and anomalous helium absorption.

The star's rotation period is approximately 0.52 days.

Abstract

Using archival spectroscopic and photometric data, we searched for massive stars with Balmer-emission consistent with magnetically confined circumstellar material. HR 7355 is a formerly unknown He-strong star showing Balmer emission. At V=6.02 mag, it is one of the brightest objects simultaneously showing anomalous helium absorption and hydrogen emission. Among similar objects, only sigma Ori E has so far been subjected to any systematic analysis of the circumstellar material responsible for the emission. We argue that the double-wave photometric period of 0.52d corresponds to the rotation period. In tandem with the high projected equatorial velocity, v sin i=320 km/s, this short period suggests that HR 7355 is the most rapidly rotating He-strong star known to date; a class that was hitherto expected to host stars with slow to moderate rotation only.