Research Note

The most rapidly rotating He-strong emission line star: HR 7355^*

¹ ESO – European Organisation for Astronomical Research in the Southern Hemisphere, Chile e-mail: tiviniu@eso.org
² Bartol Research Institute, University of Delaware, Newark, DE 19716, USA
³ ESO – European Organisation for Astronomical Research in the Southern Hemisphere, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany

Received: 24 August 2007
Accepted: 29 January 2008

Abstract

Aims. We searched for massive stars with Balmer emission consistent with magnetically confined circumstellar material.

Methods. Archival spectroscopic and photometric data were investigated.

Results. HR 7355 is a formerly unknown He-strong star showing Balmer emission. At mag, it is one of the brightest objects simultaneously showing anomalous helium absorption and hydrogen emission. Among similar objects, only σ 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 0.52 d corresponds to the rotation period. In tandem with the high projected equatorial velocity, v sin i = 320 km s^-1, 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.