August 7-10, 2017

Abstract

Pulsation of the magnetic, ultra-slowly rotating beta Cep star xi 1 CMa

Gregg Wade (Royal Military College of Canada)

Gregg Wade (RMC), Sean Begy (RMC), Gerald Handler (NCAC), Matt Shultz (Uppsala), Andrzej Pigulski (Wroclaw)

Xi 1 CMa (HD 46328) is a B0.5IV beta cep variable with a surface magnetic field of moderate strength. It exhibits slow, systematic modulation of its longitudinal field and magnetospheric Halpha emission, interpreted to result from an extraordinarily long (>30 yr) rotation period. Remarkably, its Halpha emission and X-ray emission appear to vary according to the 0.2~d pulsation period, implying that the starís magnetosphere is periodically distorted by its pulsation. Xi 1 CMa was observed by 3 BRITE satellites in two colours (BTr, BLb, and BHr) for 167 days in 2015. We have combined these data with Hipparcos photometry, two-colour ground-based Stromgren photometry, and an extensive database of radial velocity measurements. Using this combined dataset, we establish the variability characteristics of the star, demonstrating that it is a monoperiodic radial pulsator. We furthermore test claims of long-term drift of the pulsation period.

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