Combining BRITE and ground-based photometry for the Beta Cephei star Nu Eridani: impact on photometric pulsation mode identification and detection of several g modes

TL;DR

This study combines space and ground-based photometry to improve pulsation mode identification in Nu Eridani, revealing new gravity modes and highlighting challenges in optical amplitude predictions.

Contribution

It demonstrates that combining BRITE and ground data reduces aliasing and enables detection of additional g modes, advancing pulsation analysis techniques.

Findings

Detected 40 intrinsic periodic signals in Nu Eridani

Identified six new gravity modes not previously reported

Observed temporal amplitude changes affecting mode detection

Abstract

We report a simultaneous ground and space-based photometric study of the Beta Cephei star Nu Eridani. Half a year of observations have been obtained by four of the five satellites constituting BRITE-Constellation, supplemented with ground-based photoelectric photometry. We show that carefully combining the two data sets virtually eliminates the aliasing problem that often hampers time-series analyses. We detect 40 periodic signals intrinsic to the star in the light curves. Despite a lower detection limit we do not recover all the pressure and mixed modes previously reported in the literature, but we newly detect six additional gravity modes. This behaviour is a consequence of temporal changes in the pulsation amplitudes that we also detected for some of the p modes. We point out that the dependence of theoretically predicted pulsation amplitude on wavelength is steeper in visual passbands than those observationally measured, to the extent that the three dominant pulsation modes of Nu Eridani would be incorrectly identified using data in optical filters only. We discuss possible reasons for this discrepancy.