An Analysis of the Long-term Photometric Behavior of epsilon Aurigae
Abstract
The lure of a 50% reduction in light has brought a multitude of observers and researchers to epsilon Aur every twenty-seven years, but few have paid attention to the system outside of eclipse. As early as the late 1800s, it was clear that the system undergoes some form of quasi-periodic variation outside of totality, but few considered this effect in their research until the mid-1950s. In this work we focus exclusively on the out-of-eclipse (OOE) variations seen in this system. We have digitized twenty-seven sources of historic photometry from eighty-one different observers. Two of these sources provide twenty-seven years of inter-eclipse UBV photometry which we have analyzed using modern period finding techniques. We have discovered the F-star variations are multi-periodic with at least two periods that evolve in time at DP ≈ -1.5 day/year. These periods are detected when they manifest as near-sinusoidal variations at 3,200-day intervals. We discuss our work in an evolutionary context by comparing the behavior found in epsilon Aur with bona-fide supergiant and post-AGB stars of similar spectral type. Based upon our qualitative comparison, we find the photometric behavior of the F-star in the epsilon Aur system is more indicative of supergiant behavior. Therefore the star is more likely to be a "traditional supergiant" than a post-AGB object. We encourage continued photometric monitoring of this system to test our predictions.
- Publication:
-
Journal of the American Association of Variable Star Observers (JAAVSO)
- Pub Date:
- October 2012
- DOI:
- 10.48550/arXiv.1303.6871
- arXiv:
- arXiv:1303.6871
- Bibcode:
- 2012JAVSO..40..647K
- Keywords:
-
- variable stars;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Published in JAAVSO v40n2 http://www.aavso.org/jaavso-v40n2 Also see http://adsabs.harvard.edu/abs/2012JAVSO..40..647K