Gearing Up for Epsilon Aurigaes First Eclipse of the Millennium

The mysterious 3rd magnitude long period eclipsing binary star system epsilon Aurigae is predicted to be starting its 2 year eclipse in the late summer of 2009. While this is when the real excitement starts, much is to be learned before first contact. This paper discusses current observational results that have accumulated thus far, using photometric monitoring, H-alpha spectroscopy and with other data sources. Key among the findings are that (1) the low amplitude light variation quasi-period has decreased significantly over the past 20 years, and (2) that the duration of egress, eclipse-to-eclipse has been decreasing, while the duration of total eclipse has been increasing. The website for the observing campaign is: www.du.edu/~rstencel/epsaur.htm .

Three Years of Mira Variable CCD Photometry: What Has Been Learned?

The subject of micro-variability among Mira stars has received increased attention since DeLaverny et al. (1998) reported short-term brightness variations in 15 percent of the 250 Mira or Long Period Variable stars surveyed using the broadband 340 to 890 nm Hp filter on the HIPPARCOS satellite. The abrupt variations reported ranged 0.2 to 1.1 magnitudes, on time-scales between 2 to 100 hours, with a preponderance found nearer Mira minimum light phases. However, the HIPPARCOS sampling frequency was extremely sparse and required confirmation because of potentially important atmospheric dynamics and dust-formation physics that could be revealed. We report on Mira light curve sub-structure based on new CCD V and R band data, augmenting the known light curves of Hipparcos-selected long period variables [LPVs], and interpret same in terms of [1] interior structure, [2] atmospheric structure change, and/or [3] formation of circumstellar [CS] structure. We propose that the alleged micro-variability among Miras is largely undersampled, transient overtone pulsation structure in the light curves.