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Session 46 - Variable Stars - Late Type.
Display session, Thursday, January 08
Exhibit Hall,

[46.08] Studies of Long-Period Variables

J. A. Mattei, G. Foster (AAVSO)

Recently, the American Association of Variable Star Observers (AAVSO) has completed digitizing all the variable star data collected since our founding in 1911. With over 8.5 million computerized observations, the AAVSO International Database contains up to 86 years of data for roughly 3500 stars. For most of the variables included, it is the only source of light curves with uninterrupted coverage over decades. This has enabled us, over the last year, to undertake two large-scale studies of the visual light curves of long-period variables (LPVs): first, a study of 51 carbon-rich LPVs; second, an analysis of 245 LPVs observed by the Hipparcos satellite.

We highlight some of the interesting results to emerge, including: 1. The periods, amplitudes, and other parameters of most Miras show discernable trends, not just random cycle-to-cycle fluctuations. 2. Carbon-rich Miras fall in a significantly different range of periods and amplitudes than oxygen-rich Miras. 3. Oxygen-rich Miras of spectral type M show numerous strong relationships between period, amplitude, light curve shape, spectral subtype, and B-V and V-I color indices. 4. The periods and amplitudes of most SR variables are so unstable, that at some time, the amplitude of each period drops below our detection threshold (\approx 0.05 - 0.1 mag). 5. Most SR variables are multiperiodic, showing two periods in the ratio 1.7 \le P_1/P_2 \le 1.95. 6. Some SR variables have been positively confirmed as exhibiting three periods.

The above is just an example of the kind of study possible with the AAVSO database. We welcome proposals from researchers interested in collaborating on these studies.

We gratefully acknowledge NASA grant NAGW-1493 which partially supported these studies.

Program listing for Thursday