AAS 204th Meeting, June 2004
Session 7 A Walk Through the HR Diagram
Poster, Monday, May 31, 2004, 9:20am-6:30pm, Ballroom

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[7.09] Precision Photometry of Long Period Variable Stars

D.E. Mais (Palomar College), A. Bhatia, R.E. Stencel (Univ. Denver), D. Richards (Wessex Astronomy Society)

Recently, evidence has been accumulating to suggest that Mira variables may go through flare up stages which result in brightening on the order of several tenths of a magnitude or more, and may last hours to days in length (Schaefer 1991, Maffei and Tosti 1995 and de Laverny 1998). Very little is known about these events, indeed it is not clear that these events are real. If they are real events, the spectroscopic changes, which occur during these flare-up episodes, remain relatively unexplored. This project was initiated in order to monitor a group of program stars of these classes in the V and R photometric bands in the hopes of “catching” some of these stars during these flare ups, thus offering confirmation to their reality and to be able to conduct spectral analysis of the flare-ups in real time and compare these spectra to the non-flare spectra. During the course of the past year, nearly 98 program stars have been monitored to address the potential flare up episodes. These include 25 M-type, 16-S type and 57 C-type Mira’s. However, this more careful monitoring appears to not detect comparable behavior in similar stars near their minimum light, but rather exhibits a “Cepheid bump-like” phenomenon in several cases after minimum light, typically around phase 0.6-0.8 (cf. Melikian, 1999). Interpretation as an intermittent overtone pulsation is provided, and its effect on dust production discussed. We acknowledge support from the estate of William Herschel Womble, for the University of Denver astronomers participating in this effort.

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The author(s) of this abstract have provided an email address for comments about the abstract: dmais@ligand.com

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