Photoelectric Photometry Newsletter

What My Students Did Last Year

• Akos Bakos [UG] added several years' of new robotic telescope data, and AAVSO PEP program data, to my long-term database of photometric observations of bright, active Be stars, and he generated light curves of the stars to see which ones were particularly active. One example is shown in Figure 2 below:

Figure 2: The long-term V light curve of the bright, active Be star CX Dra, based on observations from a robotic telescope, and from the AAVSO PEP program.

• Heather Dunlop [UTMP] used power spectrum analysis and autocorrelation analysis to analyze AAVSO PEP data on several pulsating red giants in "Project SARV" --- a special project begun several years ago to study some neglected small-amplitude red variables. She was able to determine periods for about a dozen of these stars.
• Trevor Evans [UG] studied the long-term photometric variability of P Cygni; see the report above.

• Lola Kassim [UTMP] used power spectrum analysis and autocorrelation analysis to analyze about a dozen pulsating red giants on the AAVSO PEP program, for which we did not have sufficient data until recently. She was able to determine periods for most of these stars.

• Vince Velocci [UTMP] completed the analysis of three RS CVn stars in the AAVSO PEP program --- HK Lac, SZ Psc, and $\lambda$ And. The results will be submitted to the JAAVSO shortly.

• RV Tauri stars (of which there are two in the AAVSO PEP program, AC Her and U Mon) are characterized by alternating deep and shallow minima. But most RV Tauri stars are more irregular than this. We will try to derive a single number to characterize the regularity or irregularity of these stars, and see if it correlates with any other properties of these stars. This project was inspired by my discussions with graduate student Jenny McSaveney in New Zealand.
• We have analyzed small-amplitude red variables with power spectrum analysis, and autocorrelation analysis, but the technique of wavelet analysis can be useful for some kinds of stars, especially those which change their period, amplitude, or mode. We will use the wavelet analysis program on the AAVSO web site as a new tool for analysing AAVSO PEP program stars of this kind.
• As a star like the sun expands, and becomes a red giant, at some point it becomes unstable and starts to pulsate. What are the properties --- period(s), amplitudes, and pulsation modes --- of these transition stars --- the ones between the non-variable warmer red giants, and the small-amplitude red variables in the AAVSO PEP program? We will use robotic telescope data supplied by Greg Henry to try to answer that question.
• Autocorrelation analysis has proven to be a useful tool for investigating many kinds of variable stars, especially the pulsating red giants on the AAVSO PEP program. We have been using a rather simple autocorrelation algorithm, which we developed independently, having forgotten that G. Burki et al. (Astron. Astrophys, 65, 363 (1978)) had developed one. We are writing a program to implement this algorithm, and testing it on some data on pulsating red giants, provided by Josep Gomez, an amateur astronomer in Spain. We hope to make this program available to others through the AAVSO web site.