Amplitude Variations in Pulsating Yellow Supergiants

It was recently discovered that the amplitudes of pulsating red giants and supergiants vary significantly on time scales of 20-30 pulsation periods. Here, we analyze the amplitude variability in 29 pulsating yellow supergiants (5 RVa, 4 RVb, 9 SRd, 7 long-period Cepheid, and 4 yellow hypergiant stars), using visual observations from the AAVSO International Database, and Fourier and wavelet analysis using the AAVSO's VSTAR package. We find that these stars vary in amplitude by factors of up to 10 or more (but more typically 3-5), on a mean time scale (L) of 33 +/- 4 pulsation periods (P). Each of the five sub-types shows this same behavior, which is very similar to that of the pulsating red giants, for which the median L/P was 31. For the RVb stars, the lengths of the cycles of amplitude variability are the same as the long secondary periods, to within the uncertainty of each.Comment: To be submitted to JAAVS

Forty Years of Linking Variable Star Research with Education

In this review, I reflect on four decades of my experience in linking astronomy research and education by supervising variable-star research projects by undergraduates, and by outstanding senior high school students. I describe the evolution of my experience, the students I have supervised, the nature of their projects, the educational contexts of the projects, the need for "best practices", the journals in which we publish, and the special role of the American Association of Variable Star Observers (AAVSO). I then describe our recent research on pulsating red giants and related objects, including three astrophysical mysteries that we have uncovered. Finally, I suggest how my projects might be scaled up or extended by others who supervise student research.Comment: Submitted to the proceedings of the conference "Remote Telescopes, Student Research, and Education

Long Secondary Periods in Pulsating Red Giants: A Century of Investigation

Red giants are unstable to radial pulsation. About a third of them also show a long secondary period, 5 to 10 times the pulsation period. The long secondary periods were recently ascribed to eclipses of the red giant by a low-mass dust-enshrouded companion. Long secondary periods have been known for over a century. In this paper, I use primarily American Association of Variable Star Observers visual and photoelectric observations to look for evidence of long secondary periods in 103 red giant stars listed by Nancy Houk in 1963 as having long secondary periods, based mostly on photographic photometry. I have determined long secondary periods in 37 stars, and upper limits (some of them not very stringent) in 25. In the former, the ratio of long secondary period to pulsation period peaks strongly at 10, which suggests that most of the stars are pulsating in the first overtone. The loong secondary periods are consistent with those o0f Houk in 33 of the 37 stars. I have identified 16 stars as bimodal pulsaters;their period ratios are consistent with previous observational and theoretical results. For 14 stars,the periods in the General Catalogue of Variable Stars are incorrect or absent

Methodological Guidelines for Advertising Research

In this article, highly experienced advertising academics and advertising research consultants John R. Rossiter and Larry Percy present and discuss what they believe to be the seven most important methodological guidelines that need to be implemented to improve the practice of advertising research. Their focus is on methodology, defined as first choosing a suitable theoretical framework to guide the research study and then identifying the advertising responses that need to be studied. Measurement of those responses is covered elsewhere in this special issue in the article by Bergkvist and Langner. Most of the frameworks are derived from the authors\u27 own published work, although other frameworks are noted where appropriate