Volume 36 Number 2 JAAVSO 2008 The Journal of the American Association of Variable Star Observers Research from the University of Toronto Mentorship Program Bernadette Ho, Elena Favaro, and Jou Glasheen, co-authors of a study on pulsating red supergiant stars in this issue, with their poster at the University of Toronto Mentorship Program Research Fair. Also in this issue... • HD 208238 as a d Scuti Variable Star • The Light Curve of SU Carinae • Recent Minima of Eclipsing Binary Stars • Frequency Analysis of Long-term AAVSO Visual Observations 49 Bay State Road Cambridge, MA 02138 Complete table of contents inside... U. S. A. The Journal of the American Association of Variable Star Observers Editor Associate Editor Charles A. Whitney Elizabeth O. Waagen Harvard-Smithsonian Center for Astrophysics Assistant Editor 60 Garden Street Matthew Templeton Cambridge, MA 02138 Production Editor Michael Saladyga Editorial Board Priscilla J. Benson John R. Percy Wellesley College University of Toronto Wellesley, Massachusetts Toronto, Ontario, Canada Douglas S. Hall David B. Williams Vanderbilt University Indianapolis, Indiana Nashville, Tennessee Thomas R. Williams Houston, Texas The Council of the American Association of Variable Star Observers 2007–2008 Director Arne A. Henden President Paula Szkody Past President David B. Williams 1st Vice President Jaime Ruben Garcia 2nd Vice President Michael A. Simonsen Secretary Gary Walker Treasurer David A. Hurdis Clerk Arne A. Henden Councilors Barry B. Beaman Arlo U. Landolt James Bedient Karen Jean Meech Gary Billings Christopher Watson Pamela Gay Douglas L. Welch ISSN 0271-9053 JAAVSO The Journal of The American Association of Variable Star Observers Volume 36 Number 2 2008 49 Bay State Road Cambridge, MA 02138 ISSN 0271-9053 U. S. A. The Journal of the American Association of Variable Star Observers is a refereed scientific journal published by the American Association of Variable Star Observers, 49 Bay State Road, Cambridge, Massachusetts 02138, USA. The Journal is made available to all AAVSO members and subscribers. In order to speed the dissemination of scientific results, selected papers that have been refereed and accepted for publication in the Journal will be posted on the internet at the eJAAVSO website as soon as they have been typeset and edited. These electronic representations of the JAAVSO articles are automatically indexed and included in the NASA Astrophysics Data System (ADS). eJAAVSO papers may be referenced as J. Amer. Assoc. Var. Star Obs., in press, until they appear in the concatonated electronic issue of JAAVSO. The Journal cannot supply reprints of papers. Page Charges Unsolicited papers by non-Members will be assessed a charge of $15 per page. 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Equations should be referred to in the text as, e.g., equation (1). 2) Magnitude will be assumed to be visual unless otherwise specified. 3) Manuscripts may be submitted to referees for review without obligation of publication. © 2008 The American Association of Variable Star Observers. All rights reserved. Journal of the American Association of Variable Star Observers Volume 36, Number 2, 2008 Period Changes in Pulsating Red Supergiant Stars: A Science and Education Project John R. Percy, Elena Favaro, Jou Glasheen, Bernadette Ho, Hiromitsu Sato 145 HD 208238 as a d Scuti Variable Star Garrison Turner, Ronald Kaitchuck, Brian Skiff 156 The Light Curve of SU Carinae Alan Plummer, Mati Morel 162 Recent Minima of 155 Eclipsing Binary Stars Gerard Samolyk 171 Recent Minima of 184 Eclipsing Binary Stars Gerard Samolyk 186 Frequency Analysis of Long-term AAVSO Visual Observations of TU Cas Shawn Dvorak 207 Abstracts of Papers and Posters Presented at the 96th Annual Meeting of the AAVSO, November 1–3, 2007, Cambridge, Massachusetts, BVRI Photometry of CX Cephei (WR 151) Kate Hutton, Arne A. Henden, Michael Koppelman 214 On the Classification of V3798 Sgr David Sliski 215 AH Leo: 2004–2007 P. Gay, M. Kozubal, D. E. R. Bemrose-Fetter 215 Time Series Observations of IP Pegasi Using an Inexpensive Ambient Temperature CCD Camera George H. Keel, Keith A. Graham, Donald F. Collins 216 Search for Dwarf Novae in DASCH Scans Near M44 Sumin Tang, Silas Laycock, Jonathan Grindlay 217 High Speed Photometry of V455 Andromedae With a Small Telescope (poster) Donald F. Collins 217 The Challenge of Finding the Comet for the Deep Impact Extended Mission Karen Meech 218 Variable Star Spectroscopy: Tools, Techniques, and Recent Results Matthew M. Beaky 219 Have Scope--Will Travel Gerald P. Dyck 219 The New DASCH Web Page (poster) Edward J. Los 220 Table of Contents continued on next page HI STAR: Building Bridges Between AAVSO Observers and High School Students Catherine A. Garland, Mary Ann Kadooka, Donn R. Starkey, Michael A. Nassir 220 Hands-On Astrophysics and the Science Olympiad Donna L. Young 221 Light and Optics Demonstrations for Astronomy Mary Ann Kadooka 221 The Orbit of Venus--A Lab Exercise Ronald E. Zissell 222 Maria Mitchell: Portrayed in a New Biography Barbara L. Welther 222 Extending Maria’s Legacy Gary Walker 222 Index to Volume 36 223 Erratum 265 Percy et al., JAAVSO Volume 36, 2008 145 Period Changes in Pulsating Red Supergiant Stars: A Science and Education Project John R. Percy Elena Favaro Jou Glasheen Bernadette Ho Hiromitsu Sato Department of Astronomy and Astrophysics, University of Toronto, Toronto ON Canada M5S 3H4 David G. Turner Department of Astronomy and Physics, Saint Mary’s University, Halifax NS B3H 3C3 Based on a paper presented at the 96th Fall Meeting of the AAVSO, Cambridge MA, November 3, 2007. Received February 22, 2008; accepted March 26, 2008 Abstract We describe research done as part of the University of Toronto Mentorship Program, which enables outstanding senior high school students to work on research projects at the university. The students began with extensive background reading on variable stars, and became familiar with various forms of time-series analysis by applying them to a few red supergiant variables in the AAVSO International Database; we report on the results. They also prepared a useful manual for our publicly-available self-correlation analysis software. They undertook an intensive analysis of the period changes in BC Cyg, using the AAVSO and Turner data and the (O–C) method, in the hope that evolutionary period changes could be observed. The (O–C) diagram, however, is dominated by errors in determining the times of maximum, and by the effects of cycle-to-cycle period fluctuations. As a result, the (O–C) method is generally not effective for these stars. We also describe the Mentorship Program and its elements, and reflect on the students’ experience. 1. Introduction Red supergiants are the coolest, largest, most luminous stars, up to a thousand times larger in radius than the Sun. They are massive young stars in the final rapid stages of thermonuclear evolution. They undergo a complex variety of physical processes, including convection, pulsation, and extensive mass loss, which causes most of them to be shrouded in gas and dust. They are also all variable, though not strictly periodic, being classified as SRc if they 146 Percy et al., JAAVSO Volume 36, 2008 are semiregular, and Lc if they are not. They vary typically on time scales of hundreds to thousands of days, and amplitudes up to a few magnitudes.