Observing Variable Stars PDF
Preview Observing Variable Stars
Patrick Moore's Practic al Astronomy Series Springer-V erlag London Ltd. Other titles in this series TelescopesandTechniques ChrisKitchin TheArtand ScienceofCCDAstronomy DavidRatledge(Ed.) TheObserver'sYear PatrickMoore SeeingStars ChrisKitchinand Robert W.Forrest Photo-guide totheConstellations ChrisKitchin TheSuninEclipse MichaelMaunderand PatrickMoore Softwareand DataforPracticalAstronomers DavidRatledge Amateur TelescopeMaking StephenF.Tonkin ObservingMeteors,Comets,Supernovae and other TransientPhenomena NeilBone Astronomical Equipment forAmateurs Martin Mobberley Transit:WhenPlanetsCrosstheSun MichaelMaunderand PatrickMoore PracticalAstrophotography JeffreyR.Charles ObservingtheMoon PeterT.Wlasuk Deep-SkyObserving StevenR.Coe AstroFAQs Stephen F.Tonkin TheDeep-SkyObserver'sYear GrantPrivettand PaulParsons FieldGuidetotheDeepSkyObjects Mike Inglis Choosingand UsingaSchmidt-CassegrainTelescope RodMollise Astronomy withSmallTelescopes Stephen F.Tonkin (Ed.) SolarObservingTechniques ChrisKitchin ObservingthePlanets PeterT.Wlasuk LightPollution BobMizon UsingtheMeadeETX Mike Weasner PracticalAmateur Spectroscopy Stephen F.Tonkin (Ed.) MoreSmallAstronomicalObservatories PatrickMoore(Ed.) Observer'sGuidetoStellarEvolution Mike Inglis HowtoObservetheSunSafely LeeMacdonald ThePracticalAstronomer'sDeep-skyCompanion JessK.Gilmour ObservingComets NickJamesand GeraldNorth Gerry A. Good With 55 Figures , Springer Cover illustration: An artist's impression of an eclipsing variable star. British Library Cataloguing in Publication Data Good, Gerry A. Observing variable stars. - (Patrick Moore' s practical astronomy series) 1. Variable stars - Observers' manuals 2. Variable stars - Amateurs' manuals I. Title 523.8'44 ISBN 978-1-85233-498-7 Library of Congress Cataloging-in-Publication Data Good, Gerry A., 1954- Observing variable stars I Gerry A. Good. p. cm. - (Patrick Moore's practical astronomy series, ISSN 1617-7185) Includes bibliographical references and index. ISBN 978-1-85233-498-7 ISBN 978-1-4471-0055-3 (eBook) DOI 10.1007/978-1-4471-0055-3 1. Variable stars - Observers' manuals. I. Title. II. Series. QB835.G58 2003 523.8' 44-dc21 2002190895 Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms of licences issued by the Copyright Licensing Agency. Enquiries concerning reproduction outside those terms should be sent to the publishers. Patrick Moore's Practical Astronomy Series ISSN 1617-7185 http://www.springer.co.uk © Springer-VerIag London 2003 Origina11y published by Springer-VerIag London Limited in 2003 The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant laws and regulations and therefore free for general use. The publisher makes no representation, express or implied, with regard to the accuracy of the information contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may be made. Observing the Sun, along with a few other aspects of astronomy, can be dangerous. Ne ither the publisher nor the authors accept any legal responsibility or liability for personal loss or injury caused, or alleged to have been caused, by any information or recommendation contained in this book. Typeset by EXPO Holdings, Malaysia 58/3830-543210 Printed on acid-free paper SPIN 10836542 Acknowledgments Ibegan thisbook asasimple projectto formalize much of the information and methods that I wanted at my fingertipswhenIobservevariablestars. Soonthereafter, it was suggested that I may want to share this information. I could have written a book three times this sizebut then no one would publish it. Nobook iseverwrittenbyone person. Thisone isno exception so I would like to acknowledge the many people from whom I've received assistance, encourage ment, and advice: Dr. John Percy, University of Toronto, a strong advocate of professional-amateur collaboration within the astronomy community, for pointing me in the right direction regarding profes sional-amateur partnerships; Dr. Robert Stebbins, University of Calgary, for providing me with his excellent research studies regarding professional amateurpartnerships;Dr.JoePatterson,Columbia Uni versityand guiding mentor for the Center for Backyard Astrophysics, for allowing me to use CBA material in this book;Dr.Taichi Kato,Kyoto University, Japan, for assistance and kind words during the WZ Sagittae campaign and for permission to use VSNET data and charts; Dr. Tim Brown, High Altitude Observatory/ National Center for Atmospheric Research for allowing me to use data and charts; Dr. Michel Breger for allowingmeto usedata and informationfrom the Delta Scuti network; Dr. Douglas Hall for allowing me to use IAPPPdata;Dr. Janet Mattei, American Association of Variable Star Observers,for allowingme to useAAVSO charts and data;Dr.Arne Hendon, United States Naval Observatory, FlagstaffStation, who has answered many questions over several years and for providing much "publicdomain" advice;GaryPoyner,astronomerfrom Birmingham, England, and well-known cataclysmic variable observer, for suggesting topics concerning cataclysmic variable observations; Emile Schweitzer, past presidentofthe AFOEV forallowingme to use the organization's variable star data; Roger Pickard, Pre- v vi Observing Variable Stars sident ofthe BritishAstronomical AssociationVariable StarSectionforallowingme to use BAAVSS data;Kari Tikkannen, Finland, for allowing me to use his data and charts; Olga V. Durlevich, GCVS research team, Sternberg Astronomical Institute, Moscow, Russia, for permission to useGCVSdata and quotes; John Watson, my publisher for allowing me to proceed with kind guidance and encouragingwords;Dr.Thomas William son, good friend and observing partner, whose contagious enthusiasm for astronomy has forced me to believethat sleepisreallyaluxury; LisaWood, good friend and observing partner,whohasread and re-read many draft manuscripts of this book, provided myriad suggestions, and allowed me to spend hundreds of hours observingwithher and sharing her successesand challengesso that we can alllearn something from her experiences; and my wife, Iillian, who has tolerated months of clunking, clanking and drive motor noise during many late-night observing sessions, along with weekends spent analyzing light curves, reading manu scripts and patientlylistening to me talkabout variable stars. Thank you all. Contents Observing Variable Stars 1 2 The Variable Stars 21 3 Eruptive Variable Stars 37 4 Pulsating Variable Stars 57 5 Cataclysmic(Explosiveand Novalike) Variables 97 6 Rotating Variable Stars............... .... 127 7 CloseBinary Eclipsing Systems... .... .... . 139 8 OpticallyVariable CloseBinary Sources of Strong, Variable X-RayRadiation (X-RaySources)... .................. .... 157 9 AGeneral Approach to Observing Variable Stars .. ................................ 165 10 VSO Planning 189 11 VSO Preparations ....................... 201 12 VSO Methods 217 13 Variable Star Data Management, Reduction and Analysis 233 14 Variable Star Reporting and Recording Organizations........................... 253 15 Variable Star Observing and Amateur Astronomers. ........................... 259 vii viii ObservingVariable Stars Appendix A Database Management 265 Appendix B Time Series Analysis Using TSll .. 267 Appendix C Analysis Using Spreadsheets 269 Index 271 Weshallnot ceasefrom exploration And the end ofallour exploring Willbeto arrive wherewestarted And know the placefor the firsttime. T.S.Eliot Set free your imagination and consider one of the remarkable curiosities ofnature. Astar located 600light-years from Earth is about to do something cataclysmic. In truth, it did so 600years ago. However, as if looking through a time machine, you can see it happen tonight. It took 600years for the light record of this amazing event to reach us, even traveling at 300,000 kilometers per second. Upon close examinationofthisstar youwilldiscover that itisreally two stars, a binary system, but to your naked eye it appearsasasinglestar because ofitsimmensedistance. As a coincidence of nature, one of the stars of this binary system is much like our Sun, a relatively small yellowstar. However,the second starofthis system isa much smaller white dwarf, only about as big as the Earth and itisbright blue. Amillion Earth-sized planets would fit into our Sun so compared to its larger companion this planet-sized dwarfisas a fleato a dog. Remarkably, the two stars orbit each other in just a fewhours.Theyareverycloseto eachother;the second reason that the two stars appear as one star. Another amazing factisthat althoughthe smaller star isonlythe size ofthe Earth it isas heavy as our Sun. Ifyou could bring a piece of this star that was the size of a sugar cube to Earth, it would weigh 16tons (tonnes). Even more impressive, because gravity is so much stronger G. A. Good, Observing Variable Stars © Springer-Verlag London Limited 2003 2 Observing Variable Stars on the surface of the massive white dwarf, this sugar cubesizedpieceofstar stuffweighs470,000timesmore Figure 1.1.Artist's conception ofa dwarf at this star's surface than it would on the Earth's novo showing thetendril surface;an unbelievable 7.5million tons! of hydrogen forming on As a result of the larger star being so close to the accretion diskaround smaller star,aswellasthe massivenature ofthe dwarf thewhite dwarfstar. star, gravity allows the smaller star to steal hydrogen Copyright;GerryA.Good. fromthelargeroneatanimpressiverate.Atremendous amountofhydrogen isconstantlybeingpulledfromthe larger star forming a gigantic tendril of streaming hot gasleadingto adiskofstolenfuelthat isnowencircling the smaller star like a giant donut (Figure 1.1). Hydrogen is the fuel of stars and it is the primary source of energy that powers most of them. In this situation, the hydrogen will fuel a catastrophic explo sion and thelarcenous nature ofthe smallerstar willbe responsible fortheeventualdeath ofthisbinary system! Butthat willbe in the far future. Tonight, in a spectacular demonstration of these chaoticcircumstances and everytwoweekshence,after thediskofhydrogen gashas againgrownto asufficient size, the smaller star will proclaim its theft by
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