Eta Carinae and the Supernova Impostors Astrophysics and Space Science Library EDITORIALBOARD Chairman W.B.BURTON,NationalRadioAstronomyObservatory,Charlottesville,Virginia,U.S.A. ([email protected]);UniversityofLeiden,TheNetherlands ([email protected]) F.BERTOLA,UniversityofPadua,Italy J.P.CASSINELLI,UniversityofWisconsin,Madison,U.S.A. C.J.CESARSKY,CommissionforAtomicEnergy,Saclay,France P.EHRENFREUND,LeidenUniversity,TheNetherlands O.ENGVOLD,UniversityofOslo,Norway A.HECK,StrasbourgAstronomicalObservatory,France E.P.J.VANDENHEUVEL,UniversityofAmsterdam,TheNetherlands V.M.KASPI,McGillUniversity,Montreal,Canada J.M.E.KUIJPERS,UniversityofNijmegen,TheNetherlands H.VANDERLAAN,UniversityofUtrecht,TheNetherlands P.G.MURDIN,InstituteofAstronomy,Cambridge,UK F.PACINI,IstitutoAstronomiaArcetri,Firenze,Italy V.RADHAKRISHNAN,RamanResearchInstitute,Bangalore,India B.V.SOMOV,AstronomicalInstitute,MoscowStateUniversity,Russia R.A.SUNYAEV,SpaceResearchInstitute,Moscow,Russia Forfurthervolumes: http://www.springer.com/series/5664 Kris Davidson • Roberta M. Humphreys Editors Eta Carinae and the Supernova Impostors 123 Editors KrisDavidson RobertaM.Humphreys MinnesotaInstituteforAstrophysics MinnesotaInstituteforAstrophysics UniversityofMinnesota UniversityofMinnesota 116ChurchStreetSE 116ChurchStreetSE Minneapolis,MN55455 Minneapolis,MN55455 USA USA ISSN0067-0057 ISBN978-1-4614-2274-7 e-ISBN978-1-4614-2275-4 DOI10.1007/978-1-4614-2275-4 SpringerNewYorkDordrechtHeidelbergLondon LibraryofCongressControlNumber:2012930990 ©SpringerScience+BusinessMedia,LLC2012 Allrightsreserved.Thisworkmaynotbetranslatedorcopiedinwholeorinpartwithoutthewritten permission of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York, NY10013, USA),except forbrief excerpts inconnection with reviews orscholarly analysis. Usein connectionwithanyformofinformationstorageandretrieval,electronicadaptation,computersoftware, orbysimilarordissimilarmethodologynowknownorhereafterdevelopedisforbidden. Theuseinthispublicationoftradenames,trademarks,servicemarks,andsimilarterms,eveniftheyare notidentifiedassuch,isnottobetakenasanexpressionofopinionastowhetherornottheyaresubject toproprietaryrights. Coverillustration:Color-compositeimageoftheCarinaNebula,revealingexquisitedetails inthestarsanddustinthenebula.EtaCarinaeisatthecenterwiththeKeyholeNebulajust toitsright.NorthisupandEastistotheleft.Credit:ESO. Printedonacid-freepaper SpringerispartofSpringerScience+BusinessMedia(www.springer.com) To theobservers oftheSouthernSky. Preface Eta Carinae is well knownto astronomersforits manysuperlatives.It is the most massive, most luminous star in our region of the Milky Way. During its “Great Eruption”170yearsagoitejected10M(cid:2)ormore,creatingitsfamousHomunculus Nebula. We now know that its Great Eruption was the energetic, non-terminal explosion of a very massive star nearing the end of its short life. But ηCar and itsGreatEruptionmaynotbeunique,someweirdevent,onlyobservedonce. In1965FritzZwickyproposedaclassofsupernovaeventshecalled“TypeV”, relativelyfaintatmaximumwithlongdurations.Therewereonlytwomembersof hisType V group,ηCar andSN1961v.These stars were nottrue supernovaeand today we recognize several stars that had giant eruptions in which they increase theirtotalluminosityandbecomebrightenoughtobemistakenforunderluminous supernovae. In addition to η Car, examples include SN1961v, SN1954j, P Cyg 400 years ago, V1 in N2363 and probably the “Pistol star” near the Galactic Center. The modern supernova surveys are producing a growing list of sub- luminous outbursts from objects in other galaxies. These “supernova impostors” areapparentlyverymassivestars undergoingeruptionssimilar to ηCar andother unstablestarssuchastheLuminousBlueVariables(LBVs).Hencethetitleofthis book.Thesestarsareveryrare,however,andmosthavebeenobservedonlysparsely. The most massive stars are at the intersection of several critical areas of modern astrophysics including the chemical evolution of galaxies via their high mass loss episodes, as the likely progenitorsof gamma-raybursters and the most luminous supernovae, and as candidates for the “first stars” in the Universe. Extremely luminous supernovae, like SN2006gy, may be the terminal explosions ofverymassivestarssurroundedbyextensivecircumstellarmaterialfromprevious eruptions.TheroleofhighmasslosseventslikethatofηCaronthepre-supernova stateofthesestarsisclearlyofincreasinginterestinastrophysics. Our understanding of this remarkable object has benefited from the work and insight of numerous astronomers over the past century many of whom are now deceased. Due to the limitations on the size of this volume, it was not possible to invite all current researchers for a contribution. The editors therefore gratefullyacknowledgethecontributionsofPatriciaWhitelockandMichaelFeast, vii viii Preface ChrisSterken andAntoninVanGenderen,RobertoViotti, AugustoDamineli,Ted Gull,JohnMeaburn,OtmarStahl,NoamSoker,andBobGehrz. The contributed chapters in this volume provide a comprehensive review of η Car, including its Great Eruption, historical evolution and recovery, its wind and ejecta and its relation to other very massive unstable stars, the origin of their instabilities and eventual fate. The contributions are written by experts in their fields and hence are intended for professional astronomers, graduate students in astrophysics,andphysicistsinterestedinthefinalstagesofstellarevolution.These reviews are based on the most recent observations from space and ground-based telescopes and the currentstate of our theoreticalunderstanding,nevertheless, we mustemphasizethatηCarneverceasestosurpriseus. Minneapolis,MN KrisDavidson RobertaM.Humphreys Contents 1 EtaCarinae:From1600tothePresent .................................. 1 RobertaM.HumphreysandJohnC.Martin 2 TheCompanyEtaCarinaeKeeps:StellarandInterstellar ContentoftheCarinaNebula............................................. 25 NolanR.Walborn 3 TheCentralStar:InstabilityandRecovery............................. 43 KrisDavidson 4 TheWindsofEtaCarinaeandOtherVeryLuminousStars.......... 67 Francisco(Paco)NajarroandD.JohnHillier 5 PhysicsoftheInnerEjecta ................................................ 95 FredHamann 6 High-Resolution Studies of Eta Carinae’s Ejecta andStellarWind............................................................ 129 GerdWeigeltandStefanKraus 7 AllThingsHomunculus.................................................... 145 NathanSmith 8 TheOuterEjecta ........................................................... 171 KerstinWeis 9 X-rayVariabilityandtheSecondaryStar ............................... 195 M.F.CorcoranandK.Ishibashi 10 EtaCarinaeandtheLuminousBlueVariables ......................... 221 JorickS.Vink 11 TheSupernovaImpostors ................................................. 249 SchuylerD.VanDykandThomasMatheson ix