LBVs and the nature of the S Dor cycles the case of AG Carin

We present the results of a detailed spectroscopic analysis of 20 years of observations of AG Carinae using the radiative transfer code CMFGEN. Among the conclusions of this work, we highlight the importance of including time-dependent effects in the analy

7

2

eb

F

2

2

1

v

21

6

2

7

/

h

p

-

o

rt

sa

:v

i

X

r

aToappearin“MassiveStarsArgentina(2006)”RevMexAA(SC)LBVsANDTHENATUREOFTHESDORCYCLES:THECASEOFAGCARINAEJ.H.Groh,1A.Damineli,1andD.J.Hillier2RESUMENFavordeproporcionarunresumenenespa nol.Ifyoucannotprovideaspanishabstract,theeditorswilldothis.Wepresenttheresultsofadetailedspectroscopicanalysisof20yearsofobservationsofAGCarinaeusingtheradiativetransfercodeCMFGEN.Amongtheconclusionsofthiswork,wehighlighttheimportanceofincludingtime-dependente ectsintheanalysisofthefullSDorcycle.Weobtainedthatthemass-lossrateisapproximatelyconstantduringthecool-phases,implyingthattheSDor-typeeruptionsbeginwellearlierthanthemaximumseeninthevisuallightcurve.WealsodeterminedthattheSDorcyclesareultimatelyaconsequenceofanincrease/decreaseofthehydrostaticradiusincombinationwiththeformationofapseudo-photosphere.ABSTRACTWepresenttheresultsofadetailedspectroscopicanalysisof20yearsofobservationsofAGCarinaeusingtheradiativetransfercodeCMFGEN.Amongtheconclusionsofthiswork,wehighlighttheimportanceofincludingtime-dependente ectsintheanalysisofthefullSDorcycle.Weobtainedthatthemass-lossrateisapproximatelyconstantduringthecool-phases,implyingthattheSDor-typeeruptionsbeginwellearlierthanthemaximumseeninthevisuallightcurve.WealsodeterminedthattheSDorcyclesareultimatelyaconsequenceofanincrease/decreaseofthehydrostaticradiusincombinationwiththeformationofapseudo-photosphere.KeyWords:STARS:INDIVIDUAL:AGCAR—STARS:EARLY-TYPE—STARS:MASSLOSS1.AGCARINCONTEXTThemassivestarAGCarinaehasbeenthemostvariableobjectamongtheGalacticluminousbluevariablesduringthelast20years.Dramaticpho-tometricchangesof3magnitudesintheVbandhavebeenrecorded,whilethestellarspectrahaveindicatede ectivetemperaturesrangingfromabout9kKto25kK.AGCarisararememberoftheLBVclassthatshowsstrongSDor-typevariationsandissurroundedbyabipolarnebula.

Thisworkisaresultofamonitoringcampaignspanning20yearsofobservationsofAGCartoob-tainitsstellarandwindparametersforeachepoch.The rstresultswerediscussedinGrohetal.(2006),highlightingthe rstobservationalevidenceoffastrotationinLBVs.Theevolutionofbothstellar(ef-fectivetemperature,radius,luminosity)andwindparameters(mass-lossrateandwindterminalve-locity)alongtheSDorcycle,andthecorrelationsamongthem,providessigni cantinsightsaboutthe

We present the results of a detailed spectroscopic analysis of 20 years of observations of AG Carinae using the radiative transfer code CMFGEN. Among the conclusions of this work, we highlight the importance of including time-dependent effects in the analy

2

TABLE1GROH,DAMINELI,&HILLIER

STELLARPARAMETERSDURINGMINIMUM1985–1990

Apr2001626923,80020,5001.5×10 52.5×10 5300105