The evolution of black hole states

We discuss the evolution of black hole transients on the basis of a few systems that were intensively observed with the Rossi X-ray Timing Explorer. We focus on the global evolution and the observed state transitions. Rather than giving a numerical recipe

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aTheevolutionofblackholestatesJeroenHomanMITCenterforSpaceResearch70VassarStreet,Cambridge,MA02139,USAjeroen@space.mit.eduTomasoBelloniINAF/OsservatorioastronomicodiBreraViaE.Bianchi46,23807,Merate(LC),Italybelloni@merate.mi.astro.itAbstract.WediscusstheevolutionofblackholetransientsonthebasisofafewsystemsthatwereintensivelyobservedwiththeRossiX-rayTimingExplorer.Wefocusontheglobalevolutionandtheobservedstatetransitions.Ratherthangivinganumericalrecipeforclassifyingobservations,wetrytoidentifytimesduringoutburstsatwhichclearchangesoccurintheX-rayvariability,X-rayspectral,ormulti-wavelengthproperties.1.IntroductionSincethelaunchoftheRossiX-rayTimingExplorer(RXTE)about～20blackholeX-raytransientshavebeenobservedwithenoughcov-eragetostudytheirglobalevolution.Theseobservationshaveprovidedawealthofinformationandhavealreadyledtoaconsiderableincreaseinourunderstandingofthesesystems.InarecentreviewbyMcClin-tockandRemillard(2004)anewclassi cationschemewasproposedforthespectralandvariabilitystatesasobservedinblackholetran-sients.McClintockandRemillard(2004)approachedthestatesissuebyidentifyingthree‘stable’statesinblackholetransients.Inthispaperweapproachtheissuefromanotherangle,focusingontheobservedtransitions,theoverallevolutionduringanoutburst,andhowX-raychangesrelatetochangesatotherwavelengths.

2.Statede nitions

Untilthelate1990sitwasgenerallyassumedthatthestateofablack-hole

M˙systemwasdeterminedbytheinstantaneousmassaccretionrate,.Itwasbelievedthatasthemassaccretionrateincreased,asourcewentthroughthefollowingstates(seee.g.Esinetal.,1997):quiescence→low/hard→intermediate→high/soft→veryhigh.ObservationswithRXTEofsourceslikeXTEJ1550–564haveshownthatsuch c2008KluwerAcademicPublishers.PrintedintheNetherlands.

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