Oscillations of Static Discs around Schwarzschild Black Holes: Effect of Self-Gravitation

[摘要] Theoscillationsofaccretion-discmatteraboutroughlycircularmotionmayproduceaquasi-periodicvariationintheobservedsignal(Ipser1996,AAA65.067.047).Theywerestudiedtheoreticallyonnon-gravitating,testdiscs,inapseudo-Newtonianmanneraswellasingeneralrelativity,bothinstaticandinstationaryfields.Thepresentpapershowshowtheradialprofilesofoscillationfrequenciescanbemodifiedbytheself-gravityofthedisc.ExactsuperpositionsofaSchwarzschildblackholewiththeLemosandLetelier(1994,AAA61.067.077)annulardiscs(staticthindiscsobtainedbyinversionofthefirstMorgan-Morgansolution)areconsideredtobesimple(static)modelsofanaccretionsystem.BoththeepicyclicandperpendicularfrequenciesareplottedagainsttheSchwarzschildradius,thecircumferentialradius,andtheproperdistancefromthehorizon.Thecurvesindicatethatintheinnermostpartsmoremassivediscsaremorestablewithrespecttohorizontalperturbations,whereastheyarelessstablewithrespecttoverticalperturbations.Inthecaseofasequenceofdiscsinterpretableascounter-rotatingparticlesonstabletime-likecirculargeodesicsandhavingtheirinnerrimsjustonmarginallystablecircularorbits,oscillationsoftheinnerpartsgetfasterwithincreasingdiscmass;themaximumoftheepicyclicfrequency,importantfortrappingofthelow-frequencymodesneartheinnerradius,movestosmallerradiiandbecomessomewhathigher.

[学科分类] 天文学(综合)

[关键词] "accretion discs";"black-hole physics";relativity