In this paper, standard accretion disk models of AGNs are tested using light curves of 26 objects well observed for reverberation mapping. Time scales of variations are estimated by the most common definition of the variability time scale and the zero-cros

importanttocomparetheobservedtimelagsbetweendi erentbandswiththetheoreticalvaluespredictedbythestandardaccretiondiskmodels.

Thestructureofthispaperisasfollows.Thesampleanddataarein§2.Thecal-culationsoftemperaturepro lesaredescribedin§3.§4presentsvariabilitytimescalesandtimelags.§4.1isanalysisofvariabilitytimescale,§4.2analysisoftimelag,and§

4.3comparisontomodels.Thelastsectionisdiscussionsandconclusions.Throughoutthispaper,weusea atcosmologywithadecelerationfactorq0=0.5andaHubbleconstantH0=75kms 1Mpc 1.

2.THESAMPLEANDDATA

TheobjectslistedinTable1arebasedonthesamplesanalyzedbyKaspietal.(2000)andPetersonetal.(2004),butthelightcurvedatacomesfromavarietyofsources.Therestframewavelengthsandreferencesoflightcurvesarelistedincolumns(3)and(4)ofTable1,respectively.Theopticalvariabilitytimescalesareestimatedbythelightcurvesaround5100 A.Therearefourobjects,Fairall9,NGC4151,NGC5548,andNGC7469,thathavemulti-wavelengthlightcurveswellobservedattheoptical/UVbands.Themulti-wavelengthlightcurvesareusedtoestimatetimelagsforthefourobjects.

TheblackholemassesforAGNshavebeenwellestimatedbythereverberationmappingtechnique(e.g.,Kaspietal.2000,2005;Petersonetal.2004,2005;Vestergaard&Peterson2006).Themassesofthecentralblackholesofquasarsspanalargerangeof107M⊙ MBH 3×109M⊙,andhaveanupperlimitofMBH<1010M⊙(McLure&Dunlop2004;Vestergaard2004).TheblackholemassesusedinthispaperaretakenfromPetersonetal.(2004),andarelistedincolumn(5)ofTable1.ThebolometricluminosityLbolofobjectsexceptforMrk279aretakefromWoo&Urry(2002),andarelistedincolumn(6)ofTable

1.ThebolometricluminosityofMrk279isestimatedbyLbol≈9λLλ(5100 A)(Kaspietal.2000),withλLλ(5100 A)takenfromPetersonetal.(2004).

3.CALCULATIONSOFTEMPERATUREPROFILES

Thelocale ectivetemperaturesofaccretiondisksarefunctionsofradiird,blackhole˙(e.g.,Ebisawaetal.1991;Hanawa1989;massMBH,spina ,andmassaccretionrateM

Kubotaetal.2005;Lietal.2005;Pereyraetal.2006;Shakura&Sunyaev1973;Zim-mermanetal.2005).Thestandardaccretiondiskisthebasicmodelforaradiativelye cient,geometricallythindisk.IfthecentralblackholesareKerrones,thelocale ective