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1、LinearAcceleratingSuperluminalMotionModelJ.F.Zhou1,C.Zheng2,T.P.Li1,Y.Su3,andT.Venturi4ABSTRACTAcceleratingsuperluminalmotionsweredetectedrecentlybymulti-epochVeryLongBaselineInterferometry(VLBI)observations.Here,aLinearAcceler-atingSuperluminalMotion(LASM)modelisproposedtointerpr
2、ettheobservedphenomena.Themodelprovidesadirectandaccuratewaytoestimatetheview-ingangleofarelativisticjet.ItalsopredictsthatbothDopplerboostinganddeboostingeffectsmaytakeplaceinanacceleratingforwardjet.TheLASMmodelisappliedtothedataofthequasar3C273,andtheinitialvelocity,accel-eratio
3、nandviewingangleofitsthreecomponentsarederivedthroughmodelfits.Thevariationsoftheviewinganglesuggestthatasupermassiveblackholebinarysystemmayexistinthecenterof3C273.ThegapbetweentheinnerandouterjetinsomeradioloudAGNsmybeexplainedintermsofDopplerdeboostingeffectswhenthecomponentsacce
4、leratetoultra-relativisticspeed.Subjectheadings:galaxies:jets—techniques:interferometric—quasars:indi-vidual(3C273)1.IntroductionarXiv:astro-ph/0410231v18Oct2004SuperluminalmotionswerefirstdetectedbyVeryLongBaselineInterferometry(VLBI)in1970s(Cohenetal.1977).Theobservationscarriedo
5、utsincethenshowedthatsuchmo-tionsarequitecommoninblazars.Manymodelswereproposedtoexplainthephenomenon,whichwerereviewedbyBlandfordetal.(1977).Therelativisticjetmodel(Blandford&K¨onigl1979)hasbecomethedefactostandardmodeltodescribethesuperluminalmotion.1DepartmentofEngineeringPhysi
6、csandCenterforAstrophysics,TsinghuaUniversity,Beijing100084,China2KIPAC,StanfordUniversity,Standford,CA94309,U.S.A.3NationalAstronomicalObservatories,ChineseAcademyofSciences,ChaoyangDistrict,DatunRoad20A,Beijing,100012,China4IstitutodiRadioastronomiadelCNR,ViaGobetti101,I-40129Bo
7、logna,Italy–2–Fromasimplephysicalconsideration,accelerationisrequiredtodrivethesubrelativisticmaterialintheaccretiondiskuptotherelativisticspeedobservedinthejets.Accelerationisalsonecessarytocompensatetheradiationlossesinjets.Thereisincreasingevidencethatthecentralengineofaccelera
8、tioninAGNsisarotatingsupermassive
