SpectralvariabilityofAGNDraganaIlić
LukaČ.Popović,Andjelka Kovačević,Alla Shapovalova☨
1.DepartmentofAstronomy,FacultyofMath.- University ofBelgrade,2.AstronomicalObservatoryBelgrade,3.SAORAS
AGNopticalspectralvariability
• EVERYTHINGVARIES!– linefluxandcontinuumflux– broademissionline(BEL)profiles
• insomecasesextreme:AGNevenchangetheirtype– e.g.type1->type2– changinglookAGN
MSEScienceMeeting,Tucson,2019TheAGNspectralvariability
0.2
0.4
0.6
0.8
1
50000 51000 52000 53000 54000
Flux
(Hβ)
Julian Date [2400000+]
NGC 4151
NGC4151Hβlightcurve
NGC3516max&minstate
Shapovalova+2019
wavelengthFlux
Shapovalova+2008
• EVERYTHINGVARIES!– linefluxandcontinuumflux– broademissionline(BEL)profiles
• insomecasesextreme:AGNevenchangetheirtype– e.g.type1->type2– changinglookAGN
MSEScienceMeeting,Tucson,2019TheAGNspectralvariability
0.2
0.4
0.6
0.8
1
50000 51000 52000 53000 54000
Flux
(Hβ)
Julian Date [2400000+]
NGC 4151
NGC4151Hβlightcurve
NGC3516max&minstate
Shapovalova+2019
wavelengthFlux
Shapovalova+2008AGNopticalspectralvariability
AGNanditsBroadLineRegion(BLR)• type1(obscured)AGN- withbroad
emissionlinesà BroadLineRegion
• howdoweknowthereisaBLR?à imaging:VLT- GRAVITY(10μas,Sturm+18),and
futureELTs
à spectroscopystillimportant
• yet,BLRphysicsandgeometrynotfullyknownà e.g.whatisgastemperatureanddensity?(Ilic+12)à isitvirialized tothesupermassiveblackhole?à dowehaveoutflows,inflows?(e.g.Wang+17)à whatistheinclination?(e.g.Afanasiev+18)
MSEScienceMeeting,Tucson,2019TheAGNspectralvariability 4
SDSSmeanquasarVanden Berk+01
JURIK PETER / SHUTTERSTOCK
WhytheBELofAGN?• reverberation:directmeasureoftheunseen
(theBLRsize)andtheSMBHmass
• theeraofmultimessengerastronomy:detectbinarysupermassiveblackholes(SMBH)
– trickytodetectonparsec-scales(e.g.Popović+12,Komossa+03,Comerford+09,Ge+12,Benitez+18)
– fromspectroscopy(Bon+12,16,Liu+16)orperiodicityanalysisofphotometriclight-curves(Graham+09,17)
• theultimateaimofastronomytodayà newtoolstomeasuredistanceswithAGN
– e.g.usingopticallinesoftheBLR(e.g.Watson+11)
MSEScienceMeeting,Tucson,2019TheAGNspectralvariability 5
NASA/CXC/A.HOBART,JOSHBARNES(U.OFHAWAII),JOHNHIBBARD(NRAO)
Conclusions
ReverberationMonitoring(RM)• thereisatime-delay btwn continuumandlineflux
• onlyfor~100sAGN:directmeasureofRBLR
• empiricalRadius-Luminosityrelation(e.g.Kaspi+2000,Peterson+2004,Bentz+2009)
à cangetSMBHmassfromsingleepochobservation
à ifwedirectlymeasureRà Là distance
MSEScienceMeeting,Tucson,2019TheAGNspectralvariability
NGC4151lightcurves
time-lags from CCF
Line
continuu
m
ModifiedJD
Shapovalova+2008
Lyutyi&Cherepashchuk,1972;Blandford&McKee,1982;Gaskell&Sparke,1986
MBH = fRBLRFWHM
2
GBentz+2009
time-delay τ = size RR
RMcampaignsQUANTITY
• SDSSreverberationmonitoring– monitoring849quasars,0.1<z<4.5 (Shenetal.2014,2018)– measuredfor44quasars,z<0.3(Grier+2017)and144
quasars,z<1(Li+2017)
• Subaru/FMOSsurvey(Shultze+2018)– 234quasars,highestredshiftz=4.6
basedonHα(211),Hβ(63)andMgII(4)
• OzDES RMcampaign(King+2015,Hoormann+2019)– 23variableAGNsoutof771monitored,0.1<z<4.5
QUALITY• highfidelityRM(Horne+2012)togetvelocity-resolved
RM(DeRosa+2018,Du+2018)
MSEScienceMeeting,Tucson,2019TheAGNspectralvariability 7
2.5m,SDSS 8.2m,SUBARU 4m,AAO
Du+2018
Grier+2017
Long-termRMcampaign(long=decades)• TypicalSeyfert1s:
NGC5548– 9+years(Shapovalova+2004,Ilić2007,Popović+2008,Bon+2016)NGC4151– 11+ years(Shapovalova+2008,2010a,Ilić+2010,Bon+2012)NGC7469– 20years(Shapovalova+2017)NGC3516– 22years(Shapovalova+2019)
• NarrowLineSeyfert1:Ark564– 11years(Shapovalova+2011,Shapovalova+2012)
• DoublePeakedLineAGNs(DPLs):3C390.3– 13years(Shapovalova+2001,2010b,Popović+2011,Jovanović+2010,Kovačević+2014);Arp102B– 12years(Shapovalova+13,Popović+14,Kovačević+14,Ilić+15,Rakić+17)
• Quasar,abinaryblackholecandidate:E1821+643– 25years(Shapovalova+2016,Kovačević+2017,Kovačević+2018)
8MSEScienceMeeting,Tucson,2019TheAGNspectralvariability
6m+1m,SAO
2.1m,OANSPM
2.1m,GHO
3.5m+2.2m,CAO
Ilić+2017
Huntforparsec-scaleSMBHbinaries• time-domainphotometryofAGN
(seee.g.withCRTS,Graham+2017)à famouscase:binarySMBHcandidate
PG1302-102(Graham+2015)• novelhybridmethodtosearchforperiodic
oscillatorybehaviorà appliescontinuouswavelettransformandcorrelation
coefficientsonGaussian-processedlightcurves(seeKovačević+2018,2019fordetails)
• NGC4151:thefirstspectroscopicallyresolvedsub-parsecorbitofSMBH(Bon+2012)à orbitalperiod15.7yr, masses~107 Msun
MSEScienceMeeting,Tucson,2019TheAGNspectralvariability 9
8 Kovacevic et al.
Figure 3. The best fit with a nonstationary GP mean as a solid line with 95% of Confidence Interval
between dashed lines. The observed photometric obseravtions are given as vertical error bars.
is known a priori. A specific test for that noise colour must be applied, which we describe in more
details and apply on both observed and GP modeled light curve in the following subsection.
3.1. Noise test for the light curve
Red noise process can be interpreted as an AR(1), autoregressive process of the first order, with
positive correlation at unit lag. The pink noise can be modeled by means of the differencing parameter
d(= 0.5) of the Box - Jenkins autoregressive integrated moving average (ARIMA) strategy, taking
on it continuous values (Box & Jenkins 1970). Autoregressive fractionally integrated moving average
(ARFIMA) modelling improves the BoxJenkins approach by implementing the differencing parameter
d to have non-integer values. This allows ARFIMA to fit any long range memory in time series
remarkably (Brockwell & Davis 2002). However, these processes are stationary. If the PG1302-102
light curve is found to be non stationary, then it is different from mentioned noise processes. If the
light curve is stationary further statistical procedures must be applied to verify that the light curve
Kovačević+2019
Bon+2012
Changing-look(CL)AGN• extremevariability:appearanceordisappearance
ofBELswithinafewyears• whatisthecause?
– variableaccretionrate– variableobscuration– tidaldisruptionevent
• LAMOSThasfound21newCLAGN(Yangetal.2018)
• perfectcasestostudytheconnectionbetweenAGNanditshostgalaxy
• importanttounderstandAGNevolution
MSEScienceMeeting,Tucson,2019TheAGNspectralvariability 10
NGC3516(Shapovalova+2019)
Yang+2018
MSEwillmakeadifference• reverberationmappingcampaignof5000quasarsuptoz~3
à robustestimatesoftimelagsà accurateSMBHmassforthelargestsampleofquasarstodate(seeViraja’s talk)
• identifynewchanginglookAGN-- synergywithothermissions(e.g.LSST,Pan-STARRS)
• high-resolutionhigh-performancespectroscopyà velocityresolvedreverberationmappingà mappingofthecentralregionsà resolvethebinarySMBH
MSEScienceMeeting,Tucson,2019TheAGNspectralvariability 11
Popović 2012
11.5m,MSE
Summary
12MSEScienceMeeting,Tucson,2019TheAGNspectralvariability
• spectralmonitoringstillcrucialfortheAGNandemissionlineregioninvestigations
• theopticalspectralvariability canbeusedfor:à reverberation,i.e.measuringtheunseenà theradiusoftheBLR
à themassoftheSMBH
à constraintheradius-luminosityrelation
à discovermorechanging-lookAGN
à huntforSMBHbinaries
à constrainthephysicsandgeometryoftheBLR
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