arXiv:2001.04493v1 [astro-ph.HE] 13 Jan 2020 iesaeo aiblt agn rmmntsto minutes ( from blazars ranging for blazars. variability inferred the of of is elec- most scale whole years in the time found across gamma-ray. A time is energy variability spectrum high of tromagnetic very range wide to A radio from spectrum electromagnetic extending entire the across contin- emission non-thermal uum variable rapidly and luminous highly atr ta.2013 al. et Raiteri ottre htn rgntn nsnhornradiation synchrotron of in scattering originating ra- (SSC; (IC) photons gamma-ray Compton target energy inverse by soft high caused the the is models, inside diation leptonic synchrotron accelerated In by electrons caused jet. relativistic is of UV/X-ray to radiation radi- energy radio another low from and The ation optical, gamma-rays. to to two X-ray radio shows from from ranging blazar extending of vari- broadband one (SED) observed fast peaks, The distribution of the energy understood. origin spectral understand well the not to is but blazar ability activity, on flaring studies broadband several There variability. been rapid have entire with the lines. across spectrum, are flares emission electromagnetic blazars spectacular and broad the strong inside as strong, FS- detected phenomenon hand their energetic other highly for the emission The on known no while or are spectra weak RQs optical very their a flat shows in op- and Lacs line their Lacs) BL upon (BL spectra. depending tical FSRQ, objects quasar Lac radio BL spectrum viz., categories two esaeoine ls oteosre’ ieo sight of line observer’s the to close oriented ( are jets ry&Pdvn 1995 Padovani & Urry [email protected] rpittpstuigL using 2020 typeset 15, Preprint January version Draft lzr r ls fatv aatcnce whose nuclei galactic active of class a are Blazars RABN AIBLT N ORLTO TD F3 7 DURIN 279 3C OF STUDY CORRELATION AND VARIABILITY BROADBAND ioae l 2009 al. et Sikora r indi n-a iebn n a cl aiblt sosre.V 2.1 observed. to is region variability emission scale the gamma- day of a The and location bins period. and “harder-when time size flaring one-day A the in during binned state. X-rays are quiescent ob and were prolonged gamma-rays flares a gamma-ray both bright with Three 27 along 3C work. Optical/UV of this flares in of presented analysis are spectral and temporal multiwavelength A h oe nry rs-orlto td fteeiso rmd from emission the of study gamma in cross-correlation variable A 100% the than energy. more lower is source the the that reveals variability oee,mr e oe nmgei edhsbe bevdduring observed electron been Keywords: th in has of field power state. times magnetic ten jet flaring in as, the higher much power as jet a state, more that flaring However, the reveals SEDs during multiwavelength study flux the gamma-ray The model to e GAMERA. X-rays adopted orig code and was gamma-rays co-spatial model between emission their correlation zone suggest strong a wavebands shown different has between lag time DCF ehd hc hw togcreainbtente ihu an without them between correlation strong a shows which method, 1. .Baasaegnrlycasfidinto classified generally are Blazars ). aais cie–glxe:jt am as aais–qaas in quasars: – galaxies rays: gamma – jets galaxies: – active galaxies: A INTRODUCTION T E tl mltajv 01/23/15 v. emulateapj style X .I eea,baasexhibit blazars general, In ). retra htnfils(EC; fields photon external or ) 1 aa eerhIsiue aahvngr aglr 5600 Bangalore Sadashivanagar, Institute, Research Raman hrna ta.2007 al. et Aharonian rf eso aur 5 2020 15, January version Draft ABSTRACT a Prince Raj × 10 ; 16 mad4.4 and cm ewe pia n am-a a endn o a for a done study at been correlations has located detailed gamma-ray A hole, and black jet. optical central the between emission the compact along to a ( distance suggests close component time region, variability field fast with magnetic helical of 2015 2010 by study recent 2015 of width the lines, emission optical H estimated the broad was of hole black minosity (3–8) al. the et of of Gu mass range The the in class. its in ( 0.536 1992 al. et Dermer itnefo h oe at core, larger much the at emitted from emission distance energy high of evidence h am-a msinrgo n3 7 iscoeto close ( lies scale sub-parsec 279 at 3C jet, the in ex- of base region great the emission in that gamma-ray shows studied spec- studies ra- the multi- been electromagnetic previous and entire has The the 279 trum. optical, throughout past 3C monitored X-ray, in also blazar in tent is The facilities it that dio. other with different along and by 3C 2008 monitoring since continuously 279 is Fermi-LAT respectively. httejtsrcuei o xsmerc( suggest axisymmetric and not is model, structure evidence Compton jet and the strong that synchrotron give the gamma-rays for and (degree/angle) region emission gamma-ray axis. the jet of the community location along the the help probe will to source this on study wavelength C29hsbe lsie saFR tredshift, at FSRQ a as classified been has 279 3C h orlto td ewe pia polarization optical between study correlation The 1 .Tert fcag fteplrzto angle polarization the of change of rate The presence the suggest ). also correlation above The ). ; β aia2015a Paliya yd ta.1965 al. et Lynds ie,adfo h uioiyo h otgalaxy host the of luminosity the from and lines, × ( 2001 10 iso ihzr ielg single A lag. time zero with mission evdsmlaeul nXryand X-ray in simultaneously served uigNvme 07Jl 2018 2017–July November during 9 17 trqie o h uecn state. quiescent the for required at n hsi h rttm C279 3C time first the is This in. ffrn aead sdn using done is wavebands ifferent h uecn tt oprdto compared state quiescent the ,and ), m epciey h fractional The respectively. cm, a ih uv o l h flares the all for curve light ray aioAvrze al. et Patino-Alvarez bihe”tedi bevdin observed is trend -brighter” yuigtepbil available publicly the using by ry n tdcesstowards decreases it and -rays raiiytm osristhe constrains time ariability ; ; srqie oepanthe explain to required is s 0 India 80, ioae l 1994 al. et Sikora aiae l 2016 al. et Paliya × iso tal. et Nilsson 10 ,adi elsuidblazar well-studied a is and ), 8 ielg.Tezero The lags. time y M LR F2017-2018 OF FLARE G iiul(C279) (3C dividual ∼ ⊙ by 2p.Frhr multi- Further, pc. 42 o Urry & Woo ( 2009 aahd tal. et Hayashida ). ( .Hwvr the However, ). 2019 rmtelu- the from ) hn tal. et Zhang boe al. et Abdo on an found ) ( 2002 z of ), 2 sample of blazars by Cohen et al. (2014), and they Table 1 have found a time lag of 110 days between optical Table shows the log of the observations from Swift-XRT/UVOT and gamma-ray emission. A similar study has been telescope during the flaring state (MJD 58050 – 58350). done by Hayashida et al. (2012) for 3C 279 and they have noticed a lag of 10 days between optical and Obs-ID Exposure (ks) gamma-ray emission. They also found that the X-ray and gamma-ray emissions are not well correlated, and 00035019201 1.9 the nature of X-ray emission in blazar is still unclear. A 00035019203 1.8 correlation study between radio and gamma-rays is also 00035019204 2.0 done by Pushkarev et al. (2010), and they noticed that 00035019206 0.5 in a sample of 183 blazars most of them show that the 00035019210 0.9 00035019211 0.9 radio flares lag the gamma-ray flare. A similar result was 00035019213 0.6 found in case of Ton 599 by Prince (2019), where a lag 00035019214 0.9 of 27 days was noticed between radio and gamma-rays. 00035019218 1.1 Keeping consistency with results from earlier studies, 00035019219 1.0 00035019220 1.2 here I try to investigate the possible correlation between 00035019221 2.1 different wavelength during the 2017-2018flare of 3C 279. 00035019222 1.7 00035019224 1.8 00035019225 1.6 2. MULTIWAVELENGTH OBSERVATIONS AND DATA 00035019227 2.5 ANALYSIS 00035019228 0.2 00035019229 0.7 2.1. Fermi-LAT 00035019230 2.0 00035019231 2.0 Fermi-LAT is a pair conversion γ-ray Telescope sen- 00035019232 2.0 sitive to photon energies between 20 MeV to higher 00035019233 2.1 00035019234 1.5 than 500 GeV, with a field of view of about 2.4 sr 00035019235 0.8 (Atwood et al. 2009). The LAT’s field of view covers 00035019236 1.6 about 20% of the sky at any time, and it scans the whole 00035019237 0.5 sky every three hours. NASA launched the instrument in 00035019238 1.5 00035019239 1.5 2008 into a near earth orbit. Fermi-LAT is continuously 00035019240 1.5 monitoring 3C 279 since 2008 August. The standard data 00035019241 1.1 reduction and analysis procedure1 has been followed. I 00035019242 1.1 have chosen a circular region of radius 10◦ around the 00030867052 1.0 00030867054 1.4 source of interest during the analysis. This circular re- 00030867055 0.4 gion is also known as region of interest (ROI). Further 00030867056 1.1 analysis procedure is the same as given in Prince et al. 00030867057 1.0 (2018). I have analyzed the Fermi-LAT data for 3C 279 00030867058 1.0 00030867059 1.0 from Nov 2017 to Jul 2018 and found that source has 00030867060 1.1 shown three significant flares in these nine months. 00030867061 0.5 00030867062 1.2 00030867063 0.6 2.2. Swift-XRT/UVOT 00030867064 1.1 Swift-XRT/UVOT is the space-based telescope which observes the galactic as well as extragalactic sources in X- model with the galactic absorption column density nH = rays, Opticals, and UV simultaneously. Fermi detected − blazars could also be observed by Swift-XRT/UVOT 1.77×1020 cm 2 (Kalberla et al. 2005) is used to model telescope as a monitoring program as well as a time of the XRT spectra. opportunity (ToO) program. The blazar 3C 279 was ob- Simultaneous to XRT, the Swift /Optical served by Swift-XRT/UVOT when it was flaring dur- Telescope (UVOT, Roming et al. 2005) has also ob- ing 2017-2018, and the details of the observations are served 3C 279 in all the available six filters U, V, B, W1, present in Table 1. I processed the XRT data by us- M2, and W2. The image is extracted by selecting a circu- ing the task ‘xrtpipeline’ version 0.13.2, which produces lar region of 5 arcsecond around the source and a circular the cleaned event files for each observation. While re- region of 10 arcsecond away from the source for the back- processing the raw data, I have used the latest calibration ground. The task ’uvotimsum’ is used to sum the mul- files (CALDB version 20160609). The cleaned event files tiple observations in the same filter at the same epoch, are produced only to the Photon Counting (PC) mode and further, the task ‘uvotsource’ is used to extract the observations. The task ‘xrtpipeline’ is used to select the source magnitudes and fluxes. Magnitudes are corrected source and the background region. Circular regions of ra- for galactic extinction using RV = AV/E(B-V) = 3.1 and dius 20 arcseconds around the source and slightly away E(B-V) = 0.025 (Schlafly & Finkbeiner 2011) and con- from the source (fewer photon counts) are chosen for the verted into flux using the zero points (Breeveld et al. source and the background regions, respectively. The 2011) and conversion factors (Larionov et al. 2016). X-ray spectra were extracted in ’xselect’ and used as in- put spectra in ’Xspec’ for modeling. A simple power-law 2.3. Steward Optical Observatory Steward Optical Observatory is a part of the Fermi 1 https://fermi.gsfc.nasa.gov/ssc/data/analysis/documentation/ multiwavelength support program. It provides the op- 3

Light curve of 3C 279 during 2017 Nov - 2018 Jul

20 Fermi-LAT Flare A Flare B 1 day

GeV Flare C

15

300 10 − 1 .

0 5 Quiescent state F 0 7 Swift-XRT 2-10 KeV 6 5 keV 4 10

− 3 2 2 F 1 0 6 U 5 Swift-UVOT V 4 B

Optical 3

F 2 1

7 W1 6 M2 5 W2

UV 4 F 3 2 1 13.5 Steward V 14.0 R 14.5 15.0 Mag 15.5 16.0

25 SPOL-Polarization

) 20 15 10

PA(deg 5 0 SPOL-Polarization angle 150 ) % 100

50 DoP(

0 11 SMA(230 GHz) 10 9 8 Flux(Jy) 7 6 15.5 OVRO(15 GHz) 15.0 14.5 14.0

Flux(Jy) 13.5 13.0 58050 58100 58150 58200 58250 58300 58350 Time[MJD]

Figure 1. Multi-wavelength light curve of 3C 279 from November 2017 to July 2018. The γ-ray flux are presented in units of 10−6 ph cm−2 s−1, and X-ray/UV/Optical fluxes are in units of 10−11 erg cm−2 s−1. The vertical color line separates the quiescent state and flaring state. The vertical lines corresponding to each gamma-ray flares are drawn to recognised the flare in all wavebands. 4 tical data for the LAT-monitored blazars and also mea- constant over a long time. This period defined as “qui- sures the linear optical polarization. Archival data from escent state” showed by cyan color data points in Figure the Steward Optical Observatory, Arizona (Smith et al. 1 and separated by flaring state by a cyan color verti- 2009)2 has been used in this particular study. cal line. The average flux observed during this period is 3C 279 is being continuously monitored with the SPOL 0.73×10−6 ph cm−2 s−1. CCD Imaging/Spectrometer of the Steward Observatory. Swift-XRT/UVOT has also monitored the source dur- Optical V-band and R-band photometric and polarimet- ing the gamma-ray outburst. The X-rays, optical, and ric (degree of polarization and position angle) data is UV light curves are shown in panels 2, 3, & 4 of Figure 1. collected for the flaring period of 3C 279 from November 3C 279 has gone through the strong X-ray flaring episode 2017 to July 2018. corresponding to each gamma-ray flare. In Optical and UV band 3C 279 has shown the flaring behavior corre- 2.4. Radio data at 15 and 230 GHz sponding to “Flare A” and “Flare C”, while “Flare B” Owens Valley Radio Observatory (OVRO; of gamma-ray is missing in Optical and UV because of Richards et al. (2011) is also a part of Fermi mon- the unavailability of UVOT observations. itoring program. It monitors the Fermi blazars by a The 3C 279 has also been monitored by Steward Ob- 40-meter single disc antenna at a of 15 GHz. servatory in optical V and R band. In panel 5 of Figure More than 1800 Fermi blazars are being continuously 1, I have plotted the Steward data, and it can be seen monitored by OVRO twice a week. 3C 279 is one of that the source is highly variable in both the bands. The them, and I have collected the radio data at 15 GHz “Flare A” of gamma-ray is followed by the flare in both from November 2017 to July 2018. V and R band. The “Flare B” is observed close in time Submillimeter Array provided the 230 GHz data at optical (Steward Observatory) and gamma-ray, while (SMA) from observer center database (Gurwell et al. “Flare C” is not seen in Steward Observatory because of 2007). The data is collected for the period of 9 months poorly sparsed V and R band data points. from November 2017 to July 2018. In the 6th and 7th panel of Figure 1, I have plotted the optical degree of polarization (DoP) and polarization 3. RESULTS AND DISCUSSIONS angle (PA) from Steward Observatory. Huge variations are seen during the flaring period. DoP varies from 4%– I have analyzed the Fermi-LAT, Swift-XRT/UVOT 22% in 12 days of span (MJD 58130–58142) and on the data from November 2017 to July 2018 (MJD 58060 – other hand a slow change is seen in polarization angle MJD 58330) and the archival data from other telescopes from 25◦–60◦. like OVRO, SMA, and Steward observatory are collected The radio light curve from SMA and OVRO observa- for the same period. The multiwavelength data from all tory at 230 and 15 GHz are shown in the last two panel the above telescopes are used to study the flux and po- of Figure 1. The radio data at 230 GHz from SMA ob- larization variability, and it is discussed in this particular servatory shows that the source is variable in this energy section. I have also presented a correlation study among band, and high state radio flux has been noticed dur- different wavelength during the outburst period (MJD ing “Flare A” and “Flare B”. It is observed that there 58060 – MJD 58330). A single zone emission model is are not much variations in OVRO flux during the flaring chosen to perform the multiwavelength SED modeling. period of gamma-ray/X-ray/Optical/UV. 3.1. Multiwavelength Light Curves 3.2. Variations in Gamma-ray Blazar 3C 279 is known for its chaotic variability and In Figure 2, the gamma-ray flares are plotted sepa- active flaring behavior across the entire electromagnetic rately along with the corresponding photon spectral in- (EM) spectrum. The source was reported to be in a flar- dex. The “Flare A” is shown in the leftmost panel of ing state across the entire EM spectrum between 2017- Figure 2. The source starts showing the activity at MJD 2018. The multiwavelength light curve of 3C 279 during 58115 with a small rise in flux. The small fluctuations the flaring episode MJD 58060 – MJD 58330 is shown in continued until the source went to the higher state, where Figure 1. The first panel shows the one day binning of the flux rose above the quiescent state flux value within Fermi-LAT data in the energy range of 0.1 - 300 GeV. the 10 days of time interval (MJD 58129–58140). The Our analysis shows the source was in flaring state during flux at MJD 58129.5 is 1.89×10−6 ph cm−2 s−1 and al- end of 2017 to mid 2018. The high activity started at most after 7 days the flux rose up to 22.24×10−6 ph the end of 2017 and followed by a flaring state defined as cm−2 s−1 at MJD 58136.5 and the photon spectral index “Flare A”. After “Flare A”, the source was observed for became harder changing from 2.43 to 2.19, respectively. around two months in a low state with small fluctuations Just after three days from the peak, the flux started de- in the flux value. 3C 279 again went to higher state and creasing and within 10 days, it attained the low flux state spent around two weeks in flaring state labeled as “Flare at MJD 58149.5 with a flux of 1.08×10−6 ph cm−2 s−1 B”. After one month period of “Flare B”, the flux again and spectral index 2.31. started rising, and source attained a full flaring state la- The middle panel of Figure 2 represents the light curve beled as “Flare C”. The red bold vertical lines are drawn of “Flare B”. The activity was found to commence at in Figure 1 corresponding to each gamma-ray flare. Just MJD 58215 just after two months of “Flare A”. The before the “Flare A”, the source has been observed in a flux started rising very slowly from MJD 58216.5 with long low flux state. I have chosen 50 days period between flux 1.35×10−6 ph cm−2 s−1 and in span of two weeks it MJD 58060–58110 when the source flux is very low and achieved the maximum flux value of 19.06×10−6 ph cm−2 s−1 at MJD 58228.5. The spectral index became harder 2 http://james.as.arizona.edu/ psmith/Fermi/ from 2.84 to 2.04. Within one day the flux dropped from 5

Table 2 i.e. “Flare C”, is followed by a small fluctuations at Table shows the variability time estimated from equation (1) for the end. The highest flux observed during “Flare C” is −6 −11 −2 −1 all the different flares. The flux F1 and F2 are in units of 10 ph (3.06±0.42)×10 erg cm s , and the corresponding −2 −1 cm s and t1 & t2 are in MJDs . spectral index found to be 1.35±0.12. Figure 4 reveals “harder-when-brighter” behavior in X- Flares F1 F2 t1 t2 tvar (days) ray as well, which is also reported by Hayashida et al. (2012)& Hayashida et al. (2015). The average pho- Flare A 1.89 3.91 58129.5 58130.5 1.43±0.16 Flare B 19.06 7.49 58228.5 58229.5 1.14±0.03 ton spectral index is estimated as 1.52±0.03, that is Flare C 5.73 11.44 58268.5 58269.5 1.50±0.11 softer than the spectral index observed at highest flux i.e. 1.23±0.14 during the “Flare A”. Most of the contribu- tion of soft X-ray goes to synchrotron peak and the lower (19.06–7.49)×10−6 ph cm−2 s−1 and then the source part of the SSC/IC peak. The “harder-when-brighter” went through small fluctuations in flux for 20 days be- trend in X-ray can be interpreted as the increase in the fore reaching the quiescent state. The quiescent state SSC emission and can also shift the SSC peak towards flux noticed at MJD 58249.5 is 1.00×10−6 ph cm−2 s−1. the higher energy. Increase in the SSC/IC emission could The “Flare C” is shown in the rightmost panel of Fig- be probably due to an increase of the accretion rate. ure 2. As soon as “Flare B” ends, the flux started The variability time is a tool to find out the size and fluctuating again above the quiescent state flux value location of the emission region. In the case of X-ray emis- (0.27×10−6 ph cm−2 s−1) and it continues till one week sion, the light curve is poorly sparsed and so can not be and shows a little rise in flux (3.36×10−6 ph cm−2 s−1). used to estimate the variability time in X-ray. The loca- After spending two days in a high flux state, the source tion of the X-ray emission region can be estimated indi- comes back to low flux state, and after five days it again rectly by the correlations study between gamma-ray and rises to higher flux state. The maximum flux achieved X-ray emissions. The details of the correlations study during high flux state is 13.31×10−6 ph cm−2 s−1 at are shown in section 3.6. MJD 58271.5. One day bin light curve shown in Figure 2 are used 3.4. Spectral Ananlysis to estimate the variability time, which can be defined by The γ-ray spectral energy distributions (SEDs) have the following equation (Zhang et al. 1999), been generated for all the three flares and one quies- cent state between 0.1 – 300 GeV, from the likelihood F1 + F2 t2 − t1 analysis. The spectral data points are plotted in Fig- tvar = (1) 2 |F2 − F1| ure 5, I have used three different spectral models to fit the SEDs data points. The spectral models are Power- F F t where 1 and 2 are the fluxes measured at time 1 and law (PL), Logparabola (LP), and simple broken Power- t 2. The above equation (1) is used to scan the 1 day bin law (BPL), and corresponding expressions are given in light curve (Figure 2) to find the variability time. The Prince et al. (2018). The presence or absence of curva- shortest variability time is found to be order of days in ture in the gamma-ray SED plays a crucial role in con- all the three flares and the details are shown in Table 2. straining the location of the emission region. A break In Figure 3, the gamma-ray flux and the photon spec- in the gamma-ray spectrum is expected when the emis- tral index during the flaring period are plotted together sion region is within the broad line region (BLR), be- along the x and y-axis, respectively. A “harder-when- cause of photon- photon pair production. Earlier study brighter” trend of source is seen here. Similar trend by Liu & Bai (2006) has shown that the BLR region is is also seen previously for 3C 279 by Hayashida et al. opaque to photons of energy > 20 GeV , and as a re- (2012), Hayashida et al. (2015), & Paliya (2015a). The sult, a curvature or break can be seen in the gamma-ray spectral hardening during the flaring state can predict spectrum above 20 GeV. The curvature in the gamma- the possibility of detection of high energy photons and ray spectrum can be justified by estimating the TScurve. consequently can shift the IC peak of the SED to higher According to Nolan et al. (2012) the TS can be de- energy. A strong correlation between spectral harden- curve fined as TScurve = 2(log L(LP/BPL) - log L(PL)), where ing during flare and detection of high energy photons are L represents the likelihood function. The model param- shown by many authors (Britto et al. 2016; Shah et al. eters and the value of TS are mentioned in Table 3. 2019). curve The model which have a large positive value of TScurve is considered as the best fit to the SEDs data points 3.3. Variations in X-ray and it suggests the presence of a spectral cut-off. From Swift-XRT light curve of all the flares for 2-10 keV Table 3, it is very much clear that the log-parabola spec- is shown in Figure 4 along with the photon spectral in- tral model better explains the gamma-ray SED data. I dex. The observations done by Swift-XRT are poorly have also noticed that the break energy found in bro- sparsed, and as a result, there is no clear indication of ken power-law fit is constant irrespective of the different rising and decaying part of the flares. The maximum flux flares. This finding is also consistent with the previous achieved during “Flare A” in X-ray is (6.03±0.70)×10−11 study on this source, by Paliya (2015a), and on 3C 454.3 erg cm−2 s−1 with spectral index 1.23±0.14. After by Abdo et al. (2011). There is also an alternative way around two months period of “Flare A”, “Flare B” is to explain this curvature/cut-off. A cut-off in the energy observed in X-ray at the same time as the gamma-ray spectrum can also occur when there is already a cut-off flare. The maximum flux achieved in X-ray during this in the energy distributions of the particles. period is (4.07±0.37)×10−11 erg cm−2 s−1 and the spec- A strong break is seen in the gamma-ray spectrum tral index noticed as 1.22±0.11. The last flare in X-ray, while fitting with BPL; similar break has also been seen 6

0 0 0 GeV GeV GeV

0 300 0 300 300

− − − 1 1 1 . . . 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Figure 2. Gamma-ray light curve for all the three flares separately with corresponding photon spectral index. The y-axis of the upper panels are in units of 10−6 ph cm−2 s−1. Compton (IC) scattering and my result shows it peaks around 1 GeV which lies in the energy range of LAT (0.1- 300 GeV). Since the break energy is almost constant for all the flares, it is possible that the observed shape is a reminiscence of the electron energy distribution of the emitting electrons.

3.5. Fractional variability (Fvar) Blazars are a particular class of AGN that show strong chaotic variability at all . The variability is more evident during the flaring period and the flare pro- files mostly depend on the particle injection, particle ac- celeration, and energy dissipation in the jets of blazars. The variability amplitude can be estimated by measur- 10-1 100 101 ing all kind of jet parameters like the magnetic field in −6 −2 −1 F0.1−300 GeV [ 10 ph cm s ] the jets, viewing angle of the jet, particle density in- side the jet, and finally the efficiency of the acceleration Figure 3. The gamma-ray photon spectral index corresponding process involved within the jet. The challenge to deter- to flux observed during flare shows a “harder-when-brighter” trend. mine the variability amplitude across the energy band re- quires a good quality of data. 3C 279 is a well-observed source across the entire , and 7 ABC that makes it possible to estimate the variability ampli- 6 tude. The fractional root mean square (rms) variability 5 parameter (F ) is a tool to determine the variability 4 var

3 amplitude and that is introduced by Edelson & Malkan − 2 2 (1987); Edelson et al. (1990). The relation given in F 1 Vaughan et al. (2003) is used to determine the frac- 0 tional variability (Fvar), 2.2 2.0 S2 − σ2 1.8 F var = 2 (2)

r 1.6 r 1.4 1.2 2 2 2 2 1.0 1 σ σ 1 58100 58150 58200 58250 58300 err F . . ( var )= 2 + (3) Time [MJD] s 2N r Fvar r N r r    Figure 4. X-Ray light curve for all the observed flares. The fluxes where, σ2 = S2 – σ2, is called excess variance, S2 is × −11 −2 −1 XS are in units of 1.0 10 erg cm s . Lower panel represent the 2 corresponding photon spectral index. A “harder-when-brighter” the sample variance, σ is the mean square uncertainties trend is also seen here. of each observation and r is the sample mean. The fractional variability estimated across the entire before for other FSRQ like 3C 454.3 by Abdo et al. electromagnetic spectrum is shown in Figure 6, and the (2011) and also for 3C 279 during flare of 2014 and 2015 values are presented in Table 4. It is seen that the source (Paliya 2015a; Paliya et al. 2015b). In table 3, dur- variability is more than 100% in γ-ray, followed by X-ray ing all the flares the BPL photon index (Γ1) before the at more than 60%, and then followed by UV and Opti- break (Ebreak = 1 GeV) is ≤ 2, which suggest an increas- cal, where the source variability is more than 50%. In ing slope, and after the break the photon spectral index radio at 15 and 230 GHz, the source is very less variable (Γ2) is ≥ 2, indicates a falling spectrum. We know that (less than 10%) during this particular gamma-ray flar- the gamma-ray energy spectrum is governed by inverse ing period. The Fvar is 1.201 in γ-ray, 0.580 in UVM2- 7

3C 279 (Flare A) 3C 279 (Flare B) PL LP BPL PL LP BPL ) ) 1 1

-9 − − 10 -9 s s 10 2 2 − −

-10 10 10-10 dN/dE (erg cm dN/dE dN/dE (erg cm dN/dE 2 2 E E

10-11 10-11 10-1 100 101 102 10-1 100 101 102 Energy (GeV) Energy (GeV)

3C 279 (Flare C) 3C 279 (Quiescent State) PL LP BPL PL LP BPL 10-9 ) ) 1 1 − − s s

2 2 -10 − − 10 dN/dE (erg cm dN/dE (erg cm dN/dE 2 2

E -10 E 10 10-11

10-1 100 101 10-1 100 101 102 Energy (GeV) Energy (GeV)

Figure 5. The gamma-ray SEDs produced for all the flares and quiescent state. The data points are fitted with three different models and the modeled parameters are shown in Table 3.

Table 3 Parameters obtained from the spectral analysis fit, for the different models PL, LP, and BPL, by using the Likelihood analysis method. TScurve is estimated with respect to the TS value of the PL fit.

PowerLaw (PL)

Activity F0.1−300 GeV Γ TS TScurve (10−6 ph cm−2 s−1) Quiescent state 0.67±0.02 2.15±0.03 - - 3625.24 Flare A 4.42±0.05 2.17±0.92 - - 35533.08 - Flare B 5.59±0.05 2.11±0.01 - - 67293.68 - Flare C 3.47±0.06 2.09±0.02 - - 15163.31 - LogParabola (LP) α β Quiescent state 0.64±0.03 2.04±0.04 0.06±0.02 - 3653.27 28.03 Flare A 4.24±0.05 2.05±0.02 0.090±0.008 - 35759.77 226.69 Flare B 5.39±0.05 1.99±0.01 0.072±0.006 - 67311.92 18.24 Flare C 3.26±0.07 1.93±0.02 0.10±0.01 - 15282.46 119.15 Broken PowerLaw (BPL) Γ1 Γ2 Ebreak Quiescent state 0.65±0.03 2.04±0.05 2.33±0.08 0.98±0.17 3633.04 7.8 Flare A 4.27±0.05 2.02±0.02 2.48±0.03 0.98±0.05 35750.45 217.37 Flare B 5.42±0.05 1.98±0.01 2.35±0.02 1.00±0.03 67309.47 15.79 Flare C 3.30±0.07 1.91±0.03 2.42±0.05 1.00±0.06 15263.59 100.28 8

Table 4 negative time lag between two energy bands with strong Fractional variability in various wavebands are estimated for the correlation coefficient suggest the different emission re- time interval MJD 57980 to 58120. gion for different waveband emissions and the time lag can be used to estimate the separation between them Waveband Fvar err(Fvar) (Fuhrmann et al. 2014). The correlation study is done by using the discrete correlations function (DCF) for- γ-ray 1.201 0.008 X-ray 0.660 0.035 mulated by Edelson & Krolik (1988). When the two U 0.524 0.008 light curves, suppose LC1 and LC2 are correlated then a B 0.520 0.006 positive time lag between these two light curves implies V 0.509 0.008 that the LC1 is leading the LC2, and a negative time lag W1 0.548 0.008 M2 0.580 0.007 means the opposite. The results of DCFs are shown in W2 0.557 0.007 Figure 7, Figure 8 & Figure 9 for “Flare A” & “Flare C”, OVRO (15 GHz) 0.032 0.002 for various waveband combinations. SMA (230 GHz) 0.089 0.010 A cross-correlation study between two light curves (dif- ferent energy band) by DCF needs sufficient data points in each light curve. The “Flare B” fails to fulfil this cri- 1.4 teria since it has good quality data points only in the Gamma-ray gamma-ray light curve. It is therefore not possible to 1.2 cross-correlate two different energy band for “Flare B”. Significant correlation has been noticed between gamma- 1.0 ray and optical band (U, B, & V) emissions with zero time lag (within the time bin 2.5 days). The correla- 0.8 X-ray tion coefficient for “Flare A” is found to be 0.50±0.15, Optical/UV 0.53±0.17, 0.83±0.18 and for “Flare C” it is 0.92±0.44, 0.6 0.93±0.44, 0.91±0.44 in U, B, & V band, respectively. The cross-correlation between gamma-ray and UV band 0.4 (W1, M2, & W2) emission are very similar to the gamma- ray vs optical band emission. The correlation coefficients 0.2 Radio for “Flare A” and “Flare C” are 0.45±0.15, 0.83±0.17, Fractional variability amplitude variability Fractional 0.82±0.17 and 0.92±0.44, 0.90±0.43, 0.89±0.43 in W1, 0.0 1010 1012 1014 1016 1018 1020 1022 1024 M2, & W2 band, respectively. A strong correlation with Frequency (Hz) zero time lag is observed between gamma-ray and X- ray emission for 3C 279. In author’s knowledge this Figure 6. Fractional variability for various wavebands are plotted with respect to their frequency. is the first time the source has shown strong correla- tion with zero time lag between gamma-ray and X-ray. band, 0.520 in optical U-band and 0.032 in radio at 15 The value of correlation coefficients for “Flare A” and GHz, and 0.089 at 230 GHz. It is found that Fvar is “Flare C” are noted as 0.87±0.16 and 0.97±0.36 re- increasing with energy, suggesting that a large number spectively, at zero time lag (within the time bin). The of particles are injected in the jet, resulting in high en- significance of the DCF peaks are also estimated by ergy emission. Similar behavior of fractional variability is simulating the 1000 gamma-ray light curves. To sim- also seen for other FSRQ like Ton 599 by Prince (2019), ulate the gamma-ray light curves, I have used method where he found a trend of large fractional variability to- mentioned in Emmanoulopoulos et al. (2013). Further, wards higher energies. This is not always the case, and an I cross-correlate the simulated gamma-ray light curves opposite trend was also noticed in the past. An opposite with the observed light curves in different wavebands and trend is reported by Bonning et al. (2009), where vari- finally a DCF distribution with time lag is calculated. At ability amplitudes decrease towards shorter wavelength each time lag 95% significance was calculated, which are (IR, Optical, and UV), which suggests the presence of shown in cyan color in Figure 7, Figure 8, and Figure 9. steady thermal emission from the accretion disk.

3.6. Correlation Studies 4. MODELING THE MULTIWAVELENGTH SED In Figure 1, all the light curves are plotted together, The simultaneous observation of 3C 279 in different en- and the visual inspection suggests that the flares in γ- ergy bands during its 2017–2018 flaring period provides ray, X-ray, Optical, and UV band are mostly correlated. an opportunity to gain further insight into its multiwave- The radio light curve at 15 GHz does not show any flare length properties. In this work, theoretical modeling of for this particular period, while the light curve at 230 the observed SED is done using the publicly available GHz shows a rise in flux corresponding to “Flare A” and code GAMERA3 (Hahn 2015) which solves the time- “Flare B”. The gamma-ray “Flare C” detected in X-rays, dependent transport equation and calculates the propa- and Optical/UV have not seen in radio at 230 GHz. The gated electron distribution. cross-correlation study of flux variations in different en- This electron spectrum finally used as an input to esti- ergy bands are presented in this section. The correlations mate the synchrotron, synchrotron self-Compton (SSC), study help to reveal the location of the emission region and inverse Compton (IC) emissions. The transport in different energy bands with respect to each other. A strong and good correlation between two energy emis- sions indicates their co-spatial origin. A positive and 3 http://joachimhahn.github.io/GAMERA 9

− − −

−

− − − − − − − − − − − − − −

− − −

− − − − − − − − − − − − − − −

Figure 7. DCFs shown for “Flare A” for all the possible combinations: γ vs. Swift-U, B, V, W1, M2, W2 band. The significance shown in cyan color is 95%.

− − −

− − −

− − − − − − − − − − − − − − −

− − −

− − −

− − − − − − − − − − − − − − −

Figure 8. DCF shown for “Flare C” for all the possible combinations: γ vs. Swift-U, B, V, W1, M2, W2 band. The significance shown in cyan color is 95%.

− −

− −

− − − − − − − − Figure 9. Gamma-ray vs X-ray DCF are Shown for “Flare A” and “Flare C”. The significance shown in cyan color is 95%. 10 equation used in the code is following, central SMBH down the jet. This value is comparable to the size of the BLR and hence conculded that during the ∂N(E,t) ∂ = Q(E,t) − b(E,t)N(E,t) (4) emission of high energy photon (27 GeV) the gamma- ∂t ∂E ray emitting region must have been located at the outer   where, Q(E,t) is the injected electron spectrum, and boundary of the BLR. N(E,t) is the spectrum achieve after the radiative loss. I have also considered the contribution of the ac- The radiative loss due to synchrotron, SSC, and IC cretion disk photons in the EC emission. The pho- are represented by b(E,t). GAMERA takes care of ton energy density in the comoving frame is defined as the inverse Compton in the Klein-Nishina regime from (Dermer & Menon 2009), Blumenthal & Gould (1970). The transport equation 0.207R l L U ′ g Edd Edd does not have the diffusive loss term as it is insignificant disk = 3 2 (7) compared to the radiative loss of the electrons. The log- πcz Γ parabola spectral model is chosen as the input injected where, Rg is known as gravitational radius, and lEdd = electron spectrum, motivated from the gamma-ray spec- Ldisk/LEdd is the Eddington ratio. Here z represents tral analysis. To model the multiwavelength SEDs, my the distance of blob from the SMBH and which is esti- 17 model considers a single spherical emitting zone or blob mated to be 4.40×10 cm. For black hole mass MBH = 8 which is moving down the jet along the jet axis with a 2.51×10 M⊙ (Wu et al. 2018), the gravitaional radius δ 13 Lorentz factor, Γ, and Doppler factor, . The external found to be Rg = 3.72×10 cm. In this study, I have photon field required for external Compton emission is not considered dusty torus as a external target photon believed to be dominated by the broad line region (BLR) field since there is no observational evidence. However, photons, particularly in FSRQ like 3C 279. The BLR the contribution of NIR/optical/UV photons emitted by photon density in the comoving frame is given by, disk and dusty torus based clouds irradiated by a spine- Γ2η L sheath jet could be important (Finke 2016; Gaur et al. ′ BLR disk 2018; Breiding et al. 2018) for the EC emission in some U BLR = 2 (5) 4πcRBLR cases. There are numbers of parameters that GAMERA uses where the ηBLR represents the fraction of disk emis- sion processed in BLR, I assume it to be typically 2% as a input to model the multiwavelength emissions. The spectral index (α, β), minimum and maximum (γmin, (Pittori et al. 2018), RBLR is the size of the BLR, Ldisk denotes the disk luminosity, and c is the speed of light γmax) energies, magnetic field inside the blob (B), and in vacuum. The photon energy density in BLR is only luminosity in injected electrons are the parameters that have been optimized to obtain the best model fit to a fraction ηBLR ∼ 0.02(2%) of the disc photon energy ′ density. the SEDs. The BLR photon density (U BLR), BLR temperature = 104K (Peterson 2006), accretion disk The size of the BLR can be written as RBLR = ′ 1/2 U 6 1017L (Ghisellini & Tavecchio 2009), where L is photon density ( disk), disk temperature = 2.6×10 K d,45 d,45 (Dermer & Menon 2009) are kept fixed while modeling the accretion disk luminosity in units of 1045 erg s−1. 45 −1 the SEDs. For Ldisk = 2×10 erg s (Pian et al. 1999), the size The size of the blob can also be estimated by using the 17 of BLR is estimated to be RBLR = 1.414×10 cm. variability time and the minimum Doppler factor by the The minimum Doppler factor (δmin) during the flare relation, can be estimated from the γγ opacity arguments and − R ct δ z 1 by estimating the highest energy photon. The minimum ≤ var (1 + ) (8) Doppler factor can be calulated as (Dondi & Ghisellini where tvar is the observed flux variability time (1.14 1995; Ackermann et al. 2010), days). The size of the emitting blob is estimated to be R = 2.1×1016 cm. However, during the SED modeling σ d2 (1 + z)2f ǫ 1/6 δ ∼ T L x Doppler factor and the size of the blob are optimized to min = 4 (6) 4tvarmec best fit value.   A successful SED modeling is performed for all the which assumes that the optical depth of a photon (τγγ ) three flares and one quiescent state. The best fit model 2 with energy ǫ = E/mec to the γγ interaction is 1. The parameters are shown in Table 5. The multiwavelength luminosity distance is denoted as dL (=3.1 Gpc), σT is SEDs modeled with GAMERA are presented in Figure the Thompson scattering cross section, E is the high- 10. The low energy synchrotron peak is constrained by est photon energy detected during the flare, tvar is the the optical and UV emission and the high energy Comp- variability time, and fx is the X-ray flux in 0.3-10 keV. ton peak by gamma-ray data points. The X-ray emission Here, the values of E, fx, and tvar are estimated around observed by Swift-XRT constrains the SSC peak. More the same time period and the values are found to be magnetic field value is needed to explain the optical/UV −11 −2 −1 27 GeV at MJD 58228.45, 3.63×10 erg cm s at emission in quiescent state, which suggest that the syn- MJD 58228.38, and 1.14 days at MJD 58228.50 respec- chrotron process is more dominant here compared to the tively. The minimum Doppler factor is found to be δmin flaring state. The maximum electron energy found dur- = 10.7. The location of the gamma-ray emission region ing all the states are in very much agreement though it is can be estimated by assuming the bulk Lorentz factor Γ little higher during the flaring state. The total jet power = δmin = 10.7, then the location can be defined as d ∼ 2 is estimated by the following relation, 2 cΓ tvar/(1+z). It is found that the gamma-ray emission 17 2 2 region is located at distance of 4.40×10 cm from the Pjet = π Γ r c (Ue + UB + Up) (9) 11 where Γ is the Lorentz factor, r is the size of the blob. flares across the entire electromagnetic spectrum (Figure The energy density in electrons, magnetic field, and cold 10). The major flux change is observed in gamma-ray protons are represented by Ue, UB, and Up. Here the jet band between quiescent and flaring state. However, the composition consists of an equal number of non-thermal change in the gamma-ray flux among the different flares electrons and cold protons. The calculated jet powers (A, B, & C) are small. A relatively lesser flux change is in all components are shown in Table 5. The jet power observed in optical/UV and X-ray bands among all the is calculated for Γ=15.5 (Jorstad et al. 2005) and r = states. I have varied a few parameters to explain these 4.64×1016 cm. It is found that the magnetic field has changes and the parameters are magnetic field, minimum more jet power during the quiescent state compared to and maximum energy of electrons. I found that almost the flares. However, the jet power required in electrons ten times more jet power in electron is required to explain and protons is much higher in case of flaring state com- the gamma-ray flux observed during flares compared to pared to the quiescent state. the quiescent state. The previous study on flares of 3C 279 suggest that most of the time the emission region is located outside the BLR 5. SUMMARY (Dermer et al. 2014; Yan et al. 2015; Vittorini et al. Fermi-LAT data was collected between 2017 Novem- 2017). However, the brightest flare of 3C 279 during ber to 2018 July and three bright flares were observed. 2015 June reported by (Paliya 2015a), demands a com- To differentiate among each other the flares have been pact emission region with high photon density and such named as “Flare A”, “Flare B”, and “Flare C”. A long regions can not be far from the central source. All ear- low flux states period was observed just before the “Flare lier studies on this flare (June 2015) (Hayashida et al. A”. This low flux states is defined as quiescent state and 2015; Ackermann et al. 2016; Pittori et al. 2018) found time period of 50 days is chosen to represent it. A si- the emission region to be located within or at the bound- multaneous observation in X-ray and Optical/UV was ary of the BLR. Here, in this study too, similar result is also done by Swift-XRT/UVOT telescope. The archival obtained. A compact emission region can be inferred, data from Steward observatory for optical V and R band which is located within the boundary of the BLR. has also been collected for the whole period, and a huge January 2018 flare of 3C 279 was also studied by variation is seen in the degree of polarization and polar- Shah et al. (2019), where they have chosen BLR and ization angle. The archival radio data from OVRO and IR photons as the target photons to describe the multi- SMA are also collected for the entire flaring period. wavelength SEDs. They concluded that both cases can The day scale variability has been seen in one-day bin explain the broadband SEDs of various flaring states. light curve, which constrains the size of the emission re- However, the parameters found for EC/IR is more ac- gion to 2.1×1016 cm. The emission region is located at ceptable than EC/BLR process. Two-zone leptonic and a distance of 4.40×1017 cm, which lies at the boundary 17 a single-zone lepto-hadronic SED modeling is performed of the BLR (RBLR=1.414×10 cm). A “harder-when- by Paliya et al. (2015c) to describe the broadband SEDs brighter” trend were also observed in both gamma-ray of 3C 279 during the flare of 2013 December. However, and X-ray, which predicts detection of high energy pho- my result shows that the single emission zone is enough ton during the high state. to explain the broadband SEDs. The gamma-ray spectral data points are fitted with 3C 279 is studied by Hayashida et al. (2012) using the three different spectral models PL, LP, and BPL. The broadband data from radio to gamma-ray for the first two TScurve obtained for all the fits suggest that LP is the year (2008-2010) of Fermi operation. They found a lag of best model to describe the gamma-ray photon spec- 10 days between optical and gamma-ray emission during trum. Further, I have estimated the fractional variability the flaring episode. However, they also argue that the X- among different wavebands, and it is observed that the ray emission does not correlate with optical or gamma- fractional variability is increasing towards the higher en- ray emission. On the other hand my study exhibit a ergy. good correlation among optical, X-ray and gamma-ray The discrete cross-correlation (DCF) study has been emission. They also have plotted the optical polarization performed to find out the possible correlation in various (degree and angle) along with the gamma-ray flare and wavebands emission. The results show a good and strong found huge swing in the polarization angle correspond- correlation in all possible combinations like: gamma-ray ing to the gamma-ray flare (Period D). During the SED vs. Optical/UV, gamma-ray vs. X-rays. In author’s modeling, they constrained the location of the emission knowledge this is the first time that a strong correlation region based on the observed change in the optical polar- with zero time lag between gamma-ray, X-rays, and op- ization angle. A huge swing in the polarization angle can tical/UV are seen for 3C 279. A strong correlation and be interpreted as the precession in the jet, which allow zero time lag between optical/UV, X-rays, and gamma- the arbitrary location of the emission region within the ray emissions suggest their co-spatial origin. This out- BLR. My study also shows a huge variation in the opti- come provides an impetus to choose single emission zone cal polarization angle during the flaring episode (Flare A to explain the multiwavelength emission in SED mod- and Flare B). Considering the polarization angle swing eling. GAMERA is used to model the multiwavelength is caused by the precession of jet, I have chosen the sin- emission, and the parameters like magnetic field, injected gle emission zone within the boundary of the BLR, to electron spectrum, minimum and maximum energy of in- model the broadband SED, which is also supported by jected electrons have been optimized to get a good fit to the value estimated from the variability time. the SEDs data points. So this study suggests that a Comparing the SEDs corresponding to quiescent and single-zone model can also be good enough to explain flaring state, I observed that the flux has increased during the multi-waveband emissions from one of the brightest Fermi blazar called 3C 279. 12

Flare-A Flare-B

10-8 Total period = 40 days 10-8 Total period = 35 days

-9 EC -9 EC ) ) 10 10 1 1 − − s s

2 -10 2 10-10 Sync 10 Sync − −

10-11 10-11 (erg cm (ergcm -12 Disk -12 Disk ν ν 10 10 F F SSC ν ν BLR SSC BLR 10-13 10-13

10-14 10-14 108 1010 1012 1014 1016 1018 1020 1022 1024 1026 108 1010 1012 1014 1016 1018 1020 1022 1024 1026 ν (Hz) ν (Hz)

Flare-C Quiescent State 10-9 Total period = 50 days 10-8 Total period = 30 days EC -9 -10 ) ) 10 EC 10 1 1 Sync − − s s 2

2 -10 10 -11 − − Sync 10

10-11 10-12 Disk (erg cm (ergcm -12 Disk ν ν 10 F F BLR ν ν BLR SSC -13 -13 10 10 SSC

10-14 10-14 108 1010 1012 1014 1016 1018 1020 1022 1024 1026 108 1010 1012 1014 1016 1018 1020 1022 1024 1026 ν (Hz) ν (Hz)

Figure 10. Multi-wavelength SEDs of all the flares and one quiescent state are presented. The optimize model parameters are shown in Table 5. ACKNOWLEDGEMENTS Alexander, T. 2013, arXiv:1302.1508 Fermi Blumenthal, R., & Gould, G., 1970, RvMP, 42, 237 This work has made use of public data obtained from Bonning, E. W., Bailyn, C., et al. 2009, ApJ, 697, L81 FSSC. This research has also made use of XRT data analysis Breeveld, A. A., Landsman, W., et al., 2011, arxiv, 1358, 373-376 software (XRTDAS) developed by ASI science data center, Breiding, P., Georganpoulos, M., & Meyer, E., 2018, ApJ, 853, 19 Italy. Archival data from the Steward observatory is used in R. J., Britto et al. 2016, ApJ this research. This research has made use of radio data from Chatterjee R., Jorstad, S. G., Marscher, A. P., et al., 2008, ApJ, OVRO 40-m monitoring programme (Richards et al. 2011) 689, 79 which is supported in part by NASA grants NNX08AW31G, Cohen, D. P., Romani, R. W., et al. 2014, ApJ, 797, 137 NNX11A043G, and NNX14AQ89G and NSF grants AST- Dondi, L., & Ghisellini, G. 1995, MNRAS, 273, 583 0808050 and AST-1109911. The archival data from Submil- Dermer, C. D., Schlickeiser, R., & Mastichiadis, A. 1992, A&A, 256, L27 limeter Array observatory has also been used in this study Dermer, C. D., Menon, G., 2009, High Energy Radiation from (Gurwell et al. 2007). The Submillimeter Array is a joint Black Holes (Princeton, NJ: Princeton Univ. Press) project between the Smithsonian Astrophysical Observatory Dermer C. D., Cerruti M., Lott B., Boisson C., Zech A., 2014, and the Academia Sinica Institute of Astronomy and Astro- ApJ, 782, 82 physics and is funded by the Smithsonian Institution and the Edelson, R. A., & Malkan, M. A., 1987, ApJ, 323, 516 Acedemia Sinica. RP thanks Saikat, Manami, and Gunjan Edelson, R. A., & Krolik, 1988, J. H., ApJ, 333, 646 for manuscript reading and Arkadipta for helpful discussions Edelson, R. A., Krolik, J. H., & Pike, G, F., 1990, ApJ, 359, 86 regarding DCF. Emmanoulopoulos, D., McHardy, I. M., & Papadakis, I. E., 2013, MNRAS, 433, 907-927 Finke, J., 2016, ApJ, 830, 94 REFERENCES Fuhrmann, L., Larsson, S., Chiang, J., et al. 2014, MNRAS, 441, 1899 Abdo, A. A., et al. 2010, ApJ, 721, 1425 Gaur, H., Mohan, P., Wiercholska, A., & Gu, M., 2018, MNRAS, Abdo, A. A., Ackermann, M., Ajello, M., et al. 2011, ApJ, 733, 473, 3638 L26 Ghisellini, G., & Tavecchio, F., 2009, MNRAS, 397,985 Atwood, W. B., Abdo, A. A., et al., 2009, ApJ, 697, 1071 Gu, M., Cao, X., & Jiang, D. R. 2001, MNRAS, 327, 1111 Ackermann, M., Asano, K., Atwood, W. B., et al. 2010, ApJ, 716, Gurwell, M. A., Peck, A. B., Hostler, S. R., Darrah, M. R., & 1178 Katz, C. A. 2007, From Z-Machines to ALMA: (Sub)Millimeter Ackermann, M., Anantua, R., Asano, K., et al. 2016, ApJL, 824, Spectroscopy of Galaxies, 375, 234 L20 Hahn, J., 2015, Proc. ICRC, 34, 917 Aharonian, F., Akhperjanian, A. G., et al. 2007, ApJ, 664, L71 Hayashida, M., et al. 2012, ApJ, 754, 114 Alexander, T. 1997, in Astrophysics and Space Science Library, Hayashida M., Nalewajko, K., Madejski, G. M., et al. 2015, ApJ, Vol. 218, Astronomical Time Series, ed. D. Maoz, A. Sternberg, 807, 79 & E. M. Leibowitz, 163 13

Table 5 Results of fitted Multiwavelength SEDs showed in Figure 10. A LogParabola model is used as electron injected spectrum which is defined (−α−β∗log(E/E0)) as dN/dE = N0(E/E0) , where E0 is chosen as 90 MeV.

Activity Parameters Symbol Values Activity period (days) ′ × 4 BLR temperature Tblr 1 10 K ′ 3 BLR photon density Ublr 6.377 erg/cm ′ × 6 Disk temperature Tdisk 2.6 10 K ′ × −7 3 Disk photon density Udisk 7.9 10 erg/cm Size of the emission region R 4.64× 1016 cm Doppler factor of emission region δ 24.1 Lorentz factor of emission region Γ 15.5 Flare A Min Lorentz factor of injected electrons γmin 8.0 4 Max Lorentz factor of injected electrons γmax 1.5×10 Spectral index of injected electron spectrum (LP) α 1.7 Curvature parameter of LP electron spectrum β 0.15 magnetic field in emission region B 2.8 G 40 45 jet power in electrons Pe 1.88× 10 erg/sec 46 jet power in magnetic field PB 1.52× 10 erg/sec 46 jet power in cold protons Pp 1.87× 10 erg/sec Flare B Min Lorentz factor of injected electrons γmin 10.0 4 Max Lorentz factor of injected electrons γmax 1.7×10 Spectral index of injected electron spectrum (LP) α 1.7 Curvature parameter of LP electron spectrum β 0.12 magnetic field in emission region B 2.5 G 35 45 jet power in electrons Pe 2.42× 10 erg/sec 46 jet power in magnetic field PB 1.21× 10 erg/sec 46 jet power in cold protons Pp 2.24× 10 erg/sec Flare C Min Lorentz factor of injected electrons γmin 8.0 4 Max Lorentz factor of injected electrons γmax 1.5×10 Spectral index of injected electron spectrum (LP) α 1.7 Curvature parameter of LP electron spectrum β 0.1 magnetic field in emission region B 2.4 G 30 45 jet power in electrons Pe 1.13× 10 erg/sec 46 jet power in magnetic field PB 1.12× 10 erg/sec 46 jet power in cold protons Pp 1.56× 10 erg/sec Quiescent state Min Lorentz factor of injected electrons γmin 4.0 4 Max Lorentz factor of injected electrons γmax 1.2×10 Spectral index of injected electron spectrum (LP) α 1.7 Curvature parameter of LP electron spectrum β 0.08 magnetic field in emission region B 4.2 G 50 44 jet power in electrons Pe 2.56× 10 erg/sec 46 jet power in magnetic field PB 3.42× 10 erg/sec 45 jet power in cold protons Pp 7.17× 10 erg/sec

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