PoS(BLAZARS2008)076 http://pos.sissa.it/ ce. s. Examples of first preliminary ted. r on the project of searches for and s) requiring very long time intervals (50 tware and powerful computers allow data ch Republic ch Republic Spectrum ive Commons Attribution-NonCommercial-ShareAlike Licen † ∗ [email protected] [email protected] Speaker. A footnote may follow. The digitisation of astronomical plate archives, novel sof mining in extended plate databases foranalysis the of first supermassive binary time. black holes We (binary refe blazar years and more) which cannot bedata obtained provided from by data other mining data in source HCO plate stacks are presen ∗ † Copyright owned by the author(s) under the terms of the Creat c Workshop on Blazar Variability across the Electromagnetic April 22-25, 2008 Palaiseau, France

CZ-251 65 Ondrejov, Czech Republic E-mail: Milan Basta Astronomical Institute of the Academy ofCZ-251 Sciences 65 of Ondrejov, Czech the Republic Cze E-mail: Astronomical Institute of the Academy of Sciences of the Cze Rene Hudec Very long term observations of blazarsfor – supermassive candidates black hole binaries PoS(BLAZARS2008)076 Rene Hudec tial high–energy sources such as l life of an astronomer would be xhibit optical emission and hence k in astronomy and astrophysics. azar science requires data to prove otic telescopes is still limited and tal for understanding the nature of llions astronomical archival plates vanced detectors can provide pre- CD telescope. In the past, the data investigations are far less expensive with the observations, other events, ..19 (spectral with objective prism). e coverage of order of ten years and pid and often and thus in a short ob- ysical processes in observed objects. y high quality plates achieving limit- m several large plate collections can hey often shows long-term evolution, rovide valuable data. The multispec- ong-term evolution and changes to be tisation of plates and few of them have for automated evaluation of objects on e–consuming, however the recent wide trophysics especially by providing ex- ces, they are usually unable to provide city in the light curve, detection of qui- ing software development significantly iations. The photographic sky monitor- may be induced by underlying physical onneberg Observatory - about 220 000 ful computers and novel software allow hival records and related reductions and easily provide thousands of exposures for p to few years of continuous monitoring - aring. This can be provided by data recorded 2 The dominant fraction of the high energy celestial sources e Covering large time intervals is difficult but important tas In analogy to the most of other astrophysical branches the bl Searches for Supermassive Back Hole Binaries 1. Introduction can be also observed and investigatedthan from satellite the ground. measurements, These and despitetral approach of has this, proved can to also beAlthough crucial p the in large understanding optical of telescopescise ph astrometry, with photometry CCDs and and spectroscopy other oflong-time these ad monitoring sour with good sampling.even these The automated real devices use aremore. of usually unable rob However, to the reach long-term tim AGNs/blazars monitoring may of be many crucial of fordifferent their the activity understanding celes states, since brightness t variations and/or fl and build theory. Even though someservational features time in theory blazars can are be ra on built the which other can hand, be are confronted long-termblazars. but These at features the are same for time example:escent fundamen Long-term level, periodi detection of large-amplitude flares etc. They in astronomical plate archives. The combination of data fro the effective data extraction for the first time. any celestial position, reaching monitoring intervals of u yield up to few tensrequired of to thousands obtain the of same monitoringmining observing hours in every astronomical - clear plate one night archives was ful by laboriousdigitisation a and of tim C the plates, as well as availability of power Archival plates represent a valuabletended tool monitoring in intervals high–energy with as goodstudied, sampling, as allowing well l as detecting flaresing and is other available brightness for var morelocated than at 100 different years. observatories [9]. There These are archives can nearly 3 mi i.e. tens of thousands of hours.ing Some magnitudes of of the up archives to haveThe 20 ver ... recent efforts 23 to (direct digitise imaging)facilitate the and the plates /or extraction and 17.. of the unique correspond scientific data from arc already started extended digitisation ofplates already the scanned). plates There (e.g. arethe efforts S plates to and use creating these their data light curves. 2. Historical light curves and binary black holes in blazars analysis. Some of the archives already have devices for digi PoS(BLAZARS2008)076 Rene Hudec solar masses, major axis 8 this model the features in the ets. One of the last established odel [15] the outbursts are asso- f supermassive black holes (how- eresting blazars ever observed is azar in 1956 found by one of us rimary. The tidal influence of the ted). Sillanpaa et al. [21] assume ons show that supermassive black 12-year period are associated with ondary on the accretion disk of the ole exerts a torque on the accretion he primary. The long-term 60-year precise prediction within the binary of the orbit is difficult to constrain OJ 287 starting from the Lehto and n suggested to explain the behavior. ions that the orbital plane is nearly 1947.3, 1973.0, 1983.0, 1984.2 and solution the binary precesses by 33 ant flares were predicted [24]. The ical telescopes. In 1988 Sillanpaa et eep across our line of sight, Villata le accretion rate and thus a variable oles in blazars, stability, oscillations ast. One of the interesting branches, he bottom up scenario of galaxy for- on disk of the primary. Other models k into the black hole, caused by tidal erage of the optical light curve in the rom galaxy mergers of galaxies which ave a double peak structure with about t that supermassive binary black holes ticed a 12-year period within the major istic precession and leads to loss of or- n of the relativistic jet, which is caused the theory of supermassive binary black et etc. The study of the above mentioned he next outburst to come in 1994. After rictly constant and nor is the separation of nce of the secondary on the accretion disk d orbital period is 12.07 years, mass of the 3 solar masses, mass of the secondary = 1.3 x 10 10 the peaks). Consequently, Sillanpaa etthe al. detection [21] of predicted the t period in OJ 287, several models have bee the blazar called OJ 287, anal. easy [21] target studied both the for optical radiooutbursts light and in curve opt of the this optical blazar band and ofone-year no this separation (the blazar. 12-year The periodicity outbursts is h neither st Most of these models assume thatever the also engine of some OJ non-binary 287 black isthat a hole pair the models o light have been variations sugges areforce mass of inflows the from secondary accretion blackciated dis hole. with the In companion the blackfollowed Lehto hole - crossing and e.g. of Valtonen the m Sundelius accreti etValtonen model, al. Katz [23] [11] modeled assumes the thatdisk behavior the of of secondary the black h primaryet and al. thus causes [25] the cameand relativistic up worked jet with out a to model lighthouse sw waslight model curve with published are a by caused pair Valtonen by et ofprimary, 3 precession al. bent main of j processes: the [24]. impacts relativistic jet of In and the tidal sec influe impacts of the secondary blacktrend hole observed on in the the accretion light curve diskby results of the from t influence the of precessio thesecondary secondary on on the the accretion accretion disk diskmass of of flow the rate the primary into p the causes1994.8 jet variab are and used a tidal to outburst.Giant constructdegrees flares per a in revolution unique - orbit the solution. precessionbital is energy In due caused this to by gravitational relativ radiation,primary the = redshifte 1.77 x 10 of the orbit =with 0.056 this pc, model eccentricity but = theperpendicular 0.70. steep to The rise the inclination of plane outbursts ofnewly led the recognized to accretion and conclus disk. previously unknown(RH) The on giant next Sonneberg flare archival gi sky of patrol theprecesion plates was model. bl used for Moreover, the theoreticalmay reflections be sugges common in theholes Universe. should be Direct present and in indirectmation the observati supermassive center binary of black nearby holes galaxies. should then In result t f holes that are assumed to dwell in blazars. One of the most int of the primary. The double-peak giant flares occurring with a Searches for Supermassive Back Hole Binaries processes such as: existenceand of changes supermassive of accretion binary disk, black stability and h features changes in and the processes j requires eitherhistory, a or good an long-term excellent cov coveragethat of requires a a specific good period sampling in of the historical p light curves, is PoS(BLAZARS2008)076 14 – ∼ Rene Hudec ariability be- which shows several own TeV gamma-ray y [3]. This object was 11.6 up to 16 mag. ational campaigns in order to upermassive binary black hole 14 – 16 mag. n of suitable candidates. Based ∼ s region through historical light ˇ T since the beginning of the 20th ∼ n 1998 outburst, otherwise munity. The selected blazars are: of supermassive binary black holes trast with observations. The expla- several of these blazars). Therefore gh, UK (18,000 very deep plates), be good candidates for detection of lained in the frame of a binary black ), Harvard College Observatory, USA nteresting features (intense outbursts, re are of order of thousands of years, by many observational campaigns. Its ost a dozen of blazars as binary nature ints. The selected blazars were chosen i) Well-known blazars are preferred as hese gaps. The most valuable databases ds. Fortunately, in the mass ratio/period d blazars–binary black hole candidates l periods) where binary black holes can ties in their light curves, (ii) covered by 26]. B al crucial data gaps that disable to confirm scale of hours to years. There is a sugges- es in the X-ray and optical band. y [14]. B 4 15.5 – 19 mag in 1989 – 1994. ∼ This source is variable in many bands, it exhibits 13-month v An interesting X-ray source with possible X-ray periodicit This object was chosen because it is a well-known TeV blazar, It is the brightest BL Lac object at the UV, X-ray and a well-kn This object has been known as the variable ¸Sstar As mentioned above, the first part of the study is the selectio Mrk 421: Mrk 766: We expect to find more blazars similar to a well-established s PKS 0420-014: ON 231: Mkn 501: be detected through periodic behavior [29]. Blazars seem to 3. Selection of binary black hole candidates Searches for Supermassive Back Hole Binaries each harbor a supermassive black hole.should The be estimated relevantly number high (e.g.nation [27]) is which that seems the to orbital bewhich periods in are timescales induced con that by are the out ofplane binary any there natu observational is recor a small region (large mass ratio–short orbita such a binary motion.curves gathering We and want their to consequent analysis. search for blazars that fit– thi OJ 287.establish We long-term have optical gathered light data curves- from to of the study the periodic literature below behavior liste andflares, in quiescent observ level their behavior). light However, there curves are sever and other i we intend to go to databases ofare: astronomical plates Sonneberg to Observatory, fill Germany in (about t 280,000(about plates 500,000 plates),UKSTU plateand collection Observatory ROE Leiden, Edinbur NL (40,000 plates). tween major outbursts [28] and itshole behavior model has e.g. also [4]. been B exp source. Optical data for this sourceoptical have light also curve been suggests provided a possible 23-year periodicit added to our list to study possible relations of periodiciti century. In the optical band ittion exhibits of variability on a time 13.6-year period in17 the mag optical in band the [13]. historical B light = curve. 13 mag i periodicity or a BBH model (that has already been built up for on extended literature and data search,candidates we for have which selected we alm plan toby gather the the following historical criteria: data po (i)archival known plates or suspected and periodici be withinthe their gathered magnitude data limit, can be and used (ii more widely by the scientific com possible indications for a binary-black hole nature [19], [ PoS(BLAZARS2008)076 500 14 – ∼ ∼ 13.5-18 ∼ Rene Hudec 14 – 17 mag 550 recorded onents in this ∼ ∼ gnetic spectrum. V with large and than one year [6] eriodicities of 5 and 11 nd [16],[12] found strong 150 recorded data points). ∼ e been explained by the binary to reach the following results: (i) ry (HCO) was focused on the data dels [5]. [5] for 3C 345), emission from the Jurkevich method) in the long-term siderably improve the measurement he brightness of the target. ature of these curves, as we still work ght curves based on recent HCO data ally distorted jets ([26] for Mkn 501) storical data points for 9 blazars: derate activity (1972-1992). B . bout 11.6 years [22]. B nding theories, (iii) establish a detailed raction of the sources their magnitudes ted as due to a binary black hole nature m and Carrara [1], based on analysis of 400 recorded data points), (3) S20109+22 ht curve and 2.95-year periodicity (Fan et icity and light curve analysis, (ii) confront ∼ the best fit of a 22-year period. B 450 recorded data points), (5) ON231 ( 5 ∼ 550 recorded data points), (7) PKS2155-304 ( ∼ 250 recorded data points), and (9) BL Lac ( ∼ One of the most variable blazars across the entire electroma This object shows rapid optical variations of 2.5 mag in less A bright object in the optical band. The ejection of VLBA comp 550 recorded data points), (2) 3c66a ( 15-20 mag in the historical light curve. ∼ Exhibits extreme variability in all wavelengths. Optical p It is one of the best-monitored blazar sources. 3C 279 is an OV 275 and 64-day periodicities were observed in the optical ba ∼ Within the project described briefly in this paper, we intend (1) OJ287 ( The first part of plate analyses at Harvard College Observato 3C 345: S5 0716+71: For some of the above listed blazars the detected periods hav 3C 279: 3C66A: AO 0235+16: S2 0109+22: 450 recorded data points), (4) S50716+71 ( ∼ the new light curve of the selected blazars with the correspo recorded data points), (6) Mrk421 ( data points), (8) 3C371 ( Examples of preliminary very long–term (aboutmining 100 are years) presented li in Figs. 2on and 3. better Note calobration the of preiliminary n usedaccuracy. comparison It stars should which be also can noted con were that measured for on a the non–negligible plates f with plate limits comparable to t 5. Conclusion improve historical light curves of candidates, (ii) period ( mining in the plate stacks with the intention to gather new hi black hole nature: precessing jetless massive (e.g. binary black [20] hole for (e.g.etc. AO 0235+16; [19] for Mkn 501), helic 4. HCO Data Mining rapid outbursts. A strong period(27 of years) 7.1 near-infrared years light was curve found [7].trajectories (with and Moreover, velocities Abraha of superluminal features, got mag between 1989-2004. years have been reported followed up by binary black holes mo source may be quasi-periodic occurring every 0.7 years [10] [20]; [17]. B and possible variations of base-level flux onbetween a 1994 timescale – of 2000. a evidence for a 2.5-year period for16 the mag. time interval of the mo Suggestions for a 5.7-year periodicity [18] inal., the 2002) radio in lig the optical light curve have also been interpre Searches for Supermassive Back Hole Binaries PoS(BLAZARS2008)076 100 ∼ Rene Hudec public, grant 205/08/1207, around the maximum of the 1913 rst in 1900 added. The 2nd historical 1.5 mag) amplitude ∼ s the availability of data sets covering l conclusions, (v) provide the data to 2 -3 mag, Right: Mrk 521, 7 sharp large t combining old (crosses) and new (filled 71. 4 flaring episodes revealed over re the obvious choice. The preliminary proach, as the data are unique and cannot ∼ h large ( 6 2 mag ∼ Left: 3C66a: Several flaring episodes, amplitudes Left: The scan of the JD = 2419780.784 plate, i.e. plate taken Left: OJ287. One new, previously unknown, historical outbu We acknowledge the support by the Grant Agency of the Czech re years, amplitude results presented in this paper confirm that this is useful ap flaring episodes revealed with fast rise and decline, one wit wide scientific community. The nature ofvery the long project time require intervals, hence digitized archival plates a be provided by alternative methods. 6. Acknowledgements model at least of one of the candidates, (iv) draw statistica Figure 3: outburst in 1913 much better covered than before. Right: 3C3 Figure 2: Figure 1: Searches for Supermassive Back Hole Binaries outburst. Right: The Vcircles) HCO band plate light measurements. curve of OJ287 1913 outburs PoS(BLAZARS2008)076 Rene Hudec t during our stay at HCO. ce Series, 1999, 159 my, ASP Conf. 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