Model simulation for periodic double-peaked outbursts in blazar OJ 287: binary black hole plus lighthouse effect

The mechanism of formation for double-peaked optical outbursts observed in blazar OJ 287 is studied. It is shown that they could be explained in terms of a light- house effect for superluminal optical knots ejected from the center of the galaxy that move along helical magnetic fields. It is assumed that the orbital motion of the secondary black hole in the supermassive binary black hole system induces the 12-year quasi-periodicity in major optical outbursts by the interaction with the disk around the primary black hole. This interaction between the secondary black hole and the disk of the primary black hole （e.g. tidal effects or magnetic coupling） excites or injects plas- mons （or relativistic plasmas plus magnetic field） into the jet which form superluminal knots. These knots are assumed to move along helical magnetic field lines to produce the optical double-peaked outbursts by the lighthouse effect. The four double-peaked outbursts observed in 1972, 1983, 1995 and 2005 are simulated using this model. It is shown that such lighthouse models are quite plausible and feasible for fitting the double-flaring behavior of the outbursts. The main requirement may be that in OJ 287 there exists a rather long （～40-60 pc） highly collimated zone, where the lighthouse effect occurs.

OJ 287的引力波辐射研究

类星体OJ 287的研究已经有100多年的历史,它呈现周期性双峰爆发现象,爆发周期为12 yr,比较好地解释观测的模型是双黑洞模型,即次黑洞绕主黑洞运动,并撞击主黑洞吸积盘从而引起爆发.此模型合理地解释了OJ 287的光变曲线并正确预言了未来爆发时间,这间接证明了广义相对论进动效应以及引力波的存在.星系中心大质量黑洞是一类重要的引力波源,而精确确定了其内部组分运动学方程的星系非常少,由于双黑洞模型提供了精确的黑洞运动轨道,故可以在这个运动轨道基础上研究其引力波辐射.在已有工作基础上,采用后牛顿近似方法首次得到了引力波辐射功率和波形随时间的演化关系,根据目前引力波探测设备IPTA(International Pulsar Timing Array)的进展情况,未来十几年内对OJ 287的引力波直接探测将成为可能.

Optical multi-color monitoring of OJ 287 from 2006 to 2012

We present our optical multi-color monitoring of the BL Lac object OJ 287 from January 2006to December 2012 in the V,R and I bands.A relatively active state in OJ 287 has been found over all monitored epochs,among which the variations of average magnitude in V/R/I bands were measured with ?V=1.956 mag,?R=2.067 mag and ?I=2.115 mag,respectively.No reliable intraday variability is detected,but possible variability is detected on 16 nights.Their relative variation amplitudes fall into the range between 1% and 8%,with the majority between 2% and 4%.No time lags have been detected,but strong correlations exist among light curves in the three wavebands.The bluer-when-brighter trend is dominant over intraday timescales,which supports the shock-in-jet model.When combining with additional V/R band data obtained from SMARTS and the Steward Observatory,we also find a bluer-when-brighter trend over a long-term timescale.Some possible periods of 513,176,36,30,26,17 and 14 d are found in all time-series data sets from 2006 to 2017.Possible explanations about these periods are given.

Long-term variation time scales in OJ 287

The light curve data from 1894 to 2008 are compiled for the BL Lacertae object OJ 287 from the available literature. Periodicity analysis methods （the Discrete Correlation Function-DCF, the Jurkevich method, the power spectral （Fourier） analysis, and the CLEANest method） are performed to search for possible periodicites in the light curve of OJ 287. Significance levels are given for the possible periods. The analysis results confirm the existence of the 12.2 ± 0.6 yr time scale and show a hint of a -53 yr time scale. The 12.2 ± 0.6 yr period is used as the orbital period to investigate the supermassive binary black hole system parameters.

Optical monitoring and intra-day variabilities of BL Lac Objects OJ 287

Using the 1.26 m National Astronomical Observatory-Guangzhou University Infrared/Optical Telescope(NGT),we monitor one BL Lac object,OJ 287.For this source,we obtain 15094 gri observations(4900 at g band,5184 at r band and 5010 at i band)in 155 nights from 2014 December 13 to 2019 March15.Based on the upper observations,we obtain the following results.(1)The total variation amplitude is~2.3 mag.(2)There are intra-day variabilities(IDVs).The IDV timescales(△T)are in the range from 7.69 min(Δm=0.06±0.02 mag)to 371.09 min(Δm=0.26±0.04 mag).(3)There are strong correlations betweenΔT andΔm,△m=(2.91±0.66)×10^(-4)ΔT+(0.08±0.009),with r=0.52,p=5.33×10^(-5).(4)There are intra-day periods in this source,with the period P≈94 min on 2017 December 10.When we supplement the observations from the literature,we can obtain that the long-term period is about 12.02±0.41 yr.(5)The spectral properties of OJ 287 show the bluer-when-brighter behavior,whatever state the source is at.

Optical Photometric Observations of 7-Ray Loud Blazars

We report results of our optical photometric observations of ten gamma-ray loud blazers, namely: 0219+428 (3C66A), PKS 0420-014 (OA 129), S5 0716+714, 0754+100 (OI 090.4), 0827+243 (OJ248), 1652+398 (Mrk 501), 2200+420 (BL Lacertae), 2230+114 (CTA 102), 2251+158 (3C 454.3) and 2344+514. The observations were carried out in September-October, 2000 using the 70 cm optical telescope at Abstumani Observatory, Georgia. We found intra-day variations in 0420-014, S5 0716+714, BL Lacertae and CTA 102. A variation of 0.3 magnitude over a time scale of about 3 hours was observed in the R passband in BL Lacertae on JD 2451827. We did not detect any variation in 3C 66A, Mrk 501, or 3C 454.3 during our observations. Nor did we detect any clear evidence of variation in 1ES 2344+514 during our two weeks' observing run of the TeV gamma-ray source.