Mathematics – Probability
Scientific paper
Oct 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007acasn..48..407y&link_type=abstract
Acta Astronomica Sinica, vol. 48, no. 4, p. 407-417
Mathematics
Probability
1
Bl Lacertae Objects: Individual, Galaxies: Nucleus, Galaxies: Fundamental Parameters
Scientific paper
The optical photometric observations at I, R pass bands are carried out for Mkn501 using the 1.56 meter optical telescopes at Shanghai Astronomical Observatory at Sheshan. Combining our new observations with the published optical data, we got its long-term optical light curves, for a time coverage of near 80 years. However, the densely sampled data are in about past 30 years. Based on the available optical and infrared data in the literature, we found that the maximum optical variations are ΔU = 0.57mag, &DeltaΔB = 1.31mag, ΔV = 1.17mag, ΔR = 0.98mag, ΔI = 1.51mag; ΔJ = 2.37mag, ΔH=1.67mag, and ΔK=1.4mag respectively. We also get color indexes and find that there is a clear correlation between color index (B-V) and (B-R) with a correlation coefficient of r = 0.73 and a chance probability p< 10-4. In addition, investigating the correlation between the source brightness and the spectral index, it is found that the spectrum becomes steep with the source dimming when the source is brighter than 13mag., however, the spectrum flattens with the source becoming even fainter when the source is fainter than 13mag.. This phenomenon is consistent with the case for 3C279 Fan (1999). For the past 30 years of optical B band observations, a data compensated discrete Fourier transform-DCDFT plus CLEAN, namely the CLEANest method is used, the analysis result shows that there are 7 strong period signs. Out of the 7 period, there are two strong long-term periods of (10.06±0.04) years and (21.60±0.17) years. The long-term period is explained as the orbit of a binary black hole system (BBHS). In 2000, Rieger & Mannheim investigated the 23 day period found in the X-ray and the TeV light curves during the 1997 outburst, they found if there is a binary black hole system at the center of Mkn501 and the 23 day period is associated with the secondary black hole, then the BBHS will cause an orbit period of 6 to 14 years. Our 10.06 year period is consistent with their result. When the UMRAO data is adopted to the performance of the correlation between the optical and the radio band using a discrete correlation function (DCF) method, it is found that the variation in optical band leads the those in the radio and infrared bands by about 1.2 to 1.6 years and 0.5 years respectively. We think that these correlation should be analyzed via more observations.
Fan Junhui H.
Liu Ya-Ying
Wang Yao-Xiong
Yang Jae-Hyun
Yang Ya Sheng
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