Search

Mrk 501 is one of our long-term photometric monitoring objects with the optical telescopes at Yunnan Astronomical Observatory (YAO). In this work, observations were performed from 2010 March 11 to 2017 June 7 in the BVRI bands. We detected minute-scale rapid variabilities in the optical multi-band light curves. Durations of these rapid variabilities are from 5 to 77 minutes. The minimal decay timescale is about 3 minutes (2.330 ± 1.572 minutes on 2012 May 22 and 3.172 ± 1.626 minutes on 2017 May 20). After subtracting the host-galaxy component, The minimal decay timescale was about 8 minutes on 2017 June 3, and the corresponding duration is about 10 minutes. This fast variability requires the strength of the co-moving magnetic field in the jet larger than 38.60 G (19.69 G for corrected results, with Doppler factor δD ∼ 3). The discrete correlation function (DCF) analysis between B and I band short-term light curves show significant correlated variability; however, no significant time lags are detected. The color–magnitude variation shows significant negative correlation on intranight timescales, which is due to the superposition of multiple components. [ABSTRACT FROM AUTHOR]

We present long-term optical multi-band photometric monitoring of blazar 3C 273, from 2006 May 19 to 2015 March 31 with high temporal resolution in the BVRI bands. The source is in a steady state and showed very small variability, with the values of the fractional variability amplitude of , , and in B, V, R and I, respectively. The intra-night point-to-point fractional variability (Fpp) in each band is below 1.0%, and the Fpp variation amplitude increase from the B-band to the I-band. We find a variability with the timescale of 5.8 ± 2.9 minutes in the I-band on 2009 March 11. This fast variability requires the comoving magnetic field strength in the jet above 18 G with a Doppler factor . Using the discrete correlation function (DCF), the B- and I-band light curves are examined for correlation on whole campaign. Low significance (∼99.73 percent confidence) correlations with the I-band lags the B-band variations are observed. The spectral behaviors in the different variability episodes are studied. “Bluer-when-brighter” spectral behavior is presented for the whole campaign, while there is an opposite tendency when . The weak of the correlation between B- and I-band and the spectrum analysis indicate that the optical radiation consists of two variable components. [ABSTRACT FROM AUTHOR]