Multi-Color Optical Monitoring of MRK 501 From 2010 to 2015

Abstract

We have monitored the BL Lac object Mrk 501 in the optical V, R, and I bands from 2010 to 2015. For Mrk 501, the presence of a strong host galaxy component can affect the results of photometry. After subtracting the host galaxy contributions, the source shows intraday and long-term variabilities for optical flux and color indices. The average variability amplitudes of the V, R, and I bands are 22.05%, 22.25%, and 23.82%, respectively, and the value of the duty cycle is 14.87%. A minimal variability timescale of 106 minutes is detected. No significant time lag between the V and I bands is found on one night. The bluer-when-brighter (BWB) trend is dominant for Mrk 501 on intermediate, short, and intraday timescales, which supports the shock-in-jet model. For the long timescale, Mrk 501, in different states, can have different BWB trends. The corresponding results for non-correcting host galaxy contributions are also presented.

Multicolor Optical Monitoring of the Quasar 3C 273 from 2005 to 2016

“…The long-term achromatic trend could be due to superposition of different components (jet components, accretion disk components, Gravitational microlensing effect; Ikejiri et al 2011;Bonning et al 2012;Fan et al 2008;Gaur et al 2015;Agarwal & Gupta 2015;Xiong et al 2016). …”

“…de Diego 2010; Joshi et al 2011;Goyal et al 2012;Hu et al 2014;Agarwal & Gupta 2015;Xiong et al 2016). F value is calculated as…”

“…We use the ANOVA in our analysis because it does not rely on error measurement but derives the expected variance from subsamples of the data. Considering the time of exposure, we bin the data in a group of three or five observations (see Xiong et al 2016 andde Diego 2010 for detail). This method is used only for light curves with more than 20 observations on a given night, but if the measurements in the last group are less than 3 or 5, then it is merged with the previous group.…”

“…Optical variability is often associated with color/spectral behavior in blazars, which can be used to explore the emission mechanism (e.g. Gu & Ai 2011;Zheng et al 2008;Xiong et al 2016). The results from Dai et al (2009) implied that the spectrum becomes bluer (flatter) when the source becomes brighter both on intraday variability and long-term variability for 3C 273.…”

“…Therefore, long-term monitoring of 3C 273 is very important to better understand the physics of the quasar. (Dai et al 2015;Xiong et al 2016). The standard Johnson broadband filters were used for the two telescopes.…”