2017/03/07 by Dingrong Xiong, Jinming Bai, Haojing Zhang +4 · 2 citations
Physics and Astronomy · #astro-ph.HE #astro-ph.CO
paper · pdf · doi:10.3847/1538-4365/aa64d2
63 pages, 11 figures, 6 tables. Accepted for publication in ApJS
arxiv created 2017/03/07 · arxiv updated 2017/04/05
We have monitored the quasar 3C 273 in optical V, R and I bands from 2005 to 2016. Intraday variability (IDV) is detected on seven nights. The variability amplitudes for most of nights are less than 10% and four nights more than 20%. When considering the nights with time spans >4 hours, the value of duty cycle (DC) is 14.17 per cent. Over the twelve years, the overall magnitude and color index variabilities are \bigtriangleup I=0\rm m.67, \bigtriangleup R=0\rm m.72, \bigtriangleup V=0\rm m.68, and \bigtriangleup (V-R)=0\rm m.25 respectively. The largest clear IDV has an amplitude of 42% over just 5.8 minutes and the weakest detected IDV is 5.4% over 175 minutes. The BWB (bluer when brighter) chromatic trend is dominant for 3C 273 and appears at different flux levels on intraday timescales. The BWB trend exists for short-term timescales and intermediate-term timescales but different timescales have different correlations. There is no BWB trend for our whole time-series data sets. A significant anti-correlation between BWB trend and length of timescales is found. Combining with V-band data from previous works, we find a possible quasi-periodicity of P=3918±1112 days. The possible explanations for the observed variability, BWB chromatic trend and periodicity are discussed.