Multiband optical variability of 3C 279 on diverse time-scales

Abstract

We have monitored the flat spectrum radio quasar, 3C 279, in the optical B, V , R and I passbands from 2018 February to 2018 July for 24 nights, with a total of 716 frames, to study flux, colour and spectral variability on diverse timescales. 3C 279 was observed using seven different telescopes: two in India, two in Argentina, two in Bulgaria and one in Turkey to understand the nature of the source in optical regime. The source was found to be active during the whole monitoring period and displayed significant flux variations in B, V , R, and I passbands. Variability amplitudes on intraday basis varied from 5.20% to 17.9%. A close inspection of variability patterns during our observation cycle reveals simultaneity among optical emissions from all passbands. During the complete monitoring period, progressive increase in the amplitude of variability with frequency was detected for our target. The amplitudes of variability in B, V , R and I passbands have been estimated to be 177%, 172%, 171% and 158%, respectively. Using the structure function technique, we found intraday timescales ranging from ∼ 23 minutes to about 115 minutes. We also studied colour-magnitude relationship and found indications of mild bluer-when-brighter trend on shorter timescales. Spectral indices ranged from 2.3 to 3.0 with no clear trend on long term basis. We have also generated spectral energy distributions for 3C 279 in optical B, V , R and I passbands for 17 nights. Finally, possible emission mechanisms causing variability in blazars are discussed briefly.

Multi-band behaviour of the TeV blazar PG 1553+113 in optical range on diverse timescales

“…( 7) Variability amplitude expressed in magnitudes instead of percents (see Eq. 4 in Agarwal et al 2019). (a) For BRI-bands the January 12, 2016 (MJD ∼7400.7) data point was not taken into account in calculation of A as it has no counterpart in the V-band.…”

“…The main characteristics and technical details for telescopes A, B, C, D, and E can be found in Table 1 of Agarwal et al (2019). In addition to these, for the present work, we have used four other optical telescopes (F, G, H, I), which we describe below.…”

“…Finally, the 2.0 m telescope of the Rozhen NAO was used in two additional observing configurations compared to that reported in Agarwal et al (2019): the CCD camera VersArray:1300B attached directly to the RC focus and the two CCD cameras Andor iKon-L attached at the ports of the two-channel focal reducer FoReRo-2 (Jockers et al 2000;Bonev 2011).…”

“…The tests are described in detail in Agarwal et al (2019). Even if the comparison and control stars were appropriately selected, we applied the Γ scaling factor (Howell et al 1988) to equalize the target and control error distributions, since this procedure has been shown to give the most reliable results (e.g.…”

A Possible Quasi-Periodic Oscillation in the X-ray Emission of 3C 120

“…The weighting function w(i) is 1 if we have observation for ith interval else it is 0. Further details of SF can be found in [47] and references therein. For a sinusoidal time series with period P, the SF curve has minima at τ equal to the period (P) and its sub-harmonics (e.g., [18].…”