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Within a monitored duration of more than 7 yr, we obtained 1358 pairs of gri observations (514 at the g band, 393 at the r band, and 451 at the i band) for PKS0735+178 with a 1.26 m telescope in 20 nights from 2015 February 24 to 2016 April 28, and 98 VRI observations (27 at the V band, 35 at the R band, and 36 at the I band) with a 1.56 m telescope in 8 nights from 2009 January 13 to 2014 March 17. Based on the observations and analyses, we obtained the following results. (1) The maximum variation was 2.69 mag at the g band, and the largest intraday variations were Δmg = 0.89 ± 0.08 mag at the g band, Δmr = 0.38 ± 0.04 mag at the r band, and Δmi = 0.78 ± 0.15 mag at the i band. (2) We analyzed the intraday observations and find intraday optical variabilities with minimum timescales of ΔTg = 10.08 minutes, ΔTr = 10.08 minutes, and ΔTi = 10.08 minutes. (3) The variability rates of the magnitudes with time were consistent at three bands not only in the dimming stages but also in the brightening stages. (4) On 2016 January 19, we found intraday periodic oscillations, with a period P = 66.9 ± 4.1 minutes, based on which we calculated the mass to be in the approximate range of 1.5 × 107M⊙ to ∼8.9 × 107M⊙. (5) Based on our data and observations from the literature, we built long-term lightcurves of more than 100 yr and obtained two quasi-periods of P = 0.9 ± 0.4 yr and 12.4 ± 0.6 yr. [ABSTRACT FROM AUTHOR]

3C 273 is a well-studied FSRQ. In order to analyze its spectrum variabilities, we make spectroscopic observations of 3C 273 using the 2.16 m telescope at Xinglong Observatory of the National Astronomical Observatories. Based on these observations and some other spectra from the literature, we study the spectrum variabilities and the physical origin of the optical spectrum. The main results are as follows: (1) The continuum spectrum (S c ) shows obvious variabilities and displays quasi-periodic properties, P = 3.39 ± 1.13 yr, consistent with the result calculated from photometric observations. (2) The spectral energy distribution (SED) was modeled by a combination of blackbody emission that originated from the accretion disk and the dusty torus, synchrotron emission from the jet, the synchrotron self-Compton (SSC) emission, and the external Compton (EC) emission from the broad-line region, accretion disk, and dusty torus. The SED suggests that the optical continuum is dominated by the thermal emission from the accretion disk. (3) A time delay of τ c H β = 209.42 ± 9.38 days lies between the slope of the continuum spectrum (S c ) and H β emission line. (4) The relationships between the spectrum and polarization can be explained by the jet model. [ABSTRACT FROM AUTHOR]