南方基地知识库

In order to study short timescale optical variability of gamma-ray blazar S5 0716+714, quasi-simultaneous spectroscopic and multiband photometric observations were performed from 2018 November to 2019 March with the 2.4 m optical telescope located at Lijiang Observatory of Yunnan Observatories. The observed spectra are well fitted with a power law F-lambda = A lambda(-alpha) (spectral index alpha > 0). Correlations found between (alpha)over dot, (A)over dot, (A)over dot/A, (F)over dot(lambda), and (F)over dot(lambda)/F-lambda, and are consistent with the trend of bluer-when-brighter (BWB). It is the same case for colors, magnitudes, color variation rates, and magnitude variation rates of photometric observations. The variations of alpha lead those of F-lambda. Also, the color variations lead magnitude variations. The observational data are mostly distributed in the I(+,+) and III(-,-) quadrants of the coordinate system. Both spectroscopic and photometric observations show BWB behaviors in S5 0716+714. The observed BWB may be explained by the shock-jet model, and its appearance may depend on the relative position of the observational frequency ranges with respect to the synchrotron peak frequencies, e.g., at the left of the peak frequencies. Fractional variability amplitudes are F-var similar to 40% for both spectroscopic and photometric observations. Variations of alpha indicate variations of relativistic electron distribution producing the optical spectra.