Work

The optical spectral variations of 37 blazars with SMARTS data

Year: 2026

Type: article

Abstract: ABSTRACT The variability of blazars remains an open problem. In this work, we use the simultaneous multifrequency photometric data of Small and Moderate Aperture Research Telescope System (SMARTS) to study the optical spectral variability of 37 blazars. Our sample includes 29 flat-spectrum radio quasars (FSRQs), 6 BL Lacertae objects (BL Lacs), and 2 blazar candidates of unknown type. By performing the linear fits in the plane of the spectral index versus optical flux, we obtain the slope K for each source, which characterizes its optical spectral behaviour. Based on K, 13 sources exhibit a bluer-when-brighter (BWB) trend ($K\gt 0.1$), 14 sources show a redder-when-brighter (RWB) trend ($K\lt -0.1$), and 10 sources display achromatic behaviour ($-0.1\lt K\lt 0.1$). Most FSRQs favour the RWB trend, while most BL Lacs tend to show the BWB trend. We find a weak positive correlation between K and $\log \nu _p$, and a weak negative correlation between K and $\log \nu _p$. Based on the criteria $\Delta BIC \gt 10$, we select 7 targets with significant trend transition behaviour, and reproduce the non-linear variation behaviour quantitatively via the two-component model with the modulation of the intrinsic peak frequency. Our work elucidates the variation mechanism of blazars at optical bands.

Source: Monthly Notices of the Royal Astronomical Society

DOI: 10.1093/mnras/stag897

Authors: Di Chen, Yun-Guo Jiang

Institution: Shandong University

Language: English

Topic: Astrophysics and Cosmic Phenomena

Subfield: Nuclear and High Energy Physics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $3,046

Funder: National Natural Science Foundation of China