ItemArticle

Ultraviolet variability in radio-loud active galactic nuclei observed by UVIT onboard AstroSat

Title
Ultraviolet variability in radio-loud active galactic nuclei observed by UVIT onboard AstroSat
Creator
Reshma, M.; Stalin, C.S.; Kumar Mandal, Amit; Gudennavar, S.B.; Benedict, Senorita; Joseph, Prajwel
Description
Radio-loud active galactic nuclei (AGN) are among the most luminous objects in the Universe, emitting radiation from low-energy radio waves to high energy ? -rays. They are well known to exhibit flux variations at nearly all accessible wavelengths. However, their variability properties in the ultraviolet (UV) band remain relatively less explored compared to other wavebands. Here, we present the results of a systematic investigation of the UV flux and spectral variability characteristics of 24 radio-loud AGN spanning the redshift range 0.018 ? z ? 2.218. The sample comprises 17 BL Lac objects, 6 flat spectrum radio quasars (FSRQs) and one radio-loud narrow line Seyfert 1 galaxy. We used observations obtained with the Ultra-Violet Imaging Telescope (UVIT) onboard AstroSat during its first ten years of operation, covering both the far-UV (FUV; 1300 - 1800 and near-UV (NUV; 2000 - 3000 bands. Of the 24 sources analysed, 18 showed significant UV variability on hour timescales. We found a bluer when brighter (BWB) spectral trend in two sources: the FSRQ CTA 102 and the BL Lac PKS 0447 - 439. The observed UV variability in our sample of radio-loud AGN, together with the BWB trend detected in these two sources, supports a scenario in which the hour timescale UV variations are driven by intrinsic processes within their relativistic jets. 2026 Elsevier B.V.
Source
Journal of High Energy Astrophysics;Volume;53;Issue;;Article No.;100601;
Date
01-01-2026
Publisher
Elsevier B.V.
Subject
Active galactic nuclei; BL lacertae objects; Blazars; Flat spectrum radio quasars; Narrow-line Seyfert 1 galaxy; Ultraviolet variability
Coverage
Reshma M., Department of Physics and Electronics, CHRIST University, Karnataka, Bengaluru, 560029, India; Stalin C.S., Indian Institute of Astrophysics, Block II, Koramangala, Karnataka, Bengaluru, 560034, India; Kumar Mandal A., Center for Theoretical Physics of the Polish Academy of Sciences, Al. Lotnikow 32/46, Warsaw, 02-668, Poland; Gudennavar S.B., Department of Physics and Electronics, CHRIST University, Karnataka, Bengaluru, 560029, India; Benedict S., St. Josephs University, 36, Lal Bagh Main Road, Langford Gardens, Bengaluru, 560 027, India; Joseph P., Indian Institute of Astrophysics, Block II, Koramangala, Karnataka, Bengaluru, 560034, India
Rights
Restricted Access; Hardcopy may be available in the library
Relation
ISSN: 22144048;
Format
online
Language
English
Type
Article

Citation

Reshma, M.; Stalin, C.S.; Kumar Mandal, Amit; Gudennavar, S.B.; Benedict, Senorita; Joseph, Prajwel, “Ultraviolet variability in radio-loud active galactic nuclei observed by UVIT onboard AstroSat,” CHRIST (Deemed To Be University) Institutional Repository, accessed June 18, 2026, https://archives.christuniversity.in/items/show/22352.

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