Title:	Multiwavelength study of TeV blazar 1ES 1218 + 304 using gamma-ray,X-ray and optical obser v ations
Authors:	Diwan, Rishank Prince, Raj Agarwal, Aditi Bose, Debanjan Majumdar, Pratik ¨Ozd ¨onmez, Aykut Chandra, Sunil Khatoon, Rukaiya Ege, Erg ¨un
Keywords:	Galaxies acti ve –galaxies: Jets –gamma-rays Galaxies –radiation mechanisms Non-thermal –BL Lacertae objects Individual 1ES 1218 + 304
Issue Date:	14-Jul-2023
Publisher:	Royal Astronomical Society
Citation:	Monthly Notices of the Royal Astronomical Society,2023,Vol.524, p4333
Abstract:	We report on a multiwavelength study of the high-synchrotron-peaked BL Lac 1ES 1218 + 304 using near simultaneous dataobtained during the period from 2018 January 1 to 2021 May 31 (MJD 58119–59365) from various instruments, including Fermi–LAT , Swift–XRT , AstroSat , and optical data from Swift-UVOT and the TUBITAK observatory in Turkey. The source was reported to be flaring in the TeV γ-ray band during 2019, but no significant variation was observed with Fermi–LAT . A sub-hour variability is seen in the SXT light curve, suggesting a compact emission region for the v ariability. Ho we ver, hour-scale v ariability is observed in the γ-ray light curve. A ‘softer-when-brighter’ trend is observed in the γ-ray, and an opposite trend is seen in the X-ray, suggesting that the two emissions are produced through two different processes, as expected from a high-frequency- peaked BL Lac source. We have chosen the two epochs in 2019 January to study and compare their physical parameters. A joint fit of SXT and LAXPC provides a constraint on the synchrotron peak, estimated to be ∼1.6 keV. A clear shift in the synchrotronpeak is observed from ∼1 keV to abo v e 10 keV, revealing its extreme nature or behaviour like an extreme blazar-type source.The optical observation provides a colour-index variation as ‘blue-when-brighter’. The broad-band spectral energy distribution is fitted with a single-zone synchrotron-self Compton model, and their parameters are discussed in the context of a TeV blazar and the possible mechanism behind the broad-band emission
Description:	Open Access
URI:	http://hdl.handle.net/2289/8207
ISSN:	0035-8711 (print) 1365-2966 (online)
Alternative Location:	https://ui.adsabs.harvard.edu/abs/2023MNRAS.524.4333D/abstract https://arxiv.org/abs/2301.00991 https://doi.org/10.1093/mnras/stad2088
Copyright:	2023, The Author(s)
Appears in Collections:	Research Papers (A&A)

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