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Please use this identifier to cite or link to this item: http://hdl.handle.net/2289/7867
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dc.contributor.authorSingh, K.P.-
dc.contributor.authorKushwaha, P-
dc.contributor.authorSinha, A-
dc.contributor.authorPal, Main-
dc.contributor.authorAgarwal, Aditi-
dc.contributor.authorDewangan, G.C.-
dc.date.accessioned2021-12-23T08:47:26Z-
dc.date.available2021-12-23T08:47:26Z-
dc.date.issued2022-01-
dc.identifier.citationMonthly Notices of Royal Astronomical Society, 2022, Vol. 509, p2696-2706en_US
dc.identifier.issn0035-8711-
dc.identifier.issn1365-2966 (Online)-
dc.identifier.urihttp://hdl.handle.net/2289/7867-
dc.descriptionRestricted Access. An open-access version is available at arXiv.org (one of the alternative locations)en_US
dc.description.abstractWe present AstroSat soft X-ray, near-UV (NUV), and far-UV (FUV) observations of a blazar, OJ 287, carried out in 2017, 2018, and 2020. The simultaneous observations with NuSTAR in 2017 provide a broad-band look encompassing NUV, FUV, soft, and hard X-rays. Captured in three different broad-band spectral states in three observations, the X-ray spectrum is found to be the hardest during 2018, while the high-energy-end of the simultaneous optical-FUV spectrum shows a steepening that is modelled with a broken power-law spectrum. The spectral energy distribution (SED) in 2017 shows a relatively flatter optical-FUV and soft X-ray spectra, implying an additional emission component. The 2020 optical-FUV spectrum is harder than in 2017 and 2018, with an extremely soft X-ray spectrum and a hardening above ∼1 GeV, similar to the SEDs of High-energy-peaked BL Lac objects (HBL), thereby establishing that this additional emission component has HBL-like properties. The AstroSat multiwavelength observations trace the spectral evolution from the end-phase of the HBL component in 2017 to its disappearance in 2018 followed by its revival in 2020. A single zone leptonic model reproduces the 2018 broad-band spectrum, while the 2017 and 2020 SEDs require an additional HBL-like emitting zone. The spectral evolution of the high-energy-end of optical-UV spectrum, revealed by the FUV observations in 2017 and 2018, strongly suggests that X-ray spectral changes in the normal broad-band spectral state of OJ 287 are primarily due to the evolution of the optical-UV synchrotron spectrum.en_US
dc.language.isoenen_US
dc.publisherOxford University Press on behalf of the Royal Astronomical Societyen_US
dc.relation.urihttps://ui.adsabs.harvard.edu/abs/2021MNRAS.tmp.2885S/abstracten_US
dc.relation.urihttps://arxiv.org/abs/2110.14978en_US
dc.relation.urihttps://doi.org/10.1093/mnras/stab3161en_US
dc.rights2022 The Author(s)en_US
dc.subjectradiation mechanismsen_US
dc.subjectnon-thermalen_US
dc.subjectgalaxies: activeen_US
dc.subjectgalaxies: jetsen_US
dc.subjectgamma-raysen_US
dc.subjectgalaxiesen_US
dc.subjectX-raysen_US
dc.subjectquasarsen_US
dc.subjectOJ 287en_US
dc.titleSpectral States of OJ 287 blazar from Multiwavelength Observations with AstroSaten_US
dc.typeArticleen_US
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