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Simultaneous x-ray and optical polarization observations of the blazar Mrk 421

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dc.contributor.author Bharathan, Athira M
dc.contributor.author Stalin, C. S
dc.contributor.author Sahayanathan, S
dc.contributor.author Wani, Kiran
dc.contributor.author Mandal, A. K
dc.contributor.author Chatterjee, Rwitika
dc.contributor.author Joshi, Santosh
dc.contributor.author Pandey, J. C
dc.contributor.author Mathew, B
dc.contributor.author Agrawal, V. K
dc.date.accessioned 2024-12-03T06:58:50Z
dc.date.available 2024-12-03T06:58:50Z
dc.date.issued 2024-11-10
dc.identifier.citation The Astrophysical Journal, Vol. 975, No. 2, 185 en_US
dc.identifier.issn 1538-4357
dc.identifier.uri http://hdl.handle.net/2248/8592
dc.description Open Access en_US
dc.description Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI
dc.description.abstract We present near-simultaneous X-ray and optical polarization measurements in the high synchrotron peaked (HSP) blazar Mrk 421. The X-ray polarimetric observations were carried out using Imaging X-ray Polarimetry Explorer (IXPE) on 2023 December 6. During IXPE observations, we also carried out optical polarimetric observations using 104 cm Sampurnanand telescope at Nainital and multiband optical imaging observations using 2 m Himalayan Chandra Telescope at Hanle. From model-independent analysis of IXPE data, we detected X-ray polarization with degree of polarization (ΠX) of 8.5% ± 0.5% and an electric vector position angle (ΨX) of 10fdg6 ± 1fdg7 in the 2−8 keV band. From optical polarimetry on 2023 December 6, in B, V, and R bands, we found values of ΠB = 4.27% ± 0.32%, ΠV = 3.57% ± 0.31%, and ΠR = 3.13% ± 0.25%. The value of ΠB is greater than that observed at longer optical wavelengths, with the degree of polarization suggesting an energy-dependent trend, gradually decreasing from higher to lower energies. This is consistent with that seen in other HSP blazars and favors a stratified emission region encompassing a shock front. The emission happening in the vicinity of the shock front will be more polarized due to the ordered magnetic field resulting from shock compression. The X-ray emission, involving high-energy electrons, originates closer to the shock front than the optical emission. The difference in the spatial extension could plausibly account for the observed variation in polarization between X-ray and optical wavelengths. This hypothesis is further supported by the broadband spectral energy distribution modeling of the X-ray and optical data. en_US
dc.language.iso en en_US
dc.publisher American Astronomical Society en_US
dc.relation.uri https://doi.org/10.3847/1538-4357/ad8081
dc.rights © 2024. The Author(s).
dc.subject Active galactic nuclei en_US
dc.subject Blazars en_US
dc.subject BL Lacertae objects en_US
dc.subject Xray sources en_US
dc.subject Polarimetry en_US
dc.title Simultaneous x-ray and optical polarization observations of the blazar Mrk 421 en_US
dc.type Article en_US


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