Please use this identifier to cite or link to this item: http://hdl.handle.net/2248/8031
Full metadata record
DC FieldValueLanguage
dc.contributor.authorMondal, S-
dc.contributor.authorPriyanka Rani-
dc.contributor.authorStalin, C. S-
dc.contributor.authorChakrabarti, S. K-
dc.contributor.authorRakshit, S-
dc.date.accessioned2022-08-24T10:25:38Z-
dc.date.available2022-08-24T10:25:38Z-
dc.date.issued2022-07-
dc.identifier.citationAstronomy and Astrophysics, Vol. 663, A178en_US
dc.identifier.issn1432-0746-
dc.identifier.urihttp://hdl.handle.net/2248/8031-
dc.descriptionOpen Accessen_US
dc.description.abstractContext. The X-ray emission in BL Lac objects is believed to be dominated by synchrotron emission from their relativistic jets. However, when the jet emission is not strong, one could expect signatures of X-ray emission from inverse Compton scattering of accretion disc photons by hot and energetic electrons in the corona. Moreover, the observed X-ray variability can also originate in the disc, and get propagated and amplified by the jet. Aims. Here, we present results on the BL Lac object Mrk 421 using the Nuclear Spectroscopic Telescope Array data acquired during 2017 when the source was in a moderate X-ray brightness state. For comparison with high jet activity state, we also considered one epoch of data in April 2013 when the source was in a very high X-ray brightness state. Our aim is to explore the possibility of the signature of accretion disc emission in the overall X-ray emission from Mrk 421 and also examine changes in accretion parameters considering their contribution to spectral variations. Methods. We divided each epoch of data into different segments in order to find small-scale variability. Data for all segments were fitted using a simple power-law model. We also fitted the full epoch data using the two component advective flow (TCAF) model to extract the accretion flow parameters. Furthermore, we estimated the X-ray flux coming from the different components of the flow using the lowest normalisation method and analysed the relations between them. For consistency, we performed the spectral analysis using models available in the literature. Results. The simple power-law function does not fit the spectra well, and a cutoff needs to be added. The spectral fitting of the data using the TCAF model shows that the data can be explained with a model where (a) the size of the dynamic corona at the base of the jet is from ∼28 to 10 rs, (b) the disc mass accretion rate is from 0.021 to 0.051 ṀEdd, (c) the halo mass accretion rate is from 0.22 to 0.35 ṀEdd, and (d) the viscosity parameter of the Keplerian accretion disc from 0.18 to 0.25. In the assumed model, the total flux, disc and jet flux correlate with the radio flux observed during these epochs. Conclusions. From the spectral analysis, we conclude that the spectra of all the epochs of Mrk 421 in 2017 are well described by the accretion-disc-based TCAF model. The estimated disc and jet flux relations with radio flux show that accretion disc can contribute to the observed X-ray emission, when X-ray data (that cover a small portion of the broad band spectral energy distribution of Mrk 421) are considered in isolation. However, the present disc-based models are disfavoured with respect to the relativistic jet models when considering the X-ray data in conjunction with data at other wavelengths.en_US
dc.language.isoenen_US
dc.publisherEDP Sciencesen_US
dc.relation.urihttps://doi.org/10.1051/0004-6361/202141990-
dc.rights© The European Southern Observatory-
dc.subjectAccretionen_US
dc.subjectAccretion disksen_US
dc.subjectBlack hole physicsen_US
dc.subjectHydrodynamicsen_US
dc.subjectGalaxies: jetsen_US
dc.subjectX-rays: galaxiesen_US
dc.subjectBL Lacertae objects: individual: Mrk 421en_US
dc.titleFlux and spectral variability of Mrk 421 during its moderate activity state using NuSTAR: Possible accretion disc contribution?en_US
dc.typeArticleen_US
Appears in Collections:IIAP Publications



Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.