Rapid X-ray variability in Mkn 421 during a multiwavelength campaign. Issue 2 (7th April 2022)

• Record Type: Journal Article
• Authors: Markowitz, Alex G; Nalewajko, Krzysztof; Bhatta, Gopal; Dewangan, Gulab C; Chandra, Sunil; Dorner, Daniela; Schleicher, Bernd; Pajdosz-Śmierciak, Urszula; Stawarz, Łukasz; Zola, Staszek; Ostrowski, Michał; Carosati, Daniele; Krishnan, Saikruba; Bachev, Rumen; Benítez, Erika; Gazeas, Kosmas; Hiriart, David; Hu, Shao-Ming; Larionov, Valeri; Marchini, Alessandro; Matsumoto, Katsura; Nikiforova, A A; Pursimo, Tapio; Raiteri, Claudia M; Reichart, Daniel E; Rodriguez, Diego; Semkov, Evgeni; Strigachev, Anton; Sugiura, Yuki; Villata, Massimo; Webb, James R; Arbet-Engels, Axel; Baack, Dominik; Balbo, Matteo; Biland, Adrian; Bretz, Thomas; Buss, Jens; Eisenberger, Laura; Elsaesser, Dominik; Hildebrand, Dorothee; Iotov, Roman; Kalenski, Adelina; Mannheim, Karl; Mitchell, Alison; Neise, Dominik; Noethe, Maximilian; Paravac, Aleksander; Rhode, Wolfgang; Sliusar, Vitalii; Walter, Roland;
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 513:Issue 2(2022)
• Page Start: 1662
• Page End: 1679
• Publication Date: 2022-04-07
• Subjects: acceleration of particles -- black hole physics -- galaxies: active -- BL Lacertae objects: Mkn 421; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac917
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: The study of short-term variability properties in AGN jets has the potential to shed light on their particle acceleration and emission mechanisms. We report results from a 4-d coordinated multiwavelength campaign on the highly peaked blazar (HBL) Mkn 421 in 2019 January. We obtained X-ray data from AstroSAT, BVRI photometry with the Whole Earth Blazar Telescope (WEBT), and TeV data from First G-APD Cherenkov Telescope to explore short-term multiwavelength variability in this HBL. The X-ray continuum is rapidly variable on time-scales of tens of ks. Fractional variability amplitude increases with energy across the synchrotron hump, consistent with previous studies; we interpret this observation in the context of a model with multiple cells whose emission spectra contain cutoffs that follow a power-law distribution. We also performed time-averaged and time-resolved (time-scales of 6 ks) spectral fits; a broken power-law model fits all spectra well; time-resolved spectral fitting reveals the usual hardening when brightening behaviour. Intra-X-ray cross-correlations yield evidence for the 0.6–0.8 keV band to likely lead the other bands by an average of 4.6 ± 2.6 ks, but only during the first half of the observation. The source displayed minimal night-to-night variability at all wavebands thus precluding significant interband correlations during our campaign. The broad-band SED is modelled well with a standard one-zone leptonic model, yielding jet parameters consistent with those obtained from previous SEDs of this source.