Benvenuti nell'Anagrafe della Ricerca d'Ateneo
La valutazione delle attività di ricerca che si svolgono nelle università ha assunto un'importanza rilevante sia per l'intero sistema universitario sia all'interno di ogni singolo ateneo. Roma Tre si è quindi dotata di idonei strumenti informativi in grado di supportare al meglio le azioni di monitoraggio e di valutazione delle attività di ricerca svolte nei propri dipartimentied ha realizzato una Anagrafe della Ricerca di Ateneo.
EnglishAims. We report estimates of the X-ray coronal size of active galactic nuclei in the lamppost geometry. In this commonly adopted scenario, the corona is assumed for simplicity to be a point-like X-ray source located on the axis of the accretion disc. However, the corona must intercept a number of optical/UV seed photons from the disc consistent with the observed X-ray flux, which constrains its size. Methods. We employ a relativistic ray-tracing code, originally developed by Dovčiak and Done, that calculates the size of a Comptonizing lamppost corona illuminated by a standard thin disc. We assume that the disc extends down to the innermost stable circular orbit of a non-spinning or a maximally spinning black hole. We apply this method to a sample of 20 Seyfert 1 galaxies using simultaneous optical/UV and X-ray archival data from XMM-Newton. Results. At least for the sources accreting below the Eddington limit, we find that a Comptonizing lamppost corona can generally exist, but with constraints on its size and height above the event horizon of the black hole depending on the spin. For a maximally spinning black hole, a solution can almost always be found at any height, while for a non-spinning black hole the height must generally be higher than 5 gravitational radii. This is because, for a given luminosity, a higher spin implies more seed photons illuminating the corona, which is due to a larger and hotter inner disc area. The maximal spin solution is favoured, as it predicts an X-ray photon index in better agreement with the observations.
Ursini, F., Dovciak, M., Zhang, W., Matt, G., Petrucci, P.-., & Done, C. (2020). Estimating the size of X-ray lamppost coronae in active galactic nuclei. ASTRONOMY & ASTROPHYSICS, 644, A132.
| Titolo: | Estimating the size of X-ray lamppost coronae in active galactic nuclei | |
| Autori: | ||
| Data di pubblicazione: | 2020 | |
| Rivista: | ||
| Citazione: | Ursini, F., Dovciak, M., Zhang, W., Matt, G., Petrucci, P.-., & Done, C. (2020). Estimating the size of X-ray lamppost coronae in active galactic nuclei. ASTRONOMY & ASTROPHYSICS, 644, A132. | |
| Handle: | http://hdl.handle.net/11590/381677 | |
| Appare nelle tipologie: | 1.1 Articolo in rivista |
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