Examinando por Autor "Reynolds, C. S."

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A dynamic black hole corona in an active galaxy through X-ray reverberation mapping
(Springer Nature Research Journals, 2020-01-20) Alston, W. N.; Fabian, A. C.; Kara, E.; Parker, M. L.; Dovciak, M.; Pinto, Ciro; Jiang, J.; Middleton, M. J.; Miniutti, Giovanni; Walton, D. J.; Wilkins, D. R.; Buisson, D. J.; Caballero García, M. D.; Cackett, E. M.; De Marco, B.; Gallo, L. C.; Lohfink, A. M.; Reynolds, C. S.; Uttley, P.; Young, A. J.; Zogbhi, A.; European Research Council (ERC); Science and Technology Facilities Council (STFC); European Space Agency (ESA); European Commission (EC); Agencia Estatal de Investigación (AEI); 0000-0003-2658-6559; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
X-ray reverberation echoes are assumed to be produced in the strongly distorted spacetime around accreting supermassive black holes. This signal allows us to spatially map the geometry of the inner accretion flow1,2—a region that cannot yet be spatially resolved by any telescope—and provides a direct measure of the black hole mass and spin. The reverberation timescale is set by the light travel path between the direct emission from a hot X-ray corona and the reprocessed emission from the inner edge of the accretion disk3,4,5,6. However, there is an inherent degeneracy in the reverberation signal between black hole mass, inner disk radius and height of the illuminating corona above the disk. Here we use a long X-ray observation of the highly variable active galaxy IRAS 13224−3809 to track the reverberation signal as the system evolves on timescales of a day7,8. With the inclusion of all the relativistic effects, modelling reveals that the height of the X-ray corona increases with increasing luminosity, providing a dynamic view of the inner accretion region. This simultaneous modelling allows us to break the inherent degeneracies and obtain an independent timing-based estimate for the mass and spin of the black hole. The uncertainty on black hole mass is comparable to the leading optical reverberation method9, making X-ray reverberation a powerful technique, particularly for sources with low optical variability10.
Acceso Abierto
Estimating the Jet Power of Mrk 231 during the 2017–2018 Flare
(The Institute of Physics (IOP), 2020-03-04) Reynolds, C. S.; Punsly, B.; Miniutti, Giovanni; O´Dea, C. P.; Huerley Walker, N.; Agencia Estatal de Investigación (AEI); Punsly, B. [0000-0002-9448-2527]; Hurley Walker, N. [0000-0002-5119-4808]; Reynolds, C. [0000-0002-8978-0626]; O´Dea, C. [0000-0001-6421-054X]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Long-term 17.6 GHz radio monitoring of the broad absorption-line quasar, Mrk 231, detected a strong flare in late 2017. This triggered four epochs of Very Long Baseline Array (VLBA) observations from 8.4 to 43 GHz over a 10 week period as well as an X-ray observation with NuSTAR. This was the third campaign of VLBA monitoring that we have obtained. The 43 GHz VLBA was degraded in all epochs, with only 7 of 10 antennas available in three epochs and 8 in the first epoch. However, useful results were obtained due to a fortuitous capturing of a complete, short 100 mJy flare at 17.6 GHz, both growth and decay. This provided useful constraints on the physical model of the ejected plasma that were not available in previous campaigns. We consider four classes of models: discrete ejections (both protonic and positronic) and jetted (protonic and positronic). The most viable model is a "dissipative bright knot" in a faint background leptonic jet with an energy flux ~1043 erg s−1. Inverse Compton scattering calculations (based on these models) in the ambient quasar photon field explains the lack of a detectable increase in X-ray luminosity measured by NuSTAR. We show that the core (the bright knot) moves toward a nearby secondary at ≈0.97c. The background jet is much fainter. Evidently, the high-frequency VLBA core does not represent the point of origin of blazar jets, in general, and optical depth "core shift" estimates of jet points of origin can be misleading.