26-30 June 2023
Centro Congressi Federico II
Europe/Rome timezone

eROSITA Detection of Cloud Occultation Events in Seyfert AGN, and Contributions for Clumpy-Torus models

28 Jun 2023, 12:45
Aula Magna (Centro Congressi Federico II)

Aula Magna

Centro Congressi Federico II

Via Partenope, 36, Napoli, Italy
Contributed talk Current and Future Surveys


Alex Markowitz (Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences)


Recent years have seen broad observational support for the
circumnuclear gas around supermassive black holes to contain a clumpy
component. In the X-ray band, individual clouds can manifest
themselves when they transit the line of sight to the X-ray corona,
temporarily obscuring the X-ray continuum, and indicating the
characteristics and location of these clouds.

The eROSITA X-ray telescope aboard Spectrum X/Gamma is performing
multiple all-sky X-ray surveys, including monitoring a vast sample of
AGN and galaxies. Such monitoring can amplify rare cloud occultation
events, allowing us to accumulate observational constraints for
clumpy-torus models, including cloud distribution and composition

Here, we discuss the first cloud occultation events detected in a
Seyfert 1 galaxy by eROSITA: in this Seyfert, the soft X-ray flux
dipped abruptly for $\sim$ 10-18 months during 2020-2021, recovered,
but then dropped a second time by Spring 2022. Our two-year
multi-wavelength follow-up campaign included X-ray/UV and ground-based
optical photometric and spectroscopic observations, and confirmed that
the soft X-ray flux dips were caused by partial-covering obscuration
by two separate, single compact clouds near the black hole.
The two transiting clouds are consistent with neutral or lowly-ionized
gas, residing at radial distances commensurate with the optical Broad
Line Region and the inner dusty torus, respectively.

Primary author

Alex Markowitz (Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences)


Dr. Mirko Krumpe (Leibniz-Institut für Astrophysik Potsdam) Saikruba Krishnan (The Inter-University Centre for Astronomy and Astrophysics (IUCAA)) Tathagata Saha (Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences) David Homan (Leibniz-Insitut für Astrophysik Potsdam) Dr. Jörn Wilms (Remeis Observatory & Erlangen Centre for Astroparticle Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg,) Prof. Hartmut Winkler (University of Johannesburg) Thomas Boller (Max-Planck-Institut für Extraterrestrische Physik) Andrea Gokus (Dr. Karl Remeis-Observatory and Erlangen Centre for Astroparticle Physics) Steven Haemmerich (Dr. Karl Remeis-Observatory and Erlangen Centre for Astroparticle Physics) Dr. Malte Schramm (Graduate School of Science and Engineering, Saitama University) Dr. Mariusz Gromadzki (Astronomical Observatory, University of Warsaw)

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