2015/05/11 by L. Ballo, Ballo, L., P. Severgnini +15
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #Pulsars and Gravitational Waves Research
paper · pdf · doi:10.48550/arxiv.1505.02593
openalex publication_date 2015/05/11 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
One of the key ingredients of the Unified Model of Active Galactic Nuclei (AGN) is the presence of a torus-like optically thick medium composed by dust and gas around the putative supermassive black hole. However, the structure, size and composition of this circumnuclear medium are still matter of debate. To this end, the search for column density variations through X-ray monitoring on different timescales (months, weeks and few days) is fundamental to constrain size, kinematics and location of the X-ray absorber(s). Here we describe our project of mining the Swift-XRT archive to assemble a sample of AGN with extreme column density variability and determining the physical properties of the X-ray absorber(s). We also present the results obtained from a daily-weekly Swift-XRT follow-up monitoring recently performed on one of the most interesting new candidates for variability discovered so far, Mrk 915.