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arXiv · 2308.01841

Universality of coronal properties in accreting black holes across mass and accretion rate

Sudip Chakraborty·Ajay Ratheesh·Francesco Tombesi·Rodrigo Nemmen·Srimanta Banerjee
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Abstract

Through their radio loudness, lack of thermal UV emission from the accretion disk and power-law dominated spectra, Low Luminosity AGN (LLAGN) display similarity with the hard state of stellar-mass black hole X-Ray Binaries (BHBs). In this work we perform a systematic hard X-ray spectral study of a carefully selected sample of unobscured LLAGN using archival $NuSTAR$ data, to understand the central engine properties in the lower accretion regime. We analyze the $NuSTAR$ spectra of a sample of 16 LLAGN. We model the continuum emission with detailed Comptonization models. We find a strong anti-correlation between the optical depth and the electron temperature of the corona, previously also observed in the brighter Seyferts. This anti-correlation is present irrespective of the shape of the corona, and the slope of this anti-correlation in the log space for LLAGN (0.68-1.06) closely matches that of the higher accretion rate Seyferts (0.55-1.11) and hard state of BHBs ($\sim$0.87). This anti-correlation may indicate a departure from a fixed disk-corona configuration in radiative balance. Our result, therefore, demonstrates a possible universality in Comptonization processes of black hole X-ray sources across multiple orders of magnitude in mass and accretion rate.

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Sudip Chakraborty, Ajay Ratheesh, Francesco Tombesi, Rodrigo Nemmen, Srimanta Banerjee. 2023-08-03. Universality of coronal properties in accreting black holes across mass and accretion rate. https://doi.org/10.1051/0004-6361%2F202347181

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