Evolution of Accretion Properties in Mrk 1040 using long-term X-ray Observations

TL;DR

This study analyzes 15 years of X-ray data from Mrk 1040, revealing accretion regime changes, a variable soft excess, and evolving coronal structures, providing insights into the AGN's accretion dynamics and black hole mass.

Contribution

It offers a long-term, multi-epoch spectral and timing analysis of Mrk 1040, clarifying the nature of the soft excess and coronal evolution using physical models.

Findings

Confirmed soft excess in 2009 with warm Comptonizing corona

Observed variability in coronal geometry and absorption properties

Estimated black hole mass as (4.50 ± 1.62) × 10^7 solar masses

Abstract

We present a comprehensive long-term, multi-epoch spectral and timing study of the Seyfert 1 Active Galactic Nucleus (AGN) Mrk~1040, utilizing X-ray observations spanning from 2009 to 2024 ($\sim$15 years). The source exhibits pronounced spectral and temporal variability, indicative of transitions between different accretion regimes in the vicinity of the central supermassive black hole. The earlier reported soft excess is re-examined within a uniform, physically motivated multi-epoch framework. We confirm the presence of this soft excess in the 2009 observation, where it is well described by a warm, extended Comptonizing corona with $kT_{\rm e,warm} \sim 0.26$~keV and a radial extent of $R_{\rm warm} \sim 30~r_g$. In subsequent epochs, the soft excess is not statistically significant, possibly due to a combination of enhanced ionized absorption, intrinsic weakening of the warm Comptonizing region, or partial truncation of the inner disc. A strong correlation between the soft and hard X-ray fluxes suggests a common physical origin for both components, likely within a multi-layered Comptonizing structure that evolved into a compact and thermally stable corona after 2013. The observed spectral variability, together with changes in the Fe~K$\alpha$ line strength, reflects the evolving coronal geometry and accretion flow dynamics. Variations in the intrinsic column density ($N_H$) further indicate that Mrk~1040 is embedded within a clumpy, dynamically variable absorber responding to changes in the accretion rate. Using the TCAF model, we estimate the black hole mass as $M_{\rm BH} = (4.50 \pm 1.62) \times 10^7~M_\odot$, consistent with previous estimates.