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

TL;DR

This study presents a 15-year, multi-epoch X-ray analysis of Mrk 1040 using XMM-Newton, Suzaku, Swift, and NuSTAR, applying physical accretion-flow models to trace corona and absorber evolution. The 2009 data show a strong soft excess consistent with a warm, extended corona, while later epochs reveal disappearance or weakening of the warm component and a transition to a compact, thermally stable hot corona, as captured by TCAF and AGNSED fits. The results illustrate a dynamic disc–corona–absorber system with long-term changes in accretion rates, coronal geometry, Fe Kα strength, and intrinsic absorption, indicating transitions between different accretion states. A black hole mass of $M_{ m BH} = (4.50 \pm 1.62) \times 10^{7}\,M_\odot$ is inferred from the physical modeling, with implications for disc truncation and radiative efficiency across epochs.

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$α$ 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.

Figures (10)

• Figure 1: The light curves and correlation functions (ZDCF and ICF) for different energy bands from the XMM1, XMM2, and XMM3 observations are shown. The likelihood distributions, simulated using 120000 points, are overplotted on the ZDCF curves.
• Figure 2: The light curves and correlation functions (ZDCF and ICF) for different energy bands from the Nu1 and Nu2 observations are shown. The likelihood distributions, simulated using 120000 points, are overplotted on the ZDCF curves.
• Figure 3: The energy-dependent fractional variability of Mrk 1040 in different epochs.
• Figure 4: Left: The variation of $\chi^2$ for the primary continuum using the model: TBabs$\times$Constant$\times$(Powerlaw+zGauss). Right: The variation of $\chi^2$ over the full energy range using same baseline model. The presence of soft excess is clearly observed in the XMM1 observation (2009). However, this component is not found in any of the other observations across our $\sim$15-year observational period, from 2009 to 2024.
• Figure 5: Variation of different spectral fitting parameters with time. The corresponding values of each parameter are given in Table \ref{['tab:pm']}.