Uncovering the primary X-ray emission and possible starburst component in the polarized NLS1 Mrk 1239

TL;DR

This study analyzes 18 years of X-ray data from Mrk 1239, revealing spectral variability, the presence of starburst-related emission at low energies, and complex central region emission modeled through absorption and reflection mechanisms.

Contribution

It provides a comprehensive multi-epoch, broad-band X-ray analysis of Mrk 1239, highlighting the role of starburst components and complex absorption/reflection models in NLS1 galaxies.

Findings

Spectral variability observed in 3-10 keV band over 18 years.

Low-energy emission dominated by starburst-related hot gas.

High-energy emission characterized by ionized absorption and relativistic reflection.

Abstract

X-ray observations of the unique NLS1 galaxy Mrk 1239 spanning 18-years are presented. Data from XMM-Newton, Suzaku, Swift and NuSTAR are combined to obtain a broad-band, multi-epoch view of the source. There is spectral variability in the 3-10 keV band over the 18-years. An analysis of the NuSTAR and Suzaku light curves also suggests rapid variability in the 3-10 keV band, which is consistent with the NLS1 definition of the source. However, no variability is seen below 3 keV on any timescale. Two distinct physical models are adopted to describe the data above and below ~3 keV. The low energies are dominated by a hot, diffuse gas likely associated with a starburst component at large physical scales. The higher energy spectrum is dominated by emission from the central region. Ionised partial covering and relativistic blurred reflection are considered for the central region emission. In both cases, the underlying power law has a photon index of $\Gamma\sim2.3-2.4$. A distant reflector, a neutral partial covering component with a covering fraction near $\sim1$, and contributions from starburst emission are always required. The blurred reflection model requires a reflection dominated spectrum, which may be at odds with the low emissivity index and radio properties of the source. By contrast, the two absorption components required in the ionised partial covering model may correspond to the two distinct regions of polarization observed in the optical. Regardless of the physical model, spectral changes between epochs are driven by the absorption components and on short time scales by intrinsic AGN variability.