The X-ray variability history of Markarian 3

Abstract

Context. The unified scenario for active galactic nuclei (AGN) postulates that our orientation with respect to a parsec-scale azimuthally-symmetric gas and dust system causes the difference in their phenomenology in the optical/UV and X-ray bands. Only recently have high-resolution radio (VLBI) and IR interferometric observations provided direct constraints on the size and structure of this obscuring system (known historically as the "torus"). On the other hand, variability in optically-thick X-ray absorption and reprocessing in heavily obscured AGN often probe smaller scales, down to the broad line region and beyond. Aims. We aim at constraining the geometry of the reprocessing matter in the nearby prototypical Seyfert 2 Galaxy Markarian 3 by studying the time evolution of the spectral components associated to the primary AGN emission and to its Compton-scattering. Methods. We analyzed archival spectroscopic observations of Markarian 3 taken over the last 12 years with the XMM-Newton, Suzaku and Swift observatories, as well as data taken during a monitoring campaign activated by us in 2012.Results. The timescale of the Compton-reflection component variability (originally discovered by ASCA in the mid-'90s) is < ∼ 64 days. This upper limit improves by more than a factor of 15 on previous estimates of the Compton-reflection variability timescale for this source. When the light curve of the Compton-reflection continuum in the 4−5 keV band is correlated with the 15-150 keV Swift/BAT curve, a delay > ∼ 1200 days is found. The cross-correlation results depend on the model used to fit the spectra, although the detection of the Compton-reflection component variability is independent of the range of models employed to fit the data. Reanalysis of an archival Chandra image of Markarian 3 indicates that the Compton-reflection and the Fe K α emitting regions are extended to the north up to 300 pc. The combination of these findings suggests that the optically-thick reprocessor in Markarian 3 is clumpy.Conclusions. There is mounting experimental evidence that the structure of the optically-thick gas and dust in the nuclear environment of nearby heavily obscured AGN is extended and complex. We discuss possible modifications to the standard unification scenarios encompassing this complexity. Markarian 3, which exhibits X-ray absorption and reprocessing on widely different spatial scales, is an ideal laboratory to test these models.

X-ray spectral variability of Seyfert 2 galaxies

“…Among them, variations are found only in MARK 3, which was previously classified as a Compton-thick candidate Goulding et al 2012), with a column density of 1.1 × 10 24 cm −2 measured by BeppoSAX (Cappi et al 1999). In fact, variations in MARK 3 have already been reported by Guainazzi et al (2012), who studied its variability using XMM-Newton, Suzaku, and Swift data, and found variations on timescales of months. We found that the changes in MARK 3 are related to Norm 2 , i.e., intrinsic to the source.…”

“…This nucleus is also included in the present sample, but variations are not found here, mainly because we did not use two of the observations included in the work of Paggi et al (2012) since they were affected by a pileup fraction higher than 10%. Guainazzi et al (2012) speculate that variations at soft X-ray energies in MARK 3 may be present when comparing XMM-Newton and Swift data, but confirmation is still required. They argue that these variations are most probably due to cross-calibration uncertainties between the instruments, but if true, soft X-ray variations could be related to the innermost part of the narrow-line region.…”

“…Bianchi et al (2005b) report variations of the normalization of the absorbed power law when comparing the XMM-Newton from 2001 with Chandra and BeppoSAX data. Guainazzi et al (2012) studied the X-ray variability of this nucleus during 12 years of observations with Chandra, XMM-Newton, Suzaku, and Swift satellites. Their analysis was performed in the 4−10 keV energy band.…”

Spatially resolved Fe K spectroscopy of NGC 4945

“…Bauer et al (2015) recently confirmed this result, using NuSTAR, by spectrally discriminating three neutral reflectors, which differently contribute to the iron Kα and Compton hump emission. Other Compton-thick sources have been used to map the extended iron Kα emission line: Mrk 3 (Guainazzi et al 2012(Guainazzi et al , 2016, Circinus (Marinucci et al 2013) and they all indicate that reflecting material may extend on scales ranging from tens to thousands of parsecs. In particular, the last source showed a spatially variable Equivalent Width of the iron Kα which strongly resembles the one that we have presented for NGC 4945.…”

“…Molendi, Bianchi & Matt 2003;Arévalo et al 2014) and Mrk 3 (e.g. Bianchi et al 2005b;Pounds & Page 2005;Guainazzi et al 2012Guainazzi et al , 2016.…”