An XMM-Newton Analysis of the Supermassive Black Hole Binary Candidate MCG+11–11–032

Abstract We investigate the possibility of a binary supermassive black hole system at the center of MCG+11–11–032, a local ( z = 0.036) Seyfert 2 galaxy. Prior work with stacked Swift/XRT spectra suggested the presence of two Fe K α lines (at 6.16 and 6.56 keV) with 2 σ confidence. This could be consistent with a prediction of several hydrodynamical models, in which each black hole hosts a minidisk and contributes one Doppler-shifted Fe K α line to the total spectrum. Another study using a single exposure from Chandra/ACIS did not find evidence for a double line. Here, we conduct follow-up observations with two epochs of XMM - Newton/EPIC data spaced ∼6 months apart. After fitting our spectra with models from the previous two studies, we do not find evidence for a double iron line in either observation. Our best-fit model yields <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">Γ</mml:mi> <mml:mo>=</mml:mo> <mml:mn>1.6</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.21</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.20</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>N</mml:mi> <mml:mrow> <mml:mspace width="0.1em"/> <mml:mtext>H</mml:mtext> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:mn>1</mml:mn> <mml:msup> <mml:mn>0</mml:mn> <mml:mn>22</mml:mn> </mml:msup> <mml:msup> <mml:mrow> <mml:mtext>cm</mml:mtext> <mml:mspace width="0.1em"/> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo>=</mml:mo> <mml:mn>17</mml:mn> <mml:mo>.</mml:mo> <mml:msubsup> <mml:mn>9</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2.4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>2.7</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> for the first epoch and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">Γ</mml:mi> <mml:mo>=</mml:mo> <mml:mn>1.4</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.24</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.22</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>N</mml:mi> <mml:mrow> <mml:mspace width="0.1em"/> <mml:mtext>H</mml:mtext> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:mn>1</mml:mn> <mml:msup> <mml:mn>0</mml:mn> <mml:mn>22</mml:mn> </mml:msup> <mml:msup> <mml:mrow> <mml:mtext>cm</mml:mtext> <mml:mspace width="0.1em"/> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo>=</mml:mo> <mml:mn>17</mml:mn> <mml:mo>.</mml:mo> <mml:msubsup> <mml:mn>1</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2.4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>2.7</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> for the second. We compare our spectral parameters with those derived in past work on this source, finding broad agreement with prior data sets. Lastly, we discuss the properties of MCG+11–11–032 alongside samples of Seyfert 2 galaxies from the literature, finding that it is consistent with this population and the single active galactic nucleus scenario.