XRISM/Resolve Spectroscopy of the Central Engine in the Seyfert-1 AGN Mrk 279

Abstract High-resolution X-ray spectroscopy with XRISM gives an unprecedented view of the “central engine” in active galactic nuclei (AGN), providing unique insights into black hole accretion and feedback. We present an analysis of the first XRISM/Resolve spectrum of the Seyfert-1 galaxy Mrk 279, known for its complex line profiles and variability. The data reveal velocity components within the Fe K α emission line that can be associated with the inner face of the molecular torus ( r ≥ 10 4 GM / c 2 ), the broad-line region (BLR; <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>r</mml:mi> <mml:mo>=</mml:mo> <mml:mn>165</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1480</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>5780</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="1em"/> <mml:mi>G</mml:mi> <mml:mi>M</mml:mi> <mml:mo>/</mml:mo> <mml:msup> <mml:mrow> <mml:mi>c</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:math> ), and the inner accretion disk ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>r</mml:mi> <mml:mo>=</mml:mo> <mml:mn>8</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>75</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>280</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="1em"/> <mml:mi>G</mml:mi> <mml:mi>M</mml:mi> <mml:mo>/</mml:mo> <mml:msup> <mml:mrow> <mml:mi>c</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:math> ). We find evidence of low-velocity, highly ionized gas that contributes an H-like Fe XXVI emission line at 6.97 keV, confirming suggestions from prior low-resolution spectra. The data do not show slow winds in absorption, but two pairs of lines—consistent with He-like and H-like Fe shifted by v ≃ 0.22 c and v ≃ 0.33 c —improve the fit and could represent an ultrafast outflow (UFO). Their addition to the model only reduces the Akaike information criterion by 3.6 and 3.5, respectively, signaling modest support. Additional observations are needed to definitively test for the presence of fast X-ray winds in Mrk 279. We discuss these results in the context of the geometry of the central engine in AGN, emerging trends in XRISM studies of AGN, and the nature of the potential UFOs.