Tracing a disk wind in NGC 3516

¹ Dept. of Physics, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA e-mail: turner@milkyway.gsfc.nasa.gov
² Code 662, Exploration of the Universe Division, NASA/GSFC, Greenbelt, MD 20771, USA
³ Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire ST5 5BG, UK
⁴ Department of Physics, Catholic University of America, 620 Michigan Avenue NE, Washington, DC 20064, USA
⁵ Dept. of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK

Received: 7 October 2007
Accepted: 26 February 2008

Abstract

Context. X-ray spectra of AGN often contain signatures indicative of absorption in multiple layers of gas whose ionization-state and covering fraction may vary with time. It has been unclear to date how much of the observed X-ray spectral and timing behavior in AGN can be attributed to variations in absorption, versus variations in the strengths of emission or reflection components. Diagnostics of the inner regions of AGN cannot be reliably performed until the origin of observed effects is understood.

Aims. We investigate the role of the X-ray absorbers in the Seyfert 1 galaxy NGC 3516.

Methods. Time-averaged and flux-selected spectroscopy is used to examine the behavior of NGC 3516 observed in Chandra HETG and XMM data from Oct. 2006.

Results. New H-like and He-like emission and absorption features discovered in the Fe K regime reveal a previously unknown zone of circumnuclear gas in NGC 3516 with log and column density ~. A lower-ionization layer with log and of similar column density is confirmed from previous observations, this layer has a covering fraction around 50%, and changes in covering provide a simple explanation of a deep dip in the light curve that we interpret as an eclipse of the continuum due to passage of a cloud across the sight line within half a day. These inner zones of absorbing gas are detected to have outflow velocities in the range  km s^-1, this, and constraints on radial location are consistent with an origin as part of a disk wind in NGC 3516.