2003/06/21 by Tahir Yaqoob, T. Yaqoob, I. M. George +5 · 4 citations
Physics and Astronomy · #Adaptive optics and wavefront sensing #Astrophysical Phenomena and Observations #astro-ph
paper · pdf · doi:10.1086/377687
published as Astrophys.J.596:85-104,2003 · Accepted for publication in the Astrophysical Journal. 30 pages, six figures, five of them color. Abstract is abridged
arxiv created 2003/06/21 · openalex publication_date 2003/10/08 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We report the detection of Fe XXV and Fe XXVI Kα emission lines from a Chandra High Energy Transmission Grating Spectrometer observation of the narrow-line Seyfert 1 galaxy NGC 7314, made simultaneously with the Rossi X-Ray Timing Explorer . The lines are redshifted ( cz ~ 1500 km s -1 ) relative to the systemic velocity and unresolved by the gratings. We argue that the lines originate in a near face-on (<7°) disk having a radial line emissivity flatter than r -2 . Line emission from ionization states of Fe in the range ~Fe I up to Fe XXVI is observed. The ionization balance of Fe responds to continuum variations on timescales of less than 12.5 ks, supporting an origin of the lines close to the X-ray source. We present additional, detailed diagnostics from this rich data set. These results identify NGC 7314 as a key source to study in the future if we are to pursue reverberation mapping of spacetime near black hole event horizons. This is because it is first necessary to understand the ionization structure of accretion disks and the relation between the X-ray continuum and Fe Kα line emission. However, we also describe how our results are suggestive of a means of measuring black hole spin without a knowledge of the relation between the continuum and line emission. Finally, these data emphasize that one can study strong gravity with narrow (as opposed to very broad) disk lines. In fact, narrow lines offer higher precision, given sufficient energy resolution.