2016ApJ...824...20R -
Astrophys. J., 824, 20-20 (2016/June-2)
Discovery of broad soft X-ray absorption lines from the quasar wind in PDS 456.
REEVES J.N., BRAITO V., NARDINI E., BEHAR E., O'BRIEN P.T., TOMBESI F., TURNER T.J. and COSTA M.T.
Abstract (from CDS):
High-resolution soft X-ray spectroscopy of the prototype accretion disk wind quasar, PDS 456, is presented. Here, the XMM-Newton reflection grating spectrometer spectra are analyzed from the large 2013-2014 XMM-Newton campaign, consisting of five observations of approximately 100 ks in length. During the last observation (OBS. E), the quasar is at a minimum flux level, and broad absorption line (BAL) profiles are revealed in the soft X-ray band, with typical velocity widths of σ_{v}∼10,000 km/s. During a period of higher flux in the third and fourth observations (OBS. C and D, respectively), a very broad absorption trough is also present above 1 keV. From fitting the absorption lines with models of photoionized absorption spectra, the inferred outflow velocities lie in the range ∼0.1–0.2c . The absorption lines likely originate from He and H-like neon and L-shell iron at these energies. A comparison with earlier archival data of PDS 456 also reveals a similar absorption structure near 1 keV in a 40 ks observation in 2001, and generally the absorption lines appear most apparent when the spectrum is more absorbed overall. The presence of the soft X-ray BALs is also independently confirmed by an analysis of the XMM-Newton EPIC spectra below 2 keV. We suggest that the soft X-ray absorption profiles could be associated with a lower ionization and possibly clumpy phase of the accretion disk wind, where the latter is known to be present in this quasar from its well-studied iron K absorption profile and where the wind velocity reaches a typical value of 0.3c.
Abstract Copyright:
© 2016. The American Astronomical Society. All rights reserved.
Journal keyword(s):
black hole physics - quasars: individual: PDS 456 - X-rays: galaxies
Simbad objects:
9
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