PDS 456: an extreme accretion rate quasar?
Abstract
We present quasi-simultaneous ASCA and RXTE observations of the most luminous known active galactic nucleus in the local (z<0.3) Universe, the recently discovered quasar PDS 456. Multiwavelength observations have been conducted that show that PDS 456 has a bolometric luminosity of ~1047ergs-1peaking in the ultraviolet part of the spectrum. In the X-ray band the 2-10keV (rest-frame) luminosity is 1045ergs-1. The broad-band X-ray spectrum obtained with ASCA and RXTE contains considerable complexity. The most striking feature observed is a very deep, ionized iron K edge, observed at 8.7keV in the quasar rest-frame. We find that these features are consistent with reprocessing from highly ionized matter, probably the inner accretion disc. PDS 456 appeared to show a strong (factor of ~2.1) outburst in just ~17ks, although non-intrinsic sources cannot be completely ruled out. If confirmed, this would be an unusual event for such a high-luminosity source, with a light-crossing-time corresponding to ~2RS. The implication would be that flaring occurs within the very central regions, or else that PDS 456 is a `super-Eddington' or relativistically beamed system. Overall we conclude on the basis of the extreme blue/UV luminosity, the rapid X-ray variability and from the imprint of highly ionized material on the X-ray spectrum, that PDS 456 is a quasar with an unusually high accretion rate.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 2000
- DOI:
- 10.1046/j.1365-8711.2000.03282.x
- arXiv:
- arXiv:astro-ph/9911475
- Bibcode:
- 2000MNRAS.312L..17R
- Keywords:
-
- GALAXIES: ACTIVE;
- QUASARS: INDIVIDUAL: PDS 456;
- X-RAYS: GALAXIES;
- Astrophysics
- E-Print:
- 5 pages, 6 postscript figures. Accepted for publication in MNRAS Letters