ROSAT HRI Monitoring of Extreme X-ray Variability in the Narrow-Line Quasar PHL 1092

Details ROSAT HRI Monitoring of Extreme X-ray Variability in the Narrow-Line Quasar PHL 1092 ROSAT HRI Monitoring of Extreme X-ray Variability in the Narrow-Line Quasar PHL 1092

1999-01-25

arxiv.org/abs/astro-ph/9901353v1

Astronomy and Astrophysics

Astrophysics

6 pages, MNRAS in press, also available from http://www.astro.psu.edu/users/niel/papers/papers.html

Scientific paper

10.1046/j.1365-8711.1999.02411.x

We report results from an 18-day ROSAT HRI monitoring campaign on the ultrasoft Narrow-Line Seyfert 1 (NLS1) class quasar PHL 1092. This luminous, radio-quiet quasar showed strong X-ray variability in a short ROSAT PSPC observation, and ROSAT HRI monitoring of the similar object IRAS 13224-3809 revealed extreme variability on intermediate timescales. We wanted to determine whether remarkable X-ray variability persistently occurs in PHL 1092, and we also wanted to search for outstanding variability events that constrain emission processes. Given the large luminosity of PHL 1092 (about 5x10^{45} erg/s in the HRI band), we detect extremely rapid and large-amplitude X-ray variability throughout our monitoring. The maximum observed variability amplitude is a factor of about 14, and in the most rapid variability event the HRI count rate increases by a factor of about 3.8 in a rest-frame time interval of < 3580 s. The most rapid event has a rate change of luminosity of > 1.3x10^{42} erg/s^2, making it the most extreme such event we are aware of from a radio-quiet quasar. Standard `radiative efficiency limit' arguments imply a radiative efficiency larger than can be achieved by accretion onto a Kerr black hole rotating at the maximum plausible rate, although we point out that such arguments depend upon the geometry of initial radiation release. Relativistic motions of the X-ray source are probably causing the radiative efficiency limit to break down; such relativistic motions have also been inferred in the similar NLS1-class quasar PKS 0558--504.

Affiliated with

Also associated with

No associations

Rating

ROSAT HRI Monitoring of Extreme X-ray Variability in the Narrow-Line Quasar PHL 1092 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with ROSAT HRI Monitoring of Extreme X-ray Variability in the Narrow-Line Quasar PHL 1092, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and ROSAT HRI Monitoring of Extreme X-ray Variability in the Narrow-Line Quasar PHL 1092 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-494497