Astronomy and Astrophysics – Astrophysics
Scientific paper
2003-04-08
Astrophys.J. 589 (2003) L33-L36
Astronomy and Astrophysics
Astrophysics
13 pages including 4 figures, accepted for publication in ApJL. For more details, see http://zon.wins.uva.nl/~yuwf/xraytransie
Scientific paper
10.1086/375714
We have analyzed {\it Rossi X-ray Timing Explorer} (RXTE) data of the neutron star transient Aquila X-1 obtained during its outbursts in May/June 1999 and September/October 2000. We find that in the early rise of these outbursts, a hard flare in the energy range above 15 keV preceded the soft X-ray peak. The hard X-ray flux of the hard flares at maximum was more than a factor of three stronger than at any other point in the outbursts. The rise of the hard X-ray flare to this maximum, was consistent with a monotonically brightening low/hard state spectrum. After the peak of the hard flare, a sharp spectral transition occurred with spectral pivoting in the range 8--12 keV. Our timing analysis shows that during the hard flare the power spectra were mainly composed of band-limited noise and a $\sim$ 1--20 Hz QPO, which correlate in frequency. Immediately after the hard flare, the power spectra turned into power law noise. The spectral and timing properties during and after the hard flares are very similar to those in black hole transients during the early rise of an outburst. We suggest that these hard flares and spectral transitions in Aql X-1 are of the same origin as those observed in black hole transients. This leads to the association of the 1--20 Hz QPOs and band-limited noise in Aql X-1 with those in black hole transients. We discuss the impact of this discovery on our understanding of soft X-ray transient outbursts, state transitions and variability in X-ray binaries.
Fender Rob
Klein-Wolt Marc
van der Klis Michiel
Yu Wenfei
No associations
LandOfFree
Hard X-ray Flares Preceding Soft X-ray Outbursts in Aquila X-1: A Link between Neutron Star and Black Hole State Transitions 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 Hard X-ray Flares Preceding Soft X-ray Outbursts in Aquila X-1: A Link between Neutron Star and Black Hole State Transitions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hard X-ray Flares Preceding Soft X-ray Outbursts in Aquila X-1: A Link between Neutron Star and Black Hole State Transitions will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-603565