Low-energy X-ray spectral variability of NGC 4051

Details Low-energy X-ray spectral variability of NGC 4051 Low-energy X-ray spectral variability of NGC 4051

Apr 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995mnras.273..549m&link_type=abstract

Monthly Notices of the Royal Astronomical Society, Volume 273, Issue 3, pp. 549-558.

Astronomy and Astrophysics

Astronomy

39

Galaxies: Active, Galaxies: Individual: Ngc 4051, Galaxies: Seyfert, X-Rays: Galaxies

Scientific paper

We present ROSAT observations of NGC 4051 from 1991 November 15 (28-ks exposure) and 1991 December 12 (4.7-ks exposure). During these observations the source spectrum is well described empirically by a simple power law with energy index ~1.5 and an absorption edge with optical depth ~0.8 at ~0.85 keV or, more physically, by a warm absorber with an underlying power law of energy index 1.19, similar to that seen at higher energies, an ionization parameter xi~300 and a column of warm gas N_warm~8x10^22 cm^-2. During the November observation the source flux varies by a factor of ~10, and there is some evidence that xi may increase with increasing flux. However, the correspondence between luminosity and xi is not simple, and there is a suggestion that xi may lag behind luminosity by a few thousand seconds. If the lag represents a cooling time-scale for the warm absorber, we can crudely estimate the gas density as ~10^7 cm^-3, and hence a thickness of ~5x10^15 cm for the warm gas cloud. The December observation is not well fitted by a simple warm absorber, and the fit is much improved by the addition of an emission line at 0.63+/-0.07 keV, i.e. at the energy of OVIII Lyalpha (0.65 keV). We note that N_warm as deduced from the November observation is noticeably less than the value deduced by Pounds et al. (~3.7x10^23 cm^-2) from observations one year prior to ours, and there is an indication that the value deduced from the December observation is also different from that of the November observation, demonstrating the presence of large-scale inhomogeneities and motions in the warm gas in the nuclei of active galaxies.

Affiliated with

Also associated with

No associations

Rating

Low-energy X-ray spectral variability of NGC 4051 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 Low-energy X-ray spectral variability of NGC 4051, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Low-energy X-ray spectral variability of NGC 4051 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1830311