Extreme X-ray Behavior of the Low-Luminosity Active Nucleus in NGC 4395

Details Extreme X-ray Behavior of the Low-Luminosity Active Nucleus in NGC 4395 Extreme X-ray Behavior of the Low-Luminosity Active Nucleus in NGC 4395

2005-02-04

arxiv.org/abs/astro-ph/0502109v1

Astronomy and Astrophysics

Astrophysics

28 pages, including 10 figures. Accepted for publication in The Astronomical Journal

Scientific paper

10.1086/429522

We present the results of a 17 ks Chandra ACIS-S observation of the nearby dwarf spiral galaxy NGC 4395. Chandra affords the first high-quality, broadband X-ray detection of the active nucleus of this object that is uncontaminated by nearby sources in the field. We find the nuclear X-ray source to be unresolved and confirm the rapid, large-amplitude variability reported in previous studies. The light curve appears to show ~ 11 cycles of a quasi-periodic oscillation with a period of ~ 400 s. If associated with an orbital feature near the innermost stable orbit of the accretion disk, this period would constrain the black-hole mass to be M < 9e5 M_sun. The X-ray spectrum indicates absorption by an ionized medium, and the spectral shape appears to vary over the course of our observation. Contrary to prior reports, however, the spectral variations are uncorrelated with changes in the hard X-ray flux. It is possible that the short-term spectral variability we observe results from column density fluctuations in the ionized absorber. A power-law fit to the spectrum above 1 keV yields a photon index of Gamma ~ 0.6, much flatter than that typically observed in the spectra of Seyfert 1 galaxies. We have ruled out photon pile-up as the cause of the flat spectrum. Even when complex spectral features are considered, the photon index is constrained to be Gamma < 1.25 (90% confidence). Comparing our results with previous determinations of the photon index (Gamma = 1.46 and 1.72), we conclude that the slope of the primary continuum varies significantly on time scales of a year or less. The extreme flatness and dramatic long-term variability of the X-ray spectrum are unprecedented among active galactic nuclei.

Affiliated with

Also associated with

No associations

Rating

Extreme X-ray Behavior of the Low-Luminosity Active Nucleus in NGC 4395 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 Extreme X-ray Behavior of the Low-Luminosity Active Nucleus in NGC 4395, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Extreme X-ray Behavior of the Low-Luminosity Active Nucleus in NGC 4395 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-527721