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 \sim 11 cycles of a quasi-periodic oscillation with a period of \sim 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 < 9 \times 10 ^ { 5 } M _ { \odot } .
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 \approx 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 .