The X-ray spectral variability of the Seyfert galaxy NGC 3227

We present the results from ASCA observations of NGC 3227 performed during 1993 and 1995, along with those from a ROSAT observation performed pseudosi multaneously with the former. We find the 0.6-10 keV continuum to be consis tent with a power law with a photon index Gamma similar to 1.6, flatter tha n that typically observed in Seyfert galaxies confirming previous results. Significant Fe K-shell emission is observed during both epochs, with an equ ivalent width and profile typical of Seyfert 1 galaxies. The ASCA observati ons in 1993 reveal absorption by a screen N-H,z(ion) similar or equal to 3 x 10(21) cm(-2) of ionized material with an X-ray ionization parameter U-X similar or equal to 0.01. Both the column and ionization state of this mate rial are at the low end of the distribution of parameters observed for Seyf ert I galaxies. Joint analysis of the ASCA and ROSAT data at this epoch sho ws an additional screen of neutral material instrinsic to NGC 3227 with N-H ,z(neu) similar to few x 10(20) cm(-2). We find NGC 3227 to exhibit signifi cant spectral variability both within and between the observations. The mos t likely explanation involves short-term variability in the continuum emiss ion and longer term variability in the column density of the ionized materi al. Time-resolved spectroscopy and color-color analysis indicate that the s lope of the continuum steepened by Delta Gamma similar or equal to 0.1 duri ng a hare of duration similar to 10(4) s, within the 1993 observation. Howe ver, we were unable to distinguish between a steepening of the "primary" co ntinuum and a change in the relative strengths of the power law and a putat ive Compton-reflection component. The absorbing column increased by a facto r of similar to 10 by the 1995 epoch, while the continuum is consistent wit h that observed in 1993. The 1995 data also show evidence that the warm abs orber allows similar to 10% of the nuclear emission to escape without atten uation. We review our findings in the context of the previous results from this and similar objects and discuss the prospects of future observations.