Time resolved X-ray spectroscopy of NGC 4051 Katrien C. Steenbrugge St John’s College, University of Oxford Marjan Fenovic, Elisa Costantini, Jelle Kaastra (SRON) and Frank Verbunt (SIU)

NCG 4051 Narrow line Seyfert 1 X-ray bright Variable X-ray flux. Distance of 18.6 Mpc (Tully & Pierce 2000). Observations I discuss: LETGS 01 Jan. 2002 for 94 ks. LETGS 23 July 2003 for 96 ks.

X-ray spectroscopy Possibility to detect variation in the absorber properties with changing flux. If ionization changes with flux, then the density of the outflow can be calculated. Hence, the distance of the absorber, the energy density and mass outflow can be calculated.

X-ray lightcurve The flux decreases by a factor of 5 just before D. Spectra were extracted for periods A, B, C and D.

X-ray continua Between spectrum C and D, power-law photon index, becomes softer. Temperature of black body decreases.

X-ray spectra The spectra are of rather low signal to noise. Spectrum C: 4 absorption components are necessary: log ξ = 0.07-3.19. Spectrum D: RRC of C V and C VI.

Radiative Recombination Continua Using emission measure, temperature and maximum broadening, a BH mass of 3x105 Msun and luminosity we derive a column density that is similar to the highest ionized absorber: ~1026 m-2. However, the ionization parameter log ξ ~ 1.6 is much lower than that of the highest ionized absorber.  RRC’s might be from the accretion disk.

Absorbers None of the 4 ionization parameters does react linearly to the decrease in flux by a factor of 5 between spectra C and D. One ionization parameter shows a 2.3σ change from logξ = 0.87 to 0.52 between spectrum C and D. The other 3 ionization parameters change less than 1σ between spectrum A, B, C and D.

Long term spectral results The column densities we measure are consistent as those measured from RGS spectrum (Ogle et al. 2004) except logξ > 3. The highest ionized absorber in our spectrum has the largest outflow velocity: 4670 km/s. HETG spectrum: the highest ionized absorber has the highest outflow velocity: 2340 km/s (Collinge et al. 2001). We do not detect a 2340 km/s absorber. This component is variable on years timescale.

There is an ionization gradient in the broad line region. Broad emission lines We detect broadened emission lines from C VI and O VII. C VI FWHM is ~2000 km/s, similar to the with of Hβ. O VII triplet FWHM is ~11000 km/s broader than the He II line of ~5000 km/s. There is an ionization gradient in the broad line region.

Relativistic O VIIILyα line Detected in spectra A, B and C. Inclination angle is the same as found from XMM (Ogle et al. 2004) and for the narrow line region (Christopoulou et al. 1997).

Conclusions The spectrum has multiple components! The continuum shape does change with flux. In spectrum D we detect C V, C VI RRC. There are broad C VI and O VII, and relativistic O VIII Lyα lines present. The highest outflow component is variable on timescales of years.