time resolved x-ray spectroscopy of ngc 4051
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
Time resolved X-ray spectroscopy of NGC 4051
Katrien C. SteenbruggeSt 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.
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.