EROSITAwiki: eROSITA studies of Narrow-Line Seyfert 1 Galaxies

eROSITA studies of Narrow-Line Seyfert 1 Galaxies hier beschreiben...

1. title:
   • eROSITA studies of Narrow-Line Seyfert 1 Galaxies
2. project leader/contact person:

   • Thomas Boller bol@mpe.mpg.de

3. list of interested/contributing people
   • AGN WG members
4. description of the project
   • The capabilities of eROSITA are ideally suited to the study of ultrasoft NLS1. The proposed eROSITA observations of ultrasoft NLS1 will allow us to
   • (1) Examine the shape of the soft X-ray excess and the transition region between the soft X-ray excess and the hard X-ray power law. eROSITA will allow precision fitting of the soft X-ray excess (in ultrasoft NLS1 the soft X-

     • ray excess extends up to about 1 keV). We will use the code of Ross & Fabian (2005) to constrain the black hole mass, accretion rate and spin by fitting the precise eROSITA data. We will search for correlations between the strength and shape of the soft X-ray excess and the slope of the hard X-ray continuum. Such relations are expected if photons from the soft excess are interacting with the accretion disk corona, and there are hints of such effects based on eROSITA data (Boller 2011).

     • (2) Compare the relative amounts of soft and hard X-ray flux to explore the plausibility of isotropic reprocessing models for the creation of the soft X-ray excess. In ultrasoft NLS1 with steep 2–10 keV spectra, reasonable
       • estimates suggest that the soft X-ray excess contains several times more luminosity than the entire hard X-ray tail (e.g. Done 2008). This is important because models in which the hard X-ray tail is isotropically reprocessed into the soft X-ray excess have trouble explaining such relative luminosities.
       (3) Precisely measure the shape of the intrinsic 2–10 keV continuum. XMM-Newton observations suggest that ultrasoft NLS1 have very interesting and steep 2–10 keV continua, and eROSITA will allow these continua to be probed
       • with similar precision. eROSITA will allow a search for intrinsic 2–10 keV continuum curvature, which has been suggested for at least some NLS1.
       (4) Constrain the amount of Compton reflection and determine whether the reflection is from an ionized or a neutral accretion disk. The large effective area of eROSITA is needed. (5) Study iron K line emission. Relativistic iron K line emission will constrain the inclination and conditions of the relativistic region of the disk. (6) Study X-ray absorption by ionized gas along the line of sight. Some NLS1, including our targets IRAS 13224–3809 and 1H 0707–495, have been suggested to have blueshifted oxygen edges around 1.1 keV (Leighly et al.
       • 1997). However, the precise nature of these claimed features is not yet clear and the power of eROSITA is needed to settle this issue.
       (7) Study rapid and large-amplitude X-ray flux variability. eROSITA will allow us to measure the variability power spectra of ultrasoft NLS1. We will constrain nonlinear variability and will search for any quasi-periodic

       • oscillations (e.g. Papadakis & Lawrence 1995 and references therein).

       (8) Study X-ray spectral variability. Some NLS1 have shown strong spectral variability in which the soft X-ray excess and hard X-ray power law can vary separately. We will search for lags between soft X-ray and hard X-ray
       • variations. We will also search for variations of the slope of the hard X-ray power law, as have been seen in some NLS1. These can constrain the size of the accretion disk corona and its electron-positron pair content

         (see Haardt, Maraschi & Ghisellini 1997). It will be especially interesting to search for spectral variability during nonlinear flaring events, as this could could suggest the presence of a new X-ray emission mechanism that operates during these times.

     (9) Critically examine the possible analogy between ultrasoft NLS1 and ultrasoft Galactic black hole candidates (see Pounds, Done & Osborne 1995). (10) Measure the high-energy sharp spectral cut-offs with eROSITA and compare this with previous XMM-Newton measurements.

5. data/simulations used
   • 3600 2RXS candidates selected via their photon indices with values above 3 and significance values above the 3 sigma limit, spectroscopic confirmation follow-up work is underway
6. expected date of publication and/or conclusion of project.
   • 2RXS sources by beginning of 2015