1. Vadim Burwitz EPIC Cal., Nov 6, 2007 Update on the Low Energy Isolated Neutron Star and White Dwarf Cross-Calibration Standards Vadim Burwitz EPIC Calibration Meeting Nov. 6, 2007, Mallorca, Spain

2. Vadim Burwitz EPIC Cal., Nov 6, 2007 Overview  Well calibrated Standards needed  for Absolute Calibration  Absolute Calibration Soft X-rays  dependant on model spectra of WDs and INs what models to use?, uncertainties?  Analysis of HZ 43A, Sirius B and RX J1856.5-3754 : XMM-Newton/Chandra  determine spectral parameters  improve instrumental response at low energies.

3. Vadim Burwitz EPIC Cal., Nov 6, 2007 Simultaneous fit to RXJ1856 and the WDs

4. Vadim Burwitz EPIC Cal., Nov 6, 2007 White Dwarfs  Objects  HZ 43  Sirius B  Physical Models  White dwarf Atmosphere Models  Parameters (nH, eff. T, log(g), absolute Flux, abundance)   nH well constrained  <10 18 cm 2  Most up-to-date atmosphere codes used (Tübingen TMAP, TLUSTY Hubeny)  pure hydrogen good fit (very little Helium required)  better possibly stratified Hydrogen + Helium model  needs to tested  Instruments  ROSAT  EUVE  Chandra LETGS

5. Vadim Burwitz EPIC Cal., Nov 6, 2007 White Dwarfs  Status of Models / Parameters for HZ43 and Sirius B  Available fits are done and complete see below:  Pease et al. SPIE, 2000  LETG effective area  Beuermann, Burwitz, Rauch A&A, 2006  corr. sugg. to LETGS eff area, ROSAT and EUVE  Kaastra et al. A&A, 2007 in prep.  independent check of Models  Done  Check differences Rauch / Hubeny model fluxes for Sirius B  differences in Theoretical models (beeing looked into)  To Do  Implement corrections for LETGS effective area.  EUVE: check why effective area is too low  ROSAT improvements to instr. params. need to implemented (Beuermann et al.)

6. Vadim Burwitz EPIC Cal., Nov 6, 2007

7. NLTE pure H model spectrum of HZ43 Different bound-free and free-free absorption coefficients -- Seaton -- Karzas & Latter

8. Vadim Burwitz EPIC Cal., Nov 6, 2007 Isolated Neutron Stars  Objects  RX J1856.5-3754  Empirical Models  No NS Atmosphere Models fit the entire Spectrum from X-ray to optical  Best description of the full X-ray spectrum is given by a  2 component blackbody model  A single blackbody model provides a good description X-ray spectra above 0.2 keV  Parameters (nH, eff. T, absolute Flux, abundance)  nH is possibly an issue. Not all instruments can be used to contrain it.  Instruments  ROSAT, XMM, Chandra, SWIFT, SUZAKU  Chandra LETGS needed to constrain nH and low T component

9. Vadim Burwitz EPIC Cal., Nov 6, 2007 Isolated Neutron Stars  Status of Models / Parameters for RXJ1856  Early fits to LETGS and EPIC-pn with a single and two component blackbody model have been published:  Burwitz et al. 2002, 2004  Drake et al. 2002  Beuermann, Burwitz, Rauch A&A, 2006 (BBR06)  Fits to data from all listed instruments have started by Frank Haberl  To Do  Investigate independent measurement of nH  Compare BBR06 model to all instruments to see where improvements are need  Implement corrections for all relevant effective areas.  discuss next step  find a physical model

10. Vadim Burwitz EPIC Cal., Nov 6, 2007 Simultaneous fit to RXJ1856 and the WDs

11. Vadim Burwitz EPIC Cal., Nov 6, 2007 Parameters obtained from fit