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

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 J : XMM-Newton/Chandra  determine spectral parameters  improve instrumental response at low energies.

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

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

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.)

Vadim Burwitz EPIC Cal., Nov 6, 2007

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

Vadim Burwitz EPIC Cal., Nov 6, 2007 Isolated Neutron Stars  Objects  RX J  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

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  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

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

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