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NON-LTE MODEL ATMOSPHERE ANALYSIS OF THE LARGE MAGELLANIC CLOUD SUPERSOFT X-RAY SOURCE CAL 83
 

Summary: NON-LTE MODEL ATMOSPHERE ANALYSIS OF THE LARGE MAGELLANIC
CLOUD SUPERSOFT X-RAY SOURCE CAL 83
Thierry Lanz,1,2
Gisela A. Telis,2
Marc Audard,2
Frits Paerels,2
Andrew P. Rasmussen,2
and Ivan Hubeny3
Receivved 2004 June 14; accepted 2004 September 29
ABSTRACT
We present a non-LTE (NLTE) model atmosphere analysis of Chandra High Resolution Camera (HRC-S) and
Low Energy Transmission Grating (LETG) and XMM-Newton Reflection Grating Spectrometer (RGS) spec-
troscopy of the prototypical supersoft source CAL 83 in the Large Magellanic Cloud. Taken with a 16 month in-
terval, the Chandra and XMM-Newton spectra are very similar. They reveal a very rich absorption-line spectrum
from the hot white dwarf photosphere but no spectral signatures of a wind. We also report a third X-ray off-state
during a later Chandra observation, demonstrating the recurrent nature of CAL 83. Moreover, we found evidence
of short-timescale variability in the soft X-ray spectrum. We completed the analysis of the LETG and RGS spectra
of CAL 83 with new NLTE line-blanketed model atmospheres that explicitly include 74 ions of the 11 most
abundant species. We successfully matched the Chandra and XMM-Newton spectra assuming a model compo-
sition with LMC metallicity. We derived the basic stellar parameters of the hot white dwarf, but the current state of

  

Source: Audard, Marc - INTEGRAL Science Data Centre & Observatory of Geneva, Université de Genève

 

Collections: Physics