Carinae
The CHANDRA HETGS X-ray Grating Spectrum of Carinae
M. F. Corcoran(USRA & NASA-GSFC/LHEA), J. H. Swank, R. Petre (NASA-GSFC/LHEA), K. Ishibashi (NRC & NASA-GSFC/LASP), K. Davidson (Minnesota), L. Townsley (Penn State), R. Smith (Center for Astrophysics), S. White (UMd), R. Viotti (IAS), A. Damineli (IAGUSP)
[Contributed talk, 15min.]
Abstract
Carinae may be the most massive and luminous star in the Galaxy and is
suspected to be a massive, colliding wind binary system. The
CHANDRA X-ray observatory has obtained a calibrated, high-resolution
X-ray spectrum of the star uncontaminated by the nearby extended soft
X-ray emisssion. Our 89 ksec CHANDRA observation with the High
Energy Transmission Grating Spectrometer (HETGS) shows that the hot
gas near the star is non-isothermal. The temperature distribution may
represent the emission on either side of the colliding wind bow shock,
effectively ``resolving'' the shock. If so, the pre-shock wind
velocities are 
and 
km s-1 in our analysis,
and these velocities may be interpreted as the terminal velocities of
the winds from
Carinae and from the hidden companion star. The
forbidden-to-intercombination (f/i) line ratios for the He-like ions
of S, Si and Fe are large, indicating that the line forming region
lies far from the stellar photosphere. The iron fluorescent line at
1.93Å, first detected by ASCA, is clearly resolved from the thermal
iron line in the CHANDRA grating spectrum. The Fe fluorescent line
is weaker in our CHANDRA observation than in any of the ASCA spectra. The CHANDRA observation also provides the first high-time
resolution lightcurve of the uncontaminated stellar X-ray emission
from
Carinae and shows that there is no significant, coherent variability
during the CHANDRA observation. The
Carinae CHANDRA grating spectrum
is unlike recently published X-ray grating spectra of single massive
stars in significant ways and is generally consistent with colliding
wind emission in a massive binary.
CATEGORY: NORMAL STARS AND WHITE DWARFS