Subject:
wind profile modeling of sigma Ori
From:
David Cohen <cohen@astro.swarthmore.edu>
Date:
Tue, 20 Nov 2007 00:28:13 -0500
To:
Skinner Steve <skinners@Colorado.EDU>
CC:
"Gagne, Marc" <MGagne@wcupa.edu>, David Cohen <cohen@hven.astro.swarthmore.edu>

Steve and Marc,

I have also fit the Owocki & Cohen (2001) Doppler-broadened wind line profile model to the Fe XVII line at 15.014 in sigma Ori.

The best-fit model is here:

http://astro.swarthmore.edu/~cohen/projects/sigOri/fexvii_15014_windprof_v1060.png

It provides a decent fit to this line, but then, so does a Gaussian.

The best fit parameters are:

taustar = 0.0  (i.e. no wind attenuation; which is what makes these lines asymmetric in early O supergiants)

Rmin = 1.23 Rstar (this is the onset radius for X-ray emission; above this radius, the emissivity is assumed to scale as the density squared of the wind); this value is pretty small - hard to understand in the context of numerical simulations of the line-driving instability. The 90% upper limit is only 1.34.

norm = 7.8e-5 ph/cm2/s (similar to the normalization of the Gaussian fit).

The 90% upper limit on taustar is only 0.1.  This might be mildly interesting.

The 90% upper limit on
I assumed v_inf = 1060 km/s (Howarth and Prinja 1989).

Even with this modest terminal velocity, a small value of Rmin is required to fit the relatively narrow line.

My zeroth order summary is that these lines are not consistent with the standard picture of embedded wind shocks.

Don't know if you want to discuss this in the paper at all.

David