Astronomy and Astrophysics – Astronomy
Scientific paper
Nov 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005apj...634..712g&link_type=abstract
The Astrophysical Journal, Volume 634, Issue 1, pp. 712-713.
Astronomy and Astrophysics
Astronomy
12
Errata, Addenda
Scientific paper
Figure 13 of our paper shows the dependence of the forbidden-to-intercombination line ratio on formation radius and electron density for two He-like ions, Mg XI and S XV, assuming a 45,000 K photosphere. In calculating the PRISMSPECT line ratios, we neglected to include the flux from the upper 3P2-->1S0 transition. For lower-Z ions such as Mg XI, the intercombination doublet is dominated by flux from the lower transition. But for higher-Z elements, this omission led us to underestimate the intercombination line strength from our model.
In addition, comparing the spectral type and luminosity of θ1 Ori C with the recent calibrations of P. Massey et al. (ApJ, 628, 986 [2005]) and F. Martins et al. (ApJ, 628, 986 [2005]) suggests that θ1 Ori C is an O5.5 V star with radius R~10.6 Rsolar and effective temperature Teff~40,000 K. This new calibration makes θ1 Ori C larger and cooler than both the ``hot'' and ``cool'' models in Table 3 of our original paper.
In the revised Figure 13 below, we show the corrected PRISMSPECT line ratios for Mg XI, Si XIII, and S XV as a function of u=R*/R for Teff=40,000 K. Also shown are the predictions from the analytic parametrization of G. R. Blumenthal et al. (ApJ, 628, 986 [2005]). For Mg XI and Si XIII, we further show the predictions based on the R0 values of D. Porquet et al. (ApJ, 628, 986 [2005]). The hatched regions in Figure 13 represent the 1 σ upper and lower bounds on f/i from the HETG data and u=R*/R from the PRISMSPECT model. Although the three f/i ratios yield different bounds on the formation radius, there is a range of radii, 1.7
Thus, the only remaining discrepancy between the HETG data and the MCWS model is the overall X-ray variability, 1-LminX/LmaxX~0.33. If the X-rays are produced, on average, at R~2R*, then occultation of an X-ray torus by the photosphere would produce a ~17% dip in visible X-ray luminosity at phase 0.5, only about half the observed drop. We suggest that the remaining absorption must occur in the dense gas in the magnetic equatorial plane. To test this idea, future absorption models will need to properly account for the ionization of the outflowing circumstellar plasma.
M. R. G. and D. H. C. would like to thank Swarthmore College students Micah Walter-Range for uncovering the PRISMSPECT modeling error and Steve St. Vincent for producing Figure 5c.
Cohen David H.
Gagne Marc
MacFarlane Joseph J.
Oksala Mary E.
Owocki Stanley P.
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