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• W1971036399 abstract "The major objective of the paper was to provide a detailed tabulation of the observed HETGS X-ray emission-line flux ratios. We presented the MEG and HEG He-like f /i line ratios, the H-like to He-like (H/He) line ratios, and the He-like G-ratios. The stellar wind spatial locations of the X-ray sources were derived from the f /i ratios, and their associated X-ray temperatures were obtained from the H/He ratios (THHe). This information was used to verify the correlations between RGr and R 1⁄41 (Fig. 6) and THHe and RGr (Fig. 8). However, we have realized that some of our tabulated uncertainties for these line ratios were underestimated, primarily for those lines with low-S/N data. Hence, the primary purpose of this erratum is to provide a tabulation of the corrected line ratios and their uncertainties. The details of our line fitting procedure are discussed in x 3.3. All uncertainties were determined using standard 2 statistics (e.g., P. R. Bevington, 1969, Data Reduction and Error Analysis for the Physical Sciences [New York: McGraw-Hill]). First, we would like to clarify a statement in x 3.3 (second paragraph), which states that all parameter uncertainties were determined from 90% confidence regions, but in actuality all uncertainties were established using 68% confidence regions. With regards to the main point of this erratum, we found that our algorithm for determining the 2 covariance matrix which is used to determine the uncertainties of the fitting parameters had an indexing error in the coding logic which produced errors in some of the off-diagonal terms. From our detailed examination of the code, we found that certain cases were especially vulnerable to this coding error, in particular, those cases where the 2 normalization ranges were large (i.e., low-S/N data). This code correction has also produced changes in some of the line ratios and their derived quantities (e.g., RGr and THHe). The algorithm has been corrected and the affected Tables (Tables 3, 4, 5, 6, and 7) have been updated and are given in corrected form in this erratum. We also corrected a few entries that were originally tabulated incorrectly, and some data were removed, as they did not satisfy our S/N criterion, i.e., the HEG S xv f /i data for Ori, the MEG S xv f /i data for Oph, and the HEG Mg xi and Si xiii f /i data for Cyg OB2 No. 9. As discussed in x 3.1, we stated that if a reasonable flux had been established, these results would be used only for estimating line ratios that provide interesting limits. However, the meaning of a ‘‘reasonable‘‘ flux limit was unclear; the criterion used is that the observed total net counts from all three He-like fir lines must have a S/N 3. We also need to clarify the significance of blank entries in our tables. The blanks just indicate that the given line ratio has either an unphysical result that produces an anomalously large uncertainty, or did not satisfy our He-like S/N 3 criterion. An example of an unphysical result is when the fitting procedure predicts an He-like i-line flux that is too small. This occurs primarily in low-S/N high-energy He-like fir lines, where the effects of line overlap can lead to a poor determination of the i-line. In addition, we would like to clarify why the relative uncertainties in RGr are typically smaller than the corresponding f /i relative uncertainties. As shown in equation (2) of the paper, for / C > 1 and neTNC (valid throughout the wind except when extremely close to the star), the f /i ratio is inversely proportional to the dilution factor,W(r), which changes rapidly for small changes in radius. Hence, dramatic changes in the f /i ratio can occur for only small changes in radius, which explains the differences seen in the relative uncertainties. Another key point that was not mentioned in the original paper is that there is a lower limit on the f /i ratio for the case where neTNC determined by setting W 1⁄4 0:5. This implies that any observed f /i ratio below this limit indicates that density effects may be important. We are currently investigating this possibility. The format of the data presented in these new tables have been changed slightly: (1) all best-fit line ratios ( f /i and H/He) and their uncertainties are tabulated, regardless of the size of the uncertainty; (2) as before, all derived RGr and THHe represent an average of their respective ranges predicted by the f /i and H/He line ratios, and their associated uncertainties are equal to half the difference in these ranges; (3) for those cases where the f /i uncertainty is greater than the best-fit f /i ratio, the derived RGr average is determined using a lower limit of RGr 1⁄4 R , and an upper limit on RGr determined by the f /i + uncertainty; (4) for those cases where the minimum f /i ( f /i uncertainty) ratio predicts a finite RGr, but the upper limit in the f /i range is at or greater than its asymptotic value (i.e., the low-density and zero UV flux limit), the upper limit on RGr is undetermined (i.e., RGr ! 1), and these RGr values are tabulated as lower limits; and (5) for those cases where the H/He uncertainty is greater than the H/He ratio, upper limits on THHe are presented. The two key figures of the paper (Figs. 6 and 8) have also been corrected here. In these corrected figures only data with finite limits on RGr and THHe are plotted, i.e., data with just lower limits on RGr and upper limits on THHe are not shown. For clarity, we also chose not to display any RGr data where the uncertainty is >10R . The impact of these changes in the other figures that depend on the new derived RGr and uncertainties (Figs. 7 and 9) are found to show minimal differences from the original results. However, we did find an erroneous high-temperature data point in Figure 9 at VO(RGr)/v1 0 and Urel(THHe)/v1 0:82, which should be ignored. This same data point at low RGr was also in the original Figure 8 for the giants in both the MEG and HEG plots, and it has been removed from the corrected Figure 8 given here. The source of this data point was traced to the star Vel, originally considered in our analysis, but was dropped from our study due to its highly unusual X-ray spectra, which were deemed inappropriate for this study of ‘‘normal’’ OB stars. We have confirmed that no other data points from Vel were present in any of the original plots. We would also like to add a comment concerning the importance of obtaining high-S/N HEG data as illustrated by comparing the S xv MEG and HEG determined f /i ratios for 1 Ori C. This is a clear example of how line overlap, caused by either the physical line width or the energy resolution capabilities of the instrument, can lead to larger uncertainties. Although for this case" @default.
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• W1971036399 date "2008-06-20" @default.
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• W1971036399 title "Erratum: “An Extensive Collection of Stellar Wind X‐Ray Source Region Emission Line Parameters, Temperatures, Velocities, and Their Radial Distributions as Obtained fromChandraObservations of 17 OB Stars” (ApJ, 668, 456 [2007])" @default.
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