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Click for illustrations of anomalous saturation of Fe I and II lines

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The abundance pattern in HD 101412 may be related to those of the Lambda Boo stars. Volatile elements, those with low condensation temperatures, are generally normal, while involatile elements are depleted. This pattern is seen in HD 101412 with two noteworthy exceptions. Nitrogen is significantly enhanced in HD 101412, while the intermediate volatile zinc is depleted.

Note: The points aren't necessarily expected to fall on a straight line. Our assertion that the pattern in HD 101412 resembles that of the Lambda Boo stars rests on the fact that the centroid of the ellipse for elements with condensation temperatures less than 400K (C,N,O), lies below the centroid for the elements with condensation temperatures above 900K.

Ideally, the points for low condensation temperatures would all fall near the line with difference between the sun and star equal to zero. At some condensation temperature, the points would start to fall off the zero-point line, and (for the Lambda Boo pattern) fall above the line. There might be an approximate leveling off, indicating that all species with a condensation temperature higher than some value would be equally depleted.

The depletion pattern in some Lambda Boo stars is well correlated with condensation temperature. This is the case for Lambda Boo itself, and some others. But this is by no means true for all of the objects with abundance studies that have been labeled Lambda Boo stars. Indeed some show a scatter among the most refractory elements with no apparent correlation with condensation temperature. Calcium, for example, with the highest condensation temperature of the elements that commonly have abundances, can be less highly depleted, than iron (e.g. HD 8412, AA396,641,1002).

It is well known that the condensation temperatures of elements are correlated with their ionization energies. Here is a plot of the abundance differences in the sun and HD 101412, vs. the first ionization energy.

In this plot, it isn't clear what to expect. The points seem to fit a linear relation somewhat better than in the plot above, but zinc is still a spoiler. It's hard to look at this deviant behavior of zinc, and not think of the work by Leckrone, et al. that showed no evidence for zinc in the spectrum of Chi Lup. If there is a scenario that connects the two depletions, it does not come readily to mind.

The reddening of HD 101412 is difficult to determine. We believe the spectral type is not an accurate indication of the temperature because calcium is underabundant. The Balmer lines are still sensitive to both temperature and surface gravity in the relevant temperature range. In order to break the degeneracy between temperature and surface gravity, we have used the line excitation temperatures for several species. However, we have found that plots of abundance vs. excitation temperature are not very convincing. There is a great deal of scatter, and the plots are subject to systematic errors in the equivalent widths and log(gf) values, and especially to correlations between line strengths and excitation potentials. For this reason, we have used the old method of the curve of growth. It determines the best excitation temperature that merges lines with different ranges of excitation potential.

The plot below is for Fe II lines.

Blue circles are for lines with excitation potentials in the range 2.58-2.89eV; black squares for 3.20-3.89eV; filled red stars for 5.51-6.22eV. The assumed excitation temperature is 5040/0.7 or 7200K. The ordinates of the observed points are (W/lambda)+6, and an empirical factor Delta-y=-0.6 has been added to all of them to make the optimum fit of observed and theoretical curves. The horizontal shift, Delta-x = 5.7 is of lesser relevance.

The difference of the empirical and observational scales for the ordinates (Delta-y's) enables one to extract information on the Doppler width, which includes temperature and turbulence, the maximum depth a line can have r_o. These quantities are related. If we take T = 7200K, and accept the Delta-y = -0.6 of the above figure, it turns out that there is no real value of the microturbulence for r_o as large as 0.41. This is smaller than the maximum depth of the Mg II 4481 pair, about 0.53, possibly increased by nonLTE. The plotted points act as though they could not get deeper than about 0.40 with a microturbulence of about 0.2 km/sec. A larger microturbulence would require an even smaller value of r_o.

The plot below is for the same Fe II lines, but with a shift Delta-y of -0.8345. This value is marginally compatible with a finite microturbulence, and a theta = 5040/T_of 0.7.

What we can see is that the observations are incompatible with these parameters. The observed points, even for the weakest lines show a slope that is smaller than 45-degrees. Thus, there is already some saturation, and this is why the weak points fall at an angle to the theoretical weak-line curve of growth.

The relative positions of the observed points are the same in the two plots. The lower plot looks worse because the shift Delta-y of -0.8345, necessary for a real value of the microturbulence, pushed the points lower with respect to the theoretical curves. In this region, the weakest lines require a 45-degree slope, which The empirical points do not have.

We plot the same Fe II lines this time again with the optimum shift, Delta-y = -0.6, but with theta = 5040/T = 0.58, corresponding to a temperature of 8690K. This is the excitation temperature that would correspond to a model with an effective temperature of 9800K.

Here, we see a clear separation of the highest excitation lines, Chi = 5.51 to 6.22 eV (red stars), from the points for the lower excitation lines. It is clear that the observations are more accurately fit by assuming the effective temperature of HD 101412 is closer to 8300K (excitation temp=7200K).

We believe the upper atmosphere of HD 101412 is being heated by material infalling from a disk. This heating raises the temperature of the uppermost atmosphere, so that the maximum depth the lines can achieve (in LTE) is significantly less than would be possible with a classical model atmosphere--near 0.9.

The plot below is for Ca I lines.

The one blue circle is for the zero-volt line at 4227A. Black squares are for 1.88-1.90eV; magenta triangles, 2.52-2.71eV; filled red star, 2.93eV. The assumed excitation temperature is 5040/0.65 = 7754K.

This simple, curve of growth approach to the line spectrum of HD 101412 is adequate to give us reasonable excitation temperatures, and damping constants. The turbulent velocity, however, cannot be directly determined unless we know what value of r_o to assume.

The plot below is for Ti II lines. The oscillator strengths are from Pickering, Thorne, and Perez (ApJS 132, 403, 2001, Erratum ApJS 138, 247, 2002), and of high quality.

The assumed temperature was 7200K. The excitations are indicated by the various symbols. For Chi = 0.57 to 1.58eV, blue circles; for Chi = 1.89 to 2.06eV, black squares; and for Chi = 2.59 to 3.12eV, red diamonds.

If the effective temperature of HD 101412 were as high as 9800K, the excitation temperature would be roughly 8690K. The plot below was made using this assumed excitation. We can clearly see the separation of the points for the high-excitation (red triangles) and low-excitation lines (blue circles).