Ultraviolet Spectral Synthesis of Iota Herculis

Abstract

In this Appendix, we present separately our detailed results for every element clearly identified in the spectrum of ι Her. The following sections are presented in ascending order of atomic number. The figures shows the observation in black (solid lines), the calculated model using the assigned abundance in blue (dash-dot-dot-dot lines) and calculated model in the absence of the specified element in red (long dash lines). In all figures, the vertical axis represents the normalized flux and the horizontal axis is the wavelength in Angstrom units, in vacuum. Boron, Z=5There are only a few boron lines in our VALD line list. According to the Saha equation (see Table 3), the dominant states of ionization in the atmosphere are B II and III. We have used the B II resonance line at 1362 .461 Å (Ryabtsev, 2005 for abundance determination. This is the only boron line expected to be detectable in our spectrum, and fortunately it is not heavily blended. The oscillator strength is very precisely known (it has quality "A" on the NIST Atomic Spectra Database scale, corresponding to an uncertainty of the transition probability of only about 3 % (Kramida et al., 2014), and since this is a resonance line of a dominant ionization state, our LTE treatment should introduce no important errors. We estimate the uncertainty from fitting to be about ±0.1. Therefore the abundance is log(nB/nH)= -10.1±0.1 for this element. Figure 1 shows the fit to the observed profile.Boron is a rare and fragile light element that is not produced through stellar nucleosynthesis (except for the very minor PP III chain), but is destroyed in the interiors of stars. There are several suggestion regarding the formation of this element, such as cosmic ray interactions with the ISM, or supernova neutrino spallation on particularly 4 He or 12 C (see Vangioni-Flam et al., 2000 for extensive details).In comparison with the solar abundance of log(nB/nH) = −9.30 ± 0.03 (Asplund et al., 2009), the abundance value found here is about a factor of 6 smaller. The presence of boron may indicate that outer layers of ι Her have at most been partially mixed into the stellar interior since the period of star formation. (In contrast, for instance, in Sirius A, the absence of detectable boron is consistent with the hypothesis that the outer layers were earlier inside its companion (Landstreet, 2011).) Carbon, Z=6Carbon is a very abundant element in the spectrum of ι Herculis. In the VALD line list used here, most of the carbon lines are in neutral form. The rest are lines of C II, C III, and C IV. The distribution of carbon over ionization states in LTE in the atmosphere of ι Her is shown in Table 3. Most carbon is in the form of C II and C III, and both contribute numerous lines. However, even though it is a very minor constituent, weaker C I lines are evident throughout the spectrum. No C IV lines are detected.We determined the abundance of carbon using a simultaneous fit to lines of C I UV multiplet (4) at 1329 Å, C II UV multiplet (11) at 1324 Å and UV muliplet (1) at 1335 Å...