Forbidden Line Emission in the Eccentric Spectroscopic Binaries DQ Tauri and UZ Tauri E Monitored over an Orbital Period

We present echelle spectroscopy of the close pre-main-sequence binary star systems DQ Tau and UZ Tau-E. Over a 16 day time interval we acquired 14 nights of spectra for DQ Tau and 12 nights of spectra for UZ Tau-E. This represents the entire phase of DQ Tau, and 63 percent of the phase of UZ Tau-E. As expected, photospheric lines such as Li I 6707 clearly split into two components as the primary and secondary orbit one another, as did the permitted line He I 5876. Unlike the photospheric features, the forbidden lines of [O I] 6300 and [O I] 5577, retain the same shape throughout the orbit. Therefore these lines must originate outside of the immediate vicinity of the two stars and any circumstellar disks that participate in the orbital motion of the stars.Comment: 14 pages including 6 figures, aastex preprint, accepted to Astronomical Journa

Influence of crystallographic orientation of biogenic calcite on <i>in situ</i> Mg XANES analyses

Micro X-ray absorption near-edge spectroscopy at the Mg &lt;i&gt;K&lt;/i&gt;-edge is a useful technique for acquiring information about the environment of Mg&lt;sup&gt;2+&lt;/sup&gt; in biogenic calcite. These analyses can be applied to shell powders or intact shell structures. The advantage of the latter is that the XANES analyses can be applied to specific areas, at high (e.g. micrometre) spatial resolution, to determine the environment of Mg&lt;sup&gt;2+&lt;/sup&gt; in a biomineral context. Such in situ synchrotron analysis has to take into account the potential effect of crystallographic orientation given the anisotropy of calcite crystals and the polarized nature of X-rays. Brachiopod shells of species with different crystallographic orientations are used to assess this crystallographic effect on &lt;i&gt;in situ&lt;/i&gt; synchrotron measurements at the Mg &lt;i&gt;K&lt;/i&gt;-edge. Results show that, owing to the anisotropy of calcite, &lt;i&gt;in situ&lt;/i&gt; X-ray absorption spectra (XAS) are influenced by the crystallographic orientation of calcite crystals with a subsequent potentially erroneous interpretation of Mg&lt;sup&gt;2+&lt;/sup&gt; data. Thus, this study demonstrates the importance of crystallography for XAS analyses and, therefore, the necessity to obtain crystallographic information at high spatial resolution prior to spectroscopic analysis