[Alii] in the ultraviolet spectrum of the symbiotic star RR Telescopii

Abstract

An inspection of a GHRS/HST spectrum of the symbiotic star RR Telescopii reveals the presence of the [Alii] 3s^2 ^1S - 3s3p ^3P_2 line at a vacuum wavelength of 2661.06+/-0.08Å, 8.89+/-0.08Å away from the Alii] 3s^2 ^1S - 3s3p ^3P_1 intercombination transition at 2669.95Å, in good agreement with the theoretical prediction of Δλ=8.80Å. We also find that the Alii] line profile is asymmetric, showing a strong low-density component with a weak high-density wing, redshifted by 30kms^-1, in agreement with the findings of Schild & Schmid, which were based on optical observations. Our measurement of the emission-line ratio RI(2661.06Å)/I(2669.95Å)=0.027+/-0.003 implies logN_e=5.8+/-0.2, in good agreement with the densities found from other ions, such as Siiii. These results provide strong evidence that we have detected the [Alii] line, the first time (to our knowledge) that this feature has been reliably identified in an astrophysical or laboratory spectrum.