[Al II] 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 [Al ii] 3s 2 1 S ± 3s3p 3 P 2 line at a vacuum wavelength of 2661X06^0X08 AY 8X89^0X08A away from the Al ii] 3s 2 1 S ± 3s3p 3 P 1 intercombination transition at 2669.95 A Ê , in good agreement with the theoretical prediction of Dl 8X80A. We also find that the Al ii] line profile is asymmetric, showing a strong low-density component with a weak high-density wing, redshifted by 30 km s 21 , in agreement with the findings of Schild & Schmid, which were based on optical observations. Our measurement of the emission-line ratio R I2661X06 AaI2669X95 A 0X027^0X003 implies log N e 5X8^0X2, in good agreement with the densities found from other ions, such as Si iii. These results provide strong evidence that we have detected the [Al ii] line, the first time (to our knowledge) that this feature has been reliably identified in an astrophysical or laboratory spectrum.

The O IV and S IV intercombination lines in the ultraviolet spectra of astrophysical sources

“…Diagnostic line ratios in other species in the RR Tel spectrum, ranging from Al ii to O v , indicate an electron temperature close to 20 000 K and electron densities N e ≃ 10 5 –10 8 cm −3 (Keenan et al 1994, 1999, 2002; McKenna et al 1997; Hayes & Nussbaumer 1986). Over this temperature and density interval, the predicted O iv and S iv line ratios are effectively constant (see Figs 3 and 4), and in Table 2 we therefore list their theoretical values at T e = 20 000 K and N e = 10 6 cm −3 .…”