The fall and rise of V854 Centauri: long-term ultraviolet spectroscopy of a highly-active R Coronae Borealis star

We examine long-term low-dispersion IUE, SWP and LWP spectroscopy of the R Coronae Borealis (RCB) star V854 Cen, obtained across the deep 1991, 1992-1993 and 1994 declines. We also report the optical light curve for the star in the interval 1987-1998, including multi-color photometry obtained during 1989-1998. Analysis of the UV emission line spectra indicates most lines decay during the deep declines on characteristic timescales comparable to that reported for optical features. Fe, Mg and neutral C lines decay on timescales of typically 50-100 d. Other lines, notably ionized C lines, decay on longer timescales (> 200 d) or appear to be unaffected by the declines. The general nature of the UV emission lines and other UV features during the declines is consistent with the E1/E2/BL line-region model developed from the behavior of optical spectral features during declines. However, the detailed line-behavior indicates large intrinsic variability between decline events inconsistent with the simple E1/E2/BL model. Limited temporal coverage prevents detailed examination of the geometry of the emission line region or the obscuring dust. We also report the first detection of the transition-region line C IV 1550 in the spectrum of an RCB star.Comment: AJ in press (June), 7 figures, 4 table

Australian theses in astronomy: abstracts

Abstracts of the following Australian theses in astronomy: David Graeme Barnes' PhD thesis 'Neutral hydrogen in the nearby universe'; Douglas C.-J. Bock's PhD thesis 'Wide field aperture synthesis radio astronomy'; S. E. Byleveld's PhD thesis 'Magnetic fields and star formation'; Andrew Hopkins PhD thesis 'The Phoenix Multiwavelength Deep Survey'; Frank Masci's PhD thesis 'Obscuration of quasars by dust and the reddening mechanismin Parkes quasars'; Katrina M. Sealey's PhD thesis 'The Red Bright Quasar Survey'; Brett Anthony Holman's MSc thesis 'Optical-infrared colours of dust-obscured QSOs'; and Marco M. Maldoni's MSc thesis 'Infrared spectroscopy of interstellar H2O ice analogues'