Spectroscopic observations of the recurrent nova CI Aquilae during the 2000 outburst

Abstract

High-and low-resolution optical spectra of CI Aql were obtained during the outburst in 2000. Multiple absorption components of H I and Fe II lines were detected at the early decline stage. Their radial velocities were roughly −2500 km s −1 , −2200 km s −1 , −1700 km s −1 , and −1400 km s −1 , among which only the last components were likely still accelerating during the early decline stage. Prominent emission lines of [O III] and [N II] appeared about one month after light maximum. The duration of the nebular stage, however, was only one month and a few weeks. The ejected gas shells seem to have started to shrink about 70 days after light maximum. The amount of interstellar extinction is estimated to be E(B − V) = 0.92 ± 0.15 from the equivalent widths of the diffuse interstellar absorption bands. The helium abundance in the ejecta is estimated to be N(He) = 0.19 ± 0.05 and the mass of the ejecta to be about 2 × 10 −6 M . This object has been classified as a U Sco type recurrent nova, but its spectral evolution during the outburst resembled those of T Pyx type recurrent novae. It is doubtful whether the peak of m V 9 mag on 2000 May 5 was the true light maximum or an earlier brighter peak had been overlooked, because the spectral data suggest that the ejections of gas shells occurred prior to the discovery of the outburst on 2000 April 28.

The spectroscopic evolution of the recurrent nova T Pyxidis during its 2011 outburst

“…Observations of the known RNe, e.g. CI Aql (Iijima 2012), and the RN candidate KT Eri agree morphologically with those obtained in this study of T Pyx. The main difference, aside from the photometry, is the early presence in the most compact systems, those with orbital periods less than about 0.5 days, of an optically thick stage that closely resembles classical novae during the rise to maximum visible light.…”

On the Raman O VI and related lines in classical novae

“…The absorption feature, if due to the C I line, also matches the O I 7773 Å line and other excited state neutral species. We note that Iijima (2012) identified a line in the recurrent nova CI Aql at 6830 Å as C I…”

The slow decline of the Galactic recurrent novae T Pyxidis, IM Normae, and CI Aquilae

“…The temporal development of the electron density can also be determined using multi-epoch modeling (Schwarz 2014). Studies have been conducted for CI Aql by Iijima (2012) and for T Pyx by Shore et al (2013), resulting in the value Mej ≈ 2 · 10 −6 M for both systems. This number is on the lower end of the scale for ejecta masses of classical novae.…”

“…Optical decline time-scale t 2 and mass of the ejecta for a set of novae; M ej is measured in units of 10 −5 M and t 2 in days. The approximate positions of the recurrent systems T Pyx, CI Aql, and U Sco, based on estimates of t 2 from the light curve of T Pyx, on the light curves reported by Schaefer (2010) and on the masses of the ejecta estimated by Shore et al (2013), Iijima (2012) and Diaz et al (2012) (M ej > 3 · 10 −6 M for U Sco) have been marked in red. V382 Vel is highlighted in the article by Della Valle et al (2002) because that system was one of the main objects of study of their article.…”