Astronomy and Astrophysics – Astronomy
Scientific paper
Apr 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996mnras.279..804w&link_type=abstract
Monthly Notices of the Royal Astronomical Society, Volume 279, Issue 3, pp. 804-826.
Astronomy and Astrophysics
Astronomy
9
Stars: Individual: Pw Vul, Novae, Cataclysmic Variables, Infrared: Stars
Scientific paper
We present infrared spectroscopy of the slow nova PW Vul (Nova Vul 1984 £1) between 13 and 328 days after outburst. The hydrogen line spectrum was initially accompanied by lines of CI, OI and NI, which were strongest around 80 days after outburst. The 1.129-mumm OI line excited by Lybeta fluorescence dominated our spectra until at least 138 days after outburst and was still visible ~100 days later. The CNO lines were gradually replaced by the coronal [SiVI], [MgVIII] and [AlVI] lines, first evident ~130 days after outburst, and [SiVII] and [AlV] as the spectrum evolved. The appearance of coronal lines while the OI fluorescence persisted suggests that the ejecta were clumpy. The 1.083-μm HeI line strengthened relative to the HI lines, from ~0.4 Pagamma on Day 78 to ~27 Pagamma on Day 272, at a phase when the coronal lines were conspicuous. This HeI line came to dominate the spectrum and significantly affect photometry through the J filter. The hydrogen line strengths are in agreement with recombination theory, at low temperature (1000-3000K) and high density (10^9-10 cm^-3) on Day 78, and subsequently at higher temperatures and lower densities. The relative emission measure determined from the ratios of observed and theoretical hydrogen line strengths measured from our 1984 December and 1985 observations declined as t^-3, as expected for recombination of a fixed mass in a freely expanding shell. During the first ~130 days of the evolution of the nova characterized by irregular light variations prior to this, the emission measure did not decline, indicating continued feeding of the ejecta by the stellar wind. A comparison of infrared hydrogen lines with contemporaneous optical data yields an extinction of A_V=1.78. The strongest expected HeII and FeII lines were visible for a while, but forbidden [FeII] was not seen. Before and at maximum the optical-infrared spectral energy distribution followed F_nu~nu^1.1, as predicted by slow nova wind models. The spectrum flattened to nu^0.2 during the initial fading and varied between these values during the irregular light variations.
Geballe Thomas Ronald
Longmore Andrew J.
Williams Peredur M.
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