The Early Spectrophotometric Evolution of V1186 Scorpii (Nova Scorpii 2004 No. 1)

Abstract

A J A c c e p t e d 2 0 0 7 -2 - ABSTRACTWe report optical photometry and optical through mid-infrared spectroscopy of the classical nova V1186 Sco. This slowly developing nova had an complex light curve with multiple secondary peaks similar to those seen in PW Vul. The time to decline 2 magnitudes, t 2 , was 20 days but the erratic nature of the light curve makes determination of intrinsic properties based on the decline time (e.g., luminosity) problematic, and the often cited MMRD relationship of della Valle & Livio (1995) fails to yield a plausible distance. Spectra covering 0.35 to 35 µm were obtained in two separate epochs during the first year of outburst. The first set of spectra, taken about 2 months after visible maximum, are typical of a CO-type nova with narrow line emission from H I, Fe II, O I and He I. Later data, obtained between 260 and 380 days after maximum, reveal an emerging nebular spectrum. Spitzer spectra show weakening hydrogen recombination emission with the emergence of [Ne II] (12.81 µm) as the strongest line. Strong emission from [Ne III] (15.56 µm) is also detected. Photoionization models with low effective temperature sources and only marginal neon enhancement (Ne ∼ 1.3 Ne ⊙ ) are consistent with these IR fine-structure neon lines indicating that V1186 Sco did not occur on a ONeMg white dwarf. In contrast, the slow and erratic light curve evolution, spectral development, and photoionization analysis of the ejecta imply the outburst occurred on a low mass CO white dwarf. We note that this is the first time strong [Ne II] lines have been detected so early in the outburst of a CO nova and suggests that the presence of mid-infrared neon lines is not directly indicative of a ONeMg nova event.Subject headings: stars: individual (V1186 Sco) -stars: novae.

The peculiar dust shell of Nova DZ Cru (2003)

“…The Spitzer-derived values are broadly in agreement with the velocities reported by Rushton et al (2008) on the basis of linewidths in the 1-2.5 μm range. The presence of [Ne III] 15.5-μm and [O IV] 25.9-μm emission is common in mature novae (Lynch et al 2008;Schwarz et al 2008); this, together with the inferred expansion velocities, appears to reinforce the conclusion of Rushton et al (2008) that DZ Cru is a classical nova.…”

V723 Cassiopeia Still on in X-Rays: A Bright Super Soft Source 12 Years After Outburst

“…Iijima et al (1998) estimated a distance of 2.95 kpc from the strength of the interstellar Na i D absorption lines in the early spectra, while Iijima (2006) applied a maximum magnitude versus rate of decline (MMRD) relationship to the smoothed light curve for a distance of 2.8 kpc. Since the early light curve of V723 Cas was extremely irregular, the MMRD method is problematic (see also Schwarz et al 2007b). Another approach is to assume that novae with similar characteristics, e.g., light curve evolution, ejection velocities, etc, have the same absolute magnitudes at maximum.…”

A nova outburst powered by shocks

“…At this short distance the inferred luminosity could be consistent with the Eddington luminosity, depending on the mass of the white dwarf. Besides the MMRD technique, we assumed the peak brightness of ASASSN-16ma equal to the Eddington luminosity for a 1 M white dwarf and M V ≈ −8.7, the mean absolute magnitude of the Galactic novae at peak 33 Alpy 600 spectrograph with a low-resolution grism, mounted on a 36 cm telescope. The exposure times varied from around 1 hour (right after discovery) to 10 minutes (near optical peak).…”

“…where µ = 0.74 is the mean molecular weight of fully ionized gas with a composition typical of that of classical novae 33…”