NQ Vul Research Articles

Near‐Infrared Spectrophotometry and the CO Emission in V2274 Cygni (Nova Cygni 2001 No. 1)

Infrared spectroscopy of V2274 Cygni (=Nova Cygni 2001 No. 1) is presented for two widely separated epochs, 17 and 370 days after discovery. In addition to the Paschen and Brackett series of H I, the early-time spectrum shows strong emission lines of C I and N I, fluorescently excited lines of O I, and emission from the first overtone of carbon monoxide. Because the initial data were probably acquired no more than 18 days after outburst, CO molecule formation occurred remarkably quickly in the dense, cool, carbon and oxygen rich ejecta. Rapid formation was also seen in NQ Vul, V842 Cen, and V705 Cas, three other novae in which first-overtone CO emission has been detected. Formation of the CO molecule may occur chemically in a process that requires H2 as a precursor or directly through radiative association. The overtone emission of V2274 Cyg indicates a temperature of ~2500 K. The vibrational levels show no obvious departures from thermal equilibrium, which may indicate high optical depths in the fundamental. A large 13C/12C ratio (0.83 ± 0.3) is also indicated by the observations, consistent with the fast CNO burning expected in novae explosions. By the time of the second epoch observations, the emission lines of the neutral C, N, and O had disappeared. He I λ10830 was the dominant emission feature in the spectrum. In addition to the hydrogen lines, recombination features of He II were also strong. The common nebular lines of [S III] were seen but only two coronal line, [S VIII] λ9911 and [Si VI] λ19645, were detected. The CO emission had disappeared, but a strong thermal dust component was present. The interstellar reddening for the system was found to be E(B-V) = 1.3. This extinction, together with the absolute magnitude derived from the rate of decline of the light curve, suggest a distance of ~10.8 kpc. This places V2274 Cyg well out of the Galactic plane. The small number of novae with spectroscopic detections of carbon monoxide all have prominent C I lines, moderate speed classes and ejection velocities, exhibit marked dust formation events, and result from an explosion on a CO-type white dwarf. Based on these similarities, the spectrum of V2274 is proposed as a likely near-infrared spectral template for other novae that display carbon monoxide emission.

Upper limits for CO in the old Galactic novae NQ Vulpeculae, QU Vulpeculae, and Nova Vulpeculae 1987 from IRAM observations

Three Galactic novae were observed with the IRAM 30 M telescope at (C-12)O J = 1 - 0 and J = 2 - 1. No evidence for the previously reported emission in NQ Vul is found and strong upper limits are derived for possible CO emission in QU Vul and Nova Vul 1987. There is no evidence for extensive cold molecular material surrounding old novae.

Mm CO observation of the old nova NQ Vul

AbstractWe have observed the old nova NQ Vul in the J = 2 → 1 rotational transition of 12CO at 230.5 GHz at the University of Texas Millimetre Wave Observatory. The spectrum shows narrow features which clearly arise in the local interstellar medium. However these local features are superimposed on a broad feature which peaks at ~ 63 mK. This feature is centred on velocity VLSR ≃ 26 ± 9 km s−1–consistent with that expected for NQ Vul–and has FWHM 80 ± 20 km s−1. The peak antenna temperature corresponds to an integrated flux of 3.2 × 10−15 erg s−1 cm−2.Assuming LTE and a distance of 1.2 kpc the mass of CO is ~ 10−6M⊙ if the line is optically thin. The CO mass is comparable with the total mass ejected in 1976 (4) so the CO we detect at millimetre wavelengths has nothing to do with the 1976 outburst. If the CO/H ratio in the emitting material is similar to that in the interstellar medium (2), the total mass is ~ 0.6 M⊙.The CO mass rules out an origin both in the 1976 outburst and in the post-outburst phase: the CO must have originated in material ejected by the NQ Vul system prior to the 1976 outburst. There are two possibilities. First, the CO may have formed in material accumulated following a large number of nova outbursts. Second, the CO may have been present, or formed, in material ejected by the NQ Vul system during a previous evolutionary phase. The deduced mass is comparable to the mass of CO seen around planetary nebulae (3); the outflow velocity (~ 40 km s−1) would also be in line with this interpretation.In either case, the above mass estimate of 0.6 M⊙ (based on the interstellar CO/H ratio) is likely to be an upper limit as we would expect an enhancement of heavy elements in any ejected material. A determination of 12C/13C and other isotopic ratios would be valuable to pin down the origin of the CO.

Millimetre CO observation of the old nova NQ Vul

We have observed the old nova NQ Vul (1976) in the |$J=2\rightarrow 1$| rotational transition of 12CO. We see a broad, low-intensity feature centred at velocity 26 km s–1 relative to the local standard of rest, FWHM |$\sim80\,\text{km s}^{-1}$| and peak antenna temperature 63 mK. The central VLSR is consistent with the distance ( 1.2 ± 0.5 kpc) and galactic coordinates of NQ Vul and we conclude that the CO is associated with the NQ Vul system. We discuss possible origins of this material and suggest that it represents material ejected by the NQ Vul system prior to its 1976 outburst.

A survey of IRAS data on 41 classical novae

The IRAS database has been searched for detections of 41 classical novae using coadditions of survey scans; 15 were detected. IRAS temporal observations of novae in outburst are discussed. The observed long-wavelength infrared distributions of DQ Her, and possibly HR Del, can be explained by emission from small (a of about 0.1 microns) dust grains heated by the central object. An alternative explanation for the energy distributions of DQ Her and HR Del is emission from fine-structure lines. FH Ser and LW Ser display energy distributions that have color temperatures much too hot to be due to heating of dust by the central source in any plausible scenario. Line emission is probably the best explanation of their observed energy distributions. The novae NQ Vul and LV Vul have energy distributions that may be contaminated by emission from galactic cirrus. The unusual object PL 1547.3-5612 exhibits an energy distribution that does not resemble those of planetary nebulae or other novae detected in this sample. An IRAS low-resolution spectrum of RR Tel shows the 10-micron silicate emission feature.

The ‘Isothermal’ Phase of Nova Dust Shells

AbstractWe describe a model for the evolution of the infrared spectrum of the dust shell of nova NQ Vul. The effects of nucleation and grain growth, together with.extended, but diminishing, mass loss from the nova, are included. The variations in the effective temperature of the dust shell that occur near infrared maximum may be understood in terms of varying optical depth in a dust shell having significant temperature gradient. However, a more consistent picture is shown to combine interrelated optical depth and grain size variations.

Are Novae Shells Optically Thick in the Infrared

The optical depth of the dust shells of novae in the infrared is an important parameter in discussing the energy balance and the morphology of the nova ejecta. A recent publication has questioned our previous interpretation of infrared data for NQ Vul. We present here our argument concerning the infrared optical depths of this and other novae.

Carbon monoxide emission and the Eta Carinae stage of Nova NQ Vulpeculae

This paper announces the detection of CO emission from Nova NQ Vul. First-overtone vibration-rotation bands were detected in a 1.6--2.2 ..mu..m spectrum obtained 19 days after outburst, approx.20 days before the large visual fading. The absence of detectable /sup 13/CO bands sets the limit /sup 12/C//sup 13/C>3. CO emission at 4.8 ..mu..m is predicted to be approx.40 times stronger than the 2.2 ..mu..m emission and easily accounts for the 5 ..mu..m emission feature discovered by Ney and Hatfield. This identification implies that CO emission persisted for 3 weeks in NQ Vul and that is was also present in FH Ser.Photoionization equilibrium calculations were performed to deduce the physical conditions in the ejecta on day 19. The H/sup +/ Stroemgren sphere extends to only a small fraction of the radius of the nebula. A largely neutral region, which is heated by photoionization of heavy elements, extends to the outer edge of the ejecta. Strong Fe II, Mg II, and C I emission, a characteristic of the eta Car phase of the nova outburst, originates here. This region may provide an auspicious site for both molecule and grain formation.

PHOTOELECTRIC OBSERVATIONS OF THE NOVAE T PYXIDIS, V400 PERSEI, AND NQ VULPECULAE.

ABSTRACT Multicolor photoelectric data are presented for the three novae T Pyx, V4OO Per, and NQ Vul. Key words: novae-photometry

Optical Observations of Recent Novae

AbstractThe observations of two rather different classical novae, V 1500 Cyg (= Nova Cyg 1975) and NQ Vul (= Nova Vul 1976), are presented and compared. Nova Cyg 1975 is outstanding with respect to absolute magnitude (M = -10), range of brightening (Δm = 19), and speed of evolution (t3= 3.6 days). Its prenova object had to be fainter than about magnitude 9. The corresponding values for Nova Vul 1976 are rather conservative (M≈-7.5, Δm ≈ 12, t3=40 days, absolute magnitude of the prenova ≈4.5). The light curve of Nova Cyg 1975 is very smooth. Some superimposed photometric variations of a small and slightly variable amplitude of a period of 3.4 hours are most naturally ascribed to a binary nature of Nova Cyg 1975. Nova Vul 1976 has a completely different lighteurve with extremely strong rapid irregular variations of considerably amplitude. There is a remarkable second maximum about 14 days after discovery.