The continuing saga of Sakurai's object (V4334 Sgr): dust production and helium line emission

We report further UKIRT spectroscopic observations of Sakurai's object (V4334 Sgr) made in 1999 April/May in the 1-4.75 µm range, and find that the emission is dominated by amorphous carbon at T[subscript d] ~ 600. The estimated maximum grain size is 0.6 µm, and the mass lower limit is 1.7 ± 0.2 x 10[superscript -8] M[subscript ¤] to 8.9 ± 0.6 x 10[superscript -7] M[subscript ¤] for distances of 1.1-8 kpc. For 3.8 kpc the mass is 2.0 ± 0.1 x 10[superscript -7] M[subscript ¤]. We also report strong He i emission at 1.083 µm, in contrast to the strong absorption in this line in 1998. We conclude that the excitation is collisional, and is probably caused by a wind, consistent with the P Cygni profile observed by Eyres et al. in 1998

On the Evolved Nature of CK Vul

Original paper can be found at: http://www.astrosociety.org/pubs/cs/381.html Copyright ASPCK Vul was classified as the oldest observed nova. Recent studies have proven however, that CK Vul cannot be unambiguously classified as any known kind of eruptive variable. We present the optical and radio observations of the remnants of the eruption of CK Vul in the year 1670 in order to discuss possible scenarios for this object. We have measured the proper motion which proves that the nebula is attributed to the star observed during its 1670−1672 brightening. A large bipolar nebula of 70 arcsec is discovered in a deep Hα image. Radio observations reveal a barely resolved source placed in the expansion center of the ejecta

Infrared Space Observatory and Ground-Based Infrared Observation of the Classical Nova V723 Cassiopeiae

We present observations of the classical nova V723 Cassiopeiae (Nova Cas 1995), obtained both with the Infrared Space Observatory (ISO) and from the ground. The infrared spectrum was dominated in the first year by H and He recombination lines, and at later times by coronal lines. The H recombination lines imply a reddening of E(B-V) = 0.78, an electron temperature of 7000 K, and an electron density of 2 × 108 cm-3 on day 250. We argue that the high-ionization species in the infrared are most likely the result of collisional ionization rather than photoionization and are therefore truly "coronal"; we estimate a temperature of 3.2 × 105 K in the coronal region and abundance ratios of S/Si 2.1, Ca/Si 1.6, and Al/Si 1.5. The ejected mass as determined from the Brα line was 2.6 × 10-5 M⊙ for a distance of 4 kpc; however, the mass deduced from the free-free emission, which we conclude arises primarily in the coronal zone, is 4.3 × 10-4 M⊙. V723 Cas did not display the [O IV] 25.89 μm fine-structure line, which was typically seen in the spectra of novae observed with ISO. There was no evidence of dust emission in V723 Cas

Strong helium 10830Å absorption in Sakurai's object (V4334 Sgr)

We report the appearance and evolution during 1998 of strong neutral helium ^3S-^3P^o absorption at ~10830Å in Sakurai's Object (V4334 Sgr), which is believed to be a planetary nebula nucleus (PNN) undergoing a final helium shell-flash. First detected on 1998 March 18, the profile of the Hei feature is P Cygni-like. The absorption depth has increased in three subsequent spectra in 1998. If this is owing to a wind, the profile indicates a wind velocity of ~670+/-50kms^-1. The strong Ci 10690-Å line seen prior to the appearance of the helium feature has disappeared; however Srii and CN absorption features remain present. We tentatively identify several new features as Sii. Taken together with other observations we suggest that the data are consistent with Sakurai's Object entering a phase in which it seems to have become a member of the R Coronae Borealis-type class of stars

Far infra-red emission from NGC 7078: First detection of intra-cluster dust in a globular cluster

Improved data analysis of far infrared imaging data of the globular cluster NGC 7078 obtained with the ISO instrument ISOPHOT at 60 μm, 70 μm and 90 μm has detected the thermal emission from dust in its core, the first secure detection of intra-cluster dust in a globular cluster. The amount of dust is broadly consistent with mass-loss from evolved, metal-deficient stars in NGC 7078 in the time since it last crossed the Galactic plane.