Nebular Features Research Articles

A Case Study of a WC Nucleus

We have examined the extraordinarily rich WC spectrum of the nucleus of He 2-99, an object closely akin to BD +30°3639. In all, we log 25 lines in the UV (λ1240-λ1950; λ2550-λ3150) and 89 in the optical between λ3610 and λ7065 (including a small number of nebular features). We provide a fundamental atlas for this class of star, wherein we give fluxes and identifications of the emission lines, including a detailed accounting of blends. The most powerful emissions are those of C III followed by C II and C IV. There is good indication that C I and even C V are present as well. Oxygen is well represented by O III; O II, O IV, and O V all appear present, but are generally confused by blends. Si III and Si IV appear, as do He I and He II. Other than N V, little case can be made for stellar nitrogen. The most serious barrier to analysis of the spectrum is the problem of coincidences and blends: there are few pure lines. Analysis of the nebular spectrum, which is severely contaminated by stellar line emission, indicates enrichment in carbon, but none in nitrogen.

PROPER MOTIONS OF NEBULAR FEATURES IN THE ORION NEBULA

ABSTRACT The authors have measured relative proper motions for several nebular features within the Orion nebula, confirming previously-determined proper motions and measuring the motions for several additional features. The motions correspond to tangential velocities of up to 80 km s-1 if the motions are mass motions.

Optical spectroscopy of SN 1987A

AbstractMt John Observatory photographic spectra of SN 1987A have been obtained on 111 nights during the first year at resolutions of 1.1 Å (blue) and 1.6 Å (red). The early spectra are dominated by broad P Cygni profiles from neutral or singly ionised species. Ba absorption lines may be present. After six months nebular emission features emerged, including [OI] 630, 636 nm and two unidentified UV lines (367, 375 nm) in the previously dark region below 380 nm. Absorption line radial velocities show steep declines in the first month, but are almost constant or only slowly decline after 100 days. For the Hα absorption minimum the initial decline rate was 690 ± 70 km s−1d−1 and the initial velocity was −20.2±0.5 Mm s−1 (LMC frame). By 1988 Feb the slowest material in absorption was at −2.2 Mm s−1.The emission maxima of Hα and NaID show anomalous redshifts of about 1.0 Mm s−1. The [OI] lines show no such redshift. Recent [OI] and Hα spectra at higher resolution show ‘fine structure’ in the profiles, indicating inhomogeneity in the ejecta. Hβ, Hγ and Hδ (but not Hα) were all weaker or absent from 1987 late March to early May, but strong thereafter. From about 1987 Mar 18 to Apr 17 Hα showed a bump on the blue side of the emission at 647 nm and a double peak (658 and 668 nm). Absorption bumps in the Hα profile in early spectra (1987 Feb) may be due to circumstellar water vapour.

Ultraviolet variability and mass expulsion from R Aquarii

view Abstract Citations (61) References (45) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Ultraviolet Variability and Mass Expulsion from R Aquarii Kafatos, M. ; Michalitsianos, A. G. ; Hollis, J. M. Abstract Ultraviolet spectra in the 1200-3200 A range indicate that the extended nebular features which resemble a jet in the peculiar variable R Aquarii (M7e + pec) increased in excitation in 1985. The emission properties of the compact H II region that surrounds the unresolved binary, and those of the extended nebular jet, have been analyzed from low-resolution IUE spectra of these regions. In particular, the UV line intensities observed in the jet appear variable on a time scale of about 1.5 yr. A new accretion disk model is proposed that explains the kinematic and ionization properties of discrete components which comprise the jet emission nebulosity, the appearance of the jet in the 1980s, and morphology that uniquely characterizes the R Aquarii system at radio, optical, UV, and X-ray wavelengths. Publication: The Astrophysical Journal Supplement Series Pub Date: December 1986 DOI: 10.1086/191158 Bibcode: 1986ApJS...62..853K Keywords: Peculiar Stars; Stellar Mass Ejection; Symbiotic Stars; Ultraviolet Astronomy; Electron Density (Concentration); Emission Spectra; H Ii Regions; Iue; Line Spectra; Radio Spectra; Stellar Composition; X Ray Spectra; Astrophysics; NEBULAE: H II REGIONS; STARS: BINARIES; STARS: EMISSION-LINE; STARS: INDIVIDUAL CONSTELLATION NAME: R AQUARII; STARS: MASS LOSS; STARS: SYMBIOTIC; ULTRAVIOLET: SPECTRA full text sources ADS | data products SIMBAD (1) MAST (1)