Compact Planetary Nebulae Research Articles

A study of OH/IR stars and planetary nebula formation

view Abstract Citations (40) References (52) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Study of OH/IR Stars and Planetary Nebula Formation Bowers, P. F. ; Knapp, G. R. Abstract Seventeen objects which are candidates for newly formed planetary nebulae have been searched for radio continuum emissions at 4885 MHz with the VLA. The candidates include eight OH 1612 MHz maser sources with only a single emission component or with a large ratio of blue to redshifted emission (similar to the compact planetary nebula Vy 2-2) and the highly evolved stars IRC + 10420, CRL 2688, OH 231.8 + 4.2, and M1-92. Continuum emission from M1-92 was detected and mapped, confirming it as a young planetary nebula. The emission from the compact planetary nebula M2-9 was also mapped, and its radio structure agrees very well with that seen in the optical. Accurate VLA positions were obtained for 24 OH 1612 MHz maser sources (including the eight single-featured objects) between Galactic longitudes of 340 and 30 deg. Most or all of the sources are OH/IR stars. Publication: The Astrophysical Journal Pub Date: December 1989 DOI: 10.1086/168121 Bibcode: 1989ApJ...347..325B Keywords: Hydroxyl Emission; Infrared Stars; Interstellar Masers; Planetary Nebulae; Radio Emission; Stellar Evolution; Asymptotic Giant Branch Stars; Emission Spectra; Infrared Astronomy Satellite; Red Shift; Stellar Envelopes; Very Large Array (Vla); Astrophysics; INFRARED: SOURCES; MASERS; NEBULAE: PLANETARY; STARS: CIRCUMSTELLAR SHELLS full text sources ADS | data products SIMBAD (32)

A compact planetary nebula around the hot white dwarf EGB 6/PG 0950 + 139

The remarkable central star (0950 + 139), a very hot DA/DAO white dwarf, of the planetary nebula EGB 6 is described. Follow-up observations relevant to the analyses of both the nebula and the stellar photosphere are presented. Three kinds of scenarios are discussed to account for the existence of this peculiar nebula, but none appears very promising. The first consideration is that the nebula was ejected from the white dwarf as a discret event. This hypothesis is heavily constrained by the nebular size, density, and expansion rate; by the low luminosity and radius of the star; and by the absence of evidence for variation in density-sensitive forbidden lines from 1978 to 1987. No plausible mechanism can cause the observed amount of mass to be lost directly from a white dwarf in a steady or sporadic wind, at outflow velocities orders of magnitude below the escape velocity. Final consideration is given to the possibility that the gas is lost from a close companion star, but there is no evidence that this is a close binary system.

The near-infrared oxygen I lines of the planetary nebula IC 4997

view Abstract Citations (29) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Near-Infrared Oxygen i Lines of the Planetary Nebula IC 4997 Rudy, Richard J. ; Rossano, George S. ; Puetter, R. C. Abstract Spectrophotometry from 0.84 to 1.32 microns of the compact planetary nebula (PN) IC 4997 is presented. The O I 11287 A line is found to be comparable in strength to O I 8446 A. This observation, together with the absence of the O I line at 13164 A, indicates that Bowen fluorescence by Ly-alpha is the principal excitation mechanism for these oxygen lines. Although this is believed to be the process which creates the 8446 A line in the hot, partially ionized zones of Seyfert galaxies, such regions are not present in IC 4997. An alternative mechanism in which the O I lines arise from Bowen fluorescence in the cool, neutral shell of gas which surrounds IC 4997 is considered. Publication: The Astrophysical Journal Pub Date: November 1989 DOI: 10.1086/168060 Bibcode: 1989ApJ...346..799R Keywords: Infrared Spectra; Near Infrared Radiation; Oxygen; Planetary Nebulae; Absorption Cross Sections; Emission Spectra; Fluorescence; Gas Ionization; H Alpha Line; Lyman Beta Radiation; Astrophysics; INFRARED: SPECTRA; NEBULAE: INDIVIDUAL ALPHANUMERIC: IC 4997; NEBULAE: PLANETARY; RADIATION MECHANISMS full text sources ADS | data products SIMBAD (1)

Expanding molecular torus around the planetary nebula IRAS 21282 + 5050

The CO (J = 1-0) emission at 115.271 GHz from the compact planetary nebula IRAS 21282 + 5050 has been mapped. The results suggest that the CO gas forms an expanding torus with an axis along the east-west direction, normal to the line of sight. The kinematical age of the torus is estimated at about 21,000 D yr, where D is the distance to IRAS 21282 + 5050 in kpc. It is concluded that IRAS 21282 + 5050 is in earlier evolutionary stage of planetary nebular than NGC 7027 and NGC 2346. 20 refs.

RADIAL AND EXPANSION VELOCITIES OF COMPACT PLANETARY NEBULAE

ABSTRACT Optical spectra centered near 5000 A have been obtained of the compact planetary nebulae M1-6, IC 2149, MI-78, NGC 7027, and CN3-1. The expansion velocities of the ionized outflow and the systemic velocity of each nebula have been determined from the forbidden O III lines at 5007 A and 4958 A.

Expansion Velocities of [NII] and [OIII] from Compact Planetary Nebulae

We observed the expansion velocities, Vexp[NII] and Vexp[OIII] of angularly small planetary nebulae(PNe) and examined the relations between expansion velocities and distance free parameters like relative emission line intensities of HeIIλ4686, [OIII]A5007, and [NII]λ6583. The expansion velocities of PNe are usually obtained from the emission lines of [OIII]λ5007. But these quantities obtained from [NII]λ6583 are more suitable to investigate the evolution of PNe because 0++ region is confined within inner part for lower and intermediate excitation PNe.

IRAS 21282+5050: A Transitional Planetary Nebula

IRAS 21282+5050 is very compact planetary nebula with a substantial molecular shell. It is carbon-rich and exhibits infrared features attributed to PAH molecules. It has a far infrared color temperature higher than almost all other planetary nebulae, with IRAS flux ratios similar to low color temperature evolved stars. We present VLA images of IRAS 21282 at wavelengths of 2 and 6 cm (with FWHM beamsizes of 0.5” and 0.9”, respectively).

Near Infrared Photometry of Compact Planetary Nebulae

The study of young planetary nebulae can provide information about the ejection process of the nebular material as well as on nebular evolution and the enrichment of the interstellar medium. The youngest PN are expected to be compact and very dense, they usually show signs of variability and IR excess due to the presence of warm dust which, in some cases, seems to be mixed with the ionized gas.

A Young Planetary Nebula with OH Molecules: NGC 6302

We report the results of a sensitive survey of planetary nebulae in all four ground state OH lines. Our results confirm that evolved planetary nebulae are not OH sources in general. However, we did detect one interesting object: an OH 1612 MHz maser in the young planetary nebula NGC 6302. This nebula may be in a brief evolutionary stage, similar to the young and compact planetary nebula Vy 2-2 where OH has already been detected.

Fluorescent H2 Emission in the Planetary Nebulae BD+30 3639 and Hb 12

We report results from a program of near-infrared spectroscopic observations of the H2 emission from planetary nebulae, being carried out at McDonald Observatory using an InSb array-detector spectrometer. Our observations employ both high spatial resolution (3″ diameter aperture) and high spectral resolution (λ/Δλ = 200–600), thus avoiding potential problems with line blending and spatial registration. These observations provide simultaneous measurements of H I recombination lines and H2 emission lines, thus accurately defining the relative extent and distribution of the ionized vs. molecular material. One-dimensional cuts through the compact planetary nebulae BD+30 3639 and Hubble 12, taken along east-west and north-south axes through the nebular centers, show that the H2 emission is concentrated in a ring or shell outside the ionized nebular core. The angular extent of the H2 emission in Hb 12, with a characteristic diameter of about 8–10″ arc seconds, is strikingly larger than the dimensions of the ionized core, which is less than 2″ in diameter.

Far-infrared data for symbiotic stars. II - The IRAS survey observations

IRAS survey data for all known symbiotic binaries are reported. S type systems have 25 micron excesses much larger than those of single red giant stars, suggesting that these objects lose mass more rapidly than do normal giants. D type objects have far-IR colors similar to those of Mira variables, implying mass-loss rate of about 10 to the -6th solar masses/yr. The near-IR extinctions of the D types indicate that their Mira components are enshrouded in optically thick dust shells, while their hot companions lie outside the shells. If this interpretation of the data is correct, then the very red near-IR colors of D type symbiotic stars are caused by extreme amounts of dust absorption rather than dust emission. The small group of D prime objects possesses far-IR colors resembling those of compact planetary nebulae or extreme OH/IR stars. It is speculated that these binaries are not symbiotic stars at all, but contain a hot compact star and an exasymptotic branch giant which is in the process of ejecting a planetary nebula shell.

A young planetary nebula with OH molecules - NGC 6302

We report the results of a sensitive survey of planetary nebulae in all four ground state OH lines. Our results confirm that evolved planetary nebulae are not OH sources in general. However, we did detect one interesting object: an OH 1612 MHz maser in the young planetary nebula NGC 6302. This nebula may be in a brief evolutionary stage, similar to the young and compact planetary nebula Vy 2-2 where OH has already been detected.

Chemical and Expansion Properties of Compact Planetary Nebulae in the Galactic Anti-Center Region

A spectroscopic diagnosis on M1-5, M1-9, K3-66, and K3-67 is presented. Our sample were chosen from the catalogue of radial velocities (Schneider et al 1983) by the reason of not only their kinetic peculiarity, but also apparently compact images. Main purpose is to analyze the chemical properties which should give us an information about galactic chemical abundance distribution in the direction of galactic anti-center region based upon kinetic peculiarity. Another one is to study on an expansion characteristics by which we can recognize intrinsically compact planetary nebulae in young phase.Spectroscopic observations were made at the Okayama Astrophysical Observatory (Shibata and Tamura 1985), the Steward Observatory, and Lick Observatory (Tamura and Shaw 1987).

The shapes and shaping of the planetary nebulae IC 3568, NGC 40, and NGC 6543

Radio and optical images of three compact planetary nebulae, NGC 6543, IC 3568, and NGC 40, are found to reveal a variety of morphological and ionization signatures of wind shaping and heating. Both NGC 6543 (one of the most morphologically complex planetaries in the sky) and IC 3568 (one of the simplest) exhibit large density changes on size scales corresponding to sound-crossing times of about a century, arguing that the density gradients are sustained by shocks driven by stellar winds. All of the available data show the structure and ionization of IC 3568 to conform to simple hydrodynamic models of nebulae that are shaped by interior stellar winds. NGC 6543 also shows very local changes in optical line ratios that are best understood in the same manner. 34 references.

SPECTROPHOTOMETRY OF THE COMPACT PLANETARY NEBULAE NGC 6879 AND NGC 6881.

ABSTRACT The authors have observed the spectra of the two compact planetary nebulae NGC 6879 and NGC 6881 between λ3727 and λ6731 with both the IRS and the IIDS at Kitt Peak and calculate extinction constants, electron densities and temperatures, and a wide variety of ionic abundances. Both nebulae have high densities. NGC 6881, the more highly excited of the two, is significantly enriched in nitrogen and possibly exhibits some elevation in helium.

Ground-based and IRAS observations of compact planetary nebulae

Ground-based and IRAS observations of compact planetary nebulae

The detection of rotationally excited OH emission toward the probable young planetary nebula VY 2-2

A search for 4.7 and 6.0 GHz rotationally excited OH emission in OH/Miras, OH/IR stars, Herbig-Haro objects, Herbig Ae and Be stars, and compact planetary nebulae has been performed. Many of the objects were surveyed in all seven of the lambda doublet hyperfine transitions in the /sup 2/product/sub 3/2/, J = 5/2 and /sup 2/product/sub 1//sub ///sub 2/, J = 1/2 rotational states. In general, this is the most comprehensive and sensitive search for circumstellar rotationally excited OH yet performed. Only one new detection was made, but that was of 6035 MHz emission from the interesting object Vy 2-2. This object is a probable compact planetary nebula surrounded by a fossil molecular envelope from the progenitor red giant. The object was previously known to have a 1612 MHz ground-state OH maser. A complete summary of all observations is given. We discuss the excitation conditions and a number of pumping schemes that could explain the Vy 2-2 masers and the negative results for excited-state OH masers in the other sources. The morphology of the Vy 2-2 envelope as indicated by the velocity structure of the 6035 MHz emissions is also discussed.

High-resolution radio observations of compact planetary nebulae

High-resolution radio observations of compact planetary nebulae

High dispersion spectra of compact planetary nebulae

On a obtenu la vitesse d'expansion [O III] dans 14 nebuleuses planetaires compactes a partir de spectres de haute dispersion. Toutes ces nebuleuses se trouvent dans un etat evolutif relativement primitif (rayon de la nebuleuse <0,07 pc) avec des vitesses d'expansion inferieures a 15 km s −1 . La seule exception est BD+30°3639 qui presente des emissions a double pic avec ΔV=46 km s −1

Two-frequency VLA observations of compact planetary nebulae

Sixty-two compact planetary nebulae have been observed at wavelengths of 20.5 and 6 cm. By scaling the Very Large Array, very similar beam sizes were obtained at both wavelengths: this allows relatively accurate emission measures and angular diameters to be derived even when the nebulae are unresolved. Positions accurate to 1 arcsec are presented. It is found that compact planetaries are both younger and more distant than those which are resolved. A third of the survey objects have peak emission measures greater than 107 pc cm−6, implying that they are ionization-bounded. One object, NGC 6565, has been resolved for the first time and is shown to be bipolar.