The physical structure of the planetary nebula NGC 6781

Mavromatakis, F.; Papamastorakis, I.; Paleologou, E. V.

doi:10.1051/0004-6361:20010752

Cited by 14 publications

(51 citation statements)

References 22 publications

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“…4) we derive a distance of smaller than 1000 pc, by adopting all the reported values of A v , from the minimum value inferred by Mavromatakis et al (2001) to the maximum value obtained in this paper. We cannot be more precise since the curve is not determined within this range.…”

Section: Distance Determinations For the Ngc Samplementioning

confidence: 97%

IPHAS extinction distances to planetary nebulae

Giammanco

Sale

Corradi

et al. 2010

A&A

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Aims. The determination of reliable distances to planetary nebulae (PNe) is a major difficulty in the study of this class of objects in the Galaxy. The availability of new photometric surveys such as IPHAS (the INT/WFC photometric H α survey of the northern Galactic plane) covering large portions of the sky provide an opportunity to apply the so-called extinction method to determine the distances of a large number of objects. Methods. The technique is applied to a sample of 137 PNe located between −5 and 5 degrees in Galactic latitude, and between 29.52 and 215.49 degrees in longitude. The characteristics of the distance-extinction method and the main sources of errors are carefully discussed. Results. The data on the extinction of the PNe available in the literature, complemented by new observations, allow us to determine extinction distances for 70 PNe. A comparison with statistical distance scales from different authors is presented.

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Section: Distance Determinations For the Ngc Samplementioning

confidence: 97%

IPHAS extinction distances to planetary nebulae

Giammanco

Sale

Corradi

et al. 2010

A&A

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“…Mavromatakis et al (2001) mapped this nebula in several optical emission lines and these images display a known "C" like structure. The electron densities (see Fig.…”

Section: Ngc 6781mentioning

confidence: 98%

Electron temperature fluctuations in planetary nebulae

Krabbe¹,

Copetti²

2005

A&A

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An observational study of the spatial variation of the electron temperature and density in 10 galactic planetary nebulae is presented. The data consist of long-slit spectra of high signal-to-noise ratio in the 3100 to 6900 Å range. Electron temperatures were determined from the . An anti-correlation between temperature and density was found for NGC 2438 and NGC 3132, with the electron temperature increasing with the decrease of electron density and a correlation between temperature and density was found for NGC 2440, NGC 3242, NGC 6302, and NGC 7009, with the electron temperature increasing with the increase of electron density. These relationships seem to be associated with the structure of the nebula. The nebulae in which the correlation between temperature and density is present are ring shaped. The anti-correlation between temperature and density is found in bipolar planetary nebulae that are denser in the centre of the nebula.

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“…So far, Hα/Hβ variations were reported for a few PNe by comparing direct, narrow-band imagery, and ascribed to the presence of absorbing dust within (or around) the objects (for example, in NGC 6302 by Bohigas 1994, in NGC 6445 by Cuesta & Phillips 1999, in NGC 2440by Cuesta & Phillips 2000, and in NGC 6781 by Mavromatakis et al 2001).…”

Section: The Hα/hβ Spectral Mapsmentioning

confidence: 99%

The 3-D ionization structure of the planetary nebula NGC 6565

Turatto

Ragazzoni

Benetti

et al. 2002

A&A

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Abstract.A detailed study of the planetary nebula NGC 6565 has been carried out on long-slit echellograms (λ/∆λ = 60 000, spectral range = λλ3900-7750Å) at six, equally spaced position angles. The expansion velocity field, the c(Hβ) distribution and the radial profile of the physical conditions (electron temperature and density) are obtained. The distance, radius, mass and filling factor of the nebula and the temperature and luminosity of the central star are derived. The radial ionization structure is analyzed using both the classical method and the photo-ionization code CLOUDY. Moreover, we present the spatial structure in a series of images from different directions, allowing the reader to "see" the nebula in 3-D. NGC 6565 results to be a young (2000-2500 years), patchy, optically thick triaxial ellipsoid (a = 10.1 arcsec, a/b = 1.4, a/c = 1.7) projected almost pole-on. The matter close to major axis was swept-up by some accelerating agent (fast wind? ionization? magnetic fields?), forming two faint and asymmetric polar cups. A large cocoon of almost neutral gas completely embeds the ionized nebula. NGC 6565 is in a recombination phase, because of the luminosity drop of the massive powering star, which is reaching the white dwarf domain (log T * 5.08 K; log L * /L 2.0). The stellar decline started about 1000 years ago, but the main nebula remained optically thin for other 600 years before the recombination phase occurred. In the near future the ionization front will re-grow, since the dilution factor due to the expansion will prevail on the slower and slower stellar decline. NGC 6565 is at a distance of 2.0 (±0.5) kpc and can be divided into three radial zones: the "fully ionized" one, extending up to 0.029-0.035 pc at the equator (0.050 pc at the poles), the "transition" one, up to 0.048-0.054 pc (0.080 pc), the "halo", detectable up to 0.110 pc. The ionized mass ( 0.03 M ) is only a fraction of the total mass (≥0.15 M ), which has been ejected by an equatorial enhanced superwind of 4 (±2) × 10 −5 M yr −1 lasted for 4 (±2) × 10 3 years.

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The physical structure of the planetary nebula NGC 6781

Cited by 14 publications

References 22 publications

IPHAS extinction distances to planetary nebulae

IPHAS extinction distances to planetary nebulae

Electron temperature fluctuations in planetary nebulae

The 3-D ionization structure of the planetary nebula NGC 6565

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