2001A&A...374..280M


Query : 2001A&A...374..280M

2001A&A...374..280M - Astronomy and Astrophysics, volume 374, 280-287 (2001/7-4)

The physical structure of the planetary nebula NGC 6781.

MAVROMATAKIS F., PAPAMASTORAKIS J. and PALEOLOGOU E.V.

Abstract (from CDS):

The planetary nebula NGC 6781 was imaged in major optical emission lines. These lines allow us to construct maps of the projected, two dimensional Balmer decrement, electron density, electron temperature, ionization and abundance structure. The average electron density, determined from the [SII] lines, is ∼500cm–3, while the electron temperature distribution, determined from the [NII] lines, is flat at ∼10000K. The Balmer decrement map shows that there are variations in extinction between the north and south areas of the planetary nebula. The higher extinction observed to the north of the central star is probably caused by dust spatially associated with CO emission at blue-shifted velocities. The [NII] image reveals the known optical halo, at a flux level of ∼0.2% of the strong shell emission in the east, but now the angular extent of 216"x190" is much larger than previous measurements. The halo is also present in [OIII], where we measure an extent of 190"x162". The ionization maps indicate substantial ionization along the caps of the ellipsoid as well as in the halo. The maps also show a sharp decrease in ionization along the outer edge of the shell in the west and the east, south-east. The typical log abundances measured for He, N, O and S are 10.97, 8.14, 8.72 and 6.90, respectively.

Abstract Copyright:

Journal keyword(s): ISM: general - ISM: planetary nebulae - planetary nebulae: individual: NGC 6781

Simbad objects: 7

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Number of rows : 7
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 * 29 Psc V* 00 01 49.4471402460 -03 01 39.021673975 4.47 4.98 5.10     B7III-IV 210 0
2 NGC 2438 PN 07 41 50.5198569363 -14 44 07.484261077           ~ 277 3
3 * 108 Vir * 14 45 30.2060174766 +00 43 02.178514704   5.656 5.665     B9.5V 147 0
4 M 57 PN 18 53 35.0969571234 +33 01 44.883146221   15.405 15.769 15.901 16.062 DA(O?) 798 2
5 NGC 6781 PN 19 18 28.085 +06 32 19.29     11.8     ~ 251 0
6 * 58 Aql * 19 54 44.7954348711 +00 16 25.053387202   5.703 5.631     B9IV 200 0
7 * 42 Peg PM* 22 41 27.7207176 +10 49 52.907917 3.10 3.33 3.41 3.43 3.50 B8V 287 0

    Equat.    Gal    SGal    Ecl

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2021.07.29-17:26:40

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