PERINOTTO M., PATRIARCHI P., BALICK B. and CORRADI R.L.M.
Abstract (from CDS):
We observed the planetary nebula NGC 7662 with STIS on board the HST to investigate the physical conditions in the microstructures within the nebula at high spatial resolution and to closely examine the physical conditions in FLIERs. We aim to reveal spectroscopic differences in small scale structures moving at about the same velocity as the surrounding nebular gases, called SLOWERs. Shocks are expected to play a role in FLIERs but not in SLOWERs. The physical conditions in the two types of microstructures have been determined better than ever. In both types of substructures, the electron density shows a moderate increase inward, while the electron temperature becomes a little lower. The ionization increases from the central parts of the FLIERs to their edges. No particular increase of the line emission typical of shock excitation, such as the [SII] 6725Å doublet, is seen at the interface between the ambient gas and the microcondensations. Thus, we observe no evidence for shock effects in the FLIERs. We estimate that the thickness of the post-shock layer is too small to be detected, in spite of the brightness of the nebula. For the same reason the determinations of abundances within the FLIERs done assuming the contribution of photoionization followed by ion-electron collision excitation to be dominant in producing the observed emission lines, might be considered to be acceptable. The geometrical complexity of microstructures composed of sub and subsub-structures coupled with the need to take into account charge-exchange reaction effects, prevent us from drawing a firm conclusion on the nitrogen overabundance suggested in the literature for the FLIERs relative to the surrouding ambient gas. We however argue that our HST observations do not support this enhancement.
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Journal keyword(s):
ISM: Planetary nebulae: individual: NGC 7662 - stars: AGB and post-AGB
(Ref) Object type as listed in the reference "Ref"
(acronym) Object type linked to the acronym according to the original reference
() Anterior to 2007, before we can link the objet type to a reference, or given by the CDS team in some particular cases
Other object types:
*
(AG,BD,...),
Rad
(B3,BWE,...),
PN
(2011ARep,PK,...),
V*
(NSV),
G
(LEDA),
MIR
(WISE),
IR
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Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
ra dec : right ascension and declination (unit and frame defined according to your Output Options)
Grey values are increasing the original precision due to the computation of frame transformations
(wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
[error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
position angle (in degrees North celestial pole to East)
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
ra dec : right ascension and declination (unit and frame defined according to your Output Options)
Grey values are increasing the original precision due to the computation of frame transformations
(wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
[error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
position angle (in degrees North celestial pole to East)
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References (926 between 1850 and 2024) (Total 926)
Simbad bibliographic survey began in 1850 for stars (at least bright stars) and in 1983 for all other objects (outside the solar system).
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