Spectrophotometric Studies of Gaseous Nebulae. V. Measurement of Line Intensities in Planetary Nebulae with an Electronic Camera.

1965 ◽  
Vol 141 ◽  
pp. 1318 ◽  
Author(s):  
L. H. Aller ◽  
M. F. Walker
Keyword(s):  
Planetary Nebulae ◽  
Line Intensities ◽  
Gaseous Nebulae

scholarly journals Collisional Excitation of the 10830 He I Line and the Population of the 23S He I State in Gaseous Nebulae

1989 ◽  
Vol 131 ◽  
pp. 212-212
Author(s):  
M. Peimbert ◽  
S. Torres-Peimbert
Keyword(s):  
Optical Depth ◽  
Planetary Nebulae ◽  
H Ii Regions ◽  
Type I ◽  
Line Intensities ◽  
Gaseous Nebulae ◽  
Radiative Transitions ◽  
Ngc 7027 ◽  
Ngc 7662 ◽  
Dust Absorption

From the study of the λλ5876, 7065 and 10830 He I line intensities in NGC 6572, NGC 6803, NGC 7009, NGC 7027, NGC 7662 and IC 418, it is found that the I(10830)/I(5876) ratio is weaker than expected. By considering estimates of the optical depth at λ10830 due to dust absorption and by determining the optical depth at λ10830 due to atomic absorption, it is argued that dust absorption of λ(10830) photons is not the cause for the low I(10830)/I(5876) ratios. By assuming that the 23S He0 state is depopulated only by radiative transitions to the 11S state and by triplet-singlet exchange collisions, it is found that its population is about a factor of two smaller than expected. This result is in agreement with a previous study of the λ3889, 4472, 5876, 6678 and 7065 line intensities in a group of thirteen Type I planetary nebulae. One of the main implications of the underpopulation of the 23S level is that the collisional effects in the N(He)/N(H) abundance ratios of planetary nebulae and 0-poor extragalactic H II regions are smaller than previously thought.

scholarly journals The Remarkable Evolution of the Post-Agb Star FG SGE

1998 ◽  
Vol 11 (1) ◽  
pp. 363-363
Author(s):  
Johanna Jurcsik ◽  
Benjamin Montesinos
Keyword(s):  
Time Scales ◽  
Effective Temperature ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Central Star ◽  
Evolutionary Models ◽  
Single Star ◽  
Line Intensities ◽  
Evolutionary Changes ◽  
Evolutionary Studies

FG Sagittae is one of the most important key objects of post-AGB stellar evolutionary studies. As a consequence of a final helium shell flash, this unique variable has shown real evolutionary changes on human time scales during this century. The observational history was reviewed in comparison with predictions from evolutionary models. The central star of the old planetary nebula (Hel-5) evolved from left to right in the HR diagram, going in just hundred years from the hot region of exciting sources of planetary nebulae to the cool red supergiant domain just before our eyes becoming a newly-born post-AGB star. The effective temperature of the star was around 50,000 K at the beginning of this century, and the last estimates in the late 1980s give 5,000-6,500 K. Recent spectroscopic observations obtained by Ingemar Lundström show definite changes in the nebular line intensities. This fact undoubtedly rules out the possibility that, instead of FG Sge, a hidden hot object would be the true central star of the nebula. Consequently, the observed evolutionary changes are connected with the evolution of a single star.

scholarly journals A consolidated online database of Galactic planetary nebulae

2011 ◽  
Vol 7 (S283) ◽  
pp. 442-443
Author(s):  
Brent Miszalski ◽  
A. Acker ◽  
F. Ochsenbein ◽  
Q. A. Parker
Keyword(s):  
Planetary Nebulae ◽  
Central Star ◽  
Radial Velocities ◽  
Online Database ◽  
Line Intensities ◽  
Multi Wavelength

AbstractSince the issue of the unifying Strasbourg-ESO Catalogue of Galactic Planetary Nebulae (SECGPN) a large number of new discoveries have been made thanks to improved surveys and discovery techniques. The increasingly heterogeneous published population of Galactic PNe, that we have determined totals <2850 PNe, is becoming more difficult to study on the whole without a centralised repository. We introduce a consolidated and interactive online database with object classifications that reflect the latest multi-wavelength data and the most recent results. The extensible database, hosted by the Centre de Donnees astronomique de Strasbourg (CDS), will contain a wealth of observed data for large, well-defined samples of PNe including coordinates, multi-wavelength images, spectroscopy, line intensities, radial velocities and central star information. It is anticipated that the database will be publicly released early 2012.

Interstellar Matter, Gaseous Nebulae, Planetary Nebulae

1972 ◽  
pp. 325-342
Author(s):  
Siegfried Böhme ◽  
Walter Fricke ◽  
Ulrich Güntzel-Lingner ◽  
Frieda Henn ◽  
Dietlinde Krahn ◽  
...  
Keyword(s):  
Planetary Nebulae ◽  
Interstellar Matter ◽  
Gaseous Nebulae

scholarly journals Advances in Numerical Simulations of Gaseous Nebulae

1993 ◽  
Vol 155 ◽  
pp. 123-130 ◽  
Author(s):  
Gary J. Ferland
Keyword(s):  
Numerical Simulations ◽  
Planetary Nebulae ◽  
Stellar Atmosphere ◽  
Ionized Gas ◽  
Gaseous Nebulae ◽  
Recent Advances ◽  
New Generation

I outline recent advances in numerical simulations of gaseous nebulae. These fall into three major areas; the Opacity Project and its extensions, the role of grains within the ionized gas, and the effects of mechanical heat on the nebula. These advances, together with improvements in stellar atmosphere calculations, should lead to a new generation of more realistic simulations of conditions in planetary nebulae and predictions of their emitted spectra.

scholarly journals Gaseous abundances in planetary nebulae: What have we learned in the past five years?

2016 ◽  
Vol 12 (S323) ◽  
pp. 51-59
Author(s):  
Gloria Delgado-Inglada
Keyword(s):  
Planetary Nebulae ◽  
Chemical Compositions ◽  
Field Of Study ◽  
The Past ◽  
Gaseous Nebulae

AbstractNearly 50 years ago, in the proceedings of the first IAU symposium on planetary nebulae, Lawrence H. Aller and Stanley J. Czyzak said that “the problem of determination of the chemical compositions of planetary and other gaseous nebulae constitutes one of the most exasperating problems in astrophysics”. Although the situation has greatly improved over the years, many important problems are still open and new questions have arrived to the field, which still is an active field of study. Here I will review some of the main aspects related to the determination of gaseous abundances in PNe and some relevant results derived in the last five years, since the last IAU symposium on PNe.

scholarly journals The Chemical Composition of Planetary Nebulae

1968 ◽  
Vol 34 ◽  
pp. 209-223 ◽  
Author(s):  
Lawrence H. Aller ◽  
Stanley J. Czyzak
Keyword(s):  
Chemical Composition ◽  
Planetary Nebulae ◽  
Quantum Mechanical ◽  
Physical Parameters ◽  
Chemical Compositions ◽  
Mechanical Theory ◽  
Gaseous Nebulae ◽  
Quantum Mechanical Theory ◽  
The One

The problem of the determination of the chemical compositions of planetary and other gaseous nebulae constitutes one of the most exasperating problems in astrophysics. On the one hand, the problem appears to be conceptually simple – the mechanisms of excitation of the various lines appear to be well understood and the necessary physical parameters can be obtained by quantum mechanical theory. Yet the task is a difficult one and we want to explore some of the significant features.

scholarly journals The kinematical behavior of ORLs and CELs in PNe with [WC] central star

2016 ◽  
Vol 12 (S323) ◽  
pp. 60-64 ◽  
Author(s):  
Miriam Peña ◽  
Francisco Ruiz-Escobedo ◽  
Jackeline Rechy-García ◽  
Jorge García-Rojas
Keyword(s):  
Open Problem ◽  
Planetary Nebulae ◽  
Temperature Fluctuations ◽  
Hii Regions ◽  
Central Star ◽  
Gaseous Nebulae

AbstractIn Planetary Nebulae (PNe) and HII regions ionic abundances can be derived by using collisionally excited lines (CELs) or recombination lines (ORLs). Such abundances do not coincide for the same ion and usually abundances from ORLs are larger than those from CELs by factors of 2 or larger. The origin of the discrepancy, known as the Abundance Discrepancy Factor is an open problem in astrophysics of gaseous nebulae. It has been attributed to temperature fluctuations in the plasma, tiny metal-rich inclusions embedded in the H-rich plasma, gas inhomogeneities or other processes. In this work we analyze the kinematical behavior of CELs and ORLs in two PNe ionized by [WC] stars, finding that kinematics of ORLS is incompatible with the kinematics of CELs. In particular the expansion velocities from CELs and ORLs for the same ion are different, indicating that ORLs seem to be produced in zones nearer the central star than CELs. This is in agreement with results found by other authors for individual PNe.

scholarly journals Mg-H+ charge transfer and Mg line intensities in gaseous nebulae

1988 ◽  
Vol 235 (4) ◽  
pp. 1245-1255 ◽  
Author(s):  
R. J. Allan ◽  
R. E. S. Clegg ◽  
A. S. Dickinson ◽  
D. R. Flower
Keyword(s):  
Charge Transfer ◽  
Line Intensities ◽  
Gaseous Nebulae

scholarly journals The Absolute Spectrophotometry of 170 Planetary Nebulae

1968 ◽  
Vol 34 ◽  
pp. 55-58 ◽  
Author(s):  
B.A. Vorontsov-Velyaminov ◽  
E.B. Kostjakova ◽  
O.D. Dokuchaeva ◽  
V.P. Arhipova
Keyword(s):  
Emission Line ◽  
Planetary Nebulae ◽  
Homogeneous System ◽  
Astronomical Institute ◽  
Line Intensities ◽  
Objective Prism ◽  
The Absolute

An investigation of planetary nebulae has been underway at the Sternberg State Astronomical Institute in Moscow for several years. It was begun with the measurement of the emission-line intensities of planetary nebulae in an homogeneous system in absolute units. More than 300 long-exposure objective prism spectrograms were obtained with the 50-cm Maksutov telescope at the Crimean Station of the Institute and with the 70-cm meniscus telescope of the Abastumani Observatory. The dispersion of the spectrograms was 190 and 160 Å/mm at Hγ respectively.

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