scholarly journals Towards an improvement in the spectral description of central stars of planetary nebulae

2018 ◽  
Vol 614 ◽  
pp. A135 ◽  
Author(s):  
W. Weidmann ◽  
R. Gamen ◽  
D. Mast ◽  
C. Fariña ◽  
G. Gimeno ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
Planetary Nebulae ◽  
Emission Lines ◽  
Spectral Classification ◽  
High Quality ◽  
Isaac Newton ◽  
Type Spectrum ◽  
First Time ◽  
Central Stars ◽  
Preliminary Classification

Context. There are more than 3000 known Galactic planetary nebulae, but only 492 central stars of Galactic planetary nebulae (CSPN) have known spectral types. It is vital to increase this number in order to have reliable statistics, which will lead to an increase of our understanding of these amazing objects. Aims. We aim to contribute to the knowledge of central stars of planetary nebulae and stellar evolution. Methods. This observational study is based on Gemini Multi-Object Spectrographs (GMOS) and with the Intermediate Dispersion Spectrograph (IDS) at the Isaac Newton Telescope spectra of 78 CSPN. The objects were selected because they did not have any previous classification, or the present classification is ambiguous. These new high quality spectra allowed us to identify the key stellar lines for determining spectral classification in the Morgan-Keenan (MK) system. Results. We have acquired optical spectra of a large sample of CSPN. From the observed targets, 50 are classified here for the first time while for 28 the existing classifications have been improved. In seven objects we have identified a P-Cygni profile at the He I lines. Six of these CSPN are late O-type. The vast majority of the stars in the sample exhibit an absorption-type spectrum, and in one case we have found wide emission lines typical of [WR] stars. We give a complementary, and preliminary, classification criterion to obtain the sub-type of the O(H)-type CSPN. Finally, we give a more realistic value of the proportion of CSPN that are rich or poor in hydrogen.

scholarly journals Ultraviolet and Optical Spectra of Central Stars of Halo Planetary Nebulae

1993 ◽  
Vol 155 ◽  
pp. 90-90
Author(s):  
M. Peña ◽  
S. Torres-Peimbert ◽  
M. T. Ruiz
Keyword(s):  
Planetary Nebulae ◽  
Optical Spectra ◽  
Spectral Classification ◽  
Spectrophotometric Data ◽  
Type Spectrum ◽  
Central Stars

Optical and UV spectrophotometric data are analyzed for the central stars of the known Population II planetary nebulae. From this, we derive visual magnitudes, spectral classification, color temperatures, luminosities and masses of the objects. It is found that all the stars show absorption type spectrum and most of them have normal H and He photospheric abundances, the only possible exceptions are M 2–29 and GJJC-1 which seem to be H-deficient stars.

scholarly journals Weak emission line central stars of planetary nebulae

2011 ◽  
Vol 7 (S283) ◽  
pp. 510-511
Author(s):  
Helga Todt ◽  
Miriam Peña ◽  
Julia Zühlke ◽  
Lida Oskinova ◽  
Wolf-Rainer Hamann ◽  
...  
Keyword(s):  
Mass Loss ◽  
Emission Line ◽  
Hydrogen Content ◽  
Planetary Nebulae ◽  
Emission Lines ◽  
Detailed Knowledge ◽  
Spectral Classification ◽  
Balmer Lines ◽  
Formation And Evolution ◽  
Central Stars

AbstractTo understand the evolution and morphology of planetary nebulae, a detailed knowledge of their central stars is required. Central stars that exhibit emission lines in their spectra, indicating stellar mass-loss allow to study the evolution of planetary nebulae in action. Emission line central stars constitute about 10 % of all central stars. Half of them are practically hydrogen-free Wolf-Rayet type central stars of the carbon sequence, [WC], that show strong emission lines of carbon and oxygen in their spectra. In this contribution we address the weak emission-lines central stars (wels). These stars are poorly analyzed and their hydrogen content is mostly unknown. We obtained optical spectra, that include the important Balmer lines of hydrogen, for four weak emission line central stars. We present the results of our analysis, provide spectral classification and discuss possible explanations for their formation and evolution.

scholarly journals Catalogue of the central stars of planetary nebulae

2020 ◽  
Vol 640 ◽  
pp. A10
Author(s):  
W. A. Weidmann ◽  
M. B. Mari ◽  
E. O. Schmidt ◽  
G. Gaspar ◽  
M. M. Miller Bertolami ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
Late Stage ◽  
Planetary Nebulae ◽  
Surface Gravity ◽  
Physical Parameters ◽  
Evolutionary Models ◽  
Pertinent Information ◽  
Central Stars ◽  
Statistical Improvement ◽  
Magnitude Estimates

Planetary nebulae represent a potential late stage of stellar evolution, however, their central stars (CSPNe) are relatively faint and, therefore, pertinent information is available for merely < 20% of the Galactic sample. Consequently, the literature was surveyed to construct a new catalogue of 620 CSPNe featuring important spectral classifications and information. The catalogue supersedes the existing iteration by 25% and includes physical parameters such as luminosity, surface gravity, temperature, magnitude estimates, and references for published spectra. The marked statistical improvement enabled the following pertinent conclusions to be determined: the H-rich/H-poor ratio is 2:1, there is a deficiency of CSPNe with types [WC 5-6], and nearly 80% of binary central stars belong to the H-rich group. The last finding suggests that evolutionary scenarios leading to the formation of binary central stars interfere with the conditions required for the formation of H-poor CSPN. Approximately 50% of the sample with derived values of log L⋆, log Teff, and log g, exhibit masses and ages consistent with single stellar evolutionary models. The implication is that single stars are indeed able to form planetary nebulae. Moreover, it is shown that H-poor CSPNe are formed by higher mass progenitors. The catalogue is available through the Vizier database.

scholarly journals Ionization correction factors for sodium, potassium, and calcium in planetary nebulae

2019 ◽  
Vol 492 (1) ◽  
pp. 950-965
Author(s):  
A Amayo ◽  
G Delgado-Inglada ◽  
J García-Rojas
Keyword(s):  
Planetary Nebulae ◽  
Emission Lines ◽  
Condensation Temperature ◽  
Correction Factors ◽  
Dust Grains ◽  
Degree Of Ionization ◽  
Sodium Potassium ◽  
First Time ◽  
Analytical Expressions ◽  
Large Grid

ABSTRACT We use a large grid of photoionization models that are representative of observed planetary nebulae (PNe) to derive ionization correction factors (ICFs) for sodium, potassium, and calcium. In addition to the analytical expressions of the ICFs, we provide the range of validity where the ICFs can be safely used and an estimate of the typical uncertainties associated with the ICFs. We improved the previous ICFs for calcium and potassium in the literature and suggest for the first time an ICF for sodium. We tested our ICFs with a sample of 39 PNe with emission lines of some ion of these elements. No obvious trend is found between the derived abundances and the degree of ionization, suggesting that our ICFs do not seem to be introducing an artificial bias in the results. The abundances found in the studied PNe range from $-2.88_{-0.22}^{+0.21}$ to −2.09 ± 0.21 in log (Na/O), from $-4.20_{-0.45}^{+0.31}$ to $-3.05_{-0.47}^{+0.26}$ in log (K/O), and from $-3.71_{-0.34}^{+0.41}$ to $-1.57_{-0.47}^{+0.33}$ in log (Ca/O). These numbers imply that some of the studied PNe have up to ∼65 per cent, 75 per cent, or 95 per cent of their Na, K, and/or Ca atoms condensed into dust grains, respectively. As expected, the highest depletions are found for calcium which is the element with the highest condensation temperature.

scholarly journals Spectra of Wolf-Rayet type central stars and their analysis

1997 ◽  
Vol 180 ◽  
pp. 91-96 ◽  
Author(s):  
W.-R Hamann
Keyword(s):  
Planetary Nebulae ◽  
Emission Lines ◽  
Considerable Fraction ◽  
Broad Emission ◽  
Central Stars

Wolf-Rayet (short: WR) stars are characterized by the bright and broad emission lines which dominate their spectra. This class was originally established for Pop. I stars, distinguishing a nitrogen (WN) and carbon (WC) sequence according to the dominating lines. Wolf-Rayet (specifically, WC) type spectra are also shown by a considerable fraction of central stars of planetary nebulae.

scholarly journals Planetary nebulae with Wolf–Rayet-type central stars – I. The case of the high-excitation NGC 2371

2020 ◽  
Vol 496 (1) ◽  
pp. 959-973
Author(s):  
V M A Gómez-González ◽  
J A Toalá ◽  
M A Guerrero ◽  
H Todt ◽  
L Sabin ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
Planetary Nebula ◽  
Symmetry Axis ◽  
High Excitation ◽  
Central Cavity ◽  
Isaac Newton ◽  
Double Structure ◽  
High Ionization ◽  
Isaac Newton Telescope ◽  
Central Stars

ABSTRACT We present the analysis of the planetary nebula (PN) NGC 2371 around the [Wolf–Rayet] (WR) star WD 0722+295. Our Isaac Newton Telescope intermediate dispersion spectrograph spectra, in conjunction with archival optical and ultraviolet images, unveil in unprecedented detail the high ionization of NGC 2371. The nebula has an apparent multipolar morphology, with two pairs of lobes protruding from a barrel-like central cavity, a pair of dense low ionization knots misaligned with the symmetry axis embedded within the central cavity, and a high-excitation halo mainly detected in He ii. The abundances from the barrel-like central cavity and dense knots agree with abundance determinations for other PNe with [WR]-type central stars of PNe. We suggest that the densest knots inside NGC 2371 are the oldest structures, remnant of a dense equatorial structure, while the main nebular shell and outer lobes resulted from a latter ejection that ended the stellar evolution. The analysis of position–velocity diagrams produced from our high-quality spectra suggests that NGC 2371 has a bipolar shape with each lobe presenting a double structure protruding from a barrel-like central region. The analysis of the spectra of WD 0722+295 results in similar stellar parameters as previously reported. We corroborate that the spectral subtype corresponds with a [WO1] type.

scholarly journals An Archival Study of HST Observations of Her X-1/HZ Her

1996 ◽  
Vol 158 ◽  
pp. 381-382
Author(s):  
F. H. Cheng ◽  
S. D. Vrtilek ◽  
J. C. Raymond
Keyword(s):  
Accretion Disk ◽  
Model Fitting ◽  
Rotation Period ◽  
Emission Lines ◽  
High Quality ◽  
Detailed Model ◽  
Companion Star ◽  
X Ray ◽  
First Time ◽  
Archival Study

Her X-1 is an X-ray pulsar with a rotation period of 1.24 s and a binary period of 1.7d (Tananbaum et al. 1972). The 1.7 d variations in optical and ultraviolet flux are attributed to X-ray heating of the companion star and disk (e.g. Howarth & Wilson 1983, hereafter HW83). The system displays a 35 d period, attributed to the effects of a tilted, precessing, accretion disk. Optical and ultraviolet flux variations continue unchanged throughout. This work is motivated by the following reasons:• The observed IUE spectra have significantly flatter slopes than those predicted by previous models (e.g. HW83).• The observed strength of the Balmer jump is anomalously low compared to that expected for a normal B star (Anderson et al. 1994).• HST observations obtained by Anderson et al. (1994) in order to study emission lines have yielded high quality spectra of the continuum emission from HZ Her, enabling for the first time detailed model fitting efforts.

Ultraviolet Fe VII absorption and Fe II emission lines of central stars of planetary nebulae

1991 ◽  
Vol 377 ◽  
pp. 235 ◽  
Author(s):  
Kwang-Ping Cheng ◽  
Walter A. Feibelman ◽  
Frederick C. Bruhweiler
Keyword(s):  
Planetary Nebulae ◽  
Emission Lines ◽  
Central Stars

scholarly journals Rebrightening of Planetary Nebulae Through Interaction with the Interstellar Medium

2010 ◽  
Vol 27 (2) ◽  
pp. 220-226 ◽  
Author(s):  
C. J. Wareing
Keyword(s):  
Interstellar Medium ◽  
High Speed ◽  
Planetary Nebulae ◽  
Central Star ◽  
Bow Shock ◽  
Common Effect ◽  
Evolutionary Phase ◽  
First Time ◽  
Progenitor Stars ◽  
Central Stars

AbstractThe interaction of planetary nebulae (PNe) with the interstellar medium (ISM) as they move through it is now acknowledged to be a major shaping effect not just for ancient and large PNe, but also for relatively young PNe with high-speed central stars. The most common effect is a rebrightening as the PN shell interacts with a pre-existing bow-shock structure formed during the previous evolutionary phase of the central star. In this review we consider this rebrightening in detail for the first time and discuss its origins, highlighting some observed examples. We go on to discuss the AGB progenitor stars, reviewing the evidence for bow-shock structures, and consider the progeny of rebrightened PNe — strongly disrupted objects which bear very little resemblance to typical PNe. Sh 2-68 is inferred to be perhaps the only documented case so far of such a PN.

scholarly journals Proto-Planetary Nebulae

1978 ◽  
Vol 76 ◽  
pp. 305-313 ◽  
Author(s):  
B. Zuckerman
Keyword(s):  
Stellar Evolution ◽  
Planetary Nebula ◽  
White Dwarfs ◽  
Planetary Nebulae ◽  
Red Giants ◽  
Intermediate Mass ◽  
Gaseous Nebulae ◽  
First Time

Although rare, planetary nebulae have been extensively studied by astronomers. This affection is certainly due in part to the beauty of the gaseous nebulae but it is also due to the belief that many, probably most, stars of intermediate mass (1–4 M) become planetary nebulae at least once during their lifetimes. If the planetary nebula is an (almost) inevitable stage in stellar evolution, it is important to determine its evolutionary precursors and followers. The latter are likely to be the white dwarfs and the former are generally believed to be red giants. With the advent of infrared and radio techniques it now appears possible, for the first time, to specify the immediate progenitors of planetary nebulae.

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