scholarly journals The Proto-Planetary Nebula Vy 2-2

1989 ◽  
Vol 131 ◽  
pp. 443-443 ◽  
Author(s):  
R. E. S. Clegg ◽  
M. G. Hoare ◽  
J. R. Walsh
Keyword(s):  
Ir Spectroscopy ◽  
Electron Temperature ◽  
Empirical Analysis ◽  
Planetary Nebula ◽  
Black Body ◽  
Central Star ◽  
Speckle Interferometry ◽  
Maser Emission ◽  
Near Ir ◽  
Carbon Abundance

High and low-resolution optical and near-IR spectroscopy of the candidate proto-planetary (or very young PN) Vy 2-2 (P-K 45 - 2°1) is reported. This object has associated OH maser emission and an angular diameter of only 0.4 arcsec, found from VLA and optical speckle interferometry. Empirical analysis gives the values Ne ≈3 × 105 cm−3, Te=11000(±1500)K. The electron temperature is quite uncertain because of the high density. Abundances of He, C, N, O, Ne and Ar are reported; the carbon abundance is uncertain as it relies on the C II λ4267Å line, since the object is too highly-reddened (c=1.8 ± 0.2) to be observed with IUE. We find He/H=0.10, O/H=4 × 10−4 and C/O=0.8. The HI Zanstra temperature is 38 000 K (for black-body). The spectrum shows broad stellar lines of He II λ4686, C III λ4647 and N III λ4640; the central star may be of type Of.

scholarly journals Morphological and kinematical analysis of the planetary nebula Hu 1-2 and its irradiated bow-shocks

2011 ◽  
Vol 7 (S283) ◽  
pp. 440-441
Author(s):  
Luis F. Miranda ◽  
Mónica Blanco ◽  
Martín A. Guerrero ◽  
Angels Riera
Keyword(s):  
High Resolution ◽  
High Velocity ◽  
Planetary Nebula ◽  
Narrow Band ◽  
Central Star ◽  
Kinematical Analysis ◽  
Near Ir ◽  
Bow Shocks

AbstractWe present narrow-band optical and near-IR images, and high-resolution long-slit spectra of the planetary nebula Hu 1-2 that allow us to make a detailed description of its unusual morphology and internal kinematics. The data also reveal that the ansae of Hu 1-2 probably represent bow-shocks associated to high velocity outflows that are irradiated from the central star.

scholarly journals SOFIA observations of the planetary nebula NGC 7009

2011 ◽  
Vol 7 (S283) ◽  
pp. 67-70
Author(s):  
R. H. Rubin ◽  
S. W. J. Colgan ◽  
R. L. M. Corradi ◽  
R. Sankrit ◽  
A. G. G. M. Tielens ◽  
...  
Keyword(s):  
Fine Structure ◽  
Electron Temperature ◽  
Planetary Nebula ◽  
Central Star ◽  
Optical Measurements ◽  
Optical Line

AbstractWe report spectrophotometric observations made with SOFIA/FORCAST on 2011 June 2 UT. Optical measurements have previously shown that the abundance discrepancy factor (adf) varies with position in several high-adf PNe, and is highest close to the central star. The very low electron temperature inclusions postulated to explain the abundance discrepancy, must be cooled predominantly by fine structure IR lines. These SOFIA data will map mid-IR FS lines (and our related Herschel program will add several far-IR FS lines) in the bright, well-characterized, high-adf PN NGC 7009. We will compare these IR results with FS optical line measurements in order to correlate ratios of IR to optical fluxes with position, and thus correlate with where the adf peaks.

scholarly journals Water and OH Maser Emission from the Planetary Nebula K3-35

2003 ◽  
Vol 209 ◽  
pp. 263-266 ◽  
Author(s):  
Yolanda Gómez ◽  
Luis F. Miranda ◽  
Guillem Anglada ◽  
JosÉ M. Torrelles
Keyword(s):  
Planetary Nebula ◽  
Central Star ◽  
Minor Axis ◽  
Water Molecules ◽  
Giant Star ◽  
Maser Emission ◽  
Giant Stars ◽  
Water Masers ◽  
Unambiguous Detection ◽  
Water Maser

Water-vapour masers, typical of the envelopes in giant stars, are not expected to persist in planetary nebulae due to the ultraviolet radiation of the remnant star that progressively destroys the molecules. Recently, we have reported the first unambiguous detection of water maser emission in a planetary nebula, K 3–35 (Miranda et al. 2001). The water masers in K3–35 were detected at the center of the nebula, along the minor axis, at a radius of ~85 AU and also at the surprisingly large distance of 5000 AU from the star, at the tips of the bipolar lobes. The existence of these water molecules is puzzling, and probably we are observing the very moment of transformation of a giant star into a planetary nebula. Miranda et al. (2001) also report the presence of polarization in the OH 1665 MHz masers, which are distributed towards the central star in a torus-like structure. Here we review the main results on this source.

scholarly journals Maser emission in planetary nebulae

2007 ◽  
Vol 3 (S242) ◽  
pp. 292-298 ◽  
Author(s):  
Yolanda Gómez
Keyword(s):  
Water Vapor ◽  
Mass Loss ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Central Star ◽  
Asymptotic Giant Branch ◽  
Kinematic Modeling ◽  
Maser Emission ◽  
The Core ◽  
Unambiguous Detection

AbstractStars at the top of the asymptotic giant branch (AGB) can exhibit maser emission from molecules like SiO, H2O and OH. These masers appear in general stratified in the envelope, with the SiO masers close to the central star and the OH masers farther out in the envelope. As the star evolves to the planetary nebula (PN) phase, mass-loss stops and ionization of the envelope begins, making the masers disappear progressively. The OH masers in PNe can be present in the envelope for periods of ~1000 years but the H2O masers can survive only hundreds of years. Then, H2O maser emission is not expected in PNe and its detection suggests that these objects are in a very particular moment of its evolution in the transition from AGB to PNe. We discuss the unambiguous detection of H2O maser emission in two planetary nebulae: K 3-35 and IRAS 17347-3139. The water-vapor masers in these PNe are tracing disk-like structures around the core and in the case of K3-35 the masers were also found at the tip of its bipolar lobes. Kinematic modeling of the H2O masers in both PNe suggest the existence of a rotating and expanding disk. Both PNe exhibit a bipolar morphology and in the particular case of K 3-35 the OH masers are highly polarized close to the core in a disk-like structure. All these observational results are consistent with the models where rotation and magnetic fields have been proposed to explain the asymmetries observed in planetary nebulae.

scholarly journals Nature of the H2 Emission Around Planetary Nebulae Precursors

2003 ◽  
Vol 209 ◽  
pp. 135-135
Author(s):  
D.A. García-Hernández ◽  
A. Manchado ◽  
P. García-Lario ◽  
C. Domínguez-Tagle ◽  
G. M. Conway ◽  
...  
Keyword(s):  
Ir Spectroscopy ◽  
Strong Correlation ◽  
Molecular Hydrogen ◽  
Detection Rate ◽  
Early Stage ◽  
Central Star ◽  
Emission Lines ◽  
Evolutionary Stage ◽  
Agb Stars ◽  
Near Ir

We present near-IR spectroscopy of a sample of 30 IRAS sources recently identified as late AGB stars, post-AGB stars or early PNe. The spectra obtained are centred at various wavelengths covering the molecular hydrogen v=1→0 S(1) 2.122 μm and v=2→1 S(1) 2.248 μm emission lines, the recombination lines of hydrogen Brγ 2.166 μm, Pfγ 3.741 μm and Brα 4.052 μm, and the CO[v=2→0] first overtone bandhead at 2.294 μm. As a result of these observations we have increased from 4 to 13 the total number of proto-PNe detected in H2 and we have confirmed that the onset of H2 emission takes place in the post-AGB phase. When the molecular hydrogen is fluorescence-excited the detection rate is found to be directly correlated with the evolutionary stage of the central star, rather than with the nebular morphology. In contrast, shocked-excited H2 is detected only in strongly bipolar proto-PNe, sometimes even at an early stage in the post-AGB phase. The strong correlation of shocked-excited H2 emission with bipolarity found confirms the result previously reported by Kastner et al. (1996) in evolved PNe. However, our results show that this correlation does not exist in the case of fluorescence-excited molecular hydrogen. (to be published in A&A).

scholarly journals The ionization state of the halo planetary nebula NGC 2438

2011 ◽  
Vol 7 (S283) ◽  
pp. 338-339
Author(s):  
Silvia Dalnodar
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Planetary Nebula ◽  
Filling Factor ◽  
Narrow Band ◽  
Central Star ◽  
Emission Lines ◽  
Ionization State ◽  
Hydrodynamic Simulations ◽  
Slit Scanning

AbstractNGC 2438 is a classical multiple shell or halo planetary nebula (PN). Its central star and the main nebula are well studied. Also it was target of various hydrodynamic simulations (Corradi et al. 2000). This initiated a discussion whether the haloes are mainly containing recombined gas (Schönberner et al. 2002), or if they are still ionized (Armsdorfer et al. 2003). An analysis of narrow-band images and long slit spectra at multiple slit positions was done to obtain a deeper look on morphological details and the properties of the outer shell and halo. For this work there was data available from ESO (direct imaging and long slit spectroscopy) and from SAAO (spectroscopic observations using a small slit, scanning over the whole nebula). Using temperature measurements from emission lines resulted in an electron temperature which clearly indicates a fully ionized stage. Additionally measurements of the electron density suggest a variation of the filling factor.

scholarly journals Near- and Mid-Infrared Imaging of the PN IC 418

1993 ◽  
Vol 155 ◽  
pp. 210-210
Author(s):  
J. L. Hora ◽  
L. K. Deutsch ◽  
W. F. Hoffmann ◽  
G. G. Fazio ◽  
K. Shivanandan
Keyword(s):  
High Resolution ◽  
Planetary Nebula ◽  
Infrared Imaging ◽  
Central Star ◽  
Infrared Images ◽  
Mid Infrared ◽  
Near Ir ◽  
Ir Emission ◽  
Array Camera ◽  
Infrared Array

We present high-resolution near- and mid-infrared images of the planetary nebula IC 418 at 1.2 (J), 1.6 (H), 2.2 (K), 9.8, and 11.7 μm. The near-IR images were obtained with a 64×64 pixel Hg:Cd:Te array camera, and the mid-IR images were obtained using the new 20×64 pixel Mid-Infrared Array Camera (MIRAC). The size of IC 418 in the near-IR is seen to vary with wavelength, being largest at K and smallest at J. Differences in the morphology of the nebula are seen between the J and K images. There is excess near-IR emission in the center of the nebula, after subtracting out the emission from the central star. Faint halo emission is detected at H and K, extending to a total diameter of approximately 40″. The 9.8 μm emission is distributed nonsymmetrically, with the peak in the NE lobe.

scholarly journals Planetary Nebula Evolution Traced by Distance-Independent Parameters

1993 ◽  
Vol 155 ◽  
pp. 480-480
Author(s):  
C.Y. Zhang ◽  
S. Kwok
Keyword(s):  
Physical Properties ◽  
Mass Distribution ◽  
Planetary Nebula ◽  
Strong Support ◽  
Planetary Nebulae ◽  
Central Star ◽  
Evolution Model ◽  
The Core ◽  
Independent Parameters ◽  
Central Stars

Making use of the results from recent infrared and radio surveys of planetary nebulae, we have selected 431 nebulae to form a sample where a number of distance-independent parameters (e.g., Tb, Td, I60μm and IRE) can be constructed. In addition, we also made use of other distance-independent parameters ne and T∗ where recent measurements are available. We have investigated the relationships among these parameters in the context of a coupled evolution model of the nebula and the central star. We find that most of the observed data in fact lie within the area covered by the model tracks, therefore lending strong support to the correctness of the model. Most interestingly, we find that the evolutionary tracks for nebulae with central stars of different core masses can be separated in a Tb-T∗ plane. This implies that the core masses and ages of the central stars can be determined completely independent of distance assumptions. The core masses and ages have been obtained for 302 central stars with previously determined central-star temperatures. We find that the mass distribution of the central stars strongly peaks at 0.6 M⊙, with 66% of the sample having masses <0.64 MM⊙. The luminosities of the central stars are then derived from their positions in the HR diagram according to their core masses and central star temperatures. If this method of mass (and luminosity) determination turns out to be accurate, we can bypass the extremely unreliable estimates for distances, and will be able to derive other physical properties of planetary nebulae.

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.

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