scholarly journals Two New Planetary Nebulae and an AGN in the Galactic Plane

1999 ◽  
Vol 16 (2) ◽  
pp. 134-138 ◽  
Author(s):  
S. H. Beer ◽  
A. E. Vaughan
Keyword(s):  
Radio Emission ◽  
Planetary Nebula ◽  
Galactic Plane ◽  
Angular Size ◽  
Planetary Nebulae ◽  
Optical Spectra ◽  
Radio Flux ◽  
Low Resolution ◽  
5 Ghz

AbstractA search for planetary nebulae was carried out using candidates selected by their infrared colours and 5 GHz radio emission. One new planetary nebula was identified on the basis of its small angular size, strong [O iii] emission and infrared colours. Another object, known as the possible planetary nebula Wray 16–28, is similarly identified as a planetary nebula. An undiscovered AGN was also found, and is classed as a Seyfert 2 galaxy on the basis of its strong O iii emission, linewidths of ∼500 km s−1, and 5 GHz radio flux. Low-resolution optical spectra are presented and distance estimates discussed.

scholarly journals Further Models of Planetary Nebula Spectral Evolution

1993 ◽  
Vol 155 ◽  
pp. 477-477
Author(s):  
K. Volk
Keyword(s):  
Mass Loss ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Central Star ◽  
Radio Flux ◽  
Spectral Evolution ◽  
Star Evolution ◽  
Solar Composition ◽  
5 Ghz ◽  
Galactic Distribution

Four new calculations of planetary nebulae spectral evolution are presented, as in Volk (1992). These models use the 0.64 M⊙ central star evolution track of Schönberner (1983) but with the rate of evolution accelerated by a factor of 2, as the original models evolve to the planetary nebula phase too slowly to match the observations. Models were calculated for mass-loss rates of 2.1 × 10−5 and 5.2 × 10−5 MM⊙ yr−1 using solar composition and silicate dust, and using the average observed planetary nebula composition and graphite dust. An interacting winds shell was assumed to form. The model results were combined with an assumed Galactic distribution of 25000 planetary nebula to simulate a variety of observables including V magnitudes, Hβ fluxes, the IRAS colours, the 5 GHz radio flux densities, and the nebular radii.

scholarly journals The Edinburgh/AAO/Strasbourg Catalogue of Galactic Planetary Nebulae

2003 ◽  
Vol 209 ◽  
pp. 41-41 ◽  
Author(s):  
Q. A. Parker ◽  
M. Hartley ◽  
D. Russeil ◽  
A. Acker ◽  
F. Ochsenbein ◽  
...  
Keyword(s):  
Galactic Plane ◽  
Angular Size ◽  
Planetary Nebulae ◽  
Depth Resolution ◽  
Central Star ◽  
Isolation And Identification ◽  
Large Numbers ◽  
Low Surface Brightness ◽  
Bulge Region ◽  
Version 2.0

We report on version 1.0 of the Edinburgh/AAO/Strasbourg catalogue of new and possible Planetary Nebulae (PN) distributed via cdrom at this meeting. We provide accurate positions, designations, images and other descriptive parameters for the PN. In future releases this will be supplemented by inclusion of spectra and related material such as line ratios, velocities etc.The 900+ PN have been discovered solely from visual scrutiny of narrow-band exposures taken for the AAO/UKST H-alpha survey of the Southern Galactic Plane. Most have classic PN-type morphologies (i.e. bi-polar, rings, shells or ovals). SuperCOSMOS data will soon supersede our visual scanning but it proved an effective preliminary technique to identify candidate PN on the basis of morphology, isolation and identification as an H-alpha nebulosity. We already have confirmatory spectroscopy for ~ 700 objects. Much of our new sample are of very low surface brightness, with no obvious central star, and so have remained undetected in previous surveys. They are revealed here due to the excellent depth, resolution, coverage and uniformity of the H-alpha survey. Many PN are also well extended. The average angular size is 51″ with the median of 27″ but examples extend to several arcminutes. This may indicate many are in a highly evolved state where the central star has faded from easy optical detection and the nebula itself is dissipating into the ambient ISM. Large numbers of candidate PN have also been found in the Galactic Bulge region, most of which have been confirmed via UKST FLAIR/6dF MOS spectroscopy (Parker et al, in preparation and these proceedings).By version 2.0 (release in 2002) we will have doubled the number of Galactic PN accrued from all sources over the last 75 years. This new catalogue should have a profound impact on many aspects of PN research.

scholarly journals Radio Stars of the SKA

Universe ◽  
2021 ◽  
Vol 7 (5) ◽  
pp. 119
Author(s):  
Bin Yu ◽  
Albert Zijlstra ◽  
Biwei Jiang
Keyword(s):  
Radio Emission ◽  
Milky Way ◽  
Galactic Plane ◽  
High Sensitivity ◽  
Hii Regions ◽  
Be Stars ◽  
M Dwarfs ◽  
Ob Stars ◽  
5 Ghz ◽  
Radio Stars

Radio emission from stars can be used, for example, to study ionized winds or stellar flares. The radio emission is faint and studies have been limited to few objects. The Square Kilometer Array (SKA) brings a survey ability to the topic of radio stars. In this paper we investigate what the SKA can detect, and what sensitivity will be required for deep surveys of the stellar Milky Way. We focus on the radio emission from OB stars, Be stars, flares from M dwarfs, and Ultra Compact HII regions. The stellar distribution in the Milky Way is simulated using the Besançon model, and various relations are used to predict their radio flux. We find that the full SKA will easily detect all UltraCompact HII regions. At the limit of 10 nJy at 5 GHz, the SKA can detect 1500 Be stars and 50 OB stars per square degree, out to several kpc. It can also detect flares from 4500 M dwarfs per square degree. At 100 nJy, the numbers become about 8 times smaller. SKA surveys of the Galactic plane should be designed for high sensitivity. Deep imaging should consider the significant number of faint flares in the field, even outside the plane of the Milky Way.

scholarly journals UV and Optical Abundances for a Sample of Southern Galactic Planetary Nebulae

1993 ◽  
Vol 155 ◽  
pp. 571-571
Author(s):  
Robin L. Kingsburgh ◽  
M.J. Barlow
Keyword(s):  
Southern Hemisphere ◽  
Planetary Nebulae ◽  
Optical Spectra ◽  
Uv Spectra ◽  
Low Resolution ◽  
Low Dispersion

We present abundances for a sample of 57 southern hemisphere galactic planetary nebulae (PN). Optical spectra covering the 3100–7400 Å range were obtained at the AAT. Low resolution UV spectra obtained with the IUE satellite were available for half of these objects and were accessed via the IUE Uniform Low–Dispersion Archive. Additionally, new low resolution IUE SWP observations of Fg 1, M 3-1 and M 3-3 were obtained.

Hα and Hβ Imaging of the Planetary Nebula NGC 6302

1990 ◽  
Vol 8 (04) ◽  
pp. 360-363 ◽  
Author(s):  
Michael C. B. Ashley
Keyword(s):  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Central Star ◽  
Infrared Observations ◽  
Dust Extinction ◽  
The Core ◽  
Optical Images ◽  
5 Ghz ◽  
Good Agreement

Abstract NGC 6302 is one of the highest excitation planetary nebulae known. It has an obscured central star with a temperature estimated at 430,000 K. We present here CCD images in Hα and Hβ of NGC 6302, and interpret the differences between the images as being due to extinction caused by dust within the nebula. The dust appears to be concentrated in the core, as expected from infrared observations. There is no evidence of patchy foreground extinction, although there is a slight difference in the average extinction between the eastern and western lobes of the nebula. A comparison between the Hα image and a 5 GHz map gives a dust extinction of ΔAV~3.5 to the central star. The outer contours of the 5 GHz map are not in good agreement with the optical images, and further observations at this frequency would be useful.

scholarly journals A Clustering Method Applied to the Analysis of Planetary Nebulae

1993 ◽  
Vol 155 ◽  
pp. 44-44
Author(s):  
O.S. Yatsyk
Keyword(s):  
Planetary Nebula ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Planetary Nebulae ◽  
Spectral Lines ◽  
Radio Flux ◽  
Clustering Method ◽  
Centroid Method ◽  
Three Dimensional Space

Intensities of the observed spectral lines, radio fluxes and Hβ fluxes are used for the classification of planetary nebulae by centroid method of taxonomical analysis. Two variants of classification are proposed. The first one– in the three–dimensional space of relation of intensity of spectral lines He II λ 4686/HeI λ 4471, [OIII] λ 4959+5007/[OII] λ 3726+29, [OIII] λ 4959+5007/[OIII] 4363. The second variants is the classification in the three-dimensional space with cooordinates being radio flux, Hβ flux and [OIII] λ 4959+5007 intensity. The membership of classes (taxons) are presented. In the diagram joining the planetary nebula descriptors pairwise there are regions of complete (or predominant) of nebulae belonging to the same taxon, but there are also some regions of overlap. The corresponding taxons are not isolated but merge continuously into one another.

scholarly journals The Binary Central Star of Hf 38

2016 ◽  
Vol 12 (S323) ◽  
pp. 382-383
Author(s):  
Helen Barker
Keyword(s):  
Planetary Nebula ◽  
Galactic Plane ◽  
Planetary Nebulae ◽  
Central Star ◽  
Using Data ◽  
The Impact ◽  
Initial Results ◽  
Central Stars

AbstractDespite years of effort, the impact of central star binarity on planetary nebula formation and shaping remains unclear. This is hampered by the fact that detecting central star binarity is inherently difficult, and requires very precise observations. The fraction of planetary nebulae with binary central stars therefore remains elusive. This work presents initial results of central star analysis using data from the VST Hα Survey of the Southern Galactic Plane and Bulge (VPHAS+). The true central star of PN Hf 38 has been revealed, and it exhibits a 0.465±0.334 i band magnitude excess, indicative of a M0V companion.

scholarly journals Planetary Nebulae in M31: Abundances, and comparison with bright Planetary Nebulae in the LMC

1997 ◽  
Vol 180 ◽  
pp. 475-476
Author(s):  
M. G. Richer ◽  
G. Stasińska ◽  
M. L. McCall
Keyword(s):  
Planetary Nebula ◽  
Luminosity Function ◽  
Large Population ◽  
Wavelength Region ◽  
Planetary Nebulae ◽  
Surprising Result ◽  
Population Synthesis ◽  
Abundance Distribution ◽  
Wide Range ◽  
The Mean

We have obtained spectra of 28 planetary nebulae in the bulge of M31 using the MOS spectrograph at the Canada-France-Hawaii Telescope. Typically, we observed the [O II] λ3727 to He I λ5876 wavelength region at a resolution of approximately 1.6 å/pixel. For 19 of the 21 planetary nebulae whose [OIII]λ5007 luminosities are within 1 mag of the peak of the planetary nebula luminosity function, our oxygen abundances are based upon a measured [OIII]λ4363 intensity, so they are based upon a measured electron temperature. The oxygen abundances cover a wide range, 7.85 dex < 12 + log(O/H) < 9.09 dex, but the mean abundance is surprisingly low, 12 + log(O/H)–8.64 ± 0.32 dex, i.e., roughly half the solar value (Anders & Grevesse 1989). The distribution of oxygen abundances is shown in Figure 1, where the ordinate indicates the number of planetary nebulae with abundances within ±0.1 dex of any point on the x-axis. The dashed line indicates the mean abundance, and the dotted lines indicate the ±1 σ points. The shape of this abundance distribution seems to indicate that the bulge of M31 does not contain a large population of bright, oxygen-rich planetary nebulae. This is a surprising result, for various population synthesis studies (e.g., Bica et al. 1990) have found a mean stellar metallicity approximately 0.2 dex above solar. This 0.5 dex discrepancy leads one to question whether the mean stellar metallicity is as high as the population synthesis results indicate or if such metal-rich stars produce bright planetary nebulae at all. This could be a clue concerning the mechanism responsible for the variation in the number of bright planetary nebulae observed per unit luminosity in different galaxies (e.g., Hui et al. 1993).

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 Variable Radio Emission from X-Ray Sources

1971 ◽  
Vol 15 ◽  
pp. 173-175 ◽  
Author(s):  
L. L. E. Braes ◽  
G. K. Miley
Keyword(s):  
Radio Emission ◽  
Aperture Synthesis ◽  
Electromagnetic Spectrum ◽  
Radio Telescopes ◽  
Low Resolution ◽  
X Ray ◽  
Synthesis Technique ◽  
Variable Radio

Dr. KELLOGG has just described some exciting new observations of X-ray sources made with the UHURU satellite. We shall now move some nine orders of magnitude in wavelength to the opposite end of the electromagnetic spectrum and report measurements of weak radio emission from some of the objects he mentioned. For the detection of weak sources most radio telescopes are not noise limited, but are confusion limited by their low resolution. The aperture synthesis technique minimizes this problem because it enables one to pinpoint the position of weak sources to the order of one second of arc.

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