- ID:
- ivo://CDS.VizieR/J/A+A/382/184
- Title:
- Crystalline silicates around evolved stars
- Short Name:
- J/A+A/382/184
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the first paper in a series of three where we present the first comprehensive inventory of solid state emission bands observed in a sample of 17 oxygen-rich circumstellar dust shells surrounding evolved stars. The data were taken with the Short and Long Wavelength Spectrographs on board of the Infrared Space Observatory (ISO) and cover the 2.4 to 195{mu}m wavelength range. The spectra show the presence of broad 10 and 18{mu}m bands that can be attributed to amorphous silicates. In addition, at least 49 narrow bands are found whose position and width indicate they can be attributed to crystalline silicates. Almost all of these bands were not known before ISO.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/452/2606
- Title:
- Deep echelle spectrophotometry of NGC3918
- Short Name:
- J/MNRAS/452/2606
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The chemical content of the planetary nebula NGC 3918 is investigated through deep, high-resolution (R~40000) UVES (Ultraviolet-Visual Echelle Spectrograph) at VLT (Very Large Telescope) spectrophotometric data. We identify and measure more than 750 emission lines, making ours one of the deepest spectra ever taken for a planetary nebula. Among these lines we detect very faint lines of several neutron-capture elements (Se, Kr, Rb, and Xe), which enable us to compute their chemical abundances with unprecedented accuracy, thus constraining the efficiency of the s-process and convective dredge-up in NGC 3918 progenitor star. We find that Kr is strongly enriched in NGC 3918 and that Se is less enriched than Kr, in agreement with the results of previous papers and with predicted s-process nucleosynthesis. We also find that Xe is not as enriched by the s-process in NGC 3918 as is Kr and, therefore, that neutron exposure is typical of modestly subsolar metallicity asymptotic giant branch (AGB) stars. A clear correlation is found when representing [Kr/O] versus log(C/O) for NGC 3918 and other objects with detection of multiple ions of Kr in optical data, confirming that carbon is brought to the surface of AGB stars along with s-processed material during third dredge-up episodes, as predicted by nucleosynthesis models. We also detect numerous refractory element lines (Ca, K, Cr, Mn, Fe, Co, Ni, and Cu) and a large number of metal recombination lines of C, N, O, and Ne. We compute physical conditions from a large number of diagnostics, which are highly consistent among themselves assuming a three-zone ionization scheme. Thanks to the high ionization of NGC 3918 we detect a large number of recombination lines of multiple ionization stages of C, N, O and Ne. The abundances obtained for these elements by using recently determined state-of-the-art ionization correction factor (ICF) schemes or simply adding ionic abundances are in very good agreement, demonstrating the quality of the recent ICF scheme for high-ionization planetary nebulae.
- ID:
- ivo://CDS.VizieR/J/MNRAS/415/181
- Title:
- Deep spectroscopy of NGC 7009
- Short Name:
- J/MNRAS/415/181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present very deep CCD spectrum of the bright, medium-excitation planetary nebula NGC 7009, with a wavelength coverage from 3040 to 11000{AA}. Traditional emission line identification is carried out to identify all the emission features in the spectra, based on the available laboratory atomic transition data. Since the spectra are of medium resolution, we use multi-Gaussian line profile fitting to deblend faint blended lines, most of which are optical recombination lines (ORLs) emitted by singly ionized ions of abundant second-row elements such as C, N, O and Ne.
- ID:
- ivo://CDS.VizieR/J/ApJ/697/1138
- Title:
- Discovery of PNe in M82
- Short Name:
- J/ApJ/697/1138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using an [OIII]{lambda}5007 on-band/off-band filter technique, we identify 109 planetary nebulae (PNe) candidates in the edge-on spiral galaxy M 82, using the FOCAS instrument at the 8.2m Subaru Telescope. The use of ancillary high-resolution Hubble Space Telescope Advanced Camera for Surveys H{alpha} imaging aided in confirming these candidates, helping to discriminate PNe from contaminants such as supernova remnants and compact HII regions. Once identified, these PNe reveal a great deal about the host galaxy; our analysis covers kinematics, stellar distribution, and distance determination. Radial velocities were determined for 94 of these PNe using a method of slitless spectroscopy, from which we obtain a clear picture of the galaxy's rotation.
- ID:
- ivo://CDS.VizieR/J/AZh/74/853
- Title:
- Distances and physical parameters of PNe
- Short Name:
- J/AZh/74/853
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The distances and parameters of the central stars and the optical depth of envelopes in the Lyman limits of neutral hydrogen and neutral helium were determined in a self-consistent way for 170 galactic planetary nebulae. The generalized energy-balance method was used (Mal'kov, 1994KFNT...10e..35M).
- ID:
- ivo://CDS.VizieR/J/ApJ/689/194
- Title:
- Distances of galactic planetary nebulae
- Short Name:
- J/ApJ/689/194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galactic planetary nebula (PN) distances are derived, except in a small number of cases, through the calibration of statistical properties of PNs. Such calibrations are limited by the accuracy of individual PN distances, which are obtained with several nonhomogeneous methods, each carrying its own set of liabilities. In this paper we use the physical properties of the PNs in the Magellanic Clouds and their accurately known distances to recalibrate the Shklovsky/Daub (1982ApJ...260..612D) distance technique. Our new calibration is very similar (within 1%) to the commonly used distance scale by Cahn et al. (1992, Cat. J/A+AS/94/399), although there are important differences. We present a catalog of Galactic PN distances using our recalibration, which can be used for future applications, and compare the best individual Galactic PN distances to our new and several other distance scales, both in the literature and newly recalibrated by us, finding that our scale is the most reliable to date.
- ID:
- ivo://CDS.VizieR/J/AJ/115/1989
- Title:
- Distances of galactic planetary nebulae
- Short Name:
- J/AJ/115/1989
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is well known that the IRAS colors of planetary nebulae (PNe) are very similar to blackbody colors. Taking account of this characteristic, we define a new method to obtain some information about the distance to PNe by blackbody fitting of IRAS four-band fluxes, assuming these fluxes are due to thermal emission from the nebular dust envelope. The fit should have two free parameters - the dust temperature TD and the distance-dependent "scaling factor" A - under the assumption of uniform dust mass. We find that the A-values have a good correlation with published distances. The scaling factor A could be a more effective distance scale than others, because many PNe have been detected as IRAS sources and the extinction of IRAS fluxes is not so severe, and is known. We also find that TD is concentrated between 100 and 200K, with a typical value of about 150K.
- ID:
- ivo://CDS.VizieR/J/MNRAS/353/589
- Title:
- Distances of planetary nebula
- Short Name:
- J/MNRAS/353/589
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The distances of planetary nebulae (PNe) are still quite uncertain. Although observational estimates are available for a small proportion of PNe, based on statistical parallax and the like, such distances are very poorly determined for the majority of galactic PNe. In particular, estimates of so-called 'statistical' distance appear to differ by factors of ~2.7. We point out that there is a well-defined correlation between the 5-GHz luminosity of the sources, L_5_, and their brightness temperatures, T_B_.
- ID:
- ivo://CDS.VizieR/J/ApJ/459/606
- Title:
- Distances of planetary nebulae
- Short Name:
- J/ApJ/459/606
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe an improved method for determining the distances of planetary nebulae (PNe) based on a theoretical/empirical relationship between their radii and radio surface brightness. Like the Shklovsky (constant mass) distance method, our relationship requires only radio flux density and angular size measurements, which are widely available in the literature. Based on models matching the overall Galactic distribution of PNe, we determine how PNe observed in the direction of the Galactic center are actually distributed relative to the bulge in order to establish the usefulness of these PNe for distance studies. We then use the bulge PNe along with PNe with independent distances to establish, calibrate, and test the accuracy of the method. When compared to the best available data our distance method appears to yield distance errors consistent with a scatter of <25% (1{sigma}). And, based on our models scaled to local PNe, we find a mean Galactic center distance of 8.3+/-2.6kpc for the bulge PNe. The relationship that PNe exhibit between radius and surface brightness is in excellent agreement with our simulated nebulae from Paper I (Buckley & Schneider, 1995ApJ...446..279B). We find that no simple power law can describe the changing mass and radius of a PN as it ages; however, our empirical relationship has a limiting behavior that is almost indistinguishable from the assumption made in Shklovsky's distance method that PNe have a constant ionized mass. We reexamine the dispute about the validity of the Shklovsky's distance method as applied to Galactic center PNe in light of these results, and we argue that the Shklovsky method does predict the distances of large, low surface brightness PNe well, but it increasingly overestimates the distance of smaller PNe.
- ID:
- ivo://CDS.VizieR/J/ApJ/753/172
- Title:
- Dust classification in Galactic PNe
- Short Name:
- J/ApJ/753/172
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Spitzer/Infrared Spectrograph (IRS) spectra of 157 compact Galactic planetary nebulae (PNe). These young PNe provide insight on the effects of dust in early post-asymptotic giant branch evolution, before much of the dust is altered or destroyed by the hardening stellar radiation field. Most of the selected targets have PN-type IRS spectra, while a few turned out to be misclassified stars. We inspected the group properties of the PN spectra and classified them based on the different dust classes (featureless or F, carbon-rich dust or CRD, oxygen-rich dust or ORD, mixed-chemistry dust or MCD) and subclasses (aromatic and aliphatic, and crystalline and amorphous). All PNe are characterized by dust continuum and more than 80% of the sample shows solid-state features above the continuum, in contrast with the Magellanic Cloud sample where only ~40% of the entire sample displays solid-state features; this is an indication of the strong link between dust properties and metallicity.
