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71. Distances of planetary nebulae
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.
72. Dust classification in Galactic 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.
73. EFOSC photometry of M3-2
ID:
ivo://CDS.VizieR/J/A+A/619/A84
Title:
EFOSC photometry of M3-2
Short Name:
J/A+A/619/A84
Date:
21 Oct 2021
Publisher:
CDS
Description:
Bipolar planetary nebulae (PNe) are thought to result from binary star interactions and, indeed, tens of binary central stars of PNe have been found, in particular using photometric time-series that allow detecting post-common envelope systems. Using photometry at the NTT in La Silla we have studied the bright object close to the centre of PN M3-2 and found it to be an eclipsing binary with an orbital period of 1.88 days. However, the components of the binary appear to be two A or F stars, of almost equal masses, and are thus too cold to be the source of ionisation of the nebula. Using deep images of the central star obtained in good seeing, we confirm a previous result that the central star is more likely a much fainter star, located 2 arcsec away from the bright star. The eclipsing binary is thus a chance alignment on top of the planetary nebula. We also studied the nebular abundance and confirm it to be a Type I PN.
74. EMILI line-identification in IC 418 spectrum
ID:
ivo://CDS.VizieR/J/ApJS/149/157
Title:
EMILI line-identification in IC 418 spectrum
Short Name:
J/ApJS/149/157
Date:
21 Oct 2021
Publisher:
CDS
Description:
The identification of spectral lines can be a tedious process requiring the interrogation of large spectroscopic databases, but it does lend itself to software algorithms that can determine the characteristics of candidate line identifications. We present here criteria used for the identification of lines and a logic developed for a line identification software package called EMILI, which uses the v2.04 Atomic Line List as the basic line database. EMILI considers all possible database transitions within the wavelength uncertainties for observed optical emission lines and computes an approximate intensity for each candidate line. It searches for other multiplet members that are expected to be seen with each candidate line, and rank-orders all of the tentative line identifications for each observed line based on a set of criteria. When applied to the spectra of the Orion Nebula and the planetary nebula IC 418, EMILI's recommended line IDs agree well with those of previous traditional manual line assignments. The existence of a semiautomated procedure should give impetus to the study of very high signal-to-noise spectra, enabling the identification of previously unidentified spectral lines to be handled with ease and consistency.
75. Emission lines in 4 planetary nebulae
ID:
ivo://CDS.VizieR/J/ApJ/659/1265
Title:
Emission lines in 4 planetary nebulae
Short Name:
J/ApJ/659/1265
Date:
21 Oct 2021
Publisher:
CDS
Description:
The s-process should occur in all but the lower mass progenitor stars of planetary nebulae, and this should be reflected in the chemical composition of the gas that is expelled to create the current planetary nebula shell. Weak forbidden emission lines are expected from several s-process elements in these shells and have been searched for and in some cases detected in previous investigations. Here we extend these studies by combining very high signal-to-noise ratio echelle spectra of a sample of PNe with a critical analysis of the identification of the emission lines of Z>30 ions. Emission lines of Br, Kr, Xe, Rb, Ba, and Pb are detected with a reasonable degree of certainty in at least some of the objects studied here, and we also tentatively identify lines from Te and I, each in one object. The strengths of these lines indicate enhancement of s-process elements in the central star progenitors, and we determine the abundances of Br, Kr, and Xe, elements for which atomic data relevant for abundance determination have recently become available. As representative elements of the "light" and "heavy" s-process peaks, Kr and Xe exhibit similar enhancements over solar values, suggesting that PN progenitors experience substantial neutron exposure.
76. Emission-line stars and PNe in the SMC
ID:
ivo://CDS.VizieR/J/A+AS/102/451
Title:
Emission-line stars and PNe in the SMC
Short Name:
J/A+AS/102/451
Date:
21 Oct 2021
Publisher:
CDS
Description:
An objective-prism survey of the Small Magellanic Cloud (SMC) has been performed through an H-{alpha} + [NII] interference filter, using the 90cm Curtis Schmidt telescope of Cerro Tololo. 1898 emission-line objects have been detected in the main body of this galaxy, almost quadrupling the number of those found in the same region by the previous objective-prism surveys. Among these objects are newly discovered planetary nebulae, compact HII regions and late-type stars. Continuum intensity, as well as the shape and relative strength of the H-{alpha} emission-line have been estimated; coordinates, cross-identifications for the listed objects are provided. The original paper contains in addition finding charts.
77. Evolved stars in the MSX survey
ID:
ivo://CDS.VizieR/J/A+A/431/565
Title:
Evolved stars in the MSX survey
Short Name:
J/A+A/431/565
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the evolution of oxygen- and carbon-rich AGB stars, post-AGB objects, and planetary nebulae using data collected mainly from the MSX catalogue. Magnitudes and colour indices are compared with those calculated from a grid of synthetic spectra that describe the post-AGB evolution beginning at the onset of the superwind.
78. Extended sources in SCORPIO at 2.1GHz
ID:
ivo://CDS.VizieR/J/MNRAS/490/5063
Title:
Extended sources in SCORPIO at 2.1GHz
Short Name:
J/MNRAS/490/5063
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalogue of a large sample of extended radio sources in the Stellar Continuum Originating from Radio Physics In Ourgalaxy (SCORPIO) field, observed and resolved by the Australia Telescope Compact Array. SCORPIO, a pathfinder project for addressing the early operations of the Australia SKA Pathfinder, is a survey of ~5 square degrees between 1.4 and 3.1GHz, centred at l=343.5{deg}, b=0.75{deg}, and with an angular resolution of about 10 arcsec. It is aimed at understanding the scientific and technical challenges to be faced by future Galactic surveys. With a mean sensitivity around 100uJy/beam and the possibility to recover angular scales at least up to 4 arcmin, we extracted 99 extended sources, 35 of them detected for the first time. Among the 64 known sources 55 had at least a tentative classification in literature. Studying the radio morphology and comparing the radio emission with infrared we propose as candidates six new HII regions, two new planetary nebulae, two new luminous blue variable or Wolf-Rayet stars, and three new supernova remnants. This study provides an overview of the potentiality of future radio surveys in terms of Galactic source extraction and characterization and a discussion on the difficulty to reduce and analyse interferometric data on the Galactic plane.
79. Extremely faint planetary nebulae in SDSS
ID:
ivo://CDS.VizieR/J/MNRAS/436/718
Title:
Extremely faint planetary nebulae in SDSS
Short Name:
J/MNRAS/436/718
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using ~1700000 target- and sky-fibre spectra from the Sloan Digital Sky Survey (SDSS), we have carried out a systematic search for Galactic planetary nebulae (PNe) via detections of the [OIII] {lambda}{lambda}4959, 5007 lines. Thanks to the excellent sensitivity of the SDSS spectroscopic surveys, this is by far the deepest search for PNe ever taken, reaching a surface brightness of the [OIII] {lambda}5007 line down to about 29.0mag/arcsec^2^. The search leads to the recovery of 13 previously known PNe in the Northern and Southern Galactic Caps. In total, 44 new PN candidates are identified, including seven candidates of multiple detections and 37 candidates of single detection. The seven candidates of multiple detections are all extremely large (between 21 and 154arcmin) and faint, located mostly in the low Galactic latitude region and with a kinematics similar to disc stars. After checking their images in H{alpha} and other bands, three of them are probably HII regions, one is probably associated with a new supernova remnant, another one is possibly a true PN and the remaining two could be either PNe or supernova remnants. Based on sky positions and kinematics, seven candidates of single detection probably belong to the halo population. If confirmed, they will increase the number of known PNe in the Galactic halo significantly. All the newly identified PN candidates are very faint, with a surface brightness of the [OIII] {lambda}5007 line between 27.0-30.0mag/arcsec^2^, and very challenging to be discovered with previously employed techniques (e.g. slitless spectroscopy, narrow-band imaging), and thus may greatly increase the number of `missing' faint PNe. Our results demonstrate the power of large-scale fibre spectroscopy in hunting for ultrafaint PNe and other types of emission line nebulae. Combining the large spectral data bases provided by the SDSS and other on-going projects (e.g. the LAMOST Galactic surveys), it is possible to build a statistically meaningful sample of ultrafaint, large, evolved PNe, thus, improving the census of Galactic PNe.
80. Faint planetary nebulae in Magellanic Clouds
ID:
ivo://CDS.VizieR/J/ApJ/417/209
Title:
Faint planetary nebulae in Magellanic Clouds
Short Name:
J/ApJ/417/209
Date:
21 Oct 2021
Publisher:
CDS
Description:
The accuracy of spectrophotometry for Magellanic Cloud planetary nebulae is limited by a number of physical effects and operational difficulties: atmospheric dispersion, wavelength-dependent seeing, pointing and guiding errors, and a background of numerous stars and diffuse emission. We describe procedures to minimize the impact of some of these. We then compare our results for both bright and faint objects with published values. There are a few exceptional cases (e.g., LMC 89), but generally we find that bright planetary nebulae in the Clouds have been observed with high accuracy. On the other hand, observations of the faint sample from Jacoby (1980ApJS...42....1J) suffer seriously from many of these effects. We also compare published {lambda}5007 photometry with new CCD photometry for nine faint planetary nebulae. We find the photographic photometry presented by Jacoby (1980ApJS...42....1J) to be accurate to 0.26mag. Fluxes for the fainter objects that are derived from spectrophotometry (Boroson & Liebert, 1989ApJ...339..844B) are found to be less reliable. In comparison, spectrophotometry using the observational techniques presented in this paper provides reliable absolute fluxes. With these improved observations, we review the correlations presented by Kaler & Jacoby (1990ApJ...362..491K, 1991ApJ...382..134K) between abundance ratios and central star mass. The new results fit our earlier correlation for N/O, strengthen that for He/H, and change little about those for C/O and O/H.