Search

Start Over Subject planetary nebulae
61. CoRoT space mission. I.
ID:
ivo://CDS.VizieR/J/A+A/482/L17
Title:
CoRoT space mission. I.
Short Name:
J/A+A/482/L17
Date:
21 Oct 2021
Publisher:
CDS
Description:
The pioneer space mission for photometric planet searches, CoRoT, steadily monitors about 12000 stars in each of its fields of view. Transit candidates can be detected early in the processing of the data and before the end of a run of observation. We report the detection of the first planet discovered by CoRoT and characterizing it with the help of follow-up observations.
62. CRL618, MWC922 and M2-9 RRL spectra
ID:
ivo://CDS.VizieR/J/A+A/603/A67
Title:
CRL618, MWC922 and M2-9 RRL spectra
Short Name:
J/A+A/603/A67
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the results from a pilot search for radio recombination line (RRL) emission at millimeter wavelengths in a small sample of pre-planetary nebulae (pPNe) and young PNe (yPNe) with emerging central ionized regions. Observations of the H30{alpha}, H31{alpha}, H39{alpha}, H41{alpha}, H48{beta}, H49{beta}, H51{beta}, and H55{gamma} lines at ~1 and ~3mm have been performed with the IRAM 30m radio telescope. These lines are excellent probes of the dense inner (<~150 au) and heavily obscured regions of these objects, where the yet unknown agents for PN-shaping originate. We detected mm-RRLs in three objects: CRL 618, MWC922, and M2-9. For CRL 618, the only pPN with previous published detections of H41{alpha}, H35{alpha}, and H30{alpha} emission, we find significant changes in the line profiles indicating that current observations are probing regions of the ionized wind with larger expansion velocities and mass-loss rate than ~29 years ago. In the case of MWC922, we observe a drastic transition from single-peaked profiles at 3mm (H39{alpha} and H41{alpha}) to double-peaked profiles at 1mm (H31{alpha} and H30{alpha}), which is consistent with maser amplification of the highest frequency lines; the observed line profiles are compatible with rotation and expansion of the ionized gas, probably arranged in a disk+wind system around a ~5-10M_{sun}_ central mass. In M2-9, the mm-RRL emission appears to be tracing a recent mass outburst by one of the stars of the central binary system. We present the results from non-LTE line and continuum radiative transfer models, which enables us to constrain the structure, kinematics, and physical conditions (electron temperature and density) of the ionized cores of our sample. We find temperatures Te~6000-17000K, mean densities ne~10^5^-10^8^cm^-3^, radial density gradients ne{prop.to}r^-alpha_n_^ whit alpha_n_~2-3.5, and motions of velocities of ~10-30km/s in the ionized wind regions traced by these mm-wavelength observations. We deduce mass-loss rates of dM_pAGB_/dt~=10^-6^-10^-7^M_{sun}_/yr, which are significantly higher than the values adopted by stellar evolution models currently in use and would result in a transition from the asymptotic giant branch to the PN phase faster than hitherto assumed.
63. Crystalline silicates around evolved stars
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.
64. Deep echelle spectrophotometry of NGC3918
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.
65. Deep spectroscopy of NGC 7009
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.
66. Discovery of PNe in M82
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.
67. Distances and physical parameters of PNe
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).
68. Distances of galactic planetary nebulae
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.
69. Distances of galactic planetary nebulae
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.
70. Distances of planetary nebula
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_.