- ID:
- ivo://CDS.VizieR/J/A+A/531/A172
- Title:
- Central stars of planetary nebulae. II.
- Short Name:
- J/A+A/531/A172
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- There are more than 3000 confirmed and probably known Galactic planetary nebulae (PNe), but central star spectroscopic information is available for only 13% of them. We have undertaken a spectroscopic survey of the central stars in PNe to identify their spectral types. We performed spectroscopic observations at low resolution with the 2-m telescope at CASLEO, Argentina. We present the spectra of 46 central stars of PNe, most of them are OB-type and emission-line stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/638/A103
- Title:
- Central stars of planetary nebulae in Gaia DR2
- Short Name:
- J/A+A/638/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate distance measurements are fundamental to the study of planetary nebulae (PNe) but they have long been elusive. The most accurate and model-independent distance measurements for galactic PNe come from the trigonometric parallaxes of their central stars, which were only available for a few tens of objects prior to the Gaia mission. The accurate identification of PN central stars (CSPNe) in the Gaia source catalogues is a critical prerequisite for leveraging the unprecedented scope and precision of the trigonometric parallaxes measured by Gaia. Our aim is to build a complete sample of PN central star detections with minimal contamination. We developed and applied an automated technique based on the likelihood ratio method to match candidate central stars in Gaia Data Release 2 (DR2) to known PNe in the Hong Kong/AAO/Strasbourg H{alpha} (HASH) PN catalogue (Parker et al. 2016, 2016JPhCS.728c2008P), taking into account the BP-RP colours of the Gaia sources as well as their positional offsets from the nebula centres. These parameter distributions for both true central stars and background sources were inferred directly from the data. We present a catalogue of over 1000 Gaia sources that our method has automatically identified as likely PN central stars. We demonstrate how the best matches enable us to trace nebula and central star evolution and to validate existing statistical distance scales, and we discuss the prospects for further refinement of the matching based on additional data. We also compare the accuracy of our catalogue to that of previous works.
- ID:
- ivo://CDS.VizieR/J/ApJ/722/L120
- Title:
- Central surface brightness of 30000 SDSS galaxies
- Short Name:
- J/ApJ/722/L120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Disc central surface brightness for 30000 galaxies from the Sloan Digitized Sky Survey (SDSS) Data Release 7, in the r-band. Virtual Observatory methods and tools were used to define, retrieve and analyze the images for this unprecedentedly large sample classified as spiral galaxies in the LEDA catalogue. These parameters are also available for all other SDSS bands (u,g,i,z), and they can be retrieved from the Author.
- ID:
- ivo://CDS.VizieR/J/ApJ/827/L19
- Title:
- Central surface densities in SPARC disk galaxies
- Short Name:
- J/ApJ/827/L19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the Spitzer Photometry and Accurate Rotation Curves (SPARC) database to study the relation between the central surface density of stars {Sigma}_*_(0) and dynamical mass {Sigma}_dyn_(0) in 135 disk galaxies (S0 to dIrr). We find that {Sigma}_dyn_(0) correlates tightly with {Sigma}_*_(0) over 4dex. This central density relation can be described by a double power law. High surface brightness galaxies are consistent with a 1:1 relation, suggesting that they are self-gravitating and baryon dominated in the inner parts. Low surface brightness (LSB) galaxies systematically deviate from the 1:1 line, indicating that the dark matter contribution progressively increases but remains tightly coupled to the stellar one. The observed scatter is small (~0.2dex) and largely driven by observational uncertainties. The residuals show no correlations with other galaxy properties like stellar mass, size, or gas fraction.
- ID:
- ivo://CDS.VizieR/J/AJ/126/1362
- Title:
- Century Survey Galactic Halo Project. I.
- Short Name:
- J/AJ/126/1362
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Century Survey Galactic Halo Project is a photometric and spectroscopic survey from which we select relatively blue stars (V-R<0.30mag) as probes of the Milky Way halo. The survey strip spans the range of Galactic latitude 35{deg}<b<88{deg}, allowing us to study the nature of populations of stars and their systematic motions as a function of Galactic latitude. One of our primary goals is to use blue horizontal-branch stars to trace potential star streams in the halo, and to test the hierarchical model for the formation of the Galaxy. In this paper we discuss spectroscopy and multipassband photometry for a sample of 764 blue stars in the Century Survey region. Our sample consists predominantly of A- and F-type stars. We describe our techniques for determination of radial velocities, effective temperatures, metallicities, and surface gravities. Based on these measurements, we derive distance estimates by comparison with a set of calibrated isochrones. We devote special attention to the classification of blue horizontal-branch stars, and compare the results obtained from the application of the techniques of Kinman et al. 1994, Cat. <J/AJ/108/1722>, Wilhelm et al. (1999, Cat. <J/AJ/117/2308>), and Clewley et al. (2002MNRAS.337...87C). We identify 55 blue horizontal-branch stars. Our large sample of stars also uncovers a number of unusual objects, including three carbon-enhanced stars, a late B-type star located 0.8kpc above the Galactic plane, and a DZ white dwarf.
2976. Cep A X-Ray sources
- ID:
- ivo://CDS.VizieR/J/ApJ/626/272
- Title:
- Cep A X-Ray sources
- Short Name:
- J/ApJ/626/272
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of X-rays from both components of Cepheus A, East and West, with the XMM-Newton observatory. HH 168 joins the ranks of other energetic Herbig-Haro objects that are sources of T>=10^6^K X-ray emission. We detect 102 X-ray sources, many presumed to be premain-sequence stars on the basis of the reddening of their optical and IR counterparts.
- ID:
- ivo://CDS.VizieR/J/AJ/156/171
- Title:
- Cepheid abund.: multiphase results & spatial gradients
- Short Name:
- J/AJ/156/171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Parameters and abundances have been derived for 435 Cepheids based on an analysis of 1127 spectra. Results from five or more phases are available for 52 of the program stars. The latter set of stars span periods between 1.5 and 68 days. The parameters and abundances show excellent consistency across phase. For iron, the average range in the determined abundance is 0.11 from these 52 stars. For 163 stars with more than one phase available the average range is 0.07. The variation in effective temperature tracks well with phase, as does the total broadening velocity. The gravity and microturbulent velocity follow phase, but with less variation and regularity. Abundance gradients have been derived using Gaia DR2 (Cat. I/345) parallax data, as well as Bayesian distance estimates based upon Gaia DR2 from Bailer-Jones et al. (2018, Cat. I/347). The abundance gradient derived for iron is d[Fe/H]/dR=-0.05 dex/kpc, similar to gradients derived in previous studies.
- ID:
- ivo://CDS.VizieR/J/ApJ/522/802
- Title:
- Cepheid calibration of SN 1989B in NGC 3627
- Short Name:
- J/ApJ/522/802
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Repeated imaging observations have been made of NGC 3627 with the Hubble Space Telescope in 1997 - 1998 over an interval of 58 days. Images were obtained on 12 epochs in the F555W band and on five epochs in the F814W band. The galaxy hosted the prototypical, "Branch normal," type Ia supernova SN 1989B. A total of 83 variables have been found, of which 68 are definite Cepheid variables with periods ranging from 75 to 3.85 days. The dereddened distance modulus is determined to be (m-M)_o_=30.22{+/-}0.12 (internal uncertainty) using a subset of the Cepheid data whose reddening and error parameters are secure.
- ID:
- ivo://CDS.VizieR/J/ApJ/885/161
- Title:
- 90 cepheid candidates nearby NGC 6814
- Short Name:
- J/ApJ/885/161
- Date:
- 08 Mar 2022
- Publisher:
- CDS
- Description:
- We present a Cepheid-based distance to the nearby Seyfert galaxy NGC6814 from Hubble Space Telescope observations. We obtained F555W and F814W imaging over the course of 12 visits with logarithmic time spacing in 2013 August-October. We detected and made photometric measurements for 16469 unique sources across all images in both filters, from which we identify 90 excellent Cepheid candidates spanning a range of periods of 13-84days. We find evidence for incompleteness in the detection of candidates at periods <21days. Based on the analysis of Cepheid candidates above the incompleteness limit, we determine a distance modulus for NGC6814 relative to the LMC of {mu}_rel,LMC_=13.200_-0.031_^+0.031^mag. Adopting the recent constraint of the distance modulus to the LMC determined by Pietrzynski et al., we find m-M=31.677_-0.041_^+0.041^ which gives a distance of 21.65{+/-}0.41Mpc to NGC6814.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A8
- Title:
- Cepheid period-luminosity-metallicity relation
- Short Name:
- J/A+A/619/A8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use parallax data from the Gaia second data release (GDR2), combined with parallax data based on HIPPARCOS and HST data, to derive the period-luminosity-metallicity (PLZ) relation for Galactic classical cepheids (CCs) in the V, K, and Wesenheit WVK bands. An initial sample of 452 CCs are extracted from the literature with spectroscopically derived iron abundances. Reddening values, classifications, pulsation periods, and mean V- and K-band magnitudes are taken from the literature. Based on nine CCs with a goodness-of-fit (GOF) statistic smaller than 8 and with an accurate non-Gaia parallax ({sigma}_{pi}_ comparable to that in GDR2), a parallax zero-point offset of -0.049+/-0.018mas is derived. Selecting a GOF statistic smaller than 8 removes about 40% of the sample most likely related due to binarity. Excluding first overtone and multi-mode cepheids and applying some other criteria reduces the sample to about 200 stars. The derived PL(Z) relations depend strongly on the parallax zero-point offset. The slope of the PL relation is found to be different from the relations in the LMC at the 3{sigma} level. Fixing the slope to the value found in the LMC leads to a distance modulus (DM) to the LMC of order 18.7mag, larger than the canonical distance. The canonical DM of around 18.5 mag would require a parallax zero-point offset of order -0.1mas. Given the strong correlation between zero point, period and metallicity dependence of the PL relation, and the parallax zero-point offset there is no evidence for a metallicity term in the PLZ relation. The GDR2 release does not allow us to improve on the current distance scale based on CCs. The value of and the uncertainty on the parallax zero-point offset leads to uncertainties of order 0.15mag on the distance scale. The parallax zero-point offset will need to be known at a level of 3{mu}as or better to have a 0.01mag or smaller effect on the zero point of the PL relation and the DM to the LMC.