- ID:
- ivo://CDS.VizieR/J/A+A/640/A10
- Title:
- Catalogue of planetary nebulae central stars
- Short Name:
- J/A+A/640/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Planetary nebulae represent a potential late stage of stellar evolution, however, their central stars (CSPNe) are relatively faint and, therefore, pertinent information is available for merely <20% of the Galactic sample. Consequently, the literature was surveyed to construct a new catalogue of 620 CSPNe featuring important spectral classifications and information. The catalogue supersedes the existing iteration by 25% and includes physical parameters such as luminosity, surface gravity, temperature, magnitude estimates, and references for published spectra. The marked statistical improvement enabled the following pertinent conclusions to be determined: the H-rich/H-poor ratio is 2:1, there is a deficiency of CSPNe with types [WC 5-6], and nearly 80% of binary central stars belong to the H-rich group. The last finding suggests that evolutionary scenarios leading to the formation of binary central stars interfere with the conditions required for the formation of H-poor CSPN. Approximately 50% of the sample with derived values of logL, logT_eff_, and logg, exhibit masses and ages consistent with single stellar evolutionary models. The implication is that single stars are indeed able to form planetary nebulae. Moreover, it is shown that H-poor CSPNe are formed by higher mass progenitors.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/169/353
- Title:
- Chandra sources in M17
- Short Name:
- J/ApJS/169/353
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report here results from a Chandra ACIS observation of the stellar populations in and around the M17 HII region. The field reveals 886 sources with observed X-ray luminosities (uncorrected for absorption) between ~29.3ergs/s<logL_X_<32.8ergs/s, 771 of which have stellar counterparts in infrared images.
- ID:
- ivo://CDS.VizieR/J/A+A/490/1055
- Title:
- Chandra survey of Tr 16 low-mass stars
- Short Name:
- J/A+A/490/1055
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify and characterize low-mass stars in the ~3Myr old Trumpler 16 region by means of a deep Chandra X-ray observation, and study their optical and near-IR properties. We compare the X-ray activity of Trumpler 16 stars with the known characteristics of Orion and Cygnus OB2 stars. We analyzed a 88.4ks Chandra ACIS-I observation pointed at the center of Trumpler 16. Because of diffuse X-ray emission, source detection was performed using the PWDetect code for two different energy ranges: 0.5-8.0keV and 0.9-8.0keV. Results were merged into a single final list. We positionally correlated X-ray sources with optical and 2MASS catalogs. Source events were extracted with the IDL-based routine ACIS-Extract. X-ray variability was characterized using the Kolmogorov-Smirnov test and spectra were fitted by using XSPEC. The X-ray spectra of early-type, massive stars were analyzed individually. Our list of X-ray sources consists of 1035 entries, 660 of which have near-IR counterparts and are probably associated with Trumpler 16 members.
- ID:
- ivo://CDS.VizieR/J/A+A/367/86
- Title:
- Chemical abundances of 5 Galactic disk B stars
- Short Name:
- J/A+A/367/86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution, high signal-to-noise spectral data are presented for four young B-type stars lying towards the Galactic Centre. Determination of their atmospheric parameters from their absorption line profiles, and uvby photometric measurement of the continua indicate that they are massive objects lying slightly out of the plane, and were probably born in the disk between 2.5-5kpc from the Centre. We have carried out a detailed absolute and differential line-by-line abundance analyses of the four stars compared to two stars with very similar atmospheric parameters in the solar neighbourhood. The stars appear to be rich in all the well sampled chemical elements (C, N, Si, Mg, S, Al), except for oxygen. Oxygen abundances derived in the atmospheres of these four stars are very similar to that in the solar neighbourhood. If the photospheric composition of these young stars is reflective of the gaseous ISM in the inner Galaxy, then the values derived for the enhanced metals are in excellent agreement with the extrapolation of the Galactic abundance gradients previously derived by Rolleston et al. (2000A&A...363..537R) and others. However, the data for oxygen suggests that the inner Galaxy may not be richer than normal in this element, and the physical reasons for such a scenario are unclear.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A49
- Title:
- Chemical analysis of early-type stars with planets
- Short Name:
- J/A+A/647/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed a detailed abundance determination in a sample of early-type stars with and without planets via spectral synthesis, searching for a likely relation between lambda Bootis stars and the presence of planets. We found no unique chemical pattern for the group of early-type stars bearing giant planets. However, our results support, in principle, a suggested scenario in which giant planets orbiting pre-main-sequence stars possibly block the dust of the disk and result in a lambda Bootis-like pattern. On the other hand, we do not find a lambda Bootis pattern in different hot-Jupiter planet host stars, which does not support the idea of possible accretion from the winds of hot-Jupiters, recently proposed in the literature. As a result, other mechanisms should account for the presence of the lambda Bootis pattern between main-sequence stars. Finally, we suggest that the formation of planets around lambda Bootis stars, such as HR 8799 and HD 169142, is also possible through the core accretion process and not only gravitational instability.
- ID:
- ivo://CDS.VizieR/J/A+A/459/871
- Title:
- Chemically peculiar stars in the LMC
- Short Name:
- J/A+A/459/871
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high precision photometric Delta a observations of 417 objects in NGC 2136/7 and its surrounding field, of which five turned out to be bona fide magnetic CP stars. In addition, we discovered two Be/Ae stars. This intermediate band photometric system samples the depth of the 520nm flux depression by comparing the flux at the center with the adjacent regions with bandwidths of 11nm to 23nm. The Delta a photometric system is most suitable for detecting CP2 stars with high efficiency, but is also capable of detecting a small percentage of non-magnetic CP objects. From our investigations of NGC 1711, NGC 1866, NGC 2136/7, their surroundings, and one independent field of the LMC population, we derive an occurrence of classical chemically peculiar stars of 2.2(6)% in the LMC, which is only half the value found in the Milky Way. The mass and age distribution of the photometrically detected CP stars is not different from that of similar objects in galactic open clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A198
- Title:
- CHIPS II. O stars in Trumpler 14 CHIPS-Tr14
- Short Name:
- J/A+A/658/A198
- Date:
- 25 Feb 2022 07:07:49
- Publisher:
- CDS
- Description:
- Most massive stars belong to multiple systems, yet the formation process leading to such high multiplicity remain insufficiently understood. To help constrain the different formation scenarios that exist, insights on the low-mass end of the companion mass function of such stars is crucial. However, this is a challenging endeavour as (sub-)solar mass companions at angular separations {rho} below 1" (corresponding to 1000-3000au in nearby young open clusters and OB associations) are difficult to detect due to the large brightness contrast with the central star. With the Carina High-contrast Imaging Project of massive Stars (CHIPS), we aim to obtain statistically significant constraints on the presence and properties of low-mass companions around massive stars at a previously unreachable observing window ({Delta}mag>=10 at {rho}<= 1"). In this second paper in the series, we focus on the Trumpler 14 cluster, which harbours some of the youngest and most massive O-type stars in the Milky Way. We obtained VLT-SPHERE observations of seven O-type objects in Trumpler 14 using the IRDIFS_EXT mode. These allow us to search for companions at separations larger than 0.15" (~360au) and down to magnitude contrast >10 mag in the near-infrared. We used angular and spectral differential imaging along with PSF fitting to detect sources and measure their flux relative to that of the central object. We detected 211 sources with near-infrared magnitude contrast in the range of 2 to 12. The closest companion, at only 0.26", is characterised as a 1.4M_{sun}_ stars with an age of 0.6Myr, in excellent agreement with previous age estimates for Tr14. The mass function peaks at about 0.4M_{sun}_ and presents a dearth of stars in the 0.5 to 0.8M_{sun}_ mass range compared to previous estimates of the initial mass function in Tr14.
- ID:
- ivo://CDS.VizieR/J/AZh/73/194
- Title:
- Circumstellar Disks of Ae/Be Herbig Stars
- Short Name:
- J/AZh/73/194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The data of the photo-polarimetric activity of Ae/Be Herbig stars and the types of Ha profiles observed in their spectra was carried out using data from the literature. The analysis of the data supports the presence of a relationship between the type of Ha profile and the level of photo-polarimetric activity in young stars.
- ID:
- ivo://CDS.VizieR/J/A+A/524/A44
- Title:
- CN and CH line strengths in 12 globulars
- Short Name:
- J/A+A/524/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Globular clusters show star-to-star abundance variations for light elements that are not yet well understood. The preferred explanation involves a self-enrichment scenario, within which two subsequent generations of stars co-exist in globular clusters. Observations of chemical abundances in the main sequence and sub-giant branch stars allow us to investigate the signature of this chemically processed material without the complicating effects caused by stellar evolution and internal mixing. Our main goal is to investigate the carbon-nitrogen anti-correlation with low-resolution spectroscopy of 20-50 stars fainter than the first dredge-up in seven Galactic globular clusters (NGC288, NGC1851, NGC5927, NGC6352, NGC6388, and Pal12) with different properties. We complemented our observations with 47Tuc archival data, with four additional clusters from the literature (M15, M22, M55, NGC362), and with additional literature data on NGC288.
- ID:
- ivo://CDS.VizieR/J/A+A/536/A63
- Title:
- Collinder 69 very low mass stars and brown dwarfs
- Short Name:
- J/A+A/536/A63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have studied age dependent features in optical and near-infrared spectra of candidate members to the cluster (such as alkali lines and accretion associated indicators). In addition, we have complemented that study with the analysis of other youth indicators like X-ray emission or mid-infrared excess. We have confirmed the membership to Collinder 69 of ~90 photometric candidate members. As a byproduct we have determined a temperature scale for young M, very low-mass stars and brown dwarfs. We have assembled one of the most complete Initial Mass Functions from 0.016 to 20M_{sun}_. And, finally, we have studied the implications of the spatial distribution of the confirmed members on the proposed mechanisms of brown dwarfs formation.
