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- ID:
- ivo://CDS.VizieR/J/A+A/524/A6
- Title:
- Evolution of spectral early-type galaxies
- Short Name:
- J/A+A/524/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the evolution of spectral early-type galaxies in clusters, groups, and the field up to redshift 0.9 using the ESO Distant Cluster Survey (EDisCS) dataset. We measure structural parameters (circularized half-luminosity radii Re, surface brightness Ie, and velocity dispersions sigma) for 154 cluster and 68 field galaxies. On average, we achieve precisions of 10% in Re, 0.1dex in logIe, and 10% in sigma. We sample ~20% of cluster and ~10% of field spectral early-type galaxies to an I band magnitude in a 1arcsec radius aperture as faint as I1=22. We study the evolution of the zero point of the fundamental plane (FP) and confirm results in the literature, but now also for the low cluster velocity dispersion regime.
- ID:
- ivo://CDS.VizieR/J/ApJ/699/603
- Title:
- Evolution of Swift/BAT blazars
- Short Name:
- J/ApJ/699/603
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use three years of data from the Swift/Burst Alert Telescope (BAT) survey to select a complete sample of X-ray blazars above 15keV. This sample comprises 26 flat-spectrum radio quasars (FSRQs) and 12 BL Lacertae (BL Lac) objects detected over a redshift range of 0.03<z<4.0. We use this sample to determine, for the first time in the 15-55keV band, the evolution of blazars. We find that, contrary to the Seyfert-like active galactic nuclei (AGNs) detected by BAT, the population of blazars shows strong positive evolution. This evolution is comparable to the evolution of luminous optical quasi-stellar objects (QSOs) and luminous X-ray-selected AGNs. We also find evidence for an epoch dependence of the evolution as determined previously for radio-quiet AGNs. We interpret both these findings as a strong link between accretion and jet activity. In our sample, the FSRQs evolve strongly, while our best fit shows that BL Lac objects might not evolve at all. The blazar population accounts for 10%-20% (depending on the evolution of the BL Lac objects) of the cosmic X-ray background (CXB) in the 15-55keV band. We find that FSRQs can explain the entire CXB emission for energies above 500 keV solving the mystery of the generation of the MeV background. The evolution of luminous FSRQs shows a peak in redshift (z_c_=4.3+/-0.5) which is larger than the one observed in QSOs and X-ray-selected AGNs. We argue that FSRQs can be used as tracers of massive elliptical galaxies in the early universe.
- ID:
- ivo://CDS.VizieR/J/A+A/572/L5
- Title:
- Evolution state of red giants from seismology
- Short Name:
- J/A+A/572/L5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The detection of oscillations with a mixed character in subgiants and red giants allows us to probe the physical conditions in their cores. With these mixed modes, we aim at determining seismic markers of stellar evolution. Kepler asteroseismic data were selected to map various evolutionary stages and stellar masses. Seismic evolutionary tracks were then drawn with the combination of the frequency and period spacings.
- ID:
- ivo://CDS.VizieR/J/A+A/624/A8
- Title:
- Evolved Galactic open clusters dynamical properties
- Short Name:
- J/A+A/624/A8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stellar content of Galactic open clusters (OCs) is gradually depleted during their evolution as a result of internal relaxation and external interactions. The final residues of the long-term evolution of OCs are called open cluster remnants (OCRs).These are sparsely populated structures that can barely be distinguished from the field. We aimed to characterise and compare the dynamical states of a set of 16 objects catalogued as OCRs or OCR candidates. The sample also includes 7 objects that are catalogued as dynamically evolved OCs for comparison purposes. We used photometric data from the 2MASS catalogue, proper motions and parallaxes from the GAIA DR2 catalogue, and a decontamination algorithm that was applied to the three-dimensional astrometric space of proper motions and parallaxes ({mu}_{alpha}, {mu}_{delta}, {varpi}) for stars in the objects' areas. The investigated OCRs present masses (M) and velocity dispersions ({sigma}_v_) within well-defined ranges: M between ~10-40M_{sun} and {sigma}_v_ between ~1-7km/s. Some objects in the remnant sample have a limiting radius R_lim_<~2pc, which means that they are more compact than the investigated OCs; other remnants have R_lim_ between ~2-7pc, which is comparable to the OCs. In general, our clusters show signals of depletion of low-mass stars. This confirms their dynamically evolved states. Using results from N-body simulations, we conclude that the OCRs we studied are in fact remnants of initially very populous OCs (N_0_~10^3^-10^4^stars). The outcome of the long-term evolution is to bring the final residues of the OCs to dynamical states that are similar to each other, thus masking out the memory of the initial formation conditions of star clusters.
- ID:
- ivo://CDS.VizieR/J/AJ/107/594
- Title:
- Evolved GK stars near the Sun. II.
- Short Name:
- J/AJ/107/594
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From a sample of nearly 2000 GK giants a group of young disk stars with well determined space motions has been selected. The zero point of the luminosity calibrations, both from the ultraviolet flux (modified Stromgren system) and that in the region of 4200 to 4900A (DDO system), show a discontinuity of about a half magnitude at the border of the young disk and old disk domains. The population separation is based on the space velocity components, which are also an age discriminants with the population interface near 2x10^9yr, based on models with convective overshoot at the core. This age corresponds to giant masses near 1.7M_{sun}_, near the critical mass separating the young stars that do not burn helium in degenerate cores from older stars that do. Ten percent of both populations show CN anomalies in that the derived value of P[Fe/H] from CN(C_m_) and from Fe(M_1_) differ by more than 0.1dex and the weak and strong CN stars occur equally in the old disk but the weak CN stars predominate in the young disk. Peculiar stars, where flux distortions affect the luminosity calibrations, are of the CH+ (Ba II) and CH- (weak G band) variety and represent less than 1% of the stars in both populations. The young disk giants are restricted to ages greater than about 10^9^yr, because younger stars are bright giants or supergiants (luminosity class II or I), and younger than about 2x10^9yr, because the old disk-young disk boundary occurs near 1.7M_{sun}_. The distribution of heavy element abundances, P[Fe/H], for young disk giants is both more limited in range (+/-0.4dex) and is skewed toward higher abundances, compared with the nearly normal distribution for old disk giants. The distribution of (U,V) velocity vectors gives (U,V,W) and their dispersions =(+17.6+/-18.4, -14.8+/-8.4, -6.9+/-13.0) and (+3.6+/-38.4, -20.7+/-27.5, -6.7+/-17.3) km/s for young and old disk giants, respectively. For a description of the DDO and RI Eggen photometric system, see e.g. <GCPD/12> and <GCPD/17> , respectively.
- ID:
- ivo://CDS.VizieR/J/ApJ/902/24
- Title:
- Evolved massive stars with TESS. II.
- Short Name:
- J/ApJ/902/24
- Date:
- 14 Mar 2022 07:45:17
- Publisher:
- CDS
- Description:
- Massive stars briefly pass through the yellow supergiant (YSG) phase as they evolve redward across the H-R diagram and expand into red supergiants (RSGs). Higher-mass stars pass through the YSG phase again as they evolve blueward after experiencing significant RSG mass loss. These post-RSG objects offer us a tantalizing glimpse into which stars end their lives as RSGs and why. One telltale sign of a post-RSG object may be an instability to pulsations, depending on the star's interior structure. Here we report the discovery of five YSGs with pulsation periods faster than 1 day, found in a sample of 76 cool supergiants observed by the Transiting Exoplanet Survey Satellite (TESS) at a two-minute cadence. These pulsating YSGs are concentrated in an H-R diagram region not previously associated with pulsations; we conclude that this is a genuine new class of pulsating star, fast yellow pulsating supergiants (FYPSs). For each FYPS, we extract frequencies via iterative prewhitening and conduct a time-frequency analysis. One FYPS has an extracted frequency that is split into a triplet, and the amplitude of that peak is modulated on the same timescale as the frequency spacing of the triplet; neither rotation nor binary effects are likely culprits. We discuss the evolutionary status of FYPS and conclude that they are candidate post-RSGs. All stars in our sample also show the same stochastic low-frequency variability found in hot OB stars and attributed to internal gravity waves. Finally, we find four {alpha} Cygni variables in our sample, of which three are newly discovered.
- ID:
- ivo://CDS.VizieR/J/A+A/557/A70
- Title:
- Evolved planet hosts - stellar parameters
- Short Name:
- J/A+A/557/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is still being debated whether the well-known metallicity - giant planet correlation for dwarf stars is also valid for giant stars. For this reason, having precise metallicities is very important. Precise stellar parameters are also crucial to planetary research for several other reasons. Different methods can provide different results that lead to discrepancies in the analysis of planet hosts. To study the impact of different analyses on the metallicity scale for evolved stars, we compare different iron line lists to use in the atmospheric parameter derivation of evolved stars. Therefore, we use a sample of 71 evolved stars with planets. With these new homogeneous parameters, we revisit the metallicity - giant planet connection for evolved stars. A spectroscopic analysis based on Kurucz models in local thermodynamic equilibrium (LTE) was performed through the MOOG code to derive the atmospheric parameters. Two different iron line list sets were used, one built for cool FGK stars in general, and the other for giant FGK stars. Masses were calculated through isochrone fitting, using the Padova models. Kolmogorov-Smirnov tests (K-S tests) were then performed on the metallicity distributions of various different samples of evolved stars and red giants. All parameters compare well using a line list set, designed specifically for cool and solar-like stars to provide more accurate temperatures. All parameters derived with this line list set are preferred and are thus adopted for future analysis. We find that evolved planet hosts are more metal-poor than dwarf stars with giant planets. However, a bias in giant stellar samples that are searched for planets is present. Because of a colour cut-off, metal-rich low-gravity stars are left out of the samples, making it hard to compare dwarf stars with giant stars. Furthermore, no metallicity enhancement is found for red giants with planets (logg<3.0dex) with respect to red giants without planets.
5789. Evolved stars in M13
- ID:
- ivo://CDS.VizieR/J/AJ/139/2374
- Title:
- Evolved stars in M13
- Short Name:
- J/AJ/139/2374
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analyzed photometry from space- and ground-based cameras to identify all bright red giant branch (RGB), horizontal branch (HB), and asymptotic giant branch (AGB) stars within 10' of the center of the globular cluster M13.
- 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.