- ID:
- ivo://CDS.VizieR/J/A+A/533/A107
- Title:
- SED for 7 stellar calibrators
- Short Name:
- J/A+A/533/A107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Among late-type red giants, an interesting change occurs in the structure of the outer atmospheric layers as one moves to later spectral types in the Hertzsprung-Russell diagram: a chromosphere is always present, but the coronal emission diminishes and a cool massive wind steps in. Where most studies have focussed on short-wavelength observations, this article explores the influence of the chromosphere and the wind on long-wavelength photometric measurements. The goal of this study is to assess wether a set of standard near-infrared calibration sources are fiducial calibrators in the far-infrared, beyond 50um. The observational spectral energy distributions were compared with the theoretical model predictions for a sample of nine K- and M-giants. The discrepancies found are explained using basic models for flux emission originating in a chromosphere or an ionised wind.
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- ID:
- ivo://CDS.VizieR/J/A+A/618/A109
- Title:
- Seismic global parameters of 372 KIC
- Short Name:
- J/A+A/618/A109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Oscillation modes with a mixed character, as observed in evolved low-mass stars, are highly sensitive to the physical properties of the innermost regions. Measuring their properties is therefore extremely important to probe the core, but requires some care, due to the complexity of the mixed-mode pattern. The aim of this work is to provide a consistent description of the mixed-mode pattern of low-mass stars, based on the asymptotic expansion. We also study the variation of the gravity offset epsilon_g_ with stellar evolution. We revisit previous works about mixed modes in red giants and empirically test how period spacings, rotational splittings, mixed-mode widths, and heights can be estimated in a consistent view, based on the properties of the mode inertia ratios. From the asymptotic fit of the mixed-mode pattern of a large set of red giants at various evolutionary stages, we derive unbiased and precise asymptotic parameters. As the asymptotic expansion of gravity modes is verified with a precision close to the frequency resolution for stars on the red giant branch (10^-4^ in relative values), we can derive accurate values of the asymptotic parameters. We decipher the complex pattern in a rapidly rotating star, and explain how asymmetrical splittings can be inferred. We also revisit the stellar inclinations in two open clusters, NGC 6819 and NGC 6791: our results show that the stellar inclinations in these clusters do not have privileged orientation in the sky. The variation of the asymptotic gravity offset with stellar evolution is investigated in detail. We also derive generic properties that explain under which conditions mixed modes can be observed.
- ID:
- ivo://CDS.VizieR/J/A+A/588/A87
- Title:
- Seismic global parameters of 6111 KIC
- Short Name:
- J/A+A/588/A87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The space missions CoRoT and Kepler have provided photometric data of unprecedented quality for asteroseismology. A very rich oscillation pattern has been discovered for red giants, including mixed modes that are used to decipher the red giants' interiors. They carry information on the radiative core of red giant stars and bring strong constraints on stellar evolution. Since more than 15000 red giant light curves have been observed by Kepler, we have developed a simple and efficient method for automatically characterizing the mixed-mode pattern and measuring the asymptotic period spacing. With the asymptotic expansion of the mixed modes, we have revealed the regularity of the gravity-mode pattern. The stretched periods were used to study the evenly space periods with a Fourier analysis and to measure the gravity period spacing, even when rotation severely complicates the oscillation spectra.
- ID:
- ivo://CDS.VizieR/J/A+A/597/A30
- Title:
- Seismology and spectroscopy of CoRoGEE red giants
- Short Name:
- J/A+A/597/A30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the CoRoGEE dataset -- obtained from CoRoT lightcurves for 606 red giant stars in two fields of the Galactic disc which have been co-observed for an ancillary project of the Apache Point Observatory Galactic Evolution Experiment (APOGEE). The CoRoGEE stars cover a large radial range of the Milky Way's disc (5kpc<RGal<14kpc) and thus provide a valuable dataset for Galactic Archaeology studies. We have used the Bayesian parameter estimation code PARAM to calculate distances, extinctions, masses, and ages for these stars in a homogeneous analysis, resulting in relative statistical uncertainties of 2% in distance, 4% in radius, ~9% in mass and ~25% in age. We also assess systematic age uncertainties due to different input physics and mass loss.
- ID:
- ivo://CDS.VizieR/J/ApJ/886/154
- Title:
- Sgr stream K- & M-giants and BHB stars
- Short Name:
- J/ApJ/886/154
- Date:
- 07 Dec 2021 13:01:04
- Publisher:
- CDS
- Description:
- We characterize the kinematic and chemical properties of ~3000 Sagittarius (Sgr) stream stars, including K-giants, M-giants, and blue horizontal branch stars (BHBs), selected from SEGUE-2, Large Sky Area Multi-Object Fibre Spectroscopic Telescope, and Sloan Digital Sky Survey separately in Integrals-of-Motion space. The orbit of the Sgr stream is quite clear from the velocity vector in the X-Z plane. Stars traced by K-giants and M-giants show that the apogalacticon of the trailing steam is ~100kpc. The metallicity distributions of Sgr K-giants, M-giants, and BHBs indicate that the M-giants are on average the most metal-rich population, followed by K-giants and BHBs. All of the K-giants, M-giants, and BHBs indicate that the trailing arm is on average more metal-rich than the leading arm, and the K-giants show that the Sgr debris is the most metal-poor part. The {alpha}-abundance of Sgr stars exhibits a similar trend with the Galactic halo stars at lower metallicity ([Fe/H]<~-1.0dex), and then evolve down to lower [{alpha}/Fe] than disk stars at higher metallicity, which is close to the evolution pattern of the {alpha}-element of Milky Way dwarf galaxies. We find that VY and metallicity of K-giants have gradients along the direction of the line of sight from the Galactic center in the X-Z plane, and the K-giants show that VY increases with metallicity at [Fe/H]>~-1.5dex. After dividing the Sgr stream into bright and faint streams according to their locations in equatorial coordinates, the K-giants and BHBs show that the bright and faint streams present different VY and metallicities, the bright stream is on average higher in VY and metallicity than the faint stream.
- ID:
- ivo://CDS.VizieR/J/MNRAS/466/1963
- Title:
- Silicate crystallinities of O-rich evolved stars
- Short Name:
- J/MNRAS/466/1963
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For decades ever since the early detection in the 1990s of the emission spectral features of crystalline silicates in oxygen-rich evolved stars, there is a long-standing debate on whether the crystallinity of the silicate dust correlates with the stellar mass-loss rate. To investigate the relation between the silicate crystallinities and the mass-loss rates of evolved stars, we carry out a detailed analysis of 28 nearby oxygen-rich stars. We derive the mass-loss rates of these sources by modelling their spectral energy distributions from the optical to the far-infrared. Unlike previous studies in which the silicate crystallinity was often measured in terms of the crystalline-to-amorphous silicate mass ratio, we characterize the silicate crystallinities of these sources with the flux ratios of the emission features of crystalline silicates to that of amorphous silicates. This does not require the knowledge of the silicate dust temperatures, which are the major source of uncertainties in estimating the crystalline-to-amorphous silicate mass ratio. With a Pearson correlation coefficient of ~-0.24, we find that the silicate crystallinities and the mass-loss rates of these sources are not correlated. This supports the earlier findings that the dust shells of low mass-loss rate stars can contain a significant fraction of crystalline silicates without showing the characteristic features in their emission spectra.
- ID:
- ivo://CDS.VizieR/J/PASJ/62/391
- Title:
- SiO and H2O masers in Stephenson 2 cluster
- Short Name:
- J/PASJ/62/391
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of radio observations of red supergiants in a star cluster, Stephenson (1990AJ.....99.1867S)'s #2 (Cl Stephenson 2), and of candidates for red supergiants in three star clusters, Mercer et al. (2005ApJ...635..560M)'s #4, #8, and #13 ([MCM2005b] 4, [MCM2005b] 8 and [MCM2005b] 13), in the SiO and H_2_O maser lines. The Stephenson's #2 cluster and nearby aggregation at the southwest contain more than 15 red supergiants.
- ID:
- ivo://CDS.VizieR/J/ApJS/211/15
- Title:
- SiO and H2O maser survey toward AGB & post-AGB stars
- Short Name:
- J/ApJS/211/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Simultaneous observations of SiO(v=1,2,J=1-0) ^29^SiO(v=0,J=1-0) (43.122080GHz, 42.820587GHz and 42.879916GHz) and H_2_O(6_16_-5_23_) (22.235080GHz) maser lines were performed with three KVN (Korean VLBI Network) 21m single-dish radio telescopes (at Yonsei University campus, Ulsan University campus, and Tamna University campus) toward the 164 post-AGB and 143 AGB stars. Observations were carried out from 2011 February to 2012 March.
- ID:
- ivo://CDS.VizieR/J/PASJ/62/525
- Title:
- SiO maser survey off the Galactic Plane
- Short Name:
- J/PASJ/62/525
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A group of Mira variables in the solar neighborhood shows unusual spatial motion in the Galaxy. To study this motion on a much larger scale in the Galaxy, we newly surveyed 134 evolved stars off the Galactic plane by SiO maser lines, obtaining accurate radial velocities of 84 detected stars. Together with the past data of SiO maser sources, we analyzed the radial-velocity data of a large sample of sources distributed in a distance range of about 0.3-6kpc in the first Galactic quadrant. At Galactic longitudes between 20{deg} and 40{deg}, we found a group of stars with large negative radial velocities, which deviate by more than 100km/s from the Galactic rotation. We show that these deviant motions of maser stars are created by periodic gravitational perturbation of the Bulge bar, and that the effect appears most strongly at radii between corotation and outer Lindblad resonances. The resonance effect can explain the displacement of positions from the Galactic plane as well.
- ID:
- ivo://CDS.VizieR/J/ApJ/886/27
- Title:
- SNe IIP progenitors. I. LMC giant comparison sample
- Short Name:
- J/ApJ/886/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the evolution of massive star progenitors of supernovae of type IIP. We take the example of the nearby and well-studied SN2013ej. We explore how convective overshoot affects the stellar structure, surface abundances, and effective temperature of massive stars, using the Modules for Experiments in Stellar Astrophysics. In particular, models with moderate overshoot (f=0.02-0.031) show the presence of blue loops in the Hertzsprung-Russell diagram with a red to blue excursion (log_10_[Teff/K] from <3.6 to >4.0) and transition back to red, during the core helium-burning phase. Models with overshoot outside this range of f values kept the star in the red supergiant state throughout the post-helium-ignition phases. The surface CNO abundance shows enrichment post-main-sequence and again around the time when helium is exhausted in the core. These evolutionary changes in surface CNO abundance are indistinguishable in the currently available observations due to large observational uncertainties. However, these observations may distinguish between the ratio of surface nitrogen to oxygen at different evolutionary stages of the star. We also compare the effects of convective overshoot on various parameters related to likelihood of explosion of a star as opposed to collapse to a black hole. These parameters are the compactness parameter, M_4_, and {mu}_4_. The combination {mu}_4_xM_4_, and {mu}_4_ have similar variations with f and both peak at f=0.032. We find that all of our 13M_{sun}_ models are likely to explode.
