- ID:
- ivo://CDS.VizieR/J/A+A/622/A50
- Title:
- Calibrated grid of rotating single star models
- Short Name:
- J/A+A/622/A50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive star evolution is dominated by various physical effects, including mass loss, overshooting, and rotation, but the prescriptions of their effects are poorly constrained, even affecting our understanding of the main sequence. We aim to constrain massive star evolution models using the unique testbed eclipsing binary HD166734 with new grids of MESA stellar evolution models, adopting calibrated prescriptions of overshooting, mass loss, and rotation. We introduce a novel tool: the "mass-luminosity plane" or "M-L plane", as an equivalent to the traditional HR diagram, utilising it to reproduce the testbed binary HD166734 with newly calibrated MESA stellar evolution models for single stars. We can only reproduce the Galactic binary system with an enhanced amount of core overshooting (alpha_ov_=0.5), mass loss, and rotational mixing. We can utilise the gradient in the M-L plane to constrain the amount of mass loss to 0.5-1.5 times the standard Vink et al. (2001A&A...369..574V) prescriptions, and we can exclude extreme reduction or multiplication factors. The extent of the vectors in the M-L plane leads us to conclude that the amount of core overshooting is larger than is normally adopted in contemporary massive star evolution models. We furthermore conclude that rotational mixing is mandatory to get the nitrogen abundance ratios between the primary and secondary components to be correct (3:1) in our testbed binary system. Our calibrated grid of models, alongside our new M-L plane approach, present the possibility of a widened main sequence due to an increased demand for core overshooting. The increased amount of core overshooting is not only needed to explain the extended main sequence, but the enhanced overshooting is also needed to explain the location of the upper-luminosity limit of the red supergiants. Finally, the increased amount of core overshooting has - via the compactness parameter - implications for supernova explodibility.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/440/2026
- Title:
- Calibration of some distance scales
- Short Name:
- J/MNRAS/440/2026
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a method for distance calibration without using standard fitting procedures. Instead, we use random resampling to reconstruct the probability density function (PDF) of calibration data points in the fitting plane. The resulting PDF is then used to estimate distance-related properties. The method is applied to samples of radio surface brightness to diameter ({Sigma}-D}) data for the Galactic supernova remnants (SNRs) and planetary nebulae (PNe), and period-luminosity (PL) data for the Large Magellanic Cloud (LMC) fundamental mode classical Cepheids. We argue that resulting density maps can provide more accurate and more reliable calibrations than those obtained by standard linear fitting procedures. For the selected sample of the Galactic SNRs, the presented PDF method of distance calibration results in a smaller average distance fractional error of up to ~16 percentage points. Similarly, the fractional error is smaller for up to ~8 and ~0.5 percentage points, for the samples of Galactic PNe and LMC Cepheids, respectively. In addition, we provide a PDF-based calibration data for each of the samples.
- ID:
- ivo://CDS.VizieR/J/A+A/498/527
- Title:
- Calibration of Stromgren phot. for late-type stars
- Short Name:
- J/A+A/498/527
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The use of model atmospheres for deriving stellar fundamental parameters, such as Teff, log(g), and [Fe/H], will increase as we find and explore extreme stellar populations where empirical calibrations are not yet available. Moreover, calibrations for upcoming large satellite missions of new spectrophotometric indices, similar to the uvby-Hbeta system, will be needed. We aim to test the power of theoretical calibrations based on a new generation of MARCS models by comparisons with observational photometric data. We calculated synthetic uvby-Hbeta colour indices from synthetic spectra. A sample of 367 field stars, as well as stars in globular clusters, is used for a direct comparison of the synthetic indices versus empirical data and for scrutizing the possibilities of theoretical calibrations for temperature, metallicity, and gravity. We show that the temperature sensitivity of the synthetic (b-y) colour is very close to its empirical counterpart, whereas the temperature scale based upon Hbeta shows a slight offset. The theoretical metallicity sensitivity of the m1 index (and for G-type stars its combination with c1) is somewhat higher than the empirical one, based upon spectroscopic determinations. The gravity sensitivity of the synthetic c1 index shows satisfactory behaviour when compared to observations of F stars. For stars cooler than the sun, a deviation is significant in the c1-(b-y) diagram. The theoretical calibrations of (b-y), (v-y), and c1 seem to work well for Pop II stars and lead to effective temperatures for globular cluster stars supporting recent claims that atomic diffusion occurs in stars near the turnoff point of NGC 6397. Synthetic colours of stellar atmospheres can indeed be used, in many cases, to derive reliable fundamental stellar parameters. The deviations seen when compared to observational data could be due to incomplete linelists but are possibly also due to the effects of assuming plane-parallel or spherical geometry and LTE.
- ID:
- ivo://CDS.VizieR/J/AJ/129/1642
- Title:
- Calibration of synthetic photometry
- Short Name:
- J/AJ/129/1642
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new calibration of optical (UBV, Stroemgren uvby{beta}, and Geneva) and near-IR (Johnson RIJHK and Two Micron All Sky Survey) photometry for B and early A stars derived from Kurucz ATLAS9 model atmospheres. These models are then used to calibrate the synthetic photometry.
- ID:
- ivo://CDS.VizieR/J/A+A/581/A103
- Title:
- CALIFA survey across the Hubble sequence
- Short Name:
- J/A+A/581/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Various different physical processes contribute to the star formation and stellar mass assembly histories of galaxies. One important approach to understanding the significance of these different processes on galaxy evolution is the study of the stellar population content of today's galaxies in a spatially resolved manner. The aim of this paper is to characterize in detail the radial structure of stellar population properties of galaxies in the nearby universe, based on a uniquely large galaxy sample, considering the quality and coverage of the data. The sample under study was drawn from the CALIFA survey and contains 300 galaxies observed with integral field spectroscopy. These cover a wide range of Hubble types, from spheroids to spiral galaxies, while stellar masses range from M_*_~10^9^ to 7x10^11^M_{sun}_. We apply the fossil record method based on spectral synthesis techniques to recover the following physical properties for each spatial resolution element in our target galaxies: the stellar mass surface density ({mu}_*_), stellar extinction (A_V_), light-weighted and mass-weighted ages (<logage>_L_, <logage>_M_), and mass-weighted metallicity (<logZ_*_>_M_). To study mean trends with overall galaxy properties, the individual radial profiles are stacked in seven bins of galaxy morphology (E, S0, Sa, Sb, Sbc, Sc, and Sd). We confirm that more massive galaxies are more compact, older, more metal rich, and less reddened by dust. Additionally, we find that these trends are preserved spatially with the radial distance to the nucleus. Deviations from these relations appear correlated with Hubble type: earlier types are more compact, older, and more metal rich for a given M_*_, which is evidence that quenching is related to morphology, but not driven by mass. Negative gradients of <logage>_L_ are consistent with an inside-out growth of galaxies, with the largest <logage>_L_ gradients in Sb-Sbc galaxies. Further, the mean stellar ages of disks and bulges are correlated and with disks covering a wider range of ages, and late-type spirals hosting younger disks. However, age gradients are only mildly negative or flat beyond R~2HLR (half light radius), indicating that star formation is more uniformly distributed or that stellar migration is important at these distances. The gradients in stellar mass surface density depend mostly on stellar mass, in the sense that more massive galaxies are more centrally concentrated. Whatever sets the concentration indices of galaxies obviously depends less on quenching/morphology than on the depth of the potential well. There is a secondary correlation in the sense that at the same M_*_ early-type galaxies have steeper gradients. The {mu}_*_ gradients outside 1HLR show no dependence on Hubble type. We find mildly negative <logZ_*_>_M_ gradients, which are shallower than predicted from models of galaxy evolution in isolation. In general, metallicity gradients depend on stellar mass, and less on morphology, hinting that metallicity is affected by both - the depth of the potential well and morphology/quenching. Thus, the largest <logZ_*_>_M_ gradients occur in Milky Way-like Sb-Sbc galaxies, and are similar to those measured above the Galactic disk. Sc spirals show flatter <logZ_*_>_M_ gradients, possibly indicating a larger contribution from secular evolution in disks. The galaxies from the sample have decreasing-outward stellar extinction; all spirals show similar radial profiles, independent from the stellar mass, but redder than E and S0. Overall, we conclude that quenching processes act in manners that are independent of mass, while metallicity and galaxy structure are influenced by mass-dependent processes.
- ID:
- ivo://CDS.VizieR/J/AJ/155/89
- Title:
- California-Kepler Survey (CKS). IV. Planets
- Short Name:
- J/AJ/155/89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Probing the connection between a star's metallicity and the presence and properties of any associated planets offers an observational link between conditions during the epoch of planet formation and mature planetary systems. We explore this connection by analyzing the metallicities of Kepler target stars and the subset of stars found to host transiting planets. After correcting for survey incompleteness, we measure planet occurrence: the number of planets per 100 stars with a given metallicity M. Planet occurrence correlates with metallicity for some, but not all, planet sizes and orbital periods. For warm super-Earths having P=10-100 days and R_P_=1.0-1.7 R_{Earth}_, planet occurrence is nearly constant over metallicities spanning -0.4 to +0.4 dex. We find 20 warm super-Earths per 100 stars, regardless of metallicity. In contrast, the occurrence of warm sub-Neptunes (R_P_=1.7-4.0 R_{Earth}_) doubles over that same metallicity interval, from 20 to 40 planets per 100 stars. We model the distribution of planets as df{prop.to}10^{beta}M^dM, where {beta} characterizes the strength of any metallicity correlation. This correlation steepens with decreasing orbital period and increasing planet size. For warm super-Earths {beta}=-0.3_-0.2_^+0.2^, while for hot Jupiters {beta}=+3.4_-0.8_^+0.9^. High metallicities in protoplanetary disks may increase the mass of the largest rocky cores or the speed at which they are assembled, enhancing the production of planets larger than 1.7 R_{Earth}_. The association between high metallicity and short-period planets may reflect disk density profiles that facilitate the inward migration of solids or higher rates of planet-planet scattering.
- ID:
- ivo://CDS.VizieR/J/ApJ/858/61
- Title:
- Carbon and Oxygen local interstellar spectra
- Short Name:
- J/ApJ/858/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Local interstellar spectra (LIS) of primary cosmic ray (CR) nuclei, such as helium, oxygen, and mostly primary carbon are derived for the rigidity range from 10MV to ~200TV using the most recent experimental results combined with the state-of-the-art models for CR propagation in the Galaxy and in the heliosphere. Two propagation packages, GALPROP and HelMod, are combined into a single framework that is used to reproduce direct measurements of CR species at different modulation levels, and at both polarities of the solar magnetic field. The developed iterative maximum-likelihood method uses GALPROP- predicted LIS as input to HelMod, which provides the modulated spectra for specific time periods of the selected experiments for model-data comparison. The interstellar and heliospheric propagation parameters derived in this study are consistent with our prior analyses using the same methodology for propagation of CR protons, helium, antiprotons, and electrons. The resulting LIS accommodate a variety of measurements made in the local interstellar space (Voyager 1) and deep inside the heliosphere at low (ACE/CRIS, HEAO-3) and high energies (PAMELA, AMS-02).
- ID:
- ivo://CDS.VizieR/J/A+A/652/A116
- Title:
- CARMENES time-resolved CaII H&K catalog
- Short Name:
- J/A+A/652/A116
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Radial-velocity (RV) jitter caused by stellar magnetic activity is an important factor in state-of-the-art exoplanet discovery surveys such as CARMENES. Stellar rotation, along with heterogeneities in the photosphere and chromosphere caused by activity, can result in false-positive planet detections. Hence, it is necessary to determine the stellar rotation period and compare it to any putative planetary RV signature. Long-term measurements of activity indicators such as the chromospheric emission in the CaII H&K lines enable the identification of magnetic activity cycles. In order to determine stellar rotation periods and study the long-term behavior of magnetic activity of the CARMENES guaranteed time observations (GTO) sample, it is advantageous to extract R'HK time series from archival data, since the CARMENES spectrograph does not cover the blue range of the stellar spectrum containing the Ca II H&K lines. We have assembled a catalog of 11634 archival spectra of 186 M dwarfs acquired by seven different instruments covering the CaII H&K regime: ESPADONS, FEROS, HARPS, HIRES, NARVAL, TIGRE, and UVES. The relative chromospheric flux in these lines, R'HK, was directly extracted from the spectra by rectification with PHOENIX synthetic spectra via narrow passbands around the Ca II H&K line cores. The combination of archival spectra from various instruments results in time series for 186 stars from the CARMENES GTO sample. As an example of the use of the catalog, we report the tentative discovery of three previously unknown activity cycles of M dwarfs. We conclude that the method of extracting R'HK with the use of model spectra yields consistent results for different instruments and that the compilation of this catalog will enable the analysis of long-term activity time series for a large number of M dwarfs.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A150
- Title:
- CasA, CygA, TauA, VirA 30MHz & 77MHz models
- Short Name:
- J/A+A/635/A150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The four persistent radio sources in the northern sky with the highest flux density at metre wavelengths are Cassiopeia A, Cygnus A, Taurus A, and Virgo A; collectively they are called the A-team. Their flux densities at ultra-low frequencies (<100MHz) can reach several thousands of janskys, and they often contaminate observations of the low-frequency sky by interfering with image processing. Furthermore, these sources are foreground objects for all-sky observations hampering the study of faint signals, such as the cosmological 21cm line from the epoch of reionisation. We aim to produce robust models for the surface brightness emission as a function of frequency for the A-team sources at ultra-low frequencies. These models are needed for the calibration and imaging of wide-area surveys of the sky with low-frequency interferometers. This requires obtaining images at an angular resolution better than 1500 with a high dynamic range and good image fidelity. We observed the A-team with the Low Frequency Array (LOFAR) at frequencies between 30MHz and 77MHz using the Low Band Antenna (LBA) system. We reduced the datasets and obtained an image for each A-team source. The paper presents the best models to date for the sources Cassiopeia A, Cygnus A, Taurus A, and Virgo A between 30MHz and 77MHz. We were able to obtain the aimed resolution and dynamic range in all cases. Owing to its compactness and complexity, observations with the long baselines of the International LOFAR Telescope will be required to improve the source model for Cygnus A further.
- ID:
- ivo://CDS.VizieR/J/AJ/153/95
- Title:
- Catalog of Suspected Nearby Young Stars
- Short Name:
- J/AJ/153/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new nearby young moving group (NYMG) kinematic membership analysis code, LocAting Constituent mEmbers In Nearby Groups (LACEwING), a new Catalog of Suspected Nearby Young Stars, a new list of bona fide members of moving groups, and a kinematic traceback code. LACEwING is a convergence-style algorithm with carefully vetted membership statistics based on a large numerical simulation of the Solar Neighborhood. Given spatial and kinematic information on stars, LACEwING calculates membership probabilities in 13 NYMGs and three open clusters within 100 pc. In addition to describing the inputs, methods, and products of the code, we provide comparisons of LACEwING to other popular kinematic moving group membership identification codes. As a proof of concept, we use LACEwING to reconsider the membership of 930 stellar systems in the Solar Neighborhood (within 100 pc) that have reported measurable lithium equivalent widths. We quantify the evidence in support of a population of young stars not attached to any NYMGs, which is a possible sign of new as-yet-undiscovered groups or of a field population of young stars.
