- ID:
- ivo://CDS.VizieR/J/AJ/144/39
- Title:
- Galactic RRab stars from the GEOS RR Lyr Survey
- Short Name:
- J/AJ/144/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the GEOS database to study the Blazhko effect of galactic RRab stars. The database is continuously enriched by maxima supplied by amateur astronomers and by a dedicated survey by means of the two TAROT robotic telescopes. The same value of the Blazhko period is observed at different values of the pulsation periods and different values of the Blazhko periods are observed at the same value of the pulsation period. There are clues suggesting that the Blazhko effect is changing from one cycle to the next. The secular changes in the pulsation and Blazhko periods of Z CVn are anticorrelated. The diagrams of magnitudes against phases of the maxima clearly show that the light curves of Blazhko variables can be explained as modulated signals, both in amplitude and in frequency. The closed curves describing the Blazhko cycles in such diagrams have different shapes, reflecting the phase shifts between the epochs of the brightest maximum and the maximum O-C. Our sample shows that both clockwise and counterclockwise directions are possible for similar shapes. The improved observational knowledge of the Blazhko effect, in addition to some peculiarities of the light curves, has yet to be explained by a satisfactory physical mechanism.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/700/523
- Title:
- Galactic star clusters in SDSS. II. Colors.
- Short Name:
- J/ApJ/700/523
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform an extensive test of theoretical stellar models for main-sequence (MS) stars in ugriz, using cluster fiducial sequences obtained in the previous paper of this series. We generate a set of isochrones using the Yale Rotating Evolutionary Code with updated input physics, and derive magnitudes and colors in ugriz from MARCS model atmospheres. These models match cluster MSs over a wide range of metallicity within the errors of the adopted cluster parameters. However, we find a large discrepancy of model colors at the lower MS (T_eff_<~4500K) for clusters at and above solar metallicity. We also reach similar conclusions using the theoretical isochrones of Girardi et al. and Dotter et al., but our new models are generally in better agreement with the data. Using our theoretical isochrones, we also derive MS-fitting distances and turnoff ages for five key globular clusters, and demonstrate the ability to derive these quantities from photometric data in the Sloan Digital Sky Survey. In particular, we exploit multiple color indices (g-r, g-i, and g-z) in the parameter estimation, which allows us to evaluate internal systematic errors. Our distance estimates, with an error of {sigma}_(m-M)_=0.03-0.11mag for individual clusters, are consistent with Hipparcos-based subdwarf-fitting distances derived in the Johnson-Cousins or Stromgren photometric systems.
- ID:
- ivo://CDS.VizieR/J/PASP/124/128
- Title:
- Galactic structure toward the Carina tangent
- Short Name:
- J/PASP/124/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This investigation presents a photometric study of the Galactic structure toward the Carina arm tangent. The field is located between 280{deg} and 286{deg} Galactic longitude and -4{deg} to 4{deg} Galactic latitude. All currently available uvby{beta} data are used to obtain homogeneous color excesses and distances for more than 260 stars of spectral types O to G. We present revised distances and average extinction for the open clusters and cluster candidates NGC 3293, NGC 3114, Loden 46, and Loden 112.
- ID:
- ivo://CDS.VizieR/J/A+A/624/A19
- Title:
- GALAH survey, chemodynamical analyse with TGAS
- Short Name:
- J/A+A/624/A19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The overlap between the spectroscopic Galactic Archaeology with HERMES (GALAH) survey and Gaia provides a high-dimensional chemodynamical space of unprecedented size. We present a first analysis of a subset of this overlap, of 7066 turn-off, and sub-giant stars. These stars have spectra from the GALAH survey and high parallax precision from the Gaia DR1 Tycho-Gaia Astrometric Solution. We investigate correlations between chemical compositions, ages, and kinematics for this sample. Stellar parameters and elemental abundances are derived from the GALAH spectra with the spectral synthesis code Spectroscopy Made Easy. We determine kinematics and dynamics, including action angles, from the Gaia astrometry and GALAH radial velocities. Stellar masses and ages are determined with Bayesian isochrone matching, using our derived stellar parameters and absolute magnitudes. We report measurements of Li, C, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, as well as Ba and we note that we have employed non-LTE calculations for Li, O, Al, and Fe. We show that the use of astrometric and photometric data improves the accuracy of the derived spectroscopic parameters, especially log g. Focusing our investigation on the correlations between stellar age, iron abundance [Fe/H], and mean alpha-enhancement [{alpha}/Fe] of the magnitude-selected sample, we recover the result that stars of the high-{alpha} sequence are typically older than stars in the low-{alpha} sequence, the latter spanning iron abundances of -0.7<[Fe/H]<+0.5. While these two sequences become indistinguishable in [{alpha}/Fe] vs. [Fe/H] at the metal-rich regime, we find that age can be used to separate stars from the extended high-alpha and the low-alpha sequence even in this regime. When dissecting the sample by stellar age, we find that the old stars (>8Gyr) have lower angular momenta L_z_ than the Sun, which implies that they are on eccentric orbits and originate from the inner disc. Contrary to some previous smaller scale studies we find a continuous evolution in the high-alpha-sequence up to super-solar [Fe/H] rather than a gap, which has been interpreted as a separate 'high-alpha metal-rich' population. Stars in our sample that are younger than 10Gyr, are mainly found on the low alpha-sequence and show a gradient in L_z_ from low [Fe/H] (L_z_>L_z,{sun}_) towards higher [Fe/H] (L_z_<L_z,{sun}_), which implies that the stars at the ends of this sequence are likely not originating from the close solar vicinity.
2125. GALAH Survey DR2
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/4513
- Title:
- GALAH Survey DR2
- Short Name:
- J/MNRAS/478/4513
- Date:
- 04 Feb 2022 00:12:04
- Publisher:
- CDS
- Description:
- The Galactic Archaeology with HERMES (GALAH) survey is a large-scale stellar spectroscopic survey of the Milky Way, designed to deliver complementary chemical information to a large number of stars covered by the Gaia mission. We present the GALAH second public data release (GALAH DR2) containing 342 682 stars. For these stars, the GALAH collaboration provides stellar parameters and abundances for up to 23 elements to the community. Here we present the target selection, observation, data reduction, and detailed explanation of how the spectra were analysed to estimate stellar parameters and element abundances. For the stellar analysis, we have used a multistep approach. We use the physics-driven spectrum synthesis of Spectroscopy Made Easy (SME) to derive stellar labels (Teff, logg, [Fe/H], [X/Fe], vmic, vsini, A_KS_) for a representative training set of stars. This information is then propagated to the whole sample with the data-driven method of The Cannon. Special care has been exercised in the spectral synthesis to only consider spectral lines that have reliable atomic input data and are little affected by blending lines. Departures from local thermodynamic equilibrium (LTE) are considered for several key elements, including Li, O, Na, Mg, Al, Si, and Fe, using 1D marcs stellar atmosphere models. Validation tests including repeat observations, Gaia benchmark stars, open and globular clusters, and K2 asteroseismic targets lend confidence to our methods and results. Combining the GALAH DR2 catalogue with the kinematic information from Gaia will enable a wide range of Galactic Archaeology studies, with unprecedented detail, dimensionality, and scope.
- ID:
- ivo://CDS.VizieR/J/A+A/638/A145
- Title:
- GALAH survey. FGK binary stars
- Short Name:
- J/A+A/638/A145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Binary stellar systems form a large fraction of the Galaxy's stars. They are useful as laboratories for studying the physical processes taking place within stars, and must be correctly taken into account when observations of stars are used to study the structure and evolution of the Galaxy. We present a sample of 12760 well-characterised double-lined spectroscopic binaries that are appropriate for statistical studies of the binary populations. They were detected as SB2s using a t-distributed stochastic neighbour embedding (t-SNE) classification and a cross-correlation analysis of GALAH spectra. This sample consists mostly of dwarfs, with a significant fraction of evolved stars and several dozen members of the giant branch. To compute parameters of the primary and secondary star (Teff[1,2], logg[1,2], [Fe/H], Vr[1,2], vmic[1,2], vbroad[1,2], R[1,2], and E(B-V)), we used a Bayesian approach that includes a parallax prior from Gaia DR2, spectra from GALAH, and apparent magnitudes from APASS, Gaia DR2, 2MASS, and WISE. The derived stellar properties and their distributions show trends that are expected for a population of close binaries (a<10AU) with mass ratios 0.5<=q<=1. The derived metallicity of these binary stars is statistically lower than that of single dwarf stars from the same magnitude-limited sample.
- ID:
- ivo://CDS.VizieR/J/AJ/133/504
- Title:
- Galaxies around CenA/M83 galaxy complex
- Short Name:
- J/AJ/133/504
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Hubble Space Telescope ACS images and color-magnitude diagrams for 24 nearby galaxies in and near the constellation of Centaurus with radial velocities V_LG_<550km/s. Distances are determined based on the luminosities of stars at the tip of the red giant branch that range from 3.0 to 6.5Mpc. The galaxies are concentrated in two spatially separated groups around Cen A (NGC 5128) and M83 (NGC 5236).
2128. Galaxies around M87
- ID:
- ivo://CDS.VizieR/J/A+A/635/A135
- Title:
- Galaxies around M87
- Short Name:
- J/A+A/635/A135
- Date:
- 07 Dec 2021 09:09:23
- Publisher:
- CDS
- Description:
- This work considers the Virgo cluster of galaxies, focusing on its structure, kinematics, and morphological landscape. Our principal aim is to estimate the virial mass of the cluster. For this purpose, we present a sample of 1537 galaxies with radial velocities V_LG_<2600km/s situated within a region of 30x20 degrees around M87. About half of the galaxies have distance estimates. We selected 398 galaxies with distances in the (17+/-5)Mpc range. Based on their 1D and 2D number-density profiles and their radial velocity dispersions, we made an estimate for the virial mass of the Virgo cluster. Results. We identify the infall of galaxies towards the Virgo cluster core along the Virgo Southern Extention filament. From a 1D profile of the cluster, we obtain the virial mass estimate of (6.3+/-0.9)x10^14^ solar masses, which is in tight agreement with its mass estimate via the external infall pattern of galaxies. We conclude that the Virgo cluster outskirts between the virial radius and the zero-velocity radius do not contain significant amounts of dark matter beyond the virial radius.
- ID:
- ivo://CDS.VizieR/J/A+A/435/A135
- Title:
- Galaxies around M87 (Kashibadze+, 2020)
- Short Name:
- J/A+A/435/A135
- Date:
- 23 Mar 2020 13:32:44
- Publisher:
- CDS
- Description:
- Galaxies around M87 with supergalactic coordinates SGL=[87.9, 117.9] degrees, SGB=[-12.4, +7.6] degrees and radial velocities V_LG_<2600km/s. The table contains 1537 galaxies, among them, 738 galaxies have distance estimates: 358 from public databases and 380 distances estimated for the first time in this paper (indicated in the last column as TF or TFb).
- ID:
- ivo://CDS.VizieR/J/ApJ/653/1004
- Title:
- Galaxies at 1.4<~z<~3.0 in GOODS-North Field
- Short Name:
- J/ApJ/653/1004
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a spectroscopic survey with LRIS-B on Keck of more than 280 star-forming galaxies and AGNs at redshifts 1.4~<z~<3.0 in the GOODS-N field. Candidates are selected by their UnGR colors using the "BM/BX" criteria to target redshift 1.4~<z~<2.5 galaxies and the LBG criteria to target redshift z~3 galaxies; combined these samples account for ~25%-30% of the R and Ks band counts to R=25.5 and Ks(AB)=24.4, respectively. The 212 BM/BX galaxies and 74 LBGs constitute the largest spectroscopic sample of galaxies at z>1.4 in GOODS-N. Extensive multiwavelength data allow us to investigate the stellar populations, stellar masses, bolometric luminosities (Lbol), and extinction z~2 of galaxies. Deep Chandra and Spitzer data indicate that the sample includes galaxies with a wide range in Lbol (~10^10^ to >10^12^L_{sun}_) and 4 orders of magnitude in dust obscuration (Lbol/LUV).
