- ID:
- ivo://CDS.VizieR/J/AJ/162/100
- Title:
- PAST. II. LAMOST-Gaia-Kepler catalog of 35835 stars
- Short Name:
- J/AJ/162/100
- Date:
- 14 Mar 2022 06:40:51
- Publisher:
- CDS
- Description:
- The Kepler telescope has discovered over 4000 planets (candidates) by searching ~200000 stars over a wide range of distance (order of kpc) in our Galaxy. Characterizing the kinematic properties (e.g., Galactic component membership and kinematic age) of these Kepler targets (including the planet candidate hosts) is the first step toward studying Kepler planets in the Galactic context, which will reveal fresh insights into planet formation and evolution. In this paper, the second part of the Planets Across the Space and Time (PAST) series, by combining the data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) and Gaia and then applying the revised kinematic methods from PAST I, we present a catalog of kinematic properties (i.e., Galactic positions, velocities, and the relative membership probabilities among the thin disk, thick disk, Hercules stream, and the halo) as well as other basic stellar parameters for 35835 Kepler stars. Further analyses of the LAMOST-Gaia-Kepler catalog demonstrate that our derived kinematic age reveals the expected stellar activity-age trend. Furthermore, we find that the fraction of thin (thick) disk stars increases (decreases) with the transiting planet multiplicity (N_p_=0,1,2 and3+) and the kinematic age decreases with N_p_, which could be a consequence of the dynamical evolution of planetary architecture with age. The LAMOST-Gaia-Kepler catalog will be useful for future studies on the correlations between the exoplanet distributions and the stellar Galactic environments as well as ages.
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- ID:
- ivo://CDS.VizieR/J/A+A/589/A83
- Title:
- PCA-based inversion of stellar parameters
- Short Name:
- J/A+A/589/A83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an automated procedure that simultaneously derives the effective temperature Teff, surface gravity logg, metallicity [Fe/H], and equatorial projected rotational velocity vsini for "normal" A and Am stars. The procedure is based on the principal component analysis (PCA) inversion method, which we published in a recent paper. A sample of 322 high-resolution spectra of F0-B9 stars, retrieved from the Polarbase, SOPHIE, and ELODIE databases, were used to test this technique with real data. We selected the spectral region from 4400-5000 Ang as it contains many metallic lines and the Balmer H{beta} line. Using three data sets at resolving powers of R=42000, 65000 and 76000, about ~6.6x10^6 synthetic spectra were calculated to build a large learning database. The Online Power Iteration algorithm was applied to these learning data sets to estimate the principal components (PC). The projection of spectra onto the few PCs offered an efficient comparison metric in a low-dimensional space. The spectra of the well-known A0- and A1-type stars, Vega and Sirius A, were used as control spectra in the three databases. Spectra of other well-known A-type stars were also employed to characterize the accuracy of the inversion technique. We inverted all of the observational spectra and derived the atmospheric parameters. After removal of a few outliers, the PCA-inversion method appeared to be very efficient in determining Teff, [Fe/H], and vsini for A/Am stars. The derived parameters agree very well with previous determinations. Using a statistical approach, deviations of around 150K, 0.35dex, 0.15dex, and 2km/s were found for Teff, logg, [Fe/H], and vsini with respect to literature values for A-type stars. The PCA inversion proves to be a very fast, practical, and reliable tool for estimating stellar parameters of FGK and A stars and for deriving effective temperatures of M stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/846/145
- Title:
- PHAT. XIX. Formation history of M31 disk
- Short Name:
- J/ApJ/846/145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We map the star formation history across M31 by fitting stellar evolution models to color-magnitude diagrams of each 83"x83" (0.3x1.4kpc, deprojected) region of the Panchromatic Hubble Andromeda Treasury (PHAT) survey outside of the innermost 6'x12' portion. We find that most of the star formation occurred prior to ~8Gyr ago, followed by a relatively quiescent period until ~4Gyr ago, a subsequent star formation episode about 2Gyr ago, and a return to relative quiescence. There appears to be little, if any, structure visible for populations with ages older than 2Gyr, suggesting significant mixing since that epoch. Finally, assuming a Kroupa initial mass function from 0.1 to 100M_{sun}_, we find that the total amount of star formation over the past 14Gyr in the area over which we have fit models is 5x10^10^M_{sun}_. Fitting the radial distribution of this star formation and assuming azimuthal symmetry, (1.5+/-0.2)x10^11^M_{sun}_ of stars has formed in the M31 disk as a whole, (9+/-2)x10^10^M_{sun}_ of which has likely survived to the present after accounting for evolutionary effects. This mass is about one-fifth of the total dynamical mass of M31.
- ID:
- ivo://CDS.VizieR/J/MNRAS/466/2006
- Title:
- Phoenix dwarf galaxy RV and [Fe/H] catalog
- Short Name:
- J/MNRAS/466/2006
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Transition type dwarf galaxies are thought to be systems undergoing the process of transformation from a star-forming into a passively evolving dwarf, which makes them particularly suitable to study evolutionary processes driving the existence of different dwarf morphological types. Here we present results from a spectroscopic survey of ~200 individual red giant branch stars in the Phoenix dwarf, the closest transition type with a comparable luminosity to 'classical' dwarf galaxies. We measure a systemic heliocentric velocity Vhelio=-21.2+/-1.0km/s. Our survey reveals the clear presence of prolate rotation that is aligned with the peculiar spatial distribution of the youngest stars in Phoenix. We speculate that both features might have arisen from the same event, possibly an accretion of a smaller system. The evolved stellar population of Phoenix is relatively metal-poor (<[Fe/H]>=-1.49+/-0.04dex) and shows a large metallicity spread (sigma_[Fe/H]_=0.51+/-0.04dex), with a pronounced metallicity gradient of -0.13+/-0.01dex/arcmin similar to luminous, passive dwarf galaxies. We also report a discovery of an extremely metal-poor star candidate in Phoenix and discuss the importance of correcting for spatial sampling when interpreting the chemical properties of galaxies with metallicity gradients. This study presents a major leap forward in our knowledge of the internal kinematics of the Phoenix transition type dwarf galaxy and the first wide area spectroscopic survey of its metallicity properties.
- ID:
- ivo://CDS.VizieR/J/AJ/158/219
- Title:
- Phosphorus abundances in the Hyades and Galactic disk
- Short Name:
- J/AJ/158/219
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have measured phosphorus abundances in nine disk stars between -1< [Fe/H]< -0.5 and in 12 members of the Hyades open cluster using two P I lines at 1.06 {mu}m. High-resolution infrared spectra were obtained using Phoenix on Gemini South and abundances were determined by comparing synthetic spectra to the observations. The average abundance for the dwarf stars in our Hyades sample was <[P/Fe]>=-0.01+/-0.06 and <[P/Fe]>=0.03+/-0.03 dex for the three giants. The consistency suggests that abundances derived using the 1.06 {mu}m P I lines are not subjected to temperature- or luminosity-dependent systematic effects at high metallicities. Our [P/Fe] ratios measured in disk stars are consistent with chemical evolution models with P yields increased by a factor of 2.75. We find that [P/O], [P/Mg], [P/Si], and [P/Ti] ratios are consistent with the solar ratio over a range of -1.0<[Fe/H]<0.2 with the [P/Si] ratio increasing by ~0.1-0.2 dex at the lowest [Fe/H] ratios. Finally, the evolution of [P/Fe] with age is similar to other {alpha} elements, providing evidence that P is produced at the same sites.
- ID:
- ivo://CDS.VizieR/J/ApJ/831/116
- Title:
- Photmetry and spectroscopy of PMS stars in NGC 2264
- Short Name:
- J/ApJ/831/116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The timescale of cluster formation is an essential parameter in order to understand the formation process of star clusters. Pre-main sequence (PMS) stars in nearby young open clusters reveal a large spread in brightness. If the spread were considered to be a result of a real spread in age, the corresponding cluster formation timescale would be about 5-20Myr. Hence it could be interpreted that star formation in an open cluster is prolonged for up to a few tens of Myr. However, difficulties in reddening correction, observational errors, and systematic uncertainties introduced by imperfect evolutionary models for PMS stars can result in an artificial age spread. Alternatively, we can utilize Li abundance as a relative age indicator of PMS star to determine the cluster formation timescale. The optical spectra of 134 PMS stars in NGC 2264 have been obtained with MMT/Hectochelle. The equivalent widths have been measured for 86 PMS stars with a detectable Li line (3500<{T}_eff[K]_<=6500).
- ID:
- ivo://CDS.VizieR/J/A+A/654/A172
- Title:
- Photoionization of the CH radical
- Short Name:
- J/A+A/654/A172
- Date:
- 07 Mar 2022 07:12:57
- Publisher:
- CDS
- Description:
- The primary motivation of this paper is to provide accurate data for the photoionization of the CH radical, including absolute total photoionization cross section, partial cross sections and photo electron angular distribution. In addition,the near threshold features in the photoionization curve (which are absent in previous studies) are produced with high precision. A multichannel wavefunction based on R-matrix approach, which uses the configuration interaction (CI) method to describe electronic correlation, is carried out in the present calculations. A set of B-spline orbitals is employed to represent the accurate continuum. The distinctive feature of the present calculations allows us to generate a more accurate description of the bound and continuum states than those employed before. Total photoionization cross sections from the ground state of CH radicals and partial cross sections corresponding to 1{pi}, 3{sigma}, and 2{sigma} states of CH+ ions are presented for photon energies ranging from threshold to 80eV. Extensive resonance structures, which are absent in previous studies, near the ionization threshold, are observed for the first time. The cross-section dataset obtained from the present calculations is expected to be sufficiently accurate and comprehensive for most current modeling applications involving the photon and CH radicals scattering system.
- ID:
- ivo://CDS.VizieR/J/ApJS/254/31
- Title:
- Photometric metallicities of stars in SkyMapper DR2
- Short Name:
- J/ApJS/254/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Milky Way's metal-poor stars are nearby ancient objects that are used to study early chemical evolution and the assembly and structure of the Milky Way. Here we present reliable metallicities of ~280000 stars with -3.75<~[Fe/H]<~-0.75 down to g=17 derived using metallicity-sensitive photometry from the second data release of the SkyMapper Southern Survey. We use the dependency of the flux through the SkyMapper v filter on the strength of the CaII K absorption features, in tandem with SkyMapper u, g, i photometry, to derive photometric metallicities for these stars. We find that metallicities derived in this way compare well to metallicities derived in large-scale spectroscopic surveys, and we use such comparisons to calibrate and quantify systematics as a function of location, reddening, and color. We find good agreement with metallicities from the APOGEE, LAMOST, and GALAH surveys, based on a standard deviation of {sigma}~0.25dex of the residuals of our photometric metallicities with respect to metallicities from those surveys. We also compare our derived photometric metallicities to metallicities presented in a number of high-resolution spectroscopic studies to validate the low-metallicity end ([Fe/H]{<}-2.5) of our photometric metallicity determinations. In such comparisons, we find the metallicities of stars with photometric [Fe/H]{<}-2.5 in our catalog show no significant offset and a scatter of {sigma}~0.31dex level relative to those in high-resolution work when considering the cooler stars (g-i>0.65) in our sample. We also present an expanded catalog containing photometric metallicities of ~720000 stars as a data table for further exploration of the metal-poor Milky Way.
- ID:
- ivo://CDS.VizieR/J/ApJ/901/169
- Title:
- Photometric obs. & LAMOST sp. of 4 W UMa binaries
- Short Name:
- J/ApJ/901/169
- Date:
- 22 Feb 2022 00:36:07
- Publisher:
- CDS
- Description:
- We present new photometric data and LAMOST spectra for the W UMa binaries UV Lyn, V781 Tau, NSVS 4484038, and 2MASS J15471055+5302107. The orbital and starspot parameters are obtained using the Wilson-Devinney program. Comparing the starspot parameters at different times, there are magnetic activities in these four binaries. The orbital period of UV Lyn is increasing at a rate of dP/dt=+8.9(5)x10^-8^d/yr, which maybe due to mass transfer from the less massive component to the more massive component (dM1/dt=-6.4x10^-8^M_{sun}_/yr). The period variation of 2MASSJ15471055+5302107 is also increasing at a rate of 6.0(4)x10^-7^d/yr, which can be explained by mass transfer from the less massive component to the more massive component (dM1/dt=-2.8x10^-7^M_{sun}_/yr). The period variation of V781 Tau presents the downward parabola superimposed the cyclic oscillation. The period of V781 Tau is decreasing (dP/dt=-3.2(4)x10^-8^d/yr), which can be explained by mass transfer from the more massive component to the less massive component (dM2/dt=-2.2x10^-8^M_{sun}_/yr). The cyclic oscillation may be due to the magnetic activity with a period of 30.8(5)yr rather than a third body. The period variation of NSVS4484038 also shows the cyclic oscillation, which could be explained by the magnetic activity with 10.8(1)yr or a black hole candidate. Interestingly, there is a depth variation between the light minimum times of NSVS 4484038, which may also be caused by stellar magnetic activity.
- ID:
- ivo://CDS.VizieR/J/MNRAS/475/1633
- Title:
- Photometric study of globular clusters
- Short Name:
- J/MNRAS/475/1633
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we describe the photometric and spectroscopic properties of multiple populations in seven northern globular clusters. In this study, we employ precise ground-based photometry from the private collection of Stetson, space photometry from the Hubble Space Telescope (HST), literature abundances of Na and O, and Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey abundances for Mg, Al, C, and N. Multiple populations are identified by their position in the C_U,B,I_-V pseudo colour-magnitude diagram (pseudo-CMD) and confirmed with their chemical composition determined using abundances. We confirm the expectation from previous studies that the red giant branches (RGBs) in all seven clusters are split and the different branches have different chemical compositions. The Mg-Al anticorrelations were well explored by the APOGEE and Gaia-ESO surveys for most globular clusters, some clusters showing bimodal distributions, while others continuous distributions. Even though the structure (i.e. bimodal versus continuous) of Mg-Al can greatly vary, the Al-rich and Al-poor populations do not seem to have very different photometric properties, agreeing with theoretical calculations. There is no one-to-one correspondence between the Mg-Al anticorrelation shape (bimodal versus continuous) and the structure of the RGB seen in the HST pseudo-CMDs, with the HSTphotometric information usually implying more complex formation/evolution histories than the spectroscopic ones. We report on finding two second-generation horizontal branch (HB) stars in M5, and five second-generation asymptotic giant branch (AGB) stars in M92, which is the most metal-poor cluster to date in which second-generation AGB stars have been observed.