- ID:
- ivo://CDS.VizieR/J/AJ/157/159
- Title:
- Stellar parameters for 131 Herbig Ae/Be stars
- Short Name:
- J/AJ/157/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The present study makes use of the unprecedented capability of the Gaia mission to obtain the stellar parameters such as distance, age, and mass of HAeBe stars. The accuracy of Gaia DR2 (Cat. I/345) astrometry is demonstrated from the comparison of the Gaia DR2 distances of 131 HAeBe stars with the previously estimated values from the literature. This is one of the initial studies to estimate the age and mass of a confirmed sample of HAeBe stars using both the photometry and distance from the Gaia mission. Mass accretion rates are calculated from H{alpha} line flux measurements of 106 HAeBe stars. Since we used distances and the stellar masses derived from the Gaia DR2 data in the calculation of the mass accretion rate, our estimates are more accurate than previous studies. The mass accretion rate is found to decay exponentially with age, from which we estimated a disk dissipation timescale of 1.9+/-0.1 Myr. The mass accretion rate and stellar mass exhibit a power-law relation of the form M_acc_{prop.to}M_*_^2.8+/-0.2^. From the distinct distribution in the values of the infrared spectral index, n_2-4.6_, we suggest the possibility of difference in the disk structure between Herbig Be and Herbig Ae stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/400/939
- Title:
- Stellar parameters of 115 HQS sdB stars
- Short Name:
- J/A+A/400/939
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a spectral analysis of a large sample of subdwarf B stars selected from follow-up observations of candidates from the Hamburg Quasar Survey. Table 4 summarizes the results (effective temperatures, gravities, and helium abundances) of our analysis. Additionally, the equatorial and galactical coordinates, the B magnitudes and extinctions, the derived radial velocities, the absolute visual magnitudes, the distances from earth and from the galactic plane, and the references are given for all programme stars.
- ID:
- ivo://CDS.VizieR/J/A+A/568/A119
- Title:
- Stellar physical parameters for young stars
- Short Name:
- J/A+A/568/A119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A uvbyH{beta} Stromgren photometric survey covering 16 square degrees in the anticenter direction was carried out using the Wide Field Camera at the Isaac Newton Telescope. Physical parameters like stellar distances and extinctions for the young stars of our survey are presented here. We developed a new method for deriving physical parameters from Stromgren photometry and also implemented and tested it. This is a model-based method that uses the most recent available stellar atmospheric models and evolutionary tracks to interpolate in a 3D grid of the unreddened indexes [m1], [c1] and H{beta}. Distances derived from both this method and the classical pre-Hipparcos calibrations were tested against Hipparcos parallaxes and found to be accurate. Furthermore, a shift in the atmospheric grids in the range Teff=[7000,9000]K was detected and a correction is proposed. The two methods were used to compute distances and reddening for around 12000 OBA-type stars in our Stromgren anticenter survey. Data from the IPHAS and 2MASS catalogs were used to complement the detection of emission line stars and to break the degeneracy between early and late photometric regions. We note that photometric distances can differ by more than 20%, those derived from the empirical calibrations being smaller than those derived with the new method, which agree better with the Hipparcos data.
- ID:
- ivo://CDS.VizieR/II/226
- Title:
- Stellar polarization catalogs agglomeration
- Short Name:
- II/226
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an agglomeration of stellar polarization catalogs with results for 9286 stars. We have endeavoured to eliminate errors, provide accurate positions, sensibly weight multiple observations of the same star, and provide reasonable distances.
- ID:
- ivo://CDS.VizieR/J/AJ/156/217
- Title:
- Stellar properties for M dwarfs in MEarth-South
- Short Name:
- J/AJ/156/217
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar rotation periods are valuable both for constraining models of angular momentum loss and for understanding how magnetic features impact inferences of exoplanet parameters. Building on our previous work in the northern hemisphere, we have used long-term, ground-based photometric monitoring from the MEarth Observatory to measure 234 rotation periods for nearby, southern hemisphere M dwarfs. Notable examples include the exoplanet hosts GJ 1132, LHS 1140, and Proxima Centauri. We find excellent agreement between our data and K2 photometry for the overlapping subset. Among the sample of stars with the highest quality data sets, we recover periods in 66%; as the length of the data set increases, our recovery rate approaches 100%. The longest rotation periods we detect are around 140 days, which we suggest represent the periods that are reached when M dwarfs are as old as the local thick disk (about 9 Gyr).
- ID:
- ivo://CDS.VizieR/J/MNRAS/475/5487
- Title:
- Stellar properties of KIC stars
- Short Name:
- J/MNRAS/475/5487
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Investigations of the origin and evolution of the Milky Way disc have long relied on chemical and kinematic identifications of its components to reconstruct our Galactic past. Difficulties in determining precise stellar ages have restricted most studies to small samples, normally confined to the solar neighbourhood. Here, we break this impasse with the help of asteroseismic inference and perform a chronology of the evolution of the disc throughout the age of the Galaxy. We chemically dissect the Milky Way disc population using a sample of red giant stars spanning out to 2 kpc in the solar annulus observed by the Kepler satellite, with the added dimension of asteroseismic ages. Our results reveal a clear difference in age between the low- and high-{alpha} populations, which also show distinct velocity dispersions in the V and W components. We find no tight correlation between age and metallicity nor [{alpha}/Fe] for the high-{alpha} disc stars. Our results indicate that this component formed over a period of more than 2 Gyr with a wide range of [M/H] and [{alpha}/Fe] independent of time. Our findings show that the kinematic properties of young {alpha}-rich stars are consistent with the rest of the high-{alpha} population and different from the low-{alpha} stars of similar age, rendering support to their origin being old stars that went through a mass transfer or stellar merger event, making them appear younger, instead of migration of truly young stars formed close to the Galactic bar.
- ID:
- ivo://CDS.VizieR/J/A+A/630/A137
- Title:
- Structure and kinematics of the Taurus region
- Short Name:
- J/A+A/630/A137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We take advantage of the second data release of the Gaia space mission and the state-of-the-art astrometry delivered from very long baseline interferometry observations to revisit the structure and kinematics of the nearby Taurus star-forming region. We apply a hierarchical clustering algorithm for partitioning the stars in our sample into groups (i.e., clusters) that are associated with the various molecular clouds of the complex, and derive the distance and spatial velocity of individual stars and their corresponding molecular clouds. We show that the molecular clouds are located at different distances and confirm the existence of important depth effects in this region reported in previous studies. For example, we find that the L~1495 molecular cloud is located at d=129.9^+0.4^_-0.3_pc, while the filamentary structure connected to it (in the plane of the sky) is at d=160.0^+1.2^_-1.2_pc. We report B215 and L1558 as the closest (d=128.5^+1.6^_-1.6_pc) and most remote (d=198.1^+2.5^_-2.5_pc) substructures of the complex, respectively. The median inter-cloud distance is 25pc and the relative motion of the subgroups is on the order of a few km/s. We find no clear evidence for expansion (or contraction) of the Taurus complex, but signs of the potential effects of a global rotation. Finally, we compare the radial velocity of the stars with the velocity of the underlying ^13^CO molecular gas and report a mean difference of 0.04+/-0.12km/s (with r.m.s. of 0.63km/s) confirming that the stars and the gas are tightly coupled.
- ID:
- ivo://CDS.VizieR/J/MNRAS/477/L50
- Title:
- Structure of the Upper Scorpius association
- Short Name:
- J/MNRAS/477/L50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using new proper motion data from recently published catalogs, we revisit the membership of previously identified members of the Upper Scorpius association. We confirmed 750 of them as cluster members based on the convergent point method, compute their kinematic parallaxes and combined them with Gaia parallaxes to investigate the 3D structure and geometry of the association using a robust covariance method. We find a mean distance of 146+/-3+/-6pc and show that the morphology of the association defined by the brightest (and most massive) stars yields a prolate ellipsoid with dimensions of 74x38x32pc^3^, while the faintest cluster members define a more elongated structure with dimensions of 98x24x18pc^3^. We suggest that the different properties of both populations is an imprint of the star formation history in this region.
- ID:
- ivo://CDS.VizieR/J/MNRAS/454/1086
- Title:
- Study of the COSC Korean astronomical catalogue
- Short Name:
- J/MNRAS/454/1086
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The study of old star catalogues provides important astrometric data. Most of the researches based on the old star catalogues were manuscript published in Europe and from Arabic/Islam. However, the old star catalogues published in East Asia did not get attention. Therefore, among the East Asian star catalogues we focus on a particular catalogue recorded in a Korean almanac. Its catalogue contains 277 stars that are positioned in a region within 10{deg} of the ecliptic plane. The stars in the catalogue were identified using the modern Hipparcos catalogue (Cat. I/239). We identified 274 among 277 stars, which is a rate of 98.9 percent. The catalogue records the epoch of the stars' positions as AD 1396.0. However, by using all of the identified stars we found that the initial epoch of the catalogue is AD 1363.1+/-3.2. In conclusion, the star catalogue was compiled and edited from various older star catalogues. We assume a correlation with the Almagest by Ptolemaios. This study presents newly analysed results from the historically important astronomical data discovered in East Asia. Therefore, this star catalogue will become important data for comparison with the star catalogues published in Europe and from Arabic/Islam.
- ID:
- ivo://CDS.VizieR/J/PASJ/68/92
- Title:
- Subaru NIR obs. of Pleiades stars in SEEDS survey
- Short Name:
- J/PASJ/68/92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We find a new substellar companion to the Pleiades member star, Pleiades HII 3441, using the Subaru telescope with adaptive optics. The discovery is made as part of the high-contrast imaging survey to search for planetary-mass and substellar companions in the Pleiades and young moving groups. The companion has a projected separation of 0.49+/-0.02 (66+/-2au) and a mass of 68+/-5MJ based on three observations in the J-, H-, and Ks-bands. The spectral type is estimated to be M7 (~2700K), and thus no methane absorption is detected in the H band. Our Pleiades observations result in the detection of two substellar companions including one previously reported among 20 observed Pleiades stars, and indicate that the fraction of substellar companions in the Pleiades is about 10.0^+26.1^_-8.8_%. This is consistent with multiplicity studies of both the Pleiades stars and other open clusters.
