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- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/773/168
- Title:
- Submm fluxes of very low-mass stars and BDs
- Short Name:
- J/ApJ/773/168
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present SCUBA-2 850{mu}m observations of seven very low mass stars (VLMS) and brown dwarfs (BDs). Three are in Taurus and four in the TW Hydrae Association (TWA), and all are classical T Tauri (cTT) analogs. We detect two of the three Taurus disks (one only marginally), but none of the TWA ones. For standard grains in cTT disks, our 3{sigma} limits correspond to a dust mass of 1.2M_{Earth}_ in Taurus and a mere 0.2M_{Earth}_ in the TWA (3-10x deeper than previous work). We combine our data with other submillimeter/millimeter (sub-mm/mm) surveys of Taurus, {rho} Oph, and the TWA to investigate the trends in disk mass and grain growth during the cTT phase.
- ID:
- ivo://CDS.VizieR/J/MNRAS/403/1089
- Title:
- SUNS and DEBRIS surveys target selection
- Short Name:
- J/MNRAS/403/1089
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Debris discs - analogous to the asteroid and Kuiper-Edgeworth belts in the Solar system - have so far mostly been identified and studied in thermal emission shortward of 100um. The Herschel space observatory and the Submillimetre Common-User Bolometer Array-2 (SCUBA-2) camera on the James Clerk Maxwell Telescope will allow efficient photometric surveying at 70 to 850um, which allows for the detection of cooler discs not yet discovered, and the measurement of disc masses and temperatures when combined with shorter wavelength photometry. The SCUBA-2 Unbiased Nearby Stars survey (SUNS) and the Disc Emission via a Bias-free Reconnaissance in the Infrared/Submillimetre (DEBRIS) Herschel Open Time Key Project are complementary legacy surveys observing samples of ~500 nearby stellar systems. To maximize the legacy value of these surveys, great care has gone into the target selection process. This paper describes the target selection process and presents the target lists of these two surveys.
- ID:
- ivo://CDS.VizieR/J/MNRAS/372/1117
- Title:
- SuperWASP exoplanetary transit survey
- Short Name:
- J/MNRAS/372/1117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric transit surveys promise to complement the currently known sample of extra-solar planets (ESPs) by providing additional information on the planets and especially their radii. Here, we present ESP candidates from one such survey called, the Wide Angle Search for Planets (WASP) obtained with the SuperWASP wide-field imaging system. Observations were taken with SuperWASP North located in La Palma during the 2004 April to October observing season. The data cover fields between 23 and 03h in RA at declinations above +12{deg}. This amounts to over >>400000 stars with V magnitudes 8-13.5. For the stars brighter than 12.5, we achieve better than 1% photometric precision. Here, we present 41 sources with low-amplitude variability between >>1 and 10mmag, from which we select 12 with periods between 1.2 and 4.4d as the most promising ESP candidates. We discuss the properties of these ESP candidates, the expected fraction of transits recovered for our sample and implications for the frequency and detection of hot-Jupiters.
