- 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.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/1442
- Title:
- 78 Stripe82 galaxies masses
- Short Name:
- J/MNRAS/478/1442
- Date:
- 19 Jan 2022 11:53:49
- Publisher:
- CDS
- Description:
- We present a cross-calibration of CO- and dust-based molecular gas masses at z<=0.2. Our results are based on a survey with the IRAM 30-m telescope collecting CO(1-0) measurements of 78 massive (logM*/M_{sun}_>10) galaxies with known gas-phase metallicities and with IR photometric coverage from Wide-field Infrared Survey Explorer(WISE; 22um) and Herschel Spectral and Photometric Imaging Receiver (SPIRE; 250, 350, 500um). We find a tight relation (~0.17dex scatter) between the gas masses inferred from CO and dust continuum emission, with a minor systematic offset of 0.05dex. The two methods can be brought into agreement by applying a metallicity-dependent adjustment factor (~0.13dex scatter). We illustrate that the observed offset is consistent with a scenario in which dust traces not only molecular gas but also part of the HI reservoir, residing in the H_2_-dominated region of the galaxy. Observations of the CO(2-1) to CO(1-0) line ratio for two-thirds of the sample indicate a narrow range in excitation properties, with a median ratio of luminosities <R_21_>~0.64. Finally, we find dynamical mass constraints from spectral line profile fitting to agree well with the anticipated mass budget enclosed within an effective radius, once all mass components (stars, gas, and dark matter) are accounted for.
- ID:
- ivo://CDS.VizieR/J/A+A/327/1039
- Title:
- Structure and evolution of low-mass stars
- Short Name:
- J/A+A/327/1039
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Properties of Very Low mass stars for different initial metallicity [M/H] and Helium mass fraction: mass (in solar mass), age (in Gyrs) effective temperature (in K), log of luminosity (in solar L), radius (10^10cm), central temperature Tc (in K) and density RHOc (in gr/cm-3). Abundances of light elements are normalised to their initial abundance (see text).
- ID:
- ivo://CDS.VizieR/J/AJ/162/28
- Title:
- Studying of protoplanetary disks in SFRs with ALMA
- Short Name:
- J/AJ/162/28
- Date:
- 14 Mar 2022 06:54:01
- Publisher:
- CDS
- Description:
- Gaps in protoplanetary disks have long been hailed as signposts of planet formation. However, a direct link between exoplanets and disks remains hard to identify. We present a large sample study of ALMA disk surveys of nearby star-forming regions to disentangle this connection. All disks are classified as either structured (transition, ring, extended) or nonstructured (compact) disks. Although low-resolution observations may not identify large-scale substructure, we assume that an extended disk must contain substructure from a dust evolution argument. A comparison across ages reveals that structured disks retain high dust masses up to at least 10Myr, whereas the dust mass of compact, nonstructured disks decreases over time. This can be understood if the dust mass evolves primarily by radial drift, unless drift is prevented by pressure bumps. We identify a stellar mass dependence of the fraction of structured disks. We propose a scenario linking this dependence with that of giant exoplanet occurrence rates. We show that there are enough exoplanets to account for the observed disk structures if transitional disks are created by exoplanets more massive than Jupiter and ring disks by exoplanets more massive than Neptune, under the assumption that most of those planets eventually migrate inwards. On the other hand, the known anticorrelation between transiting super-Earths and stellar mass implies those planets must form in the disks without observed structure, consistent with formation through pebble accretion in drift-dominated disks. These findings support an evolutionary scenario where the early formation of giant planets determines the disk's dust evolution and its observational appearance.
- ID:
- ivo://CDS.VizieR/J/ApJ/771/129
- Title:
- Submillimetric Class II sources of Taurus
- Short Name:
- J/ApJ/771/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a substantial extension of the millimeter (mm) wave continuum photometry catalog for circumstellar dust disks in the Taurus star-forming region, based on a new "snapshot" {lambda}=1.3mm survey with the Submillimeter Array. Combining these new data with measurements in the literature, we construct a mm-wave luminosity distribution, f(L_mm_), for Class II disks that is statistically complete for stellar hosts with spectral types earlier than M8.5 and has a 3{sigma} depth of roughly 3mJy. The resulting census eliminates a longstanding selection bias against disks with late-type hosts, and thereby demonstrates that there is a strong correlation between L_mm_ and the host spectral type. By translating the locations of individual stars in the Hertzsprung-Russell diagram into masses and ages, and adopting a simple conversion between L_mm_ and the disk mass, M_d_, we confirm that this correlation corresponds to a statistically robust relationship between the masses of dust disks and the stars that host them. A Bayesian regression technique is used to characterize these relationships in the presence of measurement errors, data censoring, and significant intrinsic scatter: the best-fit results indicate a typical 1.3mm flux density of ~25mJy for 1M_{sun}_ hosts and a power-law scaling L_mm_{propto}M_{star}_^1.5-2.0^. We suggest that a reasonable treatment of dust temperature in the conversion from L_mm_ to M_d_ favors an inherently linear M_d_{prop.to}M_*_ scaling, with a typical disk-to-star mass ratio of ~0.2%-0.6%. The measured rms dispersion around this regression curve is +/-0.7dex, suggesting that the combined effects of diverse evolutionary states, dust opacities, and temperatures in these disks imprint a full width at half-maximum range of a factor of ~40 on the inferred M_d_ (or L_mm_) at any given host mass.
- 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/ApJ/799/155
- Title:
- Sub-stellar companions in Taurus
- Short Name:
- J/ApJ/799/155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a large, high-spatial-resolution near-infrared imaging search for stellar and sub-stellar companions in the Taurus-Auriga star-forming region. The sample covers 64 stars with masses between those of the most massive Taurus members at ~3M_{sun}_ and low-mass stars at ~0.2M_{sun}_. We detected 74 companion candidates, 34 of these reported for the first time. Twenty-five companions are likely physically bound, partly confirmed by follow-up observations. Four candidate companions are likely unrelated field stars. Assuming physical association with their host star, estimated companion masses are as low as ~2M_Jup_. The inferred multiplicity frequency within our sensitivity limits between ~10-1500AU is 26.3_-4.9_^+6.6^%. Applying a completeness correction, 62%+/-14% of all Taurus stars between 0.7 and 1.4M_{sun}_ appear to be multiple. Higher order multiples were found in 1.8_-1.5_^+4.2^% of the cases, in agreement with previous observations of the field. We estimate a sub-stellar companion frequency of ~3.5%-8.8% within our sensitivity limits from the discovery of two likely bound and three other tentative very low-mass companions. This frequency appears to be in agreement with what is expected from the tail of the stellar companion mass ratio distribution, suggesting that stellar and brown dwarf companions share the same dominant formation mechanism. Further, we find evidence for possible evolution of binary parameters between two identified sub-populations in Taurus with ages of ~2Myr and ~20Myr, respectively.
- ID:
- ivo://CDS.VizieR/J/ApJS/244/21
- Title:
- Surface rotation & activity of Kepler stars. I.
- Short Name:
- J/ApJS/244/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Brightness variations due to dark spots on the stellar surface encode information about stellar surface rotation and magnetic activity. In this work, we analyze the Kepler long-cadence data of 26521 main-sequence stars of spectral types M and K in order to measure their surface rotation and photometric activity level. Rotation-period estimates are obtained by the combination of a wavelet analysis and autocorrelation function of the light curves. Reliable rotation estimates are determined by comparing the results from the different rotation diagnostics and four data sets. We also measure the photometric activity proxy S_ph_ using the amplitude of the flux variations on an appropriate timescale. We report rotation periods and photometric activity proxies for about 60% of the sample, including 4431 targets for which McQuillan+ (2014, J/ApJS/211/24) did not report a rotation period. For the common targets with rotation estimates in this study and in McQuillan+, our rotation periods agree within 99%. In this work, we also identify potential polluters, such as misclassified red giants and classical pulsator candidates. Within the parameter range we study, there is a mild tendency for hotter stars to have shorter rotation periods. The photometric activity proxy spans a wider range of values with increasing effective temperature. The rotation period and photometric activity proxy are also related, with S_ph_ being larger for fast rotators. Similar to McQuillan+, we find a bimodal distribution of rotation periods.
- ID:
- ivo://CDS.VizieR/J/A+A/605/A111
- Title:
- Surface rotation of Kepler red giant stars
- Short Name:
- J/A+A/605/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Kepler allows the measurement of starspot variability in a large sample of field red giants for the first time. With a new method that combines autocorrelation and wavelet decomposition, we measure 361 rotation periods from the full set of 17,377 oscillating red giants in our sample. This represents 2.08% of the stars, consistent with the fraction of spectroscopically detected rapidly rotating giants in the field. The remaining stars do not show enough variability to allow us to measure a reliable surface rotation period. Because the stars with detected rotation periods have measured oscillations, we can infer their global properties, e.g. mass and radius, and quantitatively evaluate the predictions of standard stellar evolution models as a function of mass. Consistent with results for cluster giants, when we consider only the 4881 intermediate-mass stars, M>2.0M_{sun}_from our full red giant sample, we do not find the enhanced rates of rapid rotation one would expect from angular momentum conservation. We therefore suggest that either enhanced angular momentum loss or radial differential rotation must be occurring in these stars. Finally, when we examine the 575 low-mass (M<1.1M_{sun}_) red clump stars in our sample, which we would have expected to exhibit slow (non-detectable) rotation, 15% of them actually have detectable rotation. This suggests a high rate of interactions and stellar mergers on the red giant branch.
- ID:
- ivo://CDS.VizieR/J/ApJ/872/158
- Title:
- Survey of Class II sources in Taurus with ALMA
- Short Name:
- J/ApJ/872/158
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a survey of young single and multiple systems in the Taurus-Auriga star-forming region with the Atacama Large Millimeter Array (ALMA), substantially improving both the spatial resolution and sensitivity with which individual protoplanetary disks in these systems have been observed. These ALMA observations can resolve binary separations as small as 25-30au and have an average 3{sigma} detection level of 0.35mJy, equivalent to a disk mass of 4x10^-5^M_{sun}_ for an M3 star. Our sample was constructed from stars that have an infrared excess and/or signs of accretion and have been classified as Class II. For the binary and higher-order multiple systems observed, we detect {lambda}=1.3mm continuum emission from one or more stars in all of our target systems. Combined with previous surveys of Taurus, our 21 new detections increase the fraction of millimeter-detected disks to over 75% in all categories of stars (singles, primaries, and companions) earlier than spectral type M6 in the Class II sample. Given the wealth of other information available for these stars, this has allowed us to study the impact of multiplicity with a much larger sample. While millimeter flux and disk mass are related to stellar mass as seen in previous studies, we find that both primary and secondary stars in binary systems with separations of 30-4200au have lower values of millimeter flux as a function of stellar mass than single stars. We also find that for these systems, the circumstellar disk around the primary star does not dominate the total disk mass in the system and contains on average 62% of the total mass.
