- ID:
- ivo://CDS.VizieR/J/ApJ/835/61
- Title:
- Chromospherically active stars in RAVE. II.
- Short Name:
- J/ApJ/835/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A large sample of over 38000 chromospherically active candidate solar-like stars and cooler dwarfs from the RAVE survey is addressed in this paper. An improved activity identification with respect to the previous study was introduced to build a catalog of field stars in the solar neighborhood with an excess emission flux in the calcium infrared triplet wavelength region. The central result of this work is the calibration of the age-activity relation for main-sequence dwarfs in a range from a few 10Myr up to a few Gyr. It enabled an order of magnitude age estimation of the entire active sample. Almost 15000 stars are shown to be younger than 1Gyr and ~2000 younger than 100Myr. The young age of the most active stars is confirmed by their position off the main sequence in the J-K versus N_UV_-V diagram showing strong ultraviolet excess, mid-infrared excess in the J-K versus W_1_-W_2_ diagram, and very cool temperatures (J-K>0.7). They overlap with the reference pre-main-sequence RAVE stars often displaying X-ray emission. The activity level increasing with the color reveals their different nature from the solar-like stars and probably represents an underlying dynamo-generating magnetic fields in cool stars. Of the RAVE objects from DR5, 50% are found in the TGAS catalog and supplemented with accurate parallaxes and proper motions by Gaia. This makes the database of a large number of young stars in a combination with RAVE's radial velocities directly useful as a tracer of the very recent large-scale star formation history in the solar neighborhood.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/160/24
- Title:
- Circumstellar dust of 104 stars with GPIES
- Short Name:
- J/AJ/160/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a ~4yr direct imaging survey of 104 stars to resolve and characterize circumstellar debris disks in scattered light as part of the Gemini Planet Imager (GPI) Exoplanet Survey. We targeted nearby (<~150pc), young (<~500Myr) stars with high infrared (IR) excesses (LIR/L_{star}_>10^-5^), including 38 with previously resolved disks. Observations were made using the GPI high-contrast integral field spectrograph in H-band (1.6{mu}m) coronagraphic polarimetry mode to measure both polarized and total intensities. We resolved 26 debris disks and 3 protoplanetary/transitional disks. Seven debris disks were resolved in scattered light for the first time, including newly presented HD117214 and HD156623, and we quantified basic morphologies of five of them using radiative transfer models. All of our detected debris disks except HD156623 have dust-poor inner holes, and their scattered-light radii are generally larger than corresponding radii measured from resolved thermal emission and those inferred from spectral energy distributions. To assess sensitivity, we report contrasts and consider causes of nondetections. Detections were strongly correlated with high IR excess and high inclination, although polarimetry outperformed total intensity angular differential imaging for detecting low-inclination disks (<~70{deg}). Based on postsurvey statistics, we improved upon our presurvey target prioritization metric predicting polarimetric disk detectability. We also examined scattered-light disks in the contexts of gas, far-IR, and millimeter detections. Comparing H-band and ALMA fluxes for two disks revealed tentative evidence for differing grain properties. Finally, we found no preference for debris disks to be detected in scattered light if wide-separation substellar companions were present.
- ID:
- ivo://CDS.VizieR/J/ApJ/792/119
- Title:
- Companions to nearby stars from Pan-STARRS 1
- Short Name:
- J/ApJ/792/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of 57 wide (>5'') separation, low-mass (stellar and substellar) companions to stars in the solar neighborhood identified from Pan-STARRS 1 (PS1) data and the spectral classification of 31 previously known companions. Our companions represent a selective subsample of promising candidates and span a range in spectral type of K7-L9 with the addition of one DA white dwarf. These were identified primarily from a dedicated common proper motion search around nearby stars, along with a few as serendipitous discoveries from our Pan-STARRS 1 brown dwarf search. Our discoveries include 23 new L dwarf companions and one known L dwarf not previously identified as a companion. The primary stars around which we searched for companions come from a list of bright stars with well-measured parallaxes and large proper motions from the Hipparcos catalog (8583 stars, mostly A-K dwarfs) and fainter stars from other proper motion catalogs (79170 stars, mostly M dwarfs). We examine the likelihood that our companions are chance alignments between unrelated stars and conclude that this is unlikely for the majority of the objects that we have followed-up spectroscopically. We also examine the entire population of ultracool (>M7) dwarf companions and conclude that while some are loosely bound, most are unlikely to be disrupted over the course of ~10 Gyr. Our search increases the number of ultracool M dwarf companions wider than 300 AU by 88% and increases the number of L dwarf companions in the same separation range by 82%. Finally, we resolve our new L dwarf companion to HIP 6407 into a tight (0.13'', 7.4 AU) L1+T3 binary, making the system a hierarchical triple. Our search for these key benchmarks against which brown dwarf and exoplanet atmosphere models are tested has yielded the largest number of discoveries to date.
- ID:
- ivo://CDS.VizieR/J/ApJS/254/10
- Title:
- Compilation of W UMa stars
- Short Name:
- J/ApJS/254/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a statistical study of the largest bibliographic compilation of stellar and orbital parameters of W UMa stars derived by light-curve synthesis with Roche models. The compilation includes nearly 700 individually investigated objects from over 450 distinct publications. Almost 70% of this sample is comprised of stars observed in the past decade that have not been considered in previous statistical studies. We estimate the ages of the cataloged stars, model the distributions of their periods, mass ratios, temperatures, and other quantities, and compare them with the data from the Catalina Real-Time Transient Survey, LAMOST, and Gaia archives. As only a small fraction of the sample has radial-velocity curves, we examine the reliability of the photometric mass ratios in totally and partially eclipsing systems and find that totally eclipsing W UMa stars with photometric mass ratios have the same parameter distributions as those with spectroscopic mass ratios. Most of the stars with reliable parameters have mass ratios below 0.5 and orbital periods shorter than 0.5 days. Stars with longer periods and temperatures above 7000K stand out as outliers and should not be labeled W UMa binaries.
- ID:
- ivo://CDS.VizieR/J/MNRAS/454/2946
- Title:
- CSS detached eclipsing binaries
- Short Name:
- J/MNRAS/454/2946
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Eclipsing binaries play pivotal roles in our understanding of stellar properties. In the era of all-sky surveys, thousands of eclipsing binaries have been charted, yet their light curves remain unexplored. The goal of this work is to use time series and colour information to extract physical parameters of the binary systems when the spectroscopic information is not available. Inspired by the work of Devor et al., we use the Detached Eclipsing Binary Light curve fitter (DEBiL) and the Method for Eclipsing Component Identification (MECI) to derive basic properties of the binary systems identified by the Catalina Sky Surveys. We derive the mass, fractional radius, and age for 2170 binary systems. We report 211 eccentric systems and compare their properties to the tidal circularization theory. From the mass estimate, we present a subsample of low-mass M-dwarfs which warrant further follow-up to test the stellar models at the low-mass regime. With MECI, we are able to estimate the distance to individual eclipsing binary system and use them to probe the large-scale structure of the Milky Way. We demonstrate that DEBiL and MECI are instrumental to investigate eclipsing binary light curves in the era of all-sky surveys, and provide estimates of stellar parameters when the spectroscopic information is not available.
- ID:
- ivo://CDS.VizieR/J/ApJ/891/81
- Title:
- Deep optical and infrared photometry of Sh2-305
- Short Name:
- J/ApJ/891/81
- Date:
- 17 Jan 2022 00:38:10
- Publisher:
- CDS
- Description:
- Using our deep optical and near-infrared photometry along with multiwavelength archival data, we here present a detailed study of the Galactic HII region Sh 2-305 to understand the star/star-cluster formation. On the basis of excess infrared emission, we have identified 116 young stellar objects (YSOs) within a field of view of ~18.5'x18.5' around Sh 2-305. The average age, mass, and extinction (AV) for this sample of YSOs are 1.8Myr, 2.9M_{sun}_, and 7.1mag, respectively. The density distribution of stellar sources along with minimal spanning tree calculations on the location of YSOs reveals at least three stellar subclusterings in Sh 2-305. One cluster is seen toward the center (i.e., Mayer 3), while the other two are distributed toward the north and south directions. Two massive O-type stars (VM2 and VM4; ages ~5Myr) are located at the center of the Sh 2-305 HII region. The analysis of the infrared and radio maps traces the photon-dominant regions (PDRs) in Sh 2-305. The association of the younger generation of stars with the PDRs is also investigated in Sh2-305. This result suggests that these two massive stars might have influenced the star formation history in Sh 2-305. This argument is also supported by the calculation of various pressures driven by massive stars, the slope of the mass function/K-band luminosity function, star formation efficiency, fraction of Class I sources, and mass of the dense gas toward the subclusterings in Sh 2-305.
- ID:
- ivo://CDS.VizieR/J/ApJ/869/L41
- Title:
- DSHARP I. Sample, ALMA obs. log and overview
- Short Name:
- J/ApJ/869/L41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We introduce the Disk Substructures at High Angular Resolution Project (DSHARP), one of the initial large programs conducted with the Atacama Large Millimeter/submillimeter Array (ALMA). The primary goal of DSHARP is to find and characterize substructures in the spatial distributions of solid particles for a sample of 20 nearby protoplanetary disks, using very high resolution (~0.035", or 5au, Full width half maximum (FWHM)) observations of their 240GHz (1.25mm) continuum emission. These data provide a first homogeneous look at the small-scale features in disks that are directly relevant to the planet formation process, quantifying their prevalence, morphologies, spatial scales, spacings, symmetry, and amplitudes, for targets with a variety of disk and stellar host properties. We find that these substructures are ubiquitous in this sample of large, bright disks. They are most frequently manifested as concentric, narrow emission rings and depleted gaps, although large-scale spiral patterns and small arc-shaped azimuthal asymmetries are also present in some cases. These substructures are found at a wide range of disk radii (from a few astronomical units to more than 100au), are usually compact (<=10au), and show a wide range of amplitudes (brightness contrasts). Here we discuss the motivation for the project, describe the survey design and the sample properties, detail the observations and data calibration, highlight some basic results, and provide a general overview of the key conclusions that are presented in more detail in a series of accompanying articles.
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/1412
- Title:
- Dust and SSP-stellar parameters of M82
- Short Name:
- J/MNRAS/452/1412
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use near ultraviolet and optical photometry to investigate the dust properties in the nearby starburst galaxy M82. By combining imaging from the Swift/UVOT instrument and optical data from the Sloan Digital Sky Survey, we derive the extinction curve parametrized by the standard R_V_ factor, and the strength of the NUV 2175 {AA} feature - quantified by a parameter B - out to projected galactocentric distances of 4 kpc. Our analysis is robust against possible degeneracies from the properties of the underlying stellar populations. Both B and R_V_ correlate with galactocentric distance, revealing a systematic trend of the dust properties. Our results confirm previous findings that dust in M82 is better fitted by a Milky Way standard extinction curve, in contrast to a Calzetti law. We find a strong correlation between R_V_ and B, towards a stronger NUV bump in regions with higher R_V_, possibly reflecting a distribution with larger dust grain sizes. The data we use were taken before SN2014J, and therefore can be used to probe the properties of the interstellar medium before the event. Our R_V_ values around the position of the supernova are significantly higher than recent measurements post-SN2014J (R_V_~1.4). This result is consistent with a significant change in the dust properties after the supernova event, either from disruption of large grains or from the contribution by an intrinsic circumstellar component. Intrinsic variations among supernovae not accounted for could also give rise to this mismatch.
- ID:
- ivo://CDS.VizieR/J/other/NatAs/5.707
- Title:
- Dwarf stars asteroseismic rotation rates
- Short Name:
- J/other/NatAs/5.
- Date:
- 17 Jan 2022 00:29:40
- Publisher:
- CDS
- Description:
- Studies using asteroseismic ages and rotation rates from star-spot rotation have indicated that standard age-rotation relations may break down roughly half way through the main sequence lifetime, a phenomenon referred to as weakened magnetic braking. Although rotation rates from spots can be difficult to determine for older, less active stars, rotational splitting of asteroseismic oscillation frequencies can provide rotation rates for both active and quiescent stars, and so can confirm whether this effect really takes place on the main sequence. We obtained asteroseismic rotation rates of 91 main sequence stars showing high signal-to-noise modes of oscillation. Using these new rotation rates, along with effective temperatures, metallicities and seismic masses and ages, we built a hierarchical Bayesian mixture model to determine whether the ensemble more closely agreed with a standard rotational evolution scenario, or one where weakened magnetic braking takes place. The weakened magnetic braking scenario was found to be 98.4% more likely for our stellar ensemble, adding to the growing body of evidence for this stage of stellar rotational evolution. This work presents a large catalogue of seismic rotation rates for stars on the main sequence, which opens up possibilities for more detailed ensemble analysis of rotational evolution with Kepler.
- ID:
- ivo://CDS.VizieR/J/ApJ/810/61
- Title:
- Early-type EBs with intermediate orbital periods
- Short Name:
- J/ApJ/810/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze 221 eclipsing binaries (EBs) in the Large Magellanic Cloud with B-type main-sequence (MS) primaries (M_1_~4-14 M_{sun}_) and orbital periods P=20-50 days that were photometrically monitored by the Optical Gravitational Lensing Experiment. We utilize our three-stage automated pipeline to (1) classify all 221 EBs, (2) fit physical models to the light curves of 130 detached well-defined EBs from which unique parameters can be determined, and (3) recover the intrinsic binary statistics by correcting for selection effects. We uncover two statistically significant trends with age. First, younger EBs tend to reside in dustier environments with larger photometric extinctions, an empirical relation that can be implemented when modeling stellar populations. Second, younger EBs generally have large eccentricities. This demonstrates that massive binaries at moderate orbital periods are born with a Maxwellian "thermal" orbital velocity distribution, which indicates they formed via dynamical interactions. In addition, the age-eccentricity anticorrelation provides a direct constraint for tidal evolution in highly eccentric binaries containing hot MS stars with radiative envelopes. The intrinsic fraction of B-type MS stars with stellar companions q=M_2_/M_1_>0.2 and orbital periods P=20-50 days is (7+/-2)%. We find early-type binaries at P=20-50 days are weighted significantly toward small mass ratios q~0.2-0.3, which is different than the results from previous observations of closer binaries with P<20 days. This indicates that early-type binaries at slightly wider orbital separations have experienced substantially less competitive accretion and coevolution during their formation in the circumbinary disk.
