- ID:
- ivo://CDS.VizieR/J/AJ/143/4
- Title:
- Kepler cycle 1 observations of low-mass stars
- Short Name:
- J/AJ/143/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analyzed Kepler light curves for 849 stars with Teff<=5200K from our Cycle 1 Guest Observer program. We identify six new eclipsing binaries, one of which has an orbital period of 29.91 days and two of which are probably W UMa variables. In addition, we identify a candidate "warm Jupiter" exoplanet. We further examine a subset of 670 sources for variability. Of these objects, 265 stars clearly show periodic variability that we assign to rotation of the low-mass star. At the photometric precision level provided by Kepler, 251 of our objects showed no evidence for variability. We were unable to determine periods for 154 variable objects. We find that 79% of stars with Teff<=5200K are variable. The rotation periods we derive for the periodic variables span the range 0.31days<=Prot<=126.5days. A considerable number of stars with rotation periods similar to the solar value show activity levels that are 100 times higher than the Sun.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/153/71
- Title:
- Kepler follow-up observation program. I. Imaging
- Short Name:
- J/AJ/153/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from high-resolution, optical to near-IR imaging of host stars of Kepler Objects of Interest (KOIs), identified in the original Kepler field. Part of the data were obtained under the Kepler imaging follow-up observation program over six years (2009-2015). Almost 90% of stars that are hosts to planet candidates or confirmed planets were observed. We combine measurements of companions to KOI host stars from different bands to create a comprehensive catalog of projected separations, position angles, and magnitude differences for all detected companion stars (some of which may not be bound). Our compilation includes 2297 companions around 1903 primary stars. From high-resolution imaging, we find that ~10% (~30%) of the observed stars have at least one companion detected within 1'' (4''). The true fraction of systems with close (<~4'') companions is larger than the observed one due to the limited sensitivities of the imaging data. We derive correction factors for planet radii caused by the dilution of the transit depth: assuming that planets orbit the primary stars or the brightest companion stars, the average correction factors are 1.06 and 3.09, respectively. The true effect of transit dilution lies in between these two cases and varies with each system. Applying these factors to planet radii decreases the number of KOI planets with radii smaller than 2R_{Earth}_ by ~2%-23% and thus affects planet occurrence rates. This effect will also be important for the yield of small planets from future transit missions such as TESS.
- ID:
- ivo://CDS.VizieR/J/ApJ/813/130
- Title:
- Kepler multiple transiting planet systems
- Short Name:
- J/ApJ/813/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Kepler mission provides a wealth of multiple transiting planet systems (MTPSs). The formation and evolution of multi-planet systems are likely to be influenced by companion stars given the abundance of multiple stellar systems. We study the influence of stellar companions by measuring the stellar multiplicity rate of MTPSs. We select 138 bright (K_P_<13.5) Kepler MTPSs and search for stellar companions with adaptive optics (AO) imaging data and archival radial velocity data. We obtain new AO images for 73 MTPSs. Other MTPSs in the sample have archival AO imaging data from the Kepler Community Follow-up Observation Program. From these imaging data, we detect 42 stellar companions around 35 host stars. For stellar separation 1 AU<a<100 AU, the stellar multiplicity rate is 5.2+/-5.0% for MTPSs, which is 2.8{sigma} lower than 21.1+/-2.8% for the control sample, i.e., the field stars in the solar neighborhood. We identify two origins for the deficit of stellar companions within 100 AU of MTPSs: (1) a suppressive planet formation and (2) the disruption of orbital coplanarity due to stellar companions. To distinguish between the two origins, we compare the stellar multiplicity rates of MTPSs and single transiting planet systems (STPSs). However, current data are not sufficient for this purpose. For 100 AU<a<2000 AU, the stellar multiplicity rates are comparable for MTPSs (8.0+/-4.0%), STPSs (6.4+/-5.8%), and the control sample (12.5+/-2.8%).
- ID:
- ivo://CDS.VizieR/J/ApJ/871/174
- Title:
- Kepler rapid rotators and Ks-band excesses
- Short Name:
- J/ApJ/871/174
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Tens of thousands of rotation periods have been measured in the Kepler fields, including a substantial fraction of rapid rotators. We use Gaia parallaxes to distinguish photometric binaries (PBs) from single stars on the unevolved lower main sequence, and compare their distribution of rotation properties to those of single stars both with and without Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectroscopic characterization. We find that 59% of stars with 1.5day<P<7day lie 0.3mag above the main sequence, compared with 28% of the full rotation sample. The fraction of stars in the same period range is 1.7{+/-}0.1% of the total sample analyzed for rotation periods. Both the PB fraction and the fraction of rapid rotators are consistent with a population of non-eclipsing short-period binaries inferred from Kepler eclipsing binary data after correcting for inclination. This suggests that the rapid rotators are dominated by tidally synchronized binaries rather than single stars obeying traditional angular momentum evolution. We caution against interpreting rapid rotation in the Kepler field as a signature of youth. Following up on this new sample of 217 candidate tidally synchronized binaries will help further understand tidal processes in stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/426/91
- Title:
- Kepler stars with infrared excess
- Short Name:
- J/MNRAS/426/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe a search for infrared excess emission from dusty circumstellar material around 180000 stars observed by the Kepler and Wide-field Infrared Survey Explorer missions. This study is motivated by (i) the potential to find bright warm discs around planet host stars, (ii) a need to characterize the distribution of rare warm discs and (iii) the possible identification of candidates for discovering transiting dust concentrations. We find about 8000 stars that have excess emission, mostly at 12um.
- ID:
- ivo://CDS.VizieR/J/ApJ/540/236
- Title:
- KH photometry of Orion Nebula Cluster
- Short Name:
- J/ApJ/540/236
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a 0.5"-0.9" FWHM imaging survey at K (2.2{mu}m) and H (1.6{mu}m) covering ~ 5.1'x5.1' centered on {theta}^1^C Ori, the most massive star in the Orion Nebula Cluster (ONC). At the age and distance of this cluster, and in the absence of extinction, the hydrogen-burning limit (0.08M_{sun}_) occurs at K~13.5mag, while an object of mass 0.02M_{sun}_ has K~16.2mag. Our photometry is complete for source detection at the 7{sigma} level to K~17.5mag and thus is sensitive to objects as low-mass as 0.02M_{sun}_ seen through visual extinction values as high as 10mag. We use the observed magnitudes, colors, and star counts to constrain the shape of the inner ONC stellar mass function across the hydrogen-burning limit. After determining the stellar age and near-infrared excess properties of the optically visible stars in this same inner ONC region, we present a new technique that incorporates these distributions when extracting the mass function from the observed density of stars in the K-(H-K) diagram. We find that our data are inconsistent with a mass function that rises across the stellar/substellar boundary. Instead, we find that the most likely form of the inner ONC mass function is one that rises to a peak around 0.15M_{sun}_, and then declines across the hydrogen-burning limit with slope N(log M){prop.to}M^0.57^. We emphasize that our conclusions apply to the inner 0.71pc x 0.71pc of the ONC only; they may not apply to the ONC as a whole where some evidence for general mass segregation has been found.
- ID:
- ivo://CDS.VizieR/J/ApJ/847/131
- Title:
- KIC 8462852 one-yr obs. from UV to MIR
- Short Name:
- J/ApJ/847/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star over a wide wavelength range from the UV to the mid- infrared from 2015 October through 2016 December, using Swift, Spitzer and AstroLAB IRIS. The star faded in a manner similar to the long-term fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period reported is 22.1+/-9.7mmag/yr in the Swift wavebands, with amounts of 21.0+/-4.5mmag in the ground-based B measurements, 14.0+/-4.5mmag in V, and 13.0+/-4.5 in R, and a rate of 5.0+/-1.2mmag/yr averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at >~3{sigma} by three different observatories operating from the UV to the IR. The presence of long-term secular dimming means that previous spectral energy distribution models of the star based on photometric measurements taken years apart may not be accurate. We find that stellar models with Teff=7000-7100K and A_V_~0.73 best fit the Swift data from UV to optical. These models also show no excess in the near-simultaneous Spitzer photometry at 3.6 and 4.5{mu}m, although a longer wavelength excess from a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of the fading favors a relatively neutral color (i.e., R_V_>~5, but not flat across all the bands) compared with the extinction law for the general interstellar medium (R_V_=3.1), suggesting that the dimming arises from circumstellar material.
- ID:
- ivo://CDS.VizieR/J/AJ/142/112
- Title:
- KIC photometric calibration
- Short Name:
- J/AJ/142/112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the photometric calibration and stellar classification methods used by the Stellar Classification Project to produce the Kepler Input Catalog (KIC). The KIC is a catalog containing photometric and physical data for sources in the Kepler mission field of view; it is used by the mission to select optimal targets. Four of the visible-light (g, r, i, z) magnitudes used in the KIC are tied to Sloan Digital Sky Survey magnitudes; the fifth (D51) is an AB magnitude calibrated to be consistent with Castelli & Kurucz (CK) model atmosphere fluxes. We derived atmospheric extinction corrections from hourly observations of secondary standard fields within the Kepler field of view.
- ID:
- ivo://CDS.VizieR/J/ApJ/831/11
- Title:
- KIC 9777062 RVs & asteroseismology in NGC6811
- Short Name:
- J/ApJ/831/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of an eccentric, partially eclipsing long-period (P=19.23 days) binary system KIC 9777062 that contains main-sequence stars near the turnoff of the intermediate-age open cluster NGC 6811. The primary is a metal-lined Am star with a possible convective blueshift to its radial velocities, and one star (probably the secondary) is likely to be a {gamma} Dor pulsator. The component masses are 1.603+/-0.006(stat.)+/-0.016(sys.) and 1.419+/-0.003+/-0.008M_{sun}_, and the radii are 1.744+/-0.004+/-0.002 and 1.544+/-0.002+/-0.002R_{sun}_. The isochrone ages of the stars are mildly inconsistent: the age from the mass-radius combination for the primary (1.05+/-0.05+/-0.09Gyr, where the last quote was systematic uncertainty from models and metallicity) is smaller than that from the secondary (1.21+/-0.05+/-0.15Gyr) and is consistent with the inference from the color-magnitude diagram (1.00+/-0.05Gyr). We have improved the measurements of the asteroseismic parameters {Delta}{nu} and {nu}_max_ for helium-burning stars in the cluster. The masses of the stars appear to be larger (or alternately, the radii appear to be smaller) than predicted from isochrones using the ages derived from the eclipsing stars. The majority of stars near the cluster turnoff are pulsating stars: we identify a sample of 28 {delta} Sct, 15 {gamma} Dor, and 5 hybrid types. We used the period-luminosity relation for high-amplitude {delta} Sct stars to fit the ensemble of the strongest frequencies for the cluster members, finding (m-M)_V_=10.37+/-0.03. This is larger than most previous determinations, but smaller than values derived from the eclipsing binary (10.47+/-0.05).
- ID:
- ivo://CDS.VizieR/J/ApJ/844/102
- Title:
- KIC star parallaxes from asteroseismology vs Gaia
- Short Name:
- J/ApJ/844/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comparison of parallaxes and radii from asteroseismology and Gaia DR1 (TGAS) for 2200 Kepler stars spanning from the main sequence to the red-giant branch. We show that previously identified offsets between TGAS parallaxes and distances derived from asteroseismology and eclipsing binaries have likely been overestimated for parallaxes <~5-10mas (~90%-98% of the TGAS sample). The observed differences in our sample can furthermore be partially compensated by adopting a hotter Teff scale (such as the infrared flux method) instead of spectroscopic temperatures for dwarfs and subgiants. Residual systematic differences are at the ~2% level in parallax across three orders of magnitude. We use TGAS parallaxes to empirically demonstrate that asteroseismic radii are accurate to ~5% or better for stars between ~0.8-8R_{sun}_. We find no significant offset for main- sequence (<~1.5R_{sun}_) and low-luminosity RGB stars (~3-8R_{sun}_), but seismic radii appear to be systematically underestimated by ~5% for subgiants (~1.5-3R_{sun}_). We find no systematic errors as a function of metallicity between [Fe/H]~-0.8 to +0.4dex, and show tentative evidence that corrections to the scaling relation for the large frequency separation ({Delta}{nu}) improve the agreement with TGAS for RGB stars. Finally, we demonstrate that beyond ~3kpc asteroseismology will provide more precise distances than end-of-mission Gaia data, highlighting the synergy and complementary nature of Gaia and asteroseismology for studying galactic stellar populations.
