- ID:
- ivo://CDS.VizieR/J/ApJ/750/113
- Title:
- Kepler TTVs. II. Confirmed multiplanet systems
- Short Name:
- J/ApJ/750/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new method for confirming transiting planets based on the combination of transit timing variations (TTVs) and dynamical stability. Correlated TTVs provide evidence that the pair of bodies is in the same physical system. Orbital stability provides upper limits for the masses of the transiting companions that are in the planetary regime. This paper describes a non-parametric technique for quantifying the statistical significance of TTVs based on the correlation of two TTV data sets. We apply this method to an analysis of the TTVs of two stars with multiple transiting planet candidates identified by Kepler. We confirm four transiting planets in two multiple-planet systems based on their TTVs and the constraints imposed by dynamical stability. An additional three candidates in these same systems are not confirmed as planets, but are likely to be validated as real planets once further observations and analyses are possible. If all were confirmed, these systems would be near 4:6:9 and 2:4:6:9 period commensurabilities. Our results demonstrate that TTVs provide a powerful tool for confirming transiting planets, including low-mass planets and planets around faint stars for which Doppler follow-up is not practical with existing facilities. Continued Kepler observations will dramatically improve the constraints on the planet masses and orbits and provide sensitivity for detecting additional non-transiting planets. If Kepler observations were extended to eight years, then a similar analysis could likely confirm systems with multiple closely spaced, small transiting planets in or near the habitable zone of solar-type stars.
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- ID:
- ivo://CDS.VizieR/J/ApJ/750/114
- Title:
- Kepler TTVs. IV. 4 multiple-planet systems
- Short Name:
- J/ApJ/750/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Eighty planetary systems of two or more planets are known to orbit stars other than the Sun. For most, the data can be sufficiently explained by non-interacting Keplerian orbits, so the dynamical interactions of these systems have not been observed. Here we present four sets of light curves from the Kepler spacecraft, each which of shows multiple planets transiting the same star. Departure of the timing of these transits from strict periodicity indicates that the planets are perturbing each other: the observed timing variations match the forcing frequency of the other planet. This confirms that these objects are in the same system. Next we limit their masses to the planetary regime by requiring the system remain stable for astronomical timescales. Finally, we report dynamical fits to the transit times, yielding possible values for the planets' masses and eccentricities. As the timespan of timing data increases, dynamical fits may allow detailed constraints on the systems' architectures, even in cases for which high-precision Doppler follow-up is impractical.
- ID:
- ivo://CDS.VizieR/J/ApJS/225/9
- Title:
- Kepler TTVs. IX. The full long-cadence data set
- Short Name:
- J/ApJS/225/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new transit timing catalog of 2599 Kepler Objects of Interest (KOIs), using the PDC-MAP long-cadence light curves that include the full 17 quarters of the mission (ftp://wise-ftp.tau.ac.il/pub/tauttv/TTV/ver_112). The goal is to produce an easy-to-use catalog that can stimulate further analyses of interesting systems. For 779 KOIs with high enough S/N, we derived the timing, duration, and depth of 69914 transits. For 1820 KOIs with lower SNR, we derived only the timing of 225273 transits. After removal of outlier timings, we derived various statistics for each KOI that were used to indicate significant variations. Including systems found by previous works, we have detected 260 KOIs that showed significant TTVs with long-term variations (>100 days), and another 14 KOIs with periodic modulations shorter than 100 days and small amplitudes. For five of those, the periodicity is probably due to the crossing of rotating stellar spots by the transiting planets.
- ID:
- ivo://CDS.VizieR/J/ApJ/756/185
- Title:
- Kepler TTVs. V. Metrics catalog
- Short Name:
- J/ApJ/756/185
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Transit timing variations provide a powerful tool for confirming and characterizing transiting planets, as well as detecting non-transiting planets. We report the results of an updated transit timing variation (TTV) analysis for 1481 planet candidates based on transit times measured during the first sixteen months of Kepler observations. We present 39 strong TTV candidates based on long-term trends (2.8% of suitable data sets). We present another 136 weaker TTV candidates (9.8% of suitable data sets) based on the excess scatter of TTV measurements about a linear ephemeris. We anticipate that several of these planet candidates could be confirmed and perhaps characterized with more detailed TTV analyses using publicly available Kepler observations. For many others, Kepler has observed a long-term TTV trend, but an extended Kepler mission will be required to characterize the system via TTVs. We find that the occurrence rate of planet candidates that show TTVs is significantly increased (~68%) for planet candidates transiting stars with multiple transiting planet candidates when compared to planet candidates transiting stars with a single transiting planet candidate.
- ID:
- ivo://CDS.VizieR/J/ApJ/787/47
- Title:
- 106 Kepler ultra-short-period planets
- Short Name:
- J/ApJ/787/47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a survey aimed at discovering and studying transiting planets with orbital periods shorter than one day (ultra-short-period, or USP, planets), using data from the Kepler spacecraft. We computed Fourier transforms of the photometric time series for all 200000 target stars, and detected transit signals based on the presence of regularly spaced sharp peaks in the Fourier spectrum. We present a list of 106 USP candidates, of which 18 have not previously been described in the literature. This list of candidates increases the number of planet candidates with orbital periods shorter than about six hours from two to seven. In addition, among the objects we studied, there are 26 USP candidates that had been previously reported in the literature which do not pass our various tests. All 106 of our candidates have passed several standard tests to rule out false positives due to eclipsing stellar systems. A low false positive rate is also implied by the relatively high fraction of candidates for which more than one transiting planet signal was detected. By assuming these multi-transit candidates represent coplanar multi-planet systems, we are able to infer that the USP planets are typically accompanied by other planets with periods in the range 1-50 days, in contrast with hot Jupiters which very rarely have companions in that same period range. Another clear pattern is that almost all USP planets are smaller than 2 R_{earth}_, possibly because gas giants in very tight orbits would lose their atmospheres by photoevaporation when subject to extremely strong stellar irradiation. Based on our survey statistics, USP planets exist around approximately (0.51+/-0.07)% of G-dwarf stars, and (0.83+/-0.18)% of K-dwarf stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/338/253
- Title:
- K extinction near the Galactic Centre
- Short Name:
- J/MNRAS/338/253
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We extract J and Ks magnitudes from the 2MASS Point Source Catalog for approximately 6 million stars with 8<Ks<13 in order to build an A_K_ extinction map within 10 degrees of the Galactic centre. The extinction was determined by fitting the upper giant branch of (Ks, J-Ks) colour-magnitude diagrams to a dereddened upper giant branch mean locus built from previously studied Bulge fields. The extinction values vary from A_K=0.05 in the edges of the map up to A_K=3.2 close to the Galactic centre. The resulting extinction map is given in the file 'extmap.dat'.
- ID:
- ivo://CDS.VizieR/J/ApJ/884/4
- Title:
- KEYSTONE: ammonia structures in Galactic GMCs
- Short Name:
- J/ApJ/884/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present initial results from the K-band Focal Plane Array Examinations of Young STellar Object Natal Environments survey (KEYSTONE), a large project on the 100m Green Bank Telescope mapping ammonia emission across 11 giant molecular clouds at distances of 0.9-3.0kpc (Cygnus X North, Cygnus X South, M16, M17, Mon R1, Mon R2, NGC 2264, NGC 7538, Rosette, W3, and W48). This data release includes the NH_3_ (1,1) and (2,2) maps for each cloud, which are modeled to produce maps of kinetic temperature, centroid velocity, velocity dispersion, and ammonia column density. Median cloud kinetic temperatures range from 11.4+/-2.2K in the coldest cloud (Mon R1) to 23.0+/-6.5K in the warmest cloud (M17). Using dendrograms on the NH_3_ (1,1) integrated intensity maps, we identify 856 dense gas clumps across the 11 clouds. Depending on the cloud observed, 40%-100% of the clumps are aligned spatially with filaments identified in H2 column density maps derived from spectral energy distribution fitting of dust continuum emission. A virial analysis reveals that 523 of the 835 clumps (~63%) with mass estimates are bound by gravity alone. We find no significant difference between the virial parameter distributions for clumps aligned with the dust-continuum filaments and those unaligned with filaments. In some clouds, however, hubs or ridges of dense gas with unusually high mass and low virial parameters are located within a single filament or at the intersection of multiple filaments. These hubs and ridges tend to host water maser emission, multiple 70{mu}m detected protostars, and have masses and radii above an empirical threshold for forming massive stars.
- ID:
- ivo://CDS.VizieR/J/A+A/643/A83
- Title:
- K2-Gaia-ESO stellar param. and abundances
- Short Name:
- J/A+A/643/A83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The extensive stellar spectroscopic datasets that are available for studies in Galactic Archeaology thanks to, for example, the Gaia-ESO Survey, now benefit from having a significant number of targets that overlap with asteroseismology projects such as Kepler, K2, and CoRoT. Combining the measurements from spectroscopy and asteroseismology allows us to attain greater accuracy with regard to the stellar parameters needed to characterise the stellar populations of the Milky Way. The aim of this Gaia-ESO Survey special project is to produce a catalogue of self-consistent stellar parameters by combining measurements from high- resolution spectroscopy and precision asteroseismology. We carried out an iterative analysis of 90 K2@Gaia-ESO red giants. The spectroscopic values of Teff were used as input in the seismic analysis to obtain logg values. The seismic estimates of logg were then used to re- determine the spectroscopic values of Teff and [Fe/H]. Only one iteration was required to obtain parameters that are in good agreement for both methods and, thus, to obtain the final stellar parameters. A detailed analysis of outliers was carried out to ensure a robust determination of the parameters. The results were then combined with Gaia DR2 data to compare the seismic log g with a parallax-based log g and to investigate instances of variations in the velocity and possible binaries within the dataset. This analysis produced a high-quality catalogue of stellar parameters for 90 red giant stars from K2@Gaia-ESO that were determined through iterations between spectroscopy and asteroseismology. We compared the seismic gravities with those based on Gaia parallaxes to find an offset which is similar to other studies that have used asteroseismology. Our catalogue also includes spectroscopic chemical abundances and radial velocities, as well as indicators for possible binary detections.
- ID:
- ivo://CDS.VizieR/J/ApJ/835/83
- Title:
- K2 GAP data release. I. Campaign 1
- Short Name:
- J/ApJ/835/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NASA's K2 mission is observing tens of thousands of stars along the ecliptic, providing data suitable for large-scale asteroseismic analyses to inform galactic archaeology studies. Its first campaign covered a field near the north Galactic cap, a region never covered before by large asteroseismic-ensemble investigations, and was therefore of particular interest for exploring this part of our Galaxy. Here we report the asteroseismic analysis of all stars selected by the K2 Galactic Archaeology Program during the mission's "north Galactic cap" campaign 1. Our consolidated analysis uses six independent methods to measure the global seismic properties, in particular the large frequency separation and the frequency of maximum power. From the full target sample of 8630 stars we find about 1200 oscillating red giants, a number comparable with estimates from galactic synthesis modeling. Thus, as a valuable by-product we find roughly 7500 stars to be dwarfs, which provide a sample well suited for galactic exoplanet occurrence studies because they originate from our simple and easily reproducible selection function.
- ID:
- ivo://CDS.VizieR/J/ApJS/251/23
- Title:
- K2 GAP DR2: campaigns 4, 6 & 7
- Short Name:
- J/ApJS/251/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Studies of Galactic structure and evolution have benefited enormously from Gaia kinematic information, though additional, intrinsic stellar parameters like age are required to best constrain Galactic models. Asteroseismology is the most precise method of providing such information for field star populations en masse, but existing samples for the most part have been limited to a few narrow fields of view by the CoRoT and Kepler missions. In an effort to provide well-characterized stellar parameters across a wide range in Galactic position, we present the second data release of red giant asteroseismic parameters for the K2 Galactic Archaeology Program (GAP). We provide {nu}_max_ and {Delta}{nu} based on six independent pipeline analyses; first-ascent red giant branch (RGB) and red clump (RC) evolutionary state classifications from machine learning; and ready-to-use radius and mass coefficients, {kappa}_R_ and {kappa}_M_, which, when appropriately multiplied by a solar-scaled effective temperature factor, yield physical stellar radii and masses. In total, we report 4395 radius and mass coefficients, with typical uncertainties of 3.3% (stat.) +/-1% (syst.) for {kappa}_R_ and 7.7% (stat.) +/-2% (syst.) for {kappa}_M_ among RGB stars, and 5.0% (stat.) +/-1% (syst.) for {kappa}_R_ and 10.5% (stat.) +/-2% (syst.) for {kappa}_M_ among RC stars. We verify that the sample is nearly complete- except for a dearth of stars with {nu}_max_<~10-20{mu}Hz-by comparing to Galactic models and visual inspection. Our asteroseismic radii agree with radii derived from Gaia Data Release 2 parallaxes to within 2.2%+/-0.3% for RGB stars and 2.0%+/-0.6% for RC stars.