Kepler News and Results (Thread 2)

Do you like phase curves? If so, here's some good news!

Kipping, Sandford & Janesen "Two Thousand Kepler Phase Curves from Phasma"
https://arxiv.org/abs/1805.04121

Gallery is here.

Kepler-503 turns out to be a subgiant rather than a solar-type dwarf star as previously thought. The companion Kepler-503b is at the hydrogen-burning limit.

Cañas et al. "Kepler-503b: An Object at the Hydrogen Burning Mass Limit Orbiting a Subgiant Star"
https://arxiv.org/abs/1805.08820

Update on the exomoon candidate at Kepler-1625b (do we not have a thread for this?)

Reanalysis of data favors the planet-moon model over the single-planet, but the significance of the evidence depends pretty strongly on how you detrend the data. The evidence is not convincing enough at this point to positively claim a detection, though this could be remedied with more data.

Revisiting the exomoon candidate signal around Kepler-1625b
https://arxiv.org/abs/1806.04672

Sirius_Alpha wrote:

Update on the exomoon candidate at Kepler-1625b (do we not have a thread for this?)

Reanalysis of data favors the planet-moon model over the single-planet, but the significance of the evidence depends pretty strongly on how you detrend the data. The evidence is not convincing enough at this point to positively claim a detection, though this could be remedied with more data.

Revisiting the exomoon candidate signal around Kepler-1625b
https://arxiv.org/abs/1806.04672

David Kipping posted a response on Twitter here

Will be interesting to see what the HST data brings to this.

The orbital eccentricity of small planet systems
https://arxiv.org/abs/1807.00549

Quote :

We determine the orbital eccentricities of individual small Kepler planets, through a combination of asteroseismology and transit light-curve analysis. We are able to constrain the eccentricities of 51 systems with a single transiting planet, which supplement our previous measurements of 66 planets in multi-planet systems. Through a Bayesian hierarchical analysis, we find evidence that systems with only one detected transiting planet have a different eccentricity distribution than systems with multiple detected transiting planets. The eccentricity distribution of the single-transiting systems is well described by the positive half of a zero-mean Gaussian distribution with a dispersion σe=0.32±0.06, while the multiple-transit systems are consistent with σe=0.083+0.015−0.020. A mixture model suggests a fraction of 0.76+0.21−0.12 of single-transiting systems have a moderate eccentricity, represented by a Rayleigh distribution that peaks at 0.26+0.04−0.06. This finding may reflect differences in the formation pathways of systems with different numbers of transiting planets. We investigate the possibility that eccentricities are "self-excited" in closely packed planetary systems, as well as the influence of long-period giant companion planets. We find that both mechanisms can qualitatively explain the observations. We do not find any evidence for a correlation between eccentricity and stellar metallicity, as has been seen for giant planets. Neither do we find any evidence that orbital eccentricity is linked to the detection of a companion star. Along with this paper we make available all of the parameters and uncertainties in the eccentricity distributions, as well as the properties of individual systems, for use in future studies.

TTV-determined Masses for Warm Jupiters and their Close Planetary Companions
https://arxiv.org/abs/1807.02217

Quote :

Although the formation and the properties of hot Jupiters (with orbital periods P<10d) have attracted a great deal of attention, the origins of warm Jupiters (10<P<100d) are less well-studied. Using a transit timing analysis, we present the orbital parameters of five planetary systems containing warm Jupiters, Kepler 30, Kepler 117, Kepler 302, Kepler 487 and Kepler 418. Three of them, Kepler-30 c(Mp=549.4±5.6M⊕), Kepler-117 c(Mp=702±63M⊕) and Kepler 302 c(Mp=933±527M⊕), are confirmed to be real warm Jupiters based on their mass. Insights drawn from the radius-temperature relationship lead to the inference that hot Jupiters and warm Jupiters can be roughly separated by Teff,c=1123.7±3.3 K. Also, Teff,c provides a good separation for Jupiters with companion fraction consistent with zero(Teff>Teff,c) and those with companion fraction significantly different from zero (Teff<Teff,c).

I don't think this one's hit the arXiv so far...

Brady et al. (2018) "Kepler-1656b: A Dense Sub-Saturn with an Extreme Eccentricity"
http://iopscience.iop.org/article/10.3847/1538-3881/aad773/meta

32-day orbital period, eccentricity 0.84

Now on arXiv.

Kepler-1656b: a Dense Sub-Saturn With an Extreme Eccentricity
https://arxiv.org/abs/1809.08436

Transit Timing Variations and linear ephemerides of confirmed Kepler transiting exoplanets
https://arxiv.org/abs/1809.11104

Quote :

We determined new linear ephemerides of transiting exoplanets using long-cadence de-trended data from quarters Q1 to Q17 of Kepler mission. We analysed TTV diagrams of 2098 extrasolar planets. The TTVs of 121 objects were excluded (because of insufficient data-points, influence of stellar activity, etc). Finally, new linear ephemerides of 1977 exoplanets from Kepler archive are presented. The significant linear trend was observed on TTV diagrams of approximately 35% of studied exoplanets. Knowing correct linear ephemeris is principal for successful follow-up observations of transits. Residual TTV diagrams of 64 analysed exoplanets shows periodic variation, 43 of these TTV planets were not reported yet.

It looks like all 43 of these involve confirmed planets already.

I just wonder if this exoplanet planet candidate will be ever confirmed,the binary stellar parameters look quite interesting the stars it's seems A+M binary with a planet.

Modelling the circumbinary candidate KOI-1741

https://warwick.ac.uk/fac/sci/physics/research/astro/people/jamesblake/urss_poster_2016_jb.pdf

Good spot there, would be interesting to figure out what the view would be like from the planet - should be quite a colour contrast between the two stars but maybe the red dwarf would be lost in the glare.

Talking of unconfirmed circumbinary planets, whatever happened to Kepler-47d? There's also the unconfirmed planet in the KIC 7177553 quadruple system.

Lazarus wrote:

Good spot there, would be interesting to figure out what the view would be like from the planet - should be quite a colour contrast between the two stars but maybe the red dwarf would be lost in the glare.

Talking of unconfirmed circumbinary planets, whatever happened to Kepler-47d? There's also the unconfirmed planet in the KIC 7177553 quadruple system.

There is also KOI 2938 = KID 7821010 that would be the first non-transiting CBP detected by Kepler mission around F+F dwarf stars far as I known never been published.

https://www.astro.up.pt/investigacao/conferencias/toe2014/files/wwelsh.pdf

A New Planet in the Kepler-159 System From Transit Timing Variations
https://arxiv.org/abs/1810.06486

Quote :

The Kepler Space Telescope has discovered thousands of planets via the transit method. The transit timing variations of these planets allows us not only to infer the existence of other planets, transiting or not, but to characterize a number of parameters of the system. Using the transit timing variations of the planets Kepler-159b and 159c, the transit simulator TTVFast, and the Bayesian Inference tool MultiNest, we predict a new non-transiting planet, Kepler-159d, in a resonant 2:1 orbit with Kepler-159c. This configuration is dynamically stable on at least 10 Myr time scales, though we note that other less stable, higher-order resonances could also produce similar TTVs during the three-year window Kepler was in operation.

Uh oh..

NASA to Hold Media Call on Status of Kepler Space Telescope Today
https://www.nasa.gov/press-release/nasa-to-hold-media-call-on-status-of-kepler-space-telescope-today

"Uh oh" was right.

Kepler has run out of fuel, the science mission is over and the spacecraft has been retired.

https://www.jpl.nasa.gov/news/news.php?feature=7272

Kepler/K2 is dead, long live Kepler/K2!

Barentsen et al. "Kepler's Discoveries Will Continue: 21 Important Scientific Opportunities with Kepler & K2 Archive Data"
https://arxiv.org/abs/1810.12554

SOPHIE velocimetry of Kepler transit candidates planets XIX. The transiting temperate giant planet KOI-3680b
https://arxiv.org/abs/1811.09580

Quote :

Whereas thousands of transiting giant exoplanets are known today, only a few are well characterized with long orbital periods. We present here KOI-3680b, a new planet in this category. First identified by the Kepler Team as a promising candidate from the photometry of the Kepler spacecraft, we establish here its planetary nature from the radial velocity follow-up we secured over two years with the SOPHIE spectrograph at Observatoire de Haute-Provence, France. The combined analysis of the whole datasets allow us to fully characterize that new planetary system. KOI-3680b has an orbital period of 141.2417 +/- 0.0001 days, a mass of 1.93 +/- 0.20 M_Jup and a radius of 0.99 +/- 0.07 R_Jup. It exhibits a highly eccentric orbit (e = 0.50 +/- 0.03) around an early G dwarf. KOI-3680b is the transiting giant planet with the longest period characterized today around a single star; it offers opportunities to extend studies which were mainly devoted to exoplanets close to their host stars, and to compare both exoplanet populations.

This system is also designated Kepler-1657.

Re-Evaluating Small Long-Period Confirmed Planets From Kepler
https://arxiv.org/abs/1901.00506

Quote :

We re-examine the statistical confirmation of small long-period Kepler planet candidates in light of recent improvements in our understanding of the occurrence of systematic false alarms in this regime. Using the final Data Release 25 (DR25) Kepler planet candidate catalog statistics, we find that the previously confirmed single planet system Kepler-452b no longer achieves a 99% confidence in the planetary hypothesis and is not considered statistically validated in agreement with the finding of Mullally et al. (2018). For multiple planet systems, we find that the planet prior enhancement for belonging to a multiple planet system is suppressed relative to previous Kepler catalogs, and we identify the multi-planet system member, Kepler-186f, no longer achieves a 99% confidence in the planetary hypothesis. Because of the numerous confounding factors in the data analysis process that leads to the detection and characterization of a signal, it is difficult to determine whether any one planetary candidate achieves a strict criterion for confirmation relative to systematic false alarms. For instance, when taking into account a simplified model of processing variations, the additional single planet systems Kepler-443b, Kepler-441b, Kepler-1633b, Kepler-1178b, and Kepler-1653b have a non-negligible probability of falling below a 99% confidence in the planetary hypothesis. The systematic false alarm hypothesis must be taken into account when employing statistical validation techniques in order to confirm planet candidates that approach the detection threshold of a survey. We encourage those performing transit searches of K2, TESS, and other similar data sets to quantify their systematic false alarms rates. Alternatively, independent photometric detection of the transit signal or radial velocity measurements can eliminate the false alarm hypothesis.

Two Super-Earths in the 3:2 MMR around KOI-1599
https://arxiv.org/abs/1901.01435

Quote :

We validate the planetary origin of the KOI-1599 transit time variations (TTVs) with statistical and dynamical tests. We re-analysed KEPLER Q1-Q17 light-curves of the star, and we independently derived the TTVs. They appear as strongly anti-correlated, suggestive of two mutually interacting planets. We found similar radii of the candidates, 1.9±0.2R⊕ for the inner KOI-1599.02, and 1.9±0.3R⊕ for the outer KOI-1599.01. The standard MCMC TTV analysis constrains the planet masses safely below the dynamical instability limit of ≃3MJup. The best-fitting MCMC model yields (9.0±0.3)M⊕, and (4.6±0.3)R⊕, for the inner and the outer planet, respectively. The planets are trapped in 3:2 mean motion resonance (MMR) with anti-aligned apsides (Δϖ=180∘) at low-eccentric (e≃0.01) orbits. However, we found that the TTV mass determination depends on eccentricity priors with the dispersion in the (0.01,0.05) range. They permit a second family of TTV models with smaller masses of ≃7M⊕, and ≃3.6M⊕, respectively, exhibiting two modes of Δϖ=0∘,180∘ librations. The 3:2 MMR is dynamically robust and persists for both modes. In order to resolve the mass duality, we re-analysed the TTV data with a quasi-analytic model of resonant TTV signals. This model favours the smaller masses. We also reproduced this model with simulating the migration capture of the system into the 3:2 MMR.

Revisiting the Long-Period Transiting Planets from Kepler
https://arxiv.org/abs/1901.01974

Quote :

Currently, we have only limited means to probe the presence of planets at large orbital separations. Foreman-Mackey et al. (2016, FM16) searched for long-period transiting planets in the Kepler light curves using an automated pipeline. Here, we apply their pipeline, with minor modifications, to a larger sample and use the updated stellar parameters from Gaia DR2. The latter boosts the sizes for the majority of the planet candidates found by FM16, invalidating a number of them as false positives. We identify 12 good candidates, including 2 new ones. All but one have periods from 2 to 10 years, and sizes from 0.4 to 1.26 RJ. We report two main findings. First, we find a total occurrence rate of 0.43+0.13−0.11 planets per Sun-like star in the outer region, consistent with results from radial-velocity and microlensing surveys. Neptune-sized planets are a few times more common than Jupiter-sized ones, as is also derived by microlensing studies. Second, 5 out of our 12 candidates orbit stars with known transiting planets at shorter periods, including one with 5 inner planets. We interpret this high incidence rate as: (1) almost all our candidates should be genuine; (2) across a large orbital range (from ∼0.05 AU to a few AUs), mutual inclinations in these systems are at most a few degrees; (3) cold giant planets exist exclusively in systems with inner small planets.

Remember the claim that Kepler-410 had a hidden binary star orbiting at ~2.5 AU? There has been a follow-up, as Shellface noted the system can be better explained by resonance. Notably the radial velocities do not show any evidence of a stellar companion. They predict a planet ~50% more massive than Mars in an outer 2:3 resonance (~26.5 day orbital period).

Gajdoš et al. "Transit timing variations, radial velocities and long-term dynamical stability of the system Kepler-410"
https://arxiv.org/abs/1901.08485

Seems like some of the ultra-short period planets may have severe tidal distortion...

Price & Rogers "Tidally-Distorted, Iron-Enhanced Exoplanets Closely Orbiting Their Stars"
https://arxiv.org/abs/1901.10666

A giant impact as the likely origin of different twins in the Kepler-107 exoplanet system
https://arxiv.org/abs/1902.01316

Quote :

Measures of exoplanet bulk densities indicate that small exoplanets with radius less than 3 Earth radii (R⊕) range from low-density sub-Neptunes containing volatile elements to higher density rocky planets with Earth-like or iron-rich (Mercury-like) compositions. Such astonishing diversity in observed small exoplanet compositions may be the product of different initial conditions of the planet-formation process and/or different evolutionary paths that altered the planetary properties after formation. Planet evolution may be especially affected by either photoevaporative mass loss induced by high stellar X-ray and extreme ultraviolet (XUV) flux or giant impacts. Although there is some evidence for the former, there are no unambiguous findings so far about the occurrence of giant impacts in an exoplanet system. Here, we characterize the two innermost planets of the compact and near-resonant system Kepler-107. We show that they have nearly identical radii (about 1.5−1.6 R⊕), but the outer planet Kepler-107c is more than twice as dense (about 12.6 gcm−3) as the innermost Kepler-107b (about 5.3 gcm−3). In consequence, Kepler-107c must have a larger iron core fraction than Kepler-107b. This imbalance cannot be explained by the stellar XUV irradiation, which would conversely make the more-irradiated and less-massive planet Kepler-107b denser than Kepler-107c. Instead, the dissimilar densities are consistent with a giant impact event on Kepler-107c that would have stripped off part of its silicate mantle. This hypothesis is supported by theoretical predictions from collisional mantle stripping, which match the mass and radius of Kepler-107c.

Kepler-411: a four-planet system with an active host star
https://arxiv.org/abs/1902.09719

Quote :

We present a detailed characterization of the Kepler-411 system (KOI 1781). This system was previously known to host two transiting planets: one with a period of 3 days (R=2.4R⊕; Kepler-411b) and one with a period of 7.8 days (R=4.4R⊕; Kepler-411c), as well as a transiting planetary candidate with a 58-day period (R=3.3R⊕; KOI 1781.03) from Kepler photometry. Here, we combine Kepler photometry data and new transit timing variation (TTV) measurements from all the Kepler quarters with previous adaptive-optics imaging results, and dynamical simulations, in order to constrain the properties of the Kepler-411 system. From our analysis, we obtain masses of 25.6±2.6M⊕ for Kepler-411b and 26.4±5.9 M⊕ for Kepler-411c, and we confirm the planetary nature of KOI 1781.03 with a mass of 15.2±5.1M⊕, hence the name Kepler-411d. Furthermore, by assuming near-coplanarity of the system (mutual inclination below 30∘), we discover a nontransiting planet, Kepler-411e, with a mass of 10.8±1.1M⊕ on a 31.5-day orbit, which has a strong dynamical interaction with Kepler-411d. With densities of 1.71±0.39~g\,cm−3 and 2.32±0.83~g\,cm−3, both Kepler-411c and Kepler-411d belong to the group of planets with a massive core and a significant fraction of volatiles. Although Kepler-411b has a sub-Neptune size, it belongs to the group of rocky planets.

http://www.ifa.hawaii.edu/info/press-releases/Kepler1658b/

Kepler Space Telescope's First Exoplanet Candidate Confirmed, Ten Years After Launch

Kepler-1658 is 50% more massive and three times larger than the Sun. The newly confirmed planet orbits at a distance of only twice the star's diameter, making it one of the closest-in planets around a more evolved star - one that resembles a future version of our Sun. Standing on the planet, the star would appear 60 times larger in diameter than the Sun as seen from Earth.