Kepler News and Results (Thread 2)

Stalker wrote:

Old one

The paper doesn't assert it's a new planet, it presents simultaneous multi-colour photometry of the debris tail to show it to be consistent with micron-sized dust, confirming the nature of the object as a disintegrating exoplanet.

On the Detection of Exomoons
http://arxiv.org/abs/1502.05033

Very fascinating paper. By stacking up transit light curves of whole groups of planets, they find tentative evidence for exomoons orbiting intermediate-period giant planets. Furthermore, they find exomoon candidates around several specific Kepler planets. Almost all of them are better explained by systematics or stellar activity, but an exomoon candidate around Kepler-264b seems to pass all of these tests. The moon is a super-Earth-sized object orbiting a Neptune-sized planet, so the author has been cautious about asserting any sort of confirmation.

The concept of stacking many transits from different sources together to make a "super-transit" is again very interesting - its previous application being to the average albedo of small Kepler planets. Its apparent success here is perhaps not a surprise.

The paper also notes the impact of approximating an exomoon signal with a single moon when it could be due to several moons. Indeed, I suspect that the divide seen in the solar system (Jupiter-like systems with several large moons, or Saturn-like systems with one (or two) moons that contain most of the mass of the moon system) may be rather applicable here, because such large moons are less feasible than multiple small ones.

Ultimately, searching for moons in Kepler data is exceptionally difficult and unlikely to be successful. However, a strong successful identification would be extraordinarily valuable, and so the continued searches are very justified. But I expect that it will be a generation or two of telescopes until exomoons are as readily identifiable via photometry as planets are today.

Interesting if confirmed. Well greater than the 1/81 mass ratio of Earth-Moon system.

Additional exomoon candidates for Kepler-241 b & c and KOI-367.01 too.

Mass ratio for kepler 264b and potential moon will be around 1/8 or even less knowing now what density can have objects with radii 3.3 and 1.6 earth

About the Hunt for Exomoons with Kepler (HEK) project :

http://www.nas.nasa.gov/publications/articles/feature_exomoons_kipping.html

Another update from the HEK project, still no exomoons though ever-more-stringent limits, plus some indications of an additional planet in the Kepler-10 system.

Kipping et al. "The Hunt for Exomoons with Kepler (HEK): V. A Survey of 41 Planetary Candidates for Exomoons"
http://arxiv.org/abs/1503.05555

The Kepler discovery list of planets has been updated to 1022 from 1019. What ones are the 3 new ones???

http://kepler.nasa.gov/Mission/discoveries/

Not sure. I have all of the Kepler-#'s already in my notes except Kepler-72 and Kepler-73, which this page promises exist but aren't published. So maybe they added new planets in known systems.... or just finally updated to catch up with the available literature.

…That is definitely not K2.

Confirmation of one of the first KOIs:

SOPHIE velocimetry of Kepler transit candidates XVI. Tomographic measurement of the low obliquity of KOI-12b, a warm Jupiter transiting a fast rotator

Quote :

We present the detection and characterization of the transiting warm Jupiter KOI-12b, first identified with Kepler with an orbital period of 17.86 days. We combine the analysis of Kepler photometry with Doppler spectroscopy and line-profile tomography of time-series spectra obtained with the SOPHIE spectrograph to establish its planetary nature and derive its properties. To derive reliable estimates for the uncertainties on the tomographic model parameters, we devised an empirical method to calculate statistically independent error bars on the time-series spectra. KOI-12b has a radius of 1.43±0.13R_Jup and a 3σ upper mass limit of 10M_Jup. It orbits a fast-rotating star (vsini⋆ = 60.0±0.9 km s−1) with mass and radius of 1.45±0.09 M_Sun and 1.63±0.15 R_Sun, located at 426±40 pc from the Earth. Doppler tomography allowed a higher precision on the obliquity to be reached by comparison with the analysis of the Rossiter-McLaughlin radial velocity anomaly, and we found that KOI-12b lies on a prograde, slightly misaligned orbit with a low sky-projected obliquity λ = 12.6_−2.9^+3.0∘. The properties of this planetary system, with a 11.4 magnitude host-star, make of KOI-12b a precious target for future atmospheric characterization.

Again with avoiding the process of giving a confirmed KOI a Kepler name.… Well, at least the use of spectral line deformation during transit to validate another planet is impressive and encouraging.

1.43 Jupiter radii is quite large for a planet with such an orbital period, wonder what's going on. Pity it wasn't possible to determine the mass and eccentricity, with only upper limits to these quantities.

http://arxiv.org/abs/1504.04625

KOI-372: a young extrasolar system with two giant planets on wide and eccentric orbits

We confirm the planetary nature of KOI-372b (aka Kepler object of interest K00372.01), a giant transiting exoplanet orbiting a solar-analog G2V star. The mass of KOI-372b and the eccentricity of its orbit were accurately derived thanks to a series of precise radial velocity measurements obtained with the CAFE spectrograph mounted on the CAHA 2.2-m telescope. A simultaneous fit of the radial-velocity data and Kepler photometry revealed that KOI-372b is a dense Jupiter-like planet with a mass of Mp=3.25 Mjup and a radius of Rp=0.882 Rjup. KOI-372b is moving on a quite eccentric orbit, e=0.172, making a complete revolution around its parent star in 125.6 days. The semi-major axis of the orbit is 0.4937 au, implying that the planet is close to its habitable zone (roughly 0.5 au from it). By analysing the mid-transit times of the 12 transit events of KOI-372b recorded by the Kepler spacecraft, we found a clear transit time variation, which is attributable to the presence of a planet c in a wider orbit. We estimated that KOI-372c has a mass between 0.13 and 0.31 Mjup, also revolving on an eccentric orbit (e=0.17-0.24) in roughly 460 days, at a mean distance of 1.2 au from the host star, within the boundaries of its habitable zone. The analysis of the CAFE spectra revealed a relatively high photospheric lithium content, A(Li)=2.48 dex, suggesting that the parent star is relatively young. From a gyrochronological analysis, we estimate that the age of this planetary system is 1.0 Gyr.

You are right

Switched the posts to the right thread.

The Five Planets in the Kepler-296 Binary System All Orbit the Primary: A Statistical and Analytical Analysis

Quote :

Kepler-296 is a binary star system with two M-dwarf components separated by 0.2 arcsec. Five transiting planets have been confirmed to be associated with the Kepler-296 system; given the evidence to date, however, the planets could in principle orbit either star. This ambiguity has made it difficult to constrain both the orbital and physical properties of the planets. Using both statistical and analytical arguments, this paper shows that all five planets are highly likely to orbit the primary star in this system. We performed a Markov-Chain Monte Carlo simulation using a five transiting planet model, leaving the stellar density and dilution with uniform priors. Using importance sampling, we compared the model probabilities under the priors of the planets orbiting either the brighter or the fainter component of the binary. A model where the planets orbit the brighter component, Kepler-296A, is strongly preferred by the data. Combined with our assertion that all five planets orbit the same star, the two outer planets in the system, Kepler-296 Ae and Kepler-296 Af, have radii of 1.53 +/- 0.26 and 1.80 +/- 0.31 R_earth, respectively, and receive incident stellar fluxes of 1.40 +/- 0.23 and 0.62 +/- 0.10 times the incident flux the Earth receives from the Sun. This level of irradiation places both planets within or close to the circumstellar habitable zone of their parent star.

Fascinating. I can't recall seeing such a good relationship for any other Kepler system, though I admit I haven't been looking much.

Wonder if this method could also be used to disentangle Kepler-132, where we already know that the planets must be orbiting different stars.

Van Eylen & Albrecht "Eccentricity from transit photometry: small planets in Kepler multi-planet systems have low eccentricities"
http://arxiv.org/abs/1505.02814

Eccentricity constraints on a bunch of planets, plus verification of six planets in the systems Kepler-92 (already host to two confirmed planets), Kepler-449 and Kepler-450.

Lazarus wrote:

Wonder if this method could also be used to disentangle Kepler-132, where we already know that the planets must be orbiting different stars.

I think the crux of it requires the stars to have considerably different densities, which I recall is probably not true for Kepler-132.

I'm sure this methodology will see use for other systems in future, however.

http://www.nasa.gov/ames/kepler/measuring-the-mass-of-a-mars-size-exoplanet

Daniel Jontof-Hutter, a research associate at the Pennsylvania State University’s Center for Exoplanets and Habitable Worlds, led a team of astronomers in a study to measure the mass of all three planets by precisely observing the times each planet passed in front of, or transited, the star Kepler-138

Masses of exoplanets measured by ttv are not precise previously the same planets b,c had different masses and radii c is twice lighter and d 1/3 lighter both now 1.2 earth radii? Bizarre I would rather believe previous mass measurement more correct neverthelles mass of the smallest one b so close to the star seems to me very small.It is rather obvious it can not contain any hydrogen atmosphere or water ice it should be heavier than mars

http://www.nature.com/nature/journal/v522/n7556/fig_tab/nature14494_T1.html RV measurement would be very welcome

Looks like the star has been revised downwards in size a bit since the Kipping et al. paper. That would contribute to the smaller values for the radius. Stellar mass estimate is also decreased.