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 K2 News and Results

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Sunchaser
Daniel
matthew27
pochimax
jyril
PlutonianEmpire
Edasich
tommi59
Shellface
Stalker
Led_Zep
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Edasich
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Edasich


Number of posts : 2267
Location : Tau Ceti g - Mid Latitudes
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty11th July 2016, 4:13 am

K2-56 b & c actually match with K2-21 b & c. Rolling Eyes
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Lazarus
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty18th July 2016, 4:33 pm

Shellface wrote:
HIP 41378 becomes K2-93. Apparently ~50 systems are to be confirmed in the near future.
Press release: NASA's Kepler Confirms 100+ Exoplanets During Its K2 Mission

The relevant paper is Crossfield et al. (2016)
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Sirius_Alpha
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty18th July 2016, 8:28 pm


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Lazarus
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty19th July 2016, 2:16 pm

Centauri Dreams has an article from Ravi Kopparapu on the potential habitability of the K2-72 system.
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Edasich
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty20th July 2016, 4:26 am

Lazarus wrote:
Shellface wrote:
HIP 41378 becomes K2-93. Apparently ~50 systems are to be confirmed in the near future.
Press release: NASA's Kepler Confirms 100+ Exoplanets During Its K2 Mission

The relevant paper is Crossfield et al. (2016)

And EPE doesn't list any of them.
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tommi59
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty20th July 2016, 6:40 am

New stellar parameters of K2-3 star if true significantly lower the mass from 0.6 to 0.414 and radius from 0.56 to 0.371 of this star .It definitely increases rocky composition for all planets reduce stellar flux making K2 -3 d most habitable of all and give some chance for c also
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tommi59
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty20th July 2016, 6:42 am

Does anybody know putative 4th planet in this system around 100 days has transit ruled out?
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Shellface
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Number of posts : 283
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty20th July 2016, 9:20 am

I'm afraid the Huber et al. stellar parameters are systematically incorrect for M-dwarfs. For instance they will say that M0V stars have masses/radii of 0.3 Rsol, which is reached at about M3.5.

Also, see the discussion for K2-72:

Quote :
Huber et al. (2016) reports a stellar radius of 0.23 R but notes that this is likely an underestimate. The weighted mean of our four stellar density measurements is 9.0 ± 3.6 g/cm3; using the mass-radius relation of Maldonado et al. (2015) implies a stellar radius of 0.40 +0.12-0.07 R and planetary radii of 1.2–1.5 R for all planets.

The planetary insolations will have to be revised upwards from the tabulated values as a result, which will likely appear in the upcoming paper(s) on the system. I estimate S ≈ 1.5 S for e.
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Lazarus
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty20th July 2016, 12:45 pm

If I run isochrones with the magnitudes given in the NASA Exoplanet Archive, I get the following parameters for K2-72:

Mass = 0.369±0.053 MSun
Radius = 0.358±0.046 RSun
Teff = 3451±41 K
log g = 4.899 ± 0.050
log L = -1.80 ± 0.13
[Fe/H] = -0.01 ± 0.10
Distance = 73±11 pc

So for planet e I estimate the semimajor axis is 0.117 AU and corresponding Seff = 1.16 SEarth (from logL) or 1.19 SEarth (from Teff, radius)
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Lazarus
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty20th July 2016, 1:14 pm

For comparison, the same procedure for K2-3 gives me the following:

Mass = 0.532±0.021 MSun
Radius = 0.516 ± 0.020 RSun
Teff = 3946 ± 39 K
log g = 4.740 ± 0.020
log L = -1.238 ± 0.047
[Fe/H] = -0.303 ± 0.081
Distance = 42.8 ± 2.0 pc

(Note I am not using any constraints on stellar properties from the transits)
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Sirius_Alpha
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty25th July 2016, 8:06 pm

Sirius_Alpha wrote:
Now on arXiv.
Updated paper.
http://arxiv.org/abs/1607.05263

We find out that K2-40 = WASP-75, WASP-85 has the designation EPIC 201862715 (but it doesn't appear to be confirmed independently from K2 data). HAT-P-54 is listed as EPIC 202126849 and given the status of "false positive."

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Shellface
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty26th July 2016, 7:45 pm

Quote :
HAT-P-54 is listed as EPIC 202126849 and given the status of "false positive."
It appears their model found a large companion radius (40 ± 22 Rearth), which I would guess would be due to an overestimated impact parameter.

Statistical validation methods like these are somewhat prone to false negatives. This result should not be taken as "de-confirmation" - for comparison, see the discussion for HAT-P-56:
Quote :
HAT-P-56b (EPIC 202126852b) is a hot Jupiter confirmed by measuring the planet’s mass with Doppler spectroscopy (Huang et al. 2015). Our analysis indicates that the planetary hypothesis is the most probable explanation for the signal detected, with the next-most-likely scenario being an eclipsing binary (FPP=65%; see Table 9). However, the radial velocity measurements of Huang et al. (2015) rule out the eclipsing binary scenario favored by vespa and so confirm the planetary nature of this system.

As for WASP-85, the result is agnostic because the program is unable to determine which star of the binary the transits are on - indeed, the secondary star was problematic in the discovery paper.
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Lazarus
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty3rd August 2016, 1:30 pm

Some K2 candidate exoplanets in Praesepe:
http://arxiv.org/abs/1608.00459
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Sirius_Alpha
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty3rd August 2016, 8:26 pm

EPIC 211391664b: A 32-M⊕ Neptune-sized planet in a 10-day orbit transiting an F8 star
http://arxiv.org/abs/1608.01165

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Led_Zep
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty5th August 2016, 5:55 pm

http://www.nasa.gov/feature/ames/kepler/kepler-mission-manager-update-k2-campaign-10

Kepler Mission Manager Update: K2 Campaign 10

some problems...
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Sirius_Alpha
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty13th August 2016, 1:06 am


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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty15th August 2016, 6:58 pm

http://keplerscience.arc.nasa.gov/retirement-of-ccd-module-4-confirmed.html

Retirement of CCD Module 4 confirmed

« …None of the high-profile targets in future Campaigns, such as Trappist-1 or Comet Chiron, are known to be affected… »
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Shellface
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty16th August 2016, 5:43 am

As far as I can tell the only significant loss is K2-2 (HIP 116454), which was set to be re-observed in Campaign 12.

K2 observations have been limited by on-board data storage more than a lack of targets, so this should not noticeably affect the science output.
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Sirius_Alpha
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty17th August 2016, 8:34 pm

K2 Discovers a Busy Bee: An Unusual Transiting Neptune Found in the Beehive Cluster
http://arxiv.org/abs/1608.04760

Quote :
Open clusters have been the focus of several exoplanet surveys but only a few planets have so far been discovered. The \emph{Kepler} spacecraft revealed an abundance of small planets around small, cool stars, therefore, such cluster members are prime targets for exoplanet transit searches. Kepler's new mission, K2, is targeting several open clusters and star-forming regions around the ecliptic to search for transiting planets around their low-mass constituents. Here, we report the discovery of the first transiting planet in the intermediate-age (800 Myr) Beehive cluster (Praesepe). K2-95 is a faint (Kp=15.5mag) M3.0±0.5 dwarf from K2's Campaign 5 with an effective temperature of 3471±124K, approximately solar metallicity and a radius of 0.402±0.050R⊙. We detected a transiting planet with a radius of 3.47+0.78−0.53R⊕ and an orbital period of 10.134 days. We combined photometry, medium/high-resolution spectroscopy, adaptive optics/speckle imaging and archival survey images to rule out any false positive detection scenarios, validate the planet, and further characterize the system. The planet's radius is very unusual as M-dwarf field stars rarely have Neptune-sized transiting planets. The comparatively large radius of K2-95b is consistent with the other recently discovered cluster planets K2-25b (Hyades) and K2-33b (Upper Scorpius), indicating systematic differences in their evolutionary states or formation. These discoveries from K2 provide a snapshot of planet formation and evolution in cluster environments and thus make excellent laboratories to test differences between field-star and cluster planet populations.

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Shellface
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty31st August 2016, 4:00 pm

A PSF-based approach to Kepler/K2 data - III. Search for exoplanets and variable stars within the open cluster M 67 (NGC 2682)

Quote :
In the third paper of this series we continue the exploitation of Kepler/K2 data in dense stellar fields using our PSF-based method. This work is focused on a ~720-arcmin^2 region centred on the Solar-metallicity and Solar-age open cluster M 67. We extracted light curves for all detectable sources in the Kepler channels 13 and 14, adopting our technique based on the usage of a high-angular-resolution input catalogue and target-neighbour subtraction. We detrended light curves for systematic errors, and searched for variables and exoplanets using several tools. We found 451 variables, of which 299 are new detection. Three planetary candidates were detected by our pipeline in this field. Raw and detrended light curves, catalogues, and K2 stacked images used in this work will be released to the community.
None of the planet candidate hosts are members of M67, which contrasts with the same authors' result with Praesepe. I would guess that this is due to the lower brightness of M67, as only the top of the cluster main sequence (~G dwarfs) have suitable photometric precision for planet detection (in this reduction, at least).
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Shellface
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty5th September 2016, 11:33 am

EPIC 212803289: a subgiant hosting a transiting warm Jupiter in an eccentric orbit and a long-period companion

Quote :
We report the discovery from K2 of a transiting planet in an 18.25-d, eccentric (0.19± 0.04) orbit around EPIC 212803289, an 11th magnitude subgiant in Virgo. We confirm the planetary nature of the companion with radial velocities, and determine that the star is a metal-rich ([Fe/H] = 0.20 ± 0.05) subgiant, with mass 1.60 +0.14−0.10 M⊙ and radius 3.1 ± 0.1 R⊙. The planet has a mass of 0.97 ± 0.09 MJup and a radius 1.29 ± 0.05 RJup. A measured systemic radial acceleration of −2.12 ± 0.04 ms−1d−1 offers compelling evidence for the existence of a third body in the system, perhaps a brown dwarf orbiting with a period of several hundred days.

Something important that is not mentioned in the paper is that the planet is inflated. At its semi-major axis it receives an insolation ~430 times that of the Earth (roughly equivalent to a planet on a 3.9-day orbit around the Sun), but when the star was on the main sequence it would have received ~40% less flux. While not as striking as the case of EPIC 211351816 because the main-sequence star was much hotter, this planet has likely reinflated by 0.1-0.2 RJup during the brightening of its host star.

This is a relatively massive star for a planet host, and among the most massive transiting planet hosts. On the main sequence it was probably about ~F0 in spectral type, where planets are poorly known.
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty5th September 2016, 10:41 pm

More Praesepe planets.

Zodiacal Exoplanets in Time (ZEIT) IV: seven transiting planets in the Praesepe cluster
http://arxiv.org/abs/1609.00726

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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty6th September 2016, 3:27 pm

Quote :
Zodiacal Exoplanets in Time (ZEIT) IV: seven transiting planets in the Praesepe cluster
Quote :
We identify seven planet candidates, six of which we statistically validate to be real planets.
Uhh…

I had been putting some work into the K2 Praesepe systems - this paper validates 3 of the 4 systems I had investigated, which is rather nice.

While the large radius of K2-95b (EPIC 211916756 b) for a mid-M dwarf planet is noted again, something I would bring attention to is the radius of EPIC 211990866 b. Not long ago, Lundkvist et al. published a K1 paper making the case for atmosphere loss in highly irradiated low-mass planets. From their abstract, their key result is:

Quote :
…while there is an abundance of super-Earth sized exoplanets with low incident fluxes, none are found with high incident fluxes. We do not find any exoplanets with radii between 2.2 and 3.8 Earth radii with incident flux above 650 times the incident flux on Earth. This gap in the population of exoplanets is explained by evaporation of volatile elements…
From the stellar density and Teff plus the planetary period given in this paper, the incident flux of EPIC 211990866 b is 2097 +80-69 F. Its radius is 3.5 ± 0.2 R, so the planet lies well within the desert identified by Lundkvist et al.

The Kepler sample used by Lundkvist et al. is dominated by stars considerably older than 1 Gyr. In contrast, Praesepe is only 0.8 Gyr old. The logical conclusion is that planets that were originally in this desert have lost most-to-all of their volatile atmospheres, but EPIC 211990866 b is young enough that its atmosphere has not yet been ablated. This planet is therefore extremely important for understanding atmosphere loss in low-mass planets.

Unfortunately the star is extremely active, so a planetary mass measurement would be extraordinarily difficult despite the relatively bright host star.
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Daniel
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty23rd October 2016, 6:03 pm

Kepler finds scores of planets around cool dwarf stars

http://www.nature.com/news/kepler-finds-scores-of-planets-around-cool-dwarf-stars-1.20853

hopefully some details about this new K2 exoplanets around cool dwarfs come soon...
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PostSubject: Re: K2 News and Results   K2 News and Results - Page 6 Empty23rd October 2016, 7:27 pm

It looks like the article is a summary of already released data ... unless I'm missing something.

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