K2 News and Results

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Re: K2 News and Results

Post by Led_Zep on 8th July 2016, 5:36 pm

From Davos meeting : preliminary results of K2 campaign 9 !!!!!!!!!!!!!!!!

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Re: K2 News and Results

Post by Daniel on 10th July 2016, 5:42 pm


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Re: K2 News and Results

Post by Daniel on 10th July 2016, 5:45 pm

some of K2 planets Exocon1

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Post by matthew27 on 10th July 2016, 11:31 pm

New planetary and EB candidates from Campaigns 1-6 of the K2 mission
S. C. C. Barros (1, 2), O. Demangeon (2), M. Deleuil (2) (1-Instituto de Astrofisica e Ciencias do Espaco, 2-Laboratoire d'Astrophysique de Marseille)
(Submitted on 8 Jul 2016)
http://arxiv.org/abs/1607.02339

With only two functional reaction wheels, Kepler cannot maintain stable pointing at its original target field and entered a new mode of observation called K2. Our method is based on many years of experience in planet hunting for the CoRoT mission. Due to the unstable pointing, K2 light curves present systematics that are correlated with the target position in the CCD. Therefore, our pipeline also includes a decorrelation of this systematic noise. Our pipeline is optimised for bright stars for which spectroscopic follow-up is possible. We achieve a maximum precision on 6 hours of 6 ppm. The decorrelated light curves are searched for transits with an adapted version of the CoRoT alarm pipeline. We present 172 planetary candidates and 327 eclipsing binary candidates from campaigns 1, 2, 3, 4, 5 and 6 of K2. Both the planetary candidates and eclipsing binary candidates lists are made public to promote follow-up studies. The light curves will also be available to the community.

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Re: K2 News and Results

Post by Edasich on 11th July 2016, 4:13 am

K2-56 b & c actually match with K2-21 b & c. Rolling Eyes
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Re: K2 News and Results

Post by Lazarus on 18th 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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Re: K2 News and Results

Post by Sirius_Alpha on 18th July 2016, 8:28 pm

Now on arXiv.
http://arxiv.org/abs/1607.05263

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Re: K2 News and Results

Post by Lazarus on 19th 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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Re: K2 News and Results

Post by Edasich on 20th 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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Re: K2 News and Results

Post by tommi59 on 20th 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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Re: K2 News and Results

Post by tommi59 on 20th 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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Re: K2 News and Results

Post by Shellface on 20th 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:

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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Re: K2 News and Results

Post by Lazarus on 20th 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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Re: K2 News and Results

Post by Lazarus on 20th 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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Re: K2 News and Results

Post by Sirius_Alpha on 25th 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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Re: K2 News and Results

Post by Shellface on 26th July 2016, 7:45 pm

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:
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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Re: K2 News and Results

Post by Lazarus on 3rd August 2016, 1:30 pm

Some K2 candidate exoplanets in Praesepe:
http://arxiv.org/abs/1608.00459
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Re: K2 News and Results

Post by Sirius_Alpha on 3rd 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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Re: K2 News and Results

Post by Led_Zep on 5th 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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Re: K2 News and Results

Post by Sirius_Alpha on 13th August 2016, 1:06 am

Follow-up update. Another detector failure.
http://www.nasa.gov/feature/ames/kepler/kepler-mission-manager-update-photometer-update

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Re: K2 News and Results

Post by Led_Zep on 15th 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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Re: K2 News and Results

Post by Shellface on 16th 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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Re: K2 News and Results

Post by Sirius_Alpha on 17th 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

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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Re: K2 News and Results

Post by Shellface on 31st 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)

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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Re: K2 News and Results

Post by Shellface on 5th September 2016, 11:33 am

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

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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