K2 News and Results

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Re: K2 News and Results

Post by Sunchaser on 11th April 2016, 6:24 pm

Whew! That gave me a bit of a fright!

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Re: K2 News and Results

Post by Stalker on 13th April 2016, 3:18 am

Adams et al. (2016) present the detection of a planet candidate whose orbital period around its host star is one of the shortest known. Identified as EPIC 203533312, this planet candidate goes around its host star in only 4.2 hours. The host star of EPIC 203533312 has 0.73 ± 0.03 times the radius of the Sun and an effective temperature of 4630 K. By measuring how much light EPIC 203533312 obscures when it transits its host star, the planet candidate is found to have 1.92 ± 0.12 times the radius of Earth. EPIC 203533312 is so close to its host star that its density has to be at least 8.9 g/cm³ in order for it to be massive enough for its own self-gravity to keep it from being tidally disrupted by its host star.

http://arxiv.org/abs/1603.06488
http://beyondearthlyskies.blogspot.fr/2016/04/completing-year-in-42-hours.html?utm_source=BP_recent

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Re: K2 News and Results

Post by Lazarus on 14th April 2016, 5:25 pm

Sirius_Alpha wrote:EPIC210957318b and EPIC212110888b: two inflated hot-Jupiters around Solar-type stars
http://arxiv.org/abs/1601.07635

EPIC 210957318 b = K2-30 b
http://exoplanetarchive.ipac.caltech.edu/cgi-bin/DisplayOverview/nph-DisplayOverview?objname=k2-30+b&type=CONFIRMED_PLANET
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Re: K2 News and Results

Post by Led_Zep on 16th April 2016, 4:47 am

http://www.nasa.gov/feature/ames/mission-manager-update-kepler-remains-stable-as-health-check-continues

Mission Manager Update: Kepler Remains Stable as Health Check Continues
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Re: K2 News and Results

Post by Sirius_Alpha on 21st April 2016, 11:22 pm

Zodiacal Exoplanets in Time (ZEIT) III: A Neptune-sized planet orbiting a pre-main-sequence star in the Upper Scorpius OB Association
http://arxiv.org/abs/1604.06165

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Re: K2 News and Results

Post by Led_Zep on 22nd April 2016, 1:09 pm

http://www.nasa.gov/feature/ames/kepler/mission-manager-update-kepler-recovered-and-returned-to-the-k2-mission

Good news : Wink
« …The spacecraft is now ready for science operations, officially starting K2's new gravitational microlensing campaign, known as Campaign 9 or C9... »
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Re: K2 News and Results

Post by Lazarus on 23rd April 2016, 5:15 am

Power-cycling the onboard computers and subsystems appears to have cleared the problem.
Ah yes, the good old "turn it off and turn it back on again". Glad to see that also works in space Smile
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Re: K2 News and Results

Post by Sirius_Alpha on 5th May 2016, 8:56 pm

Some newly assigned K2-# designations.
K2-31 = EPIC 204129699
K2-32 = EPIC 205071984
K2-34 = EPIC 212110888

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Re: K2 News and Results

Post by Lazarus on 12th May 2016, 4:25 pm

K2 and Herschel help to pin down the size of the dwarf planet (225088) 2007 OR10

SpaceRef: 2007 OR10 Is The Largest Unnamed World in Our Solar System

Pál et al. (2016) "Large size and slow rotation of the trans-Neptunian object (225088) 2007 OR10 discovered from Herschel and K2 observations"
http://arxiv.org/abs/1603.03090

Maybe it won't be the largest unnamed object in the solar system for much longer...
"The names of Pluto-sized bodies each tell a story about the characteristics of their respective objects. In the past, we haven't known enough about 2007 OR10 to give it a name that would do it justice," said Schwamb. "I think we're coming to a point where we can give 2007 OR10 its rightful name."
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Re: K2 News and Results

Post by Sunchaser on 12th May 2016, 10:47 pm

Hopefully they won't throw the naming process to the public like they did in the exoplanet debacle...

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Re: K2 News and Results

Post by Sirius_Alpha on 15th May 2016, 8:36 pm

EPIC212521166 b: a Neptune-mass planet with Earth-like density
http://arxiv.org/abs/1605.04291

We report the discovery of the exoplanet EPIC212521166 b from K2 photometry orbiting on a 13.8637d period around an old, metal-poor K3 dwarf star. A joint analysis of K2 photometry and high-precision RVs from HARPS reveals it to have a radius of 2.6±0.1R⊕ and a mass of 18.3±2.8M⊕, making it the most massive planet with a sub-Neptune radius (i.e. mini-Neptune) yet found. When accounting for compression, the resulting Earth-like density is best fit by a 0.2M⊕ hydrogen atmosphere over an 18M⊕ Earth-like core, although the planet could also have significant water content. At 0.1AU, even taking into account the old stellar age of 8±3 Gyr, the planet is unlikely to have been significantly affected by EUV evaporation or tides. However the planet likely disc-migrated to its current position making the lack of a thick H2 atmosphere puzzling. With a V-band magnitude of 11.9 it is particularly amenable to follow-up observations, making EPIC-1166 b a rare and extremely important planetary system.

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Re: K2 News and Results

Post by Lazarus on 16th May 2016, 4:47 am

Good to have another representative of this interesting class of planets.
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Re: K2 News and Results

Post by Shellface on 16th May 2016, 12:19 pm

I must hesitantly warn that the RV data barely covers 2 orbits of the planet (27 days) and only covers ~1/2 of its phase, so if there is another significant source of RV variability this single-keplerian model may significantly misrepresent the mass of the planet.

That is not to detract from the quick and capable efforts of the authors, however, and I commend the rapid acquisition of RVs.

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Re: K2 News and Results

Post by tommi59 on 17th May 2016, 3:15 am

You are right Shellface but they surely will keep going to improve confidence level. Nevertheless more such planets will be revealed ,small fraction can be completely solid. Mass measurement by RV (where possible) is needed for all even ttv planets as ttv almost always underestimates planet masses.Recent paper about true radius of corot 24 b is quite interesting assessing subneptune class planets
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Re: K2 News and Results

Post by Led_Zep on 23rd May 2016, 6:45 pm

https://blog.planethunters.org/2016/05/23/new-candidates-from-k2-from-planet-hunters-and-their-nearest-neighbors/?utm_content=buffer1f15b&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

New Candidates from K2 from Planet Hunters and Their Nearest Neighbors
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Re: K2 News and Results

Post by Sirius_Alpha on 30th May 2016, 8:36 pm

The K2-ESPRINT Project V: a short-period giant planet orbiting a subgiant star
http://arxiv.org/abs/1605.09180

We report on the discovery and characterization of the transiting planet K2-39b (EPIC 206247743b). With an orbital period of 4.6 days, it is the shortest-period planet orbiting a subgiant star known to date. Such planets are rare, with only a handful of known cases. The reason for this is poorly understood, but may reflect differences in planet occurrence around the relatively high-mass stars that have been surveyed, or may be the result of tidal destruction of such planets. K2-39 is an evolved star with a spectroscopically derived stellar radius and mass of 3.88+0.48−0.42 R⊙ and 1.53+0.13−0.12 M⊙, respectively, and a very close-in transiting planet, with a/R⋆=3.4. Radial velocity (RV) follow-up using the HARPS, FIES and PFS instruments leads to a planetary mass of 50.3+9.7−9.4 M⊕. In combination with a radius measurement of 8.3±1.1 R⊕, this results in a mean planetary density of 0.50+0.29−0.17 g~cm−3. We furthermore discover a long-term RV trend, which may be caused by a long-period planet or stellar companion. Because K2-39b has a short orbital period, its existence makes it seem unlikely that tidal destruction is wholly responsible for the differences in planet populations around subgiant and main-sequence stars. Future monitoring of the transits of this system may enable the detection of period decay and constrain the tidal dissipation rates of subgiant stars.

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Re: K2 News and Results

Post by Lazarus on 7th June 2016, 2:45 pm

More planet candidates:

Benjamin J. S. Pope, Hannu Parviainen, Suzanne Aigrain, "Transiting exoplanet candidates from K2 Campaigns 5 and 6"
http://arxiv.org/abs/1606.01264
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Re: K2 News and Results

Post by Led_Zep on 20th June 2016, 5:14 pm

NASA press release about K2-33b :
http://www.nasa.gov/feature/jpl/nasas-k2-finds-newborn-exoplanet-around-young-star
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Re: K2 News and Results

Post by Sirius_Alpha on 21st June 2016, 5:12 pm

A super-Earth around a K dwarf near (but not a member of) the Pleaides.
http://arxiv.org/abs/1606.05812

A gas giant in a 8 day orbit around a red giant. The planet appears to have been re-inflated by the stellar evolution, suggesting that the inflation mechanism is not a result of delayed contraction and heatloss, but rather an effect determined entirely by the stellar insolation.
http://arxiv.org/abs/1606.05818

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Re: K2 News and Results

Post by Lazarus on 22nd June 2016, 12:46 pm

K2-33b paper on arXiv

David et al. (arXiv:1606.06729) "A Neptune-sized transiting planet closely orbiting a 5-10-million-year-old star"
http://arxiv.org/abs/1606.06729
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Re: K2 News and Results

Post by Stalker on 23rd June 2016, 12:27 pm

EPIC 201702477 b is a massive brown dwarf.

https://arxiv.org/abs/1606.04047

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Re: K2 News and Results

Post by Sirius_Alpha on 28th June 2016, 8:46 pm

Wow!

Five Planets Transiting a Ninth Magnitude Star
http://arxiv.org/abs/1606.08441

The Kepler mission has revealed a great diversity of planetary systems and architectures, but most of the planets discovered by Kepler orbit faint stars. Using new data from the K2 mission, we present the discovery of a five planet system transiting a bright (V = 8.9, K = 7.7) star called HIP 41378. HIP 41378 is a slightly metal-poor late F-type star with moderate rotation (v sin(i) = 7 km/s) and lies at a distance of 116 +/- 18 from Earth. We find that HIP 41378 hosts two sub-Neptune sized planets orbiting 3.5% outside a 2:1 period commensurability in 15.6 and 31.7 day orbits. In addition, we detect three planets which each transit once during the 75 days spanned by K2 observations. One planet is Neptune sized in a likely ~160 day orbit, one is sub-Saturn sized likely in a ~130 day orbit, and one is a Jupiter sized planet in a likely ~1 year orbit. We show that these estimates for the orbital periods can be made more precise by taking into account dynamical stability considerations. We also calculate the distribution of stellar reflex velocities expected for this system, and show that it provides a good target for future radial velocity observations. If a precise orbital period can be determined for the outer Jovian planet through future observations, it will be an excellent candidate for follow-up transit observations to study its atmosphere and measure its oblateness.

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Re: K2 News and Results

Post by Lazarus on 29th June 2016, 2:47 am

Interesting discovery, looking forward to follow-up on this one. Looks like they're all too close to the star to be habitable (though the uncertainties on the outer planet are quite large), maybe there's enough space between HIP 41378 f and the HZ for a planet to be stable there.
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Re: K2 News and Results

Post by Shellface on 29th June 2016, 3:23 pm

A week ago, I posted an independent study of this system to Planet Hunters. Vanderburg emailed me not long after, commenting that the results I reached were quite similar to those in this paper. I had no idea it was so close to being put to the presses, however! Martti, the third name on the author list, is a prominent member at PH, and I congratulate him on the recognition.

As far as I am aware, this is the second-brightest K2 system in the V-band. It is also the highest multiplicity planetary system identified by K2 to date - if K2 observations had been at a different time, it is quite likely that at least one of the mono-transiters would have been missed, so there is certainly some serendipity in these results

As it is bright and observable from most of the Earth, this is an exemplary system for planet characterisation. Mass measurements for all planets are plausible with modern technology, and atmospheric observations will be possible in the near future. In particular this is currently the brightest star with a transiting AU Jovian, so f is an excellent target for many projects; observing its Rossiter-McLaughlin effect, determining its oblateness, attempting to detect moons, to name a few. Determining the outer orbital periods is a priority, and I understand dedicated RV observations are underway.

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Re: K2 News and Results

Post by Shellface on 8th July 2016, 3:06 pm

HIP 41378 becomes K2-93. Apparently ~50 systems are to be confirmed in the near future.

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