K2 News and Results

What a pity there is no mass measurement for these planets but I think they were mentioned before

matthew27 wrote:

Two new K2 confirmed planets! K2-21 b http://goo.gl/QTJ9IP & K2-21 c http://goo.gl/q26sli

a.k.a. EPIC 206011691 b and c.

EPIC 201637175 b receives K2-22 b designation

Double paper release concerning K2-19/EPIC-201505350 system, both with mass estimates for inner and outer planet.

Characterization of the K2-19 Multiple-Transiting Planetary System via High-Dispersion Spectroscopy, AO Imaging, and Transit Timing Variations

Quote :

K2-19 (EPIC201505350) is a unique planetary system in which two transiting planets with radii ~ 7 $R_{Earth}$ (inner planet b) and ~ 4 $R_{Earth}$ (outer planet c) have orbits that are nearly in a 3:2 mean-motion resonance. Here, we present results of ground-based follow-up observations for the K2-19 planetary system. We have performed high-dispersion spectroscopy and high-contrast adaptive-optics imaging of the host star with the HDS and HiCIAO on the Subaru 8.2m telescope. We find that the host star is relatively old (>8 Gyr) late G-type star ($T_{eff}$ ~ 5350 K, $M_s$ ~ 0.9 $M_{Sun}$, and $R_{s}$ ~ 0.9 $R_{Sun}$). We do not find any contaminating faint objects near the host star which could be responsible for (or dilute) the transit signals. We have also conducted transit follow-up photometry for the inner planet with KeplerCam on the FLWO 1.2m telescope, TRAPPISTCAM on the TRAPPIST 0.6m telescope, and MuSCAT on the OAO 1.88m telescope. We confirm the presence of transit-timing variations, as previously reported by Armstrong and coworkers. We model the observed transit-timing variations of the inner planet using the synodic chopping formulae given by Deck & Agol (2015). We find two statistically indistinguishable solutions for which the period ratios ($P_{c}/P_{b}$) are located slightly above and below the exact 3:2 commensurability. Despite the degeneracy, we derive the orbital period of the inner planet $P_b$ ~ 7.921 days and the mass of the outer planet $M_c$ ~ 20 $M_{Earth}$. Additional transit photometry (especially for the outer planet) as well as precise radial-velocity measurements would be helpful to break the degeneracy and to determine the mass of the inner planet.

Photo-dynamical mass determination of the multi-planetary system K2-19

Quote :

K2-19 is the second multi-planetary system discovered with K2 observations. The system is composed of two Neptune size planets close to the 3:2 mean-motion resonance. To better characterise the system we obtained two additional transit observations of K2-19b and five additional radial velocity observations. These were combined with K2 data and fitted simultaneously with the system dynamics (photo-dynamical model) which increases the precision of the transit time measurements. The higher transit time precision allows us to detect the chopping signal of the dynamic interaction of the planets that in turn permits to uniquely characterise the system. Although the reflex motion of the star was not detected, dynamic modelling of the system allowed us to derive planetary masses of $M_b= 44 \pm 12\, M_{\oplus}$ and $M_c = 15.9 \pm 7.0\, M_{\oplus}$ for the inner and the outer planets respectively, leading to densities close to Uranus. We also show that our method allows the derivation of mass ratios using only the 80 days of observations during the first campaign of K2.

NASA’s K2 Finds Dead Star Vaporizing a Mini “Planet” (extrasolar asteroid(s))

http://www.nasa.gov/ames/kepler/nasa-k2-finds-dead-star-vaporizing-mini-planet

An extrasolar asteroid transiting a white dwarf? Interesting.

Here is discovery paper:

A disintegrating minor planet transiting a white dwarf

Quote :

White dwarfs are the end state of most stars, including the Sun, after they exhaust their nuclear fuel. Between 1/4 and 1/2 of white dwarfs have elements heavier than helium in their atmospheres, even though these elements should rapidly settle into the stellar interiors unless they are occasionally replenished. The abundance ratios of heavy elements in white dwarf atmospheres are similar to rocky bodies in the Solar system. This and the existence of warm dusty debris disks around about 4% of white dwarfs suggest that rocky debris from white dwarf progenitors' planetary systems occasionally pollute the stars' atmospheres. The total accreted mass can be comparable to that of large asteroids in the solar system. However, the process of disrupting planetary material has not yet been observed. Here, we report observations of a white dwarf being transited by at least one and likely multiple disintegrating planetesimals with periods ranging from 4.5 hours to 4.9 hours. The strongest transit signals occur every 4.5 hours and exhibit varying depths up to 40% and asymmetric profiles, indicative of a small object with a cometary tail of dusty effluent material. The star hosts a dusty debris disk and the star's spectrum shows prominent lines from heavy elements like magnesium, aluminium, silicon, calcium, iron, and nickel. This system provides evidence that heavy element pollution of white dwarfs can originate from disrupted rocky bodies such as asteroids and minor planets.

EPIC 203868608 AB (or A-b?), a young brown dwarf binary detected by K2 in Upper Scorpius with masses within planetary domain:

K2 Discovery of Young Eclipsing Binaries in Upper Scorpius: Direct Mass and Radius Determinations for the Lowest Mass Stars and Initial Characterization of an Eclipsing Brown Dwarf Binary

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We report the discovery of three low-mass double-lined eclipsing binaries in the pre-main sequence Upper Scorpius association, revealed by K2 photometric monitoring of the region over ∼ 78 days. The orbital periods of all three systems are <5 days. We use the K2 photometry plus multiple Keck/HIRES radial velocities and spectroscopic flux ratios to determine fundamental stellar parameters for both the primary and secondary components of each system, along with the orbital parameters. We present tentative evidence that EPIC 203868608 is a hierarchical triple system comprised of an eclipsing pair of ∼25 MJup brown dwarfs with a wide M-type companion. If confirmed, it would constitute only the second double-lined eclipsing brown dwarf binary system discovered to date. The double-lined system EPIC 203710387 is composed of nearly identical M4.5-M5 stars with fundamentally determined masses and radii measured to better than 3% precision (M1=0.1169±0.0031M⊙, M2=0.1065±0.0027M⊙ and R1=0.4338±0.0071R⊙, R2=0.4377±0.0080R⊙) from combination of the light curve and radial velocity time series. These stars have the lowest masses of any stellar mass double-lined eclipsing binary to date. Finally, EPIC 203476597 is a compact single-lined system with a G8-KO primary and a likely mid-K secondary whose line are revealed in spectral ratios. Continued measurement of radial velocities and spectroscopic flux ratios will better constrain fundamental parameters and should elevate the objects to benchmark status. We also present revised parameters for the double-lined eclipsing binary UScoCTIO 5 (M1=0.3336±0.0022M⊙, M2=0.3200±0.0022M⊙ and R1=0.862±0.012, R2=0.852±0.013R⊙). We discuss the implications of our results on these ∼0.1-1.5 M⊙ stars for pre-main-sequence evolutionary models.

A new hot Jupiter

EPIC 204129699b, a grazing transiting hot Jupiter on an 1.26-day orbit around a bright solar like star

Quote :

We report the discovery of EPIC 204129699b, the first confirmed transiting hot Jupiter detected by the K2 space mission. We combined K2 photometry with FastCam lucky imaging and FIES and HARPS high-resolution spectroscopy to confirm the planetary nature of the transiting object and derived the system parameters. EPIC 204129699b is a 1.8-Jupiter-mass planet on an 1.26-day-orbit around a G7V star (M* = 0.91 Msun, R* = 0.78 Rsun). The planetary radius is poorly constrained (0.7 < Rp < 1.4 RJup ), owing to the grazing transit and the low sampling rate of the K2 photometry. The short orbital period and the brightness of the host star (V = 10.8 mag) make the system amenable to atmospheric characterization.

First K2 science conference today:

http://lcogt.net/k2scicon-agenda/

#K2SciCon On Twitter amazing finds of K2 mission specially about M dwarf planets.

Any details?

Some news from K2 science conference :

Two Transiting Low Density Sub-Saturns from K2

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We report the discovery and confirmation of two sub-Saturn planets orbiting a bright (V = 11.3), metal-rich ([Fe/H] = 0.42 ± 0.04 dex) G3 dwarf in the K2 Campaign 2 field. The planets are 5.68 ± 0.56 Earth-radii and 7.82 ± 0.72 Earth-radii and have orbital periods of 20.8851 ± 0.0003 d and 42.3633±0.0006 d, near to the 2:1 mean-motion resonance. We obtained 32 radial velocities (RVs) with Keck/HIRES and detected the reflex motion due to EPIC-203771098b and c. These planets have masses of 21.0 ± 5.4 Earth-masses and 27.0 ± 6.9 Earth-masses, respectively. With low densities of 0.63 ± 0.25 g/cc and 0.31 ± 0.12 g/cc, respectively, the planets require thick envelopes of H/He to explain their large sizes and low masses. Interior structure models predict that the planets have fairly massive cores of 17.6 ± 4.3 Earth-masses and 16.1 ± 4.2 Earth-masses, respectively. They may have formed exterior to their present locations, accreted their H/He envelopes at large orbital distances, and migrated in as a resonant pair. The proximity to resonance, large transit depths, and host star brightness offer rich opportunities for TTV follow-up. Finally, the low surface gravities of the EPIC-203771098 planets make them favorable targets for transmission spectroscopy by HST, Spitzer, and JWST.

Planetary Candidates from the First Year of the K2 Mission
http://arxiv.org/abs/1511.07820

Quote :

The Kepler Space Telescope is currently searching for planets transiting stars along the ecliptic plane as part of its extended K2 mission. We processed the publicly released data from the first year of K2 observations (Campaigns 0, 1, 2, and 3) and searched for periodic eclipse signals consistent with planetary transits. Out of 59,174 targets we searched, we detect 234 planetary candidates around 208 stars. These candidates range in size from gas giants to smaller than the Earth, and range in orbital periods from hours to over a month. We conducted initial reconnaissance spectroscopy of 68 of the brighter candidate host stars, and present high resolution optical spectra for these stars. We make all of our data products, including light curves, spectra, and vetting diagnostics available to users online.

K2 mission first science conference presentations:

http://lcogt.net/k2scicon-talks/

Going to have to find something to open Keynote files...

On IPhone5s open all this files without anything special that's how I see the keynote and other files.

The K2-ESPRINT Project III: A Close-in Super-Earth around a Metal-rich Mid-M Dwarf
http://arxiv.org/abs/1511.08508

GJ 1214b analogue, nice. Maybe "sub-Neptune" is a better name for such planets though...

Ten Multi-planet Systems from K2 Campaigns 1 & 2 and the Masses of Two Hot Super-Earths
http://arxiv.org/abs/1511.09213

Zodiacal Exoplanets In Time (ZEIT) I: A Neptune-sized planet orbiting an M4.5 dwarf in the Hyades Star Cluster
http://arxiv.org/abs/1512.00483

Quote :

Studying the properties of young planetary systems can shed light on how the dynamics and structure of planets evolve during their most formative years. Recent K2 observations of nearby young clusters (10-800 Myr) have enabled the discovery of such planetary systems. Here we report the discovery of a Neptune-sized planet transiting an M4.5 dwarf (EPIC 210490365) in the Hyades cluster (650-800 Myr). The lightcurve shows a strong periodic signal at 1.88 days, which we attribute to spot coverage and rotation. We confirm the planet host is a member of the Hyades by measuring the radial velocity of the system with the high-resolution near-infrared spectrograph IGRINS. This enables us to calculate a distance based on EPIC 210490365's kinematics and membership to the Hyades, which in turn provides a stellar radius and mass to 5-10%, better than what is currently possible for most Kepler M dwarfs (12-20%). We use the derived stellar density as a prior on fitting the K2 transit photometry, which provides weak constraints on eccentricity. Utilizing a combination of adaptive optics imaging and high-resolution spectra we rule out the possibility that the signal is due to a bound or background eclipsing binary, confirming the transits' planetary origin. EPIC 210490365b has a radius (3.43+0.95−0.31RE) much larger than older Kepler planets with similar orbital periods (3.484 days) and host-star masses (0.29M⊙). This suggests that close-in planets lose some of their atmospheres past the first few hundred Myr. Additional transiting planets around the Hyades, Pleiades, and Praesepe clusters from K2 will help confirm if this planet is atypical or representative of other close-in planets of similar age.

Two Small Temperate Planets Transiting Nearby M Dwarfs in K2 Campaigns 0 and 1
http://arxiv.org/abs/1601.02706

Quote :

The prime Kepler mission revealed that small planets (<4 R_earth) are common, especially around low-mass M dwarfs. K2, the re-purposed Kepler mission, continues this exploration of small planets around small stars. Here we combine K2 photometry with spectroscopy, adaptive optics imaging, and archival survey images to analyze two small planets orbiting the nearby, field age, M dwarfs K2-26 (EPIC 202083828) and K2-9. K2-26 is an M1.0 +/- 0.5 dwarf at 93 +/- 7 pc from K2 Campaign 0. We validate its 14.5665 d period planet and estimate a radius of 2.67^+0.46_-0.42 R_earth. K2-9 is an M2.5 +/- 0.5 dwarf at 110 +/- 12 pc from K2 Campaign 1. K2-9b was first identified by Montet et al. 2015; here we present spectra and adaptive optics imaging of the host star and independently validate and characterize the planet. Our analyses indicate K2-9b is a 2.25^+0.53_-0.96 R_earth planet with a 18.4498 d period. K2-26b exhibits a transit duration that is too long to be consistent with a circular orbit given the measured stellar radius. Thus, the long transits are likely due to the photoeccentric effect and our transit fits hint at an eccentric orbit. Both planets receive low incident flux from their host stars and have estimated equilibrium temperatures <500 K. K2-9b may receive approximately Earth-like insolation. However, its host star exhibits strong GALEX UV emission which could affect any atmosphere it harbors. K2-26b and K2-9b are representatives of a poorly studied class of small planets with cool temperatures that have radii intermediate to Earth and Neptune. Future study of these systems can provide key insight into trends in bulk composition and atmospheric properties at the transition from silicate dominated to volatile rich bodies.

Pity K2-9b another possible super-earth in HZ than turning to be likely a mini-neptune with odds of life as we know very small.

A nearby Earth-size M dwarf HZ discovery by K2 mission would be fascinating.