K2 News and Results

If you all think that's funny, Earth (and Mars) will probably be observed in campaign 9. I can hear the news headlines from here - "Kepler confirms Earth-like planet bears life"…

In other news, campaign 5 started on the 26th of April, which again includes Praesepe and M67. Get hyped!

Also, Vanderburg et al.'s reduction of the Campaign 2 data has been made public, so we'll surely be seeing a lot of discoveries here, in the direction of Upper Scorpius and Rho Ophiuchi. I'm already seeing candidates over at Planet Hunters.

Led_Zep wrote:

KEPLER finds two moons around a Neptune!!!

Lazarus wrote:

Does Neptune get a K2 designation now?

I wonder what level of photometric stability Kepler got for Neptune. I wonder if it might be possible to detect, in transit, some of the "rocks" that orbit closer to the planet. Granted I haven't checked the orbit geometries yet.

Several EPIC# stars have been assigned K2-# designations. (No word on Neptune)
http://exoplanetarchive.ipac.caltech.edu./docs/exonews_archive.html#17July2015


EPIC 201367065 = K2-3
EPIC 201208431 = K2-4
EPIC 201338508 = K2-5
EPIC 201384232 = K2-6
EPIC 201393098 = K2-7
EPIC 201445392 = K2-8
EPIC 201465501 = K2-9
EPIC 201577035 = K2-10
EPIC 201596316 = K2-11
EPIC 201613023 = K2-12
EPIC 201629650 = K2-13
EPIC 201635569 = K2-14
EPIC 201736247 = K2-15
EPIC 201754305 = K2-16
EPIC 201855371 = K2-17
EPIC 201912552 = K2-18
EPIC 201505350 = K2-19

K2-9b very interesting object another super earth in HZ around dim M dwarf and K2 -18b minineptune in HZ around M dwarf

K2-19  Two planet system around late G star super neptune and neptune in 2:3 resonance thanks for link sirius

These are all from the paper Edasich linked to on page 2, so these are all just from the first campaign of observations! It's no Kepler, and it isn't TESS either, but K2 is looking to be a valuable mission.

EPIC 206011691: two super-Earth planets orbiting an M0 dwarf 65 parsecs away.

Petigura et al. (2015) "Two Transiting Earth-size Planets Near Resonance Orbiting a Nearby Cool Star"
http://arxiv.org/abs/1507.08256

(Not sure radii of 1.59 and 1.92 times Earth really count as "Earth-size", even if you want to be optimistic with the error bars)

Both added to EPE:

http://exoplanet.eu/catalog/epic-20601169_b/
http://exoplanet.eu/catalog/epic-20601169_c/

Nevertheless many Kepler and "non-Kepler" exoplanets are still missing in EPE.

The NASA Exoplanet Archive now has a K2 names table available. HAT-P-56b has received the K2 identifier K2-20b.

It does not make any sense for me for what HAT-P56b has now name K2-20 b what is purpose ?Maybe I miss something relevant?

This is the K2 naming policy: http://exoplanetarchive.ipac.caltech.edu/docs/K2Numbers.html

Relevant part:

Quote :

K2 numbers will be assigned to all confirmed or validated planets where K2 data of that object appear in accepted, peer-reviewed journal papers.

The discovery paper for HAT-P-56 incorporates K2 data in the analysis. Therefore according to the K2 names policy, it should receive a K2 designation. (As far as I can tell, it has not been published in the journal yet, so perhaps they've jumped the gun a bit?)

Probably because HAT-P-56b was observed by K2. Remember that TrES-2 got the designation Kepler-1, HAT-P-7 received the designation Kepler-2, and HAT-P-11 got the designation Kepler-3. Giving  all observed targets a catalogue ID is a matter of convenience.

Lazarus wrote:

This is the K2 naming policy: http://exoplanetarchive.ipac.caltech.edu/docs/K2Numbers.html

it's a relief, the EPIC naming convention is terrible. but K2-2b etc it is also something confusing, not as good as Kepler initial namings (Kepler-50b and so). Some imagination, pls.

I proposed KSC -kepler second mission nobody agreed

KSC- sounds better, for me. What a pity, it was a good idea.

K2 data detects starspot modulation (and transits of spots by the planet) and constraints the spin-orbit angle to > 10 degrees.

http://arxiv.org/abs/1508.07281

http://arxiv.org/abs/1509.02917

A HARPS view on K2-3

K2 space observations recently found that three super-Earths transit the nearby M dwarf K2-3. The apparent brightness and the small physical radius of their host star rank these planets amongst the most favourable for follow-up characterisations. The outer planet orbits close to the inner edge of the habitable zone and might become one of the first exoplanets searched for biomarkers using transmission spectroscopy. We used the HARPS velocimeter to measure the mass of the planets. The mass of planet b is 8.4±2.1 M⊕, while our determination of those planets c and d are affected by the stellar activity. With a density of 4.32+2.0−0.76 gcm−3, planet b is probably mostly rocky, but it could contain up to 50% water

http://arxiv.org/pdf/1509.02917v1.pdf
Interesting results small RV data of planetary system K2-3 containing probably 4 planets.Despite stellar activity affecting rv measurement it looks like is surprisingly big difference in densities between planet b  c and d .especially c and d.Fourth planet has period around 100 days I am very curious if is transiting

Should not planet b have density higher? around 5.32 g/cm3 ? Kepler 48 d has almost identical radius  and mass smaller about 5.5% and has density 5.08 g/cm 3 ? Or I am wrong

up to 24 planets for k2!


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


Discoveries from the prime Kepler mission demonstrated that small planets (< 3 Earth-radii) are common outcomes of planet formation. While Kepler detected many such planets, all but a handful orbit faint, distant stars and are not amenable to precise follow up measurements. Here, we report the discovery of two small planets transiting K2-21, a bright (K = 9.4) M0 dwarf located 65$\pm$6 pc from Earth. We detected the transiting planets in photometry collected during Campaign 3 of NASA's K2 mission. Analysis of transit light curves reveals that the planets have small radii compared to their host star, 2.60 $\pm$ 0.14% and 3.15 $\pm$ 0.20%, respectively. We obtained follow up NIR spectroscopy of K2-21 to constrain host star properties, which imply planet sizes of 1.59 $\pm$ 0.43 Earth-radii and 1.92 $\pm$ 0.53 Earth-radii, respectively, straddling the boundary between high-density, rocky planets and low-density planets with thick gaseous envelopes. The planets have orbital periods of 9.32414 days and 15.50120 days, respectively, and have a period ratio of 1.6624, very near to the 5:3 mean motion resonance, which may be a record of the system's formation history. Transit timing variations (TTVs) due to gravitational interactions between the planets may be detectable using ground-based telescopes. Finally, this system offers a convenient laboratory for studying the bulk composition and atmospheric properties of small planets with low equilibrium temperatures.

Two Transiting Earth-size Planets Near Resonance Orbiting a Nearby Cool Star

http://arxiv.org/pdf/1507.08256v2.pdf

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.