Three transiting Super-Earths around a nearby M dwarf star

A nearby M star with three transiting super-Earths discovered by K2

Quote :

Small, cool planets represent the typical end-products of planetary formation. Studying the archi- tectures of these systems, measuring planet masses and radii, and observing these planets' atmospheres during transit directly informs theories of planet assembly, migration, and evolution. Here we report the discovery of three small planets orbiting a bright (Ks = 8.6 mag) M0 dwarf using data collected as part of K2, the new transit survey using the re-purposed Kepler spacecraft. Stellar spectroscopy and K2 photometry indicate that the system hosts three transiting planets with radii 1.5-2.1 R_Earth, straddling the transition region between rocky and increasingly volatile-dominated compositions. With orbital periods of 10-45 days the planets receive just 1.5-10x the flux incident on Earth, making these some of the coolest small planets known orbiting a nearby star; planet d is located near the inner edge of the system's habitable zone. The bright, low-mass star makes this system an excellent laboratory to determine the planets' masses via Doppler spectroscopy and to constrain their atmospheric compositions via transit spectroscopy. This discovery demonstrates the power of K2 and future space-based transit searches to find many fascinating objects of interest.

Anyone have any idea what star this is? None of the identifiers given are found by SIMBAD, but a coordinate search for nearby stars reveals a few stars that might be candidates.

You can see the star at the middle of the Aladin view on this SIMBAD search page, but the star doesn't have an entry of its own yet. The Kepler team has said they're working on designations for K2 systems, so this should become K2-2 or whatever.

The K2 campaign 1 data was made public almost 1 month ago, so this paper was certainly rushed out. Still, the analysis is good enough to validate the planets, and this seems to be quite a normal system based on the K1 sample. It is, as they note, brighter than most similar K1 systems, which is the major advantage of K2 at the current time.

As the star is fairly bright (1 magnitude fainter than Gliese 581, for instance), and lies near to the celestial equator in Leo, I expect RV observations of the star will be carried out by many capable spectrographs as soon as possible. This will probably be one of the more useful transiting M-dwarf systems for some time, and K2 will likely detect several more like it.

Epic.

(Sorry, couldn't resist)

Press release :

http://newscenter.berkeley.edu/2015/01/16/three-nearly-earth-size-planets-found-orbiting-nearby-star/

For those who are interested the star is located in Leo.

Edasich wrote:

For those who are interested the star is located in Leo.

I wrote:

…and lies near to the celestial equator in Leo…

;-;

Here is an (extremely) crude visualisation of the campaign 1 location, with the star marked with a blue dot. It lies between Upsilon and e Leonis.

Also, that press release says the signals were detected on the 6th. That means all the analysis, follow-up, and writing was done in a week or so. Criminy.

Don't see a blue dot on Shellface's map. Ran area searches through XHIP, the old Yale Parallax Catalog, and my own pet project, and nothing surfaced. RECONS probably has the star in their database, but they hold that data tight. Next step would be to check the old NLTT surveys, specifically Weis, but I don't have the energy for that.

I could find the star in the 2MASS database on NASA/IPAC Infrared Science Archive.

ThinkerX wrote:

Don't see a blue dot on Shellface's map

On his map, the blue dot is to the upper-left of the lowest star in the K2 field he drew on there.

Lazarus wrote:

Epic.

Shellface wrote:

;-;

Haha,

Thank you. I was searching the wrong area altogether.

According to XHIP, most likely candidate is Hip 56367, a M0V star 33.97 parsecs distant...but there are a lot of M stars out there, and the overwhelming majority are not in XHIP.

YPC lists a double in that area (DM -3 3109) but the one is Spectral class G.

I drew another blank with my pet project, but that only goes down to K8/9 with a mere handful of M's.

Quote :

Don't see a blue dot on Shellface's map.

Apologies, could have done with choosing a better colour.

The star does not have any common designations. This wasn't much of a problem for K1 because of the KIC - KOI system, but K2 doesn't seem to have much anything of the latter catalogue. The paper gives the most relevant catalogue numbers:

Quote :

EPIC 201367065, PMI11293-0127, UCAC4 443-054906, PPMX 112920.3-012717

Quote :

[2MASS] 11292037-0127173

SIMBAD will probably have an entry for the star in a day or two.

I just use to enter stellar coordinates at Your Sky - Virtual Telescope and I get star's position (red circle added by me).



"Sandwiched" between Virgo and Sextans in Leo sky field.

Found it in the UCAC4 catalog. V Magnitude of 13.4 But I'm a bit puzzled. B-V = 1.053 and V-J = 1.741 make it a K3/4 star, and my quickie distance estimate came to better than 630 light years!

I think you still have the wrong star - this one has (from the paper) V = 12.17, B-V = 1.35, and V-J = 2.75.

Querying the Vizier catalogue gives me the right star, too.

Shellface's link didn't work for me, looks like it is to step 4 of the query process (VizieR doesn't put query information in the link at that point)

Here's a direct link to the UCAC4 record info.

Whoops.  Thanks for the correction.

Dang, I must have punched in the wrong number last night.

::Memo to self - post while awake::

Anyhow, this time around B-V of 1.357 and V-J of 2.746 result in a Spectral type of K 8/9 and a distance of about 180 light years. Much closer to what was reported.

This system is really great opportunity to measure precisely masses of the planets in regime the most interesting(sought) us all.We have 3 planets with different radii far outside significant mass loss zone.We have currently only 2 planets colder than 700 K with radii 1.6 earth (KOI 314) with mass measurement obtained with help ttv but not really precisely.Personally I do not believe planets so close each other with the same radii similar temperature have such big difference in density like KOI314.I think measurement of masses (RV) these planets should have top priority.I am very curious if planets around 1.5 earth radius but much colder will have also high density as much hotter worlds

Just as reminder for future forum users that should stumble upon this topic (as I casually did) the star is K2-3. At that time I didn’t realize this discussion to be so long!