118 new M dwarf planets

Frequency of planets orbiting M dwarfs in the Solar neighbourhood
https://arxiv.org/abs/1906.04644

Quote :

The most abundant stars in the Galaxy, M dwarfs, are very commonly hosts to diverse systems of low-mass planets. Their abundancy implies that the general occurrence rate of planets is dominated by their occurrence rate around such M dwarfs. In this article, we combine the M dwarf surveys conducted with the HIRES/Keck, PFS/Magellan, HARPS/ESO, and UVES/VLT instruments supported with data from several other instruments. We analyse the radial velocities of an approximately volume- and brightness-limited sample of 426 nearby M dwarfs in order to search for Doppler signals of cadidate planets. In addition, we analyse spectroscopic activity indicators and ASAS photometry to rule out radial velocity signals corresponding to stellar activity as Doppler signals of planets. We calculate estimates for the occurrence rate of planets around the sample stars and study the properties of this occurrence rate as a function of stellar properties. Our analyses reveal a total of 118 candidate planets orbiting nearby M dwarfs. Based on our results accounting for selection effects and sample detection threshold, we estimate that M dwarfs have on average at least 2.39+4.58−1.36 planets per star orbiting them. Accounting for the different sensitivities of radial velocity surveys and Kepler transit photometry implies that there are at least 3.0 planets per star orbiting M dwarfs. We also present evidence for a population of cool mini-Neptunes and Neptunes with indications that they are found an order of magnitude more frequently orbiting the least massive M dwarfs in our sample.

GJ 160.2 was reported by Tuomi (2014) with a period of 5.2354 days and a m sin i of 10.2 earth-masses. This is revised to 9.7471 days and a minimum mass of 7.8 earth-masses.

GJ 163 is re-worked. The planet orbits are much more circular, the e planet is moved further out (from 19 days to 349 days).

For GJ 191 (Kapteyn's Star) they report two planets, but they don't seem to comment on the controversy over the legitimacy of the planetary interpretation of the RV variability.

For GJ 317, they report it as a two-planet system but not the one we all know and love. The outer planet has been replaced with a planet at half the orbital period of what was the inner planet. Rather than a planet at 5312 days, there's a planet at 397 days.

Some of these systems are *very* nearby. A planet is reported at AD Leo, and two planets at Wolf 359(!!).

They find a planet at Lalande 21185 but they report a period of 9.8684 days instead of 12.9532 found by Díaz, et al.

For Gliese 581, they assert four planets, corresponding to the four planets that we accepted were there before the claims of an f and g planet appeared. Like with Kapteyn's Star, they just throw that out there without any commentary on past controversy, and as seems to be the norm, they don't bother to stick with the naming convention that has been previously established.

Additional planets at known systems:

A second planet at GJ 176, and at GJ 179.
A fourth planet at GJ 221, though they don't seem to use the same naming convention as the system's prior discoverers.
Luyten's Star now hosts four planets, again though they don't follow prior naming conventions.
GJ 357 (TOI-562) is shown to have a third planet.

*Overwhelmed with bliss*

These are the discovery papers I love the most.

https://twitter.com/mustapipa/status/1138894921392427009

Quote :

"The naming is subjective anyway"

That's not particularly helpful for the people trying to maintain the catalogues... Even more amusingly, they refer to the 67-day planet as "d" on page 14... apparently even being self-consistent is just a subjective concern?

Also from a "maybe I will want to add these to a space simulator at some stage" point of view, I wish they'd included ω and some indication of orbital phase (e.g. time of conjunction) in the planet parameters table.

Meanwhile, looks like GJ 229 Ab is no more.

Hey you found my twitter conversation.
Yeah... I was quite surprised at that response, so clearly in contrast with over a decade of literature precedent. I can only hope the peer-review process asks them to fix this.

Ah, didn't realise that was you! It's a small internet...

Further readthrough of the paper, the planet candidates that didn't survive are:

• GJ 54.1 b (YZ Ceti b) - didn't meet detection threshold
  
• GJ 229 Ab - UVES data issues
  
• GJ 317 c - orbital period not constrained from above, need to consider dynamics of b and the inner planet candidate in case they account for the acceleration
  
• GJ 422 b - disappears after removing outliers with suspicious activity measurements
  
• GJ 433 c - UVES data issues
  
• GJ 682 bc - not supported by HARPS
  
• GJ 3293 de - not detected (note they do not reference Astudillo-Defru et al. 2017, only the earlier Astudillo-Defru et al. 2015 paper, so do not discuss planet e)