Monthly Exoplanet Paper Roundup: K2-146, System Architectures, a Mass-Period Gap, and Tidally Locked Habitability

Okay, so maybe I haven’t been the most on top of this, but in my defense it’s been a very crazy few months for me. Hopefully will be able to get to this more regularly!

Note that all links are to arXiv papers, which are free and available to the public. You can also follow links from arXiv to the peer-reviewed, published versions when available.

Quick Bites

K2-146 planets b and c, characterized by Lam et al. 2019 and Hamann et al. 2019.

K2-146: Discovery of Planet c, Precise Masses from Transit Timing, and Observed Precession (Hamann et al.) and It takes two planets in resonance to tango around K2-146 (Lam et al.): Dropping onto the arXiv within one day of each other, both these papers detect a new planet, K2-146 c. I read a draft of Aaron’s paper (a fellow UChicago dynamicist) back in the fall, so it just goes to show how much work and time goes into something like this! As you can see from this little plot I made, both teams found similar results, a testament to the accuracy of their methods.

Architectures of Exoplanetary Systems. I: A Clustered Forward Model for Exoplanetary Systems around Kepler’s FGK Stars (Ye et al.): This is a very cool paper that uses clusters to reproduce the observed distribution of Kepler systems, implying that there is some level of intra-system correlation, particularly for periods and multiplicity. They also find that the Kepler dichotomy might be explained by higher mutual inclinations rather than a separate population of single planet systems.

A Gap in the Mass Distribution for Warm Neptune and Terrestrial Planets (Armstrong et al.): One thing that is really exciting to me as the number of detected exoplanets continues to climb is that we can really start to tease out real patterns in the population of planets. Things like the Fulton gap, which was identified in Kepler data. A similar gap is presented in this paper, but it’s defined in the mass-period plane (and doesn’t seem to coincide with the Fulton radius-period gap). Explanation still TBD!

The Bio-habitable Zone and atmospheric properties for Planets of Red Dwarfs (Wandel & Gale): Small, cool stars are the most common type of star, and some of the most promising targets for finding terrestrial planets in the habitable zone. Because the HZ is so close to the star, however, these potentially habitable planets might be tidally locked. This paper dives into whether tidally locked planets can be habitable—spoiler, the answer is YES!

Monthly Exoplanet Paper Roundup: Circumbinaries, Quantum Chemistry, Wide-Orbit Giants, and April Fools’

Hi folks! I wanted to start a new feature to get me back on track of blogging more frequently, so I’m introducing a monthly series about exoplanet papers that I found interesting. The plan is to post on the last Monday of every month to point out papers were particularly intriguing and spotlight one or maybe two for a more in-depth description (although not this month for the in-depth ones). I hope this will help you connect with some new exoplanet science that you find interesting!

Note that all links are to arXiv papers, which are free and available to the public. You can also follow links from arXiv to the peer-reviewed, published versions when available.

Quick Bites

I’m going to try to limit myself to about 5 papers, which is harder than it might sound. An arXiv search for papers with the word “planet” in the abstract from the last month in the astro-ph section returns 160 results!

Discovery of a Third Transiting Planet in the Kepler-47 Circumbinary System (Orosz et al.): Circumbinary planets are a really interesting set of planets that are orbiting both of the stars in a binary system—think Tattoine. We only know of 9 such systems, and Kepler-47 is the only one that has multiple planets. There were two known previously, and this paper announces the discovery of a third planet that is orbiting in between the two known planets.

The binary mass ratios of circumbinary planet hosts (Martin): Speaking of circumbinary planets, my UChicago colleague here examines how the mass ratio of the binary biases transits of circumbinary planets. There are several competing effects, but surprisingly they tend to cancel one another out, and so the transit detections are essentially unbiased.

Impacts of Quantum Chemistry Calculations on Exoplanetary Science, Planetary Astronomy, and Astrophysics (Kao et al.): This is a white paper written for the Astro 2020 Decadal Survey on Astronomy and Astrophysics. I’m including this one because it illustrates some of the non-research paper content that can be found on arXiv as well as the incredibly interdisciplinary nature of the exoplanets field. Quantum chemistry? Yep, that matters!

On the Mass Function, Multiplicity, and Origins of Wide-Orbit Giant Planets (Wagner et al.): Direct imaging is a great technique for observing wide-orbit planets, but it’s very biased towards young, massive planets. The authors here use survival analysis statistics on the currently-detected population of wide-orbit giant planets to predict an underlying relative mass function. They find that the mass distribution rises a lot for lower masses (aka more like planets, less like brown dwarfs) and that there are a lot of less-massive companions out there waiting to be imaged in future surveys.

The Long Night: Modeling the Climate of Westeros (Paradise et al.): Yes, you read that right! This month happens to encompass April 1, which means a chance for scientists to let loose and publish some perhaps oddball papers. A previous April 1 paper (Freistetter & Grützbauch 2018) had provided a possible orbital solution to explain the strange Westerosi seasons, a very unique case called a Sitnikov orbit. This paper applies a 3-D global climate model to a Sitnikov-orbiting Westeros, and they find—well, no spoilers, but it might involve the Children of the Forest constructing orbital megastructures…