systemic

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Data data data. Robert Wittenmyer and his colleagues at the University of Texas have just posted a paper on astro-ph that contains a slew of new radial velocities for several famous planet-bearing stars, including 47 UMa, 14 Her, and 16 Cyg B. The velocities are all tabulated in the paper, so we’ll have them up on the systemic backend very shortly. [I'll post a comment to this post when they're up on the site. If you're totally gung ho to get them right away, you can extract them from the posted latex file at astro-ph, and then add them manually to systemic's datafiles directory.]

We always try to add new radial velocity data sets as soon as they become publicly available, and lately, these updates have been occurring roughly once per week. For the time being, the simplest way to get your fresh V’s is to rename your old systemic directory, and then download a new console. When the new console and catalog data are downloaded and unzipped, you can copy any previous fits and soundfiles that you’ve created into the new fits and soundClips directories.

The data in the Wittenmyer paper come from both the Harlan J. Smith 2.7-meter telescope and the Hobbey-Eberly 9.2-meter telescope. The cadence of the Smith telescope observations typifies the usual pattern of radial velocity survey data. The individual points are spaced essentially randomly in time, with many days separating each point. The Hobbey-Ebery data, on the other hand, are quite different. These data are much more densely sampled, and many nights contain several velocities in succession. In many stretches, the star is observed every few nights. This pattern results from queue-scheduling, which enables very intensive monitoring of systems that are of particular interest. I think queue scheduling is the wave of the future, and in the systemic simulation, we’ll have many synthetic data sets whose cadences correspond to the queue-scheduled approach.

The most prominent planet orbiting 14 Her has been known since the late 1990s. This world, known as 14 Her “b”, has a minimum mass about 4.6 times that of Jupiter, and a period of ~1770 days. If it were in our solar system, it would orbit in the asteroid belt. The parent star 14 Her is about 90% as massive as the Sun, and is more than twice as metal-rich. Given the planet-metallicity connection, it’s absolutely no surprise that 14 Her has a heavy-duty planetary system. I bet that 14 Her “b” has a very interesting system of satellites.

It’s pretty clear from the one planet fit that 14 Her “b” is not the only planet in the system, and over the weekend, several systemic users have submitted interesting fits to the data that reduce the chi-square by adding a second planet. For example, on August 30, user mikevald uploaded a two-planet fit in which the second planet, 14 Her “c”, has a period of 6159 days and an eccentricity e=0.52. This model currently fields the lowest chi-square statistic of any of the submitted 14 Her fits. The orbits in this best-fit system are crossing, however, indicating that the model may not be dynamically stable over the long run. On September 5th, allanfloering submitted a fit with nearly as good a chi-square, in which the outer planet has a 14,669 day period and an eccentricity e=0.09. Allanfloering’s world, if it exists, lies 11.77 AU from 14 Her, out at a Saturn-like distance.

Wittenmyer et al. show that the addition of their new 14 Her data suggests that 14 Her “c” has a period of order 6900 days, albeit with a low eccentricity. In their models, “c” and “b” may be participating in 4:1 resonance. A quick fit on the console with the Wittenmyer et al data included gives a radial velocity curve that looks like this:

corresponding to a planetary configuration that has an outer planet with a modest eccentricity e=0.20.

As soon as the data go up on the site, feel free to try working up improvements. It will be interesting to see how many fits to the full 3-telescope data set are participating in 4:1 resonance.