A big day for our understanding of RV jitter!
Penn State graduate student Jacob Luhn has just posted two important papers to the arXiv. You can read his excellent writeup of the first of them here:
It took Jacob a HUGE amount of work to determine the *empirical* RV jitter of hundreds of stars from decades of observations from Keck/HIRES. These are “hand crafted” jitter values, free of planets, containing only the HIRES instrumental jitter plus astrophysical jitter.
(Along the way, we wondered how to put error bars on jitter, which is itself a deviation. What’s the standard deviation of a standard deviation? Jacob found the formula—it’s in the paper if you’d like to see how it’s done (you have to use the kurtosis). )
You may have seen Jacob’s work at various meetings: young stars and evolved have high jitter, so there is a “jitter minimum” where they are quietest.
But this paper has more! It turns out the location of the jitter minimum depends in a predictable way on a star’s mass.
The second paper describes the properties of F stars with low jitter.
But don’t F stars all have high jitter?
Nope. Jacob has found many stars in the “jitter minimum” are F stars with < 5 m/s of RV jitter. This has important implications for following up transiting planets.
My favorite consequence of this work is that we will be able to now *predict* the RV jitter of a star from its mass, R’HK, and log(g) *empirically*, incorporating *all* sources of RV noise . Right now, such predictions are only good to ~factor of 2. Jacob can predict it to <25%!
But predicting RV jitter is a story for another paper, coming soon. For now, enjoy these papers at AJ and on @jacobkluhn’s blog:
https://iopscience.iop.org/article/10.3847/1538-3881/ab855a
https://iopscience.iop.org/article/10.3847/1538-3881/ab775c