This data release is based on our 2017 Astronomical Journal paper “The LCES HIRES/Keck Precision Radial Velocity Exoplanet Survey” (Butler, Vogt, Laughlin, Burt, Rivera, Tuomi, Teske, Arriagada, Diaz, Holden, Keiser). A copy of this paper can be found here, and in the “Planet” papers section of this website.
The paper contains 60,949 Doppler velocity measurements covering 1,624 stars taken over 20 years. These are typically the nearest and brightest F,G,K, and M dwarf stars that can be seen from Mauna Kea.
A brief history of the Keck/HIRES planet search can be found here.
Since we finalized the targets for the paper we have continued to mine the NASA/Keck data archive for new data. Starting with the raw images, we generate a logsheet, reduce the raw images to 1-D spectra, and measure Doppler velocities from the spectra, all with our proprietary software. Our latest update includes 64,480 Doppler velocity measurements of 1,699 stars. This updated data set is what we are releasing here.
There are two data sets below. The first is the complete un-binned set of velocities (keck_vels). The second is the binned set of data (keck_vels_binned). We often take two or more consecutive observations of a star. We do this for faint stars because we are starved for photons, but we don’t want our exposure times to go longer than 10 or 15 minutes. Longer exposures suffer from more cosmic ray hits, and they have a larger uncertainty in the photon-weighted mid-point of the observation. We also take multiple exposures of bright stars because they would saturate the CCD detector in less than 5 minutes. We prefer that the total exposure time on a star be 5 minutes or longer to average over the stellar seismology timescale. The “keck_vels_binned” file averages all the observations of a given star taken within 2 hours.
These are both “tar” files. Upon downloading them you will need to “un-tar” them. In a standard UNIX X-windows environment you can do this as follows:
UNIX> tar xvf keck_vels
As an example, we show the first 5 observations for HD10700. The columns are:
|Julian Date||Velocity (m/s||Uncertainty (m/s)||S_value||Halpha||median photons per pixel||exposure time (seconds)|
A -1 for S_value or Halpha indicates that a measurement could not be made. Halpha values begin in August 2004 when the CCD was upgraded.
We would appreciate it if any use of this data cites our paper (Butler, Vogt, Laughlin et al. 2017, AJ, in print)