MARVELS Spectra Overview
MARVELS DR12 is the first release of data from the Multi-object APO Radial Velocity Exoplanet Large-area Survey, covering all four years of data collected. The release includes ~3500 unique stars, with ~20-40 RV points per star. For any particular star, the time baseline between first and last observation was typically two years.
Scope and status
Data collection began in Fall 2008 and ended in Summer 2012. Each star was observed approximately 20-40 times, with a typical exposure lasting 50-60 min. These exposure times were designed to reach a S/N capable of yielding per-epoch RV precisions as good as tens of m/s on stars of 7.6<V<12. The total number of observations was chosen to enable orbital parameters of companions to be uniquely determined without the need for follow-up RV points using additional telescopes.
The MARVELS survey uses a new interferometric technique which combines an interferometer and a spectrograph. The survey then extracts radial velocity information from both 1-D spectra and the interferometric fringes. In order to gain a better understanding of how the MARVELS survey generates radial velocity data please visit the Understanding MARVELS page.
In this release, two different pipelines were used to derive RV’s. The data products for the pipeline designed to simply collapse the spectra to 1-D, then produce RV’s without using the fringe information comprise DR12. The data products from a preliminary pipeline that produced RV’s from the fringe information are referred to as DR11, which is being released as a subset of DR12.
The DR11 pipeline produces, as its final output, one .fits table for each field observed (see naming scheme from the Data Model), which contains the RV curves of all the stars on that plate. DR11 also includes intermediate .fits files, one per exposure, which contain the collapsed 1-D spectra as well as reduced information about the 2-D spectra.
The DR12 pipeline produces six .fits files for each observational field (platename in the Data Model). A file containing the 1D stellar spectra and associated metadata, a file of the Tungsten Iodine (Tio) 1D spectra used for calibration, a file of all the exposure information and associated headers of the original observation files, a file of all the stellar y-profiles (flux sum of a spectrum’s y-axis), a file of all the Tio y-profiles, and a file containing the University of Florida 1D pipeline’s radial velocity outputs and associated errors.