State of the Field: Extreme Precision Radial Velocities

Abstract

The Second Workshop on Extreme Precision Radial Velocities defined circa 2015\nthe state of the art Doppler precision and identified the critical path\nchallenges for reaching 10 cm/s measurement precision. The presentations and\ndiscussion of key issues for instrumentation and data analysis and the workshop\nrecommendations for achieving this precision are summarized here.\n Beginning with the HARPS spectrograph, technological advances for precision\nradial velocity measurements have focused on building extremely stable\ninstruments. To reach still higher precision, future spectrometers will need to\nproduce even higher fidelity spectra. This should be possible with improved\nenvironmental control, greater stability in the illumination of the\nspectrometer optics, better detectors, more precise wavelength calibration, and\nbroader bandwidth spectra. Key data analysis challenges for the precision\nradial velocity community include distinguishing center of mass Keplerian\nmotion from photospheric velocities, and the proper treatment of telluric\ncontamination. Success here is coupled to the instrument design, but also\nrequires the implementation of robust statistical and modeling techniques.\nCenter of mass velocities produce Doppler shifts that affect every line\nidentically, while photospheric velocities produce line profile asymmetries\nwith wavelength and temporal dependencies that are different from Keplerian\nsignals.\n Exoplanets are an important subfield of astronomy and there has been an\nimpressive rate of discovery over the past two decades. Higher precision radial\nvelocity measurements are required to serve as a discovery technique for\npotentially habitable worlds and to characterize detections from transit\nmissions. The future of exoplanet science has very different trajectories\ndepending on the precision that can ultimately be achieved with Doppler\nmeasurements.\n