All-sky radial velocity surveys using a multi-object fixed-delay interferometer

Abstract

Multi-object dispersed fixed-delay interferometry provides a powerful way for all sky Doppler radial velocity (RV) searches for extrasolar planets. This technique takes advantage of high sensitivity of a fixed-delay interferometer for precision Doppler RV measurements. The interferometer fringes are dispersed by a moderate resolution spectrometer for broad band observing. Compared to current state-of-the-art high resolution echelle techniques responsible for detection of more than 100 exoplanets, this technique offers several new capabilities such as wide field multiple object observation capability, high instrument throughput and stable instrument responses. The instrument can be used in the visible as well as in the near-IR and UV for observing stars with all spectral types from early A type to later M and L types. Once this kind of instrument is coupled with wide field telescopes (a few degrees of field of view, such as Sloan and WIYN), hundreds of stars with m v < 12 or brighter can be simultaneously monitored with Doppler precision of σ = 15 m/s or better within an hour integration. Millions of stars can be monitored annually. Tens of thousands of extrasolar planets will be uncovered by this proposed all sky RV technique in a decade for studying planet formation and evolution. A prototype instrument has been observed at the KPNO 2.1m telescope in 2002, demonstrating a short term Doppler precision of ~ 3 m/s with eta Cas (V = 3.5), a RV stable star. It also helped to uncover a RV curve for 51 Peg (V = 5.5), confirming previous planet detection using the echelles. The total measured detection efficiency from the above the atmosphere to the CCD detector is about 5% without iodine absorption under 1.5 arcsec seeing conditions, comparable to all of the echelle spectrometers for planet detection. A new instrument, fed with both interferometer outputs, is being developed with a higher efficiency Volume phase holographic grating and better optical design for an initial planet search at the KPNO 2.1m telescope in 2003. It will provide about 20% total detection efficiency. In this paper, we will present principle of the technique, new results from our current instruments and grand plans for all sky Doppler surveys for extrasolar planets.