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S. Mahadevan, J. Ge, J. van Eyken, C. DeWitt, D. Berger, L. W. Ramsey (PSU)
A new instrument has been designed and developed at Penn State for high precision Doppler radial velocity measurements using the Moire fringe technique. The Moire fringes generated by superimposing a digital comb on two dimensional stellar spectra allow us to translate Doppler shifts in the dispersion direction into much larger Moire fringe shifts (3-5 times larger) in the slit direction. The magnification of Moire fringes and a much simpler phase shift of a sinosoidal pattern enable precision Doppler velocity measurements.
This prototype instrument using a medium resolution spectrograph( R ~ 10,000) can provide much higher throughput (5-10 times more) than conventional high resolution echelle spectrographs. We have demonstrated velocity measurements in the 30 m/s range with this virtual interferometer and further work will allow us to improve the accuracy to 5-10 m/s. The Virtual Interferometer will fill a niche in the 5-50 m/s range allowing a much deeper survey of stellar objects. This can be important in setting constraints on SIM grid stars as well as finding companions around fainter stars.
The author(s) of this abstract have provided an email address for comments about the abstract: suvrath@astro.psu.edu