In-situ determination of astro-comb calibrator lines to better than 10 cm s(-1).
Improved wavelength calibrators for high-resolution astrophysical spectrographs will be essential for precision radial velocity (RV) detection of Earth-like exoplanets and direct observation of cosmological deceleration. The astro-comb is a combination of an octave-spanning femtosecond laser frequency comb and a Fabry-Pérot cavity used to achieve calibrator line spacings that can be resolved by an astrophysical spectrograph. Systematic spectral shifts associated with the cavity can be 0.1-1 MHz, corresponding to RV errors of 10-100 cm/s, due to the dispersive properties of the cavity mirrors over broad spectral widths. Although these systematic shifts are very stable, their correction is crucial to high accuracy astrophysical spectroscopy. Here, we demonstrate an in-situ technique to determine the systematic shifts of astro-comb lines due to finite Fabry-Pérot cavity dispersion. The technique is practical for implementation at a telescope-based spectrograph to enable wavelength calibration accuracy better than 10 cm/s.
Li
Chih-Hao
CH
Department of Physics, Harvard University, USA. chli@cfa.harvard.edu
Glenday
Alexander G
AG
Benedick
Andrew J
AJ
Chang
Guoqing
G
Chen
Li-Jin
LJ
Cramer
Claire
C
Fendel
Peter
P
Furesz
Gabor
G
Kärtner
Franz X
FX
Korzennik
Sylvain
S
Phillips
David F
DF
Sasselov
Dimitar
D
Szentgyorgyi
Andrew
A
Walsworth
Ronald L
RL