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We study the properties of line bisectors in the spectrum of theSun-as-a-star, as observed using the Integrated Sunlight Spectrometer (ISS) ofthe SOLIS project. Our motivation is to determine whether changes in lineshape, due to magnetic modulation of photospheric convection can be separatedfrom the 9 cm/sec Doppler reflex of the Earth's orbit. Measuring bisectors of21 lines over a full solar cycle, our results overwhelmingly indicate thatsolar magnetic activity modulates photospheric convection so as to reduce theasymmetries of line profiles in the spectrum of the Sun-as-a-star (having bothC-shaped and reversed-C-shaped bisectors). However, some lines are constant orhave variations in shape that are too small to measure.  We inject a 9 cm/sec radial velocity signal with a 1-year period into the ISSspectra. Informed by a principal component analysis of the line bisectors, wefit the most significant components to the bisectors of each line by linearregression, including a zero-point offset in velocity that is intended tocapture the injected radial velocity signal. Averaging over lines, we are ableto recover that signal to solid statistical significance in the presence ofmuch larger changes in the line shapes. Although our work has limitations (thatwe discuss), we establish that changes in absorption line shapes do not inthemselves prevent the detection of an Earth-like planet orbiting a Sun-likestar using precise radal velocity techniques.

Precise Radial Velocities Using Line Bisectors