Characterization of a Double-Peaked Gravitational Microlensing Event with SALT Spectra

Gravitational microlensing events in the Milky Way occur when a massive foreground object (“lens”) passes within a few milliarseconds of the line of sight of a background star (“source”), causing an apparent increase in the source flux. The lens mass and distance, and the relative lens-source proper motion can be constrained by modeling the characteristic microlensing light curve, especially when slight aberrations are present due to parallax and non-zero angular size and limb-darkening of the source. Strong light curve anomalies can be indicative of a multiple-lens system and thus gravitational microlensing has been used to detect exoplanets. A double-peaked anomalous event can be caused by two sources or a binary-lens system. We have used the High Resolution Spectrograph and the Robert Stobie Spectrograph of the Southern African Large Telescope to obtain spectra of the double-peaked microlensing event MOA-2019-BLG-035 / OGLE-2019-BLG-0033. Our analyses of these spectra will help to clarify the double-source or double-lens nature of this event.