Katie Vandorou (U.Maryland/NASA Goddard)
Measuring the Masses of Microlensing Events with Keck
Gravitational microlensing is an excellent way to probe the diverse framework of our galaxy, from stellar black holes to unique planetary systems, as well as free floating planets. Although microlensing makes the detection of such objects possible, measuring their individual masses accurately is only feasible when two second-order effects are present on the light curve. The detection of one of these effects however, known as the microlensing parallax, is uncommon. Therefore, measuring masses this way is not always possible. This has motivated us to conduct follow-up observations of microlensing events with telescopes such as Keck or HST. With the high angular resolution that these telescopes can provide we can resolve the source and lens, and thus measure their individual fluxes and relative proper motion. This information lets us get accurate measurements of the physical properties of the system. Using Keck we have observed a number of planetary microlensing events, revealing their true nature, which in some cases differs to the initial conclusions reported at the time of detection. An example of such a case is OGLE-2016-BLG-1195, which I will discuss along with other events that have been observed by Keck, in addition to the status of our ongoing projects.