Searching for hidden compact objects in the Milky Way

The Milky Way is thought to be teeming with the most exotic objects in the Universe - black holes and neutron stars, with the numbers of these 'compact objects' estimated in the tens of millions. Existing techniques are only able to locate a small number of these objects and the systems they reside in.

I propose to develop and deploy a completely new method where the compact objects transits in front of its companion star, bends and magnifies the light.

This `self-lensing' should be periodic, immediately indicates the presence of a compact object, and provides a reliable means by which to probe the mass 'gap' between black holes and neutron stars.

Not only does this method allow us to discover otherwise electromagnetically hidden systems, most of the compact objects they contain should be effectively pristine; as a result, the systems we will discover through self-lensing hold the promise of addressing several major questions in astrophysics.

One of the biggest challenges for practically detecting self-lensing is the presence of noise (from the star being lensed and the instrument) so we need to develop new software which can search in noisy data using advanced statistical techniques.

Once written, this new software will be deployed across the vast wealth of data taken by the Transiting Exoplanet Survey Satellite (TESS) and the Zwicky Transient Facility (ZTF) which look at the majority of the sky to varying depths and cadence. In addition to the automated search, I am proposing to create two new citizen science programs hosted by Zooniverse.

In the same vein as my successful Black Hole Hunters: Super-Wasp program, these projects will allow citizen scientists to search through the data by hand and alert us to likely instances of self-lensing. This is important, as the human eye is often better at extrapolating signals than algorithms.

Finally, any likely candidates will need to be proven to be periodic but once they are we can model the events and determine the nature of the lens. The first discovered self-lensing neutron star or black hole will be a major result in modern astronomy.