The purpose of the DENSE project is to identify and accurately characterize all white dwarfs in the Sun's vicinity (currently defined to be within 25 pc - consistent with the NStars and Catalog of Nearby Stars horizons). This type-specific initiative stems from the broader goals of the RECONS effort that attempts to characterize all nearby stars. We aim to collect photometric, spectroscopic, and astrometric data for white dwarfs known or suspected to belong to this sample. Through a partnership in the SMARTS consortium that operates four small telescopes at the Cerro Tololo Inter-American Observatory, we are currently focusing on white dwarfs in the southern hemisphere. In particular, our parallax program, CTIOPI, is measuring trigonometric parallaxes to dozens of nearby white dwarfs for the first time, as well as better constraining distances to white dwarfs with previous trigonometric parallax measurements.
In addition, we have identified nearby white dwarfs that are overluminous and presumably have multiple components in the system. We are observing these systems using
Hubble Space Telescope's Fine Guidance Sensors (FGS) in hopes of resolving the components. If resolved, we will track the orbits astrometrically and obtain dynamical masses for the components. To date, only three white dwarf systems have dynamical masses measured to better than 5% and all of them are within 6 pc of the Sun (Sirius B, Procyon B, and 40 Eridani B). Hence, proximity is a necessary condition that favors the liklihood of astrometrically resolving systems and obtaining precise masses.