John Subasavage
Georgia State University
How confident are we that all of the nearest white dwarfs (WDs) have been identified. In an effort to answer this question, we have begun a spectroscopic, photometric, and astrometric initiative to identify and characterize new nearby WDs. We target objects with high proper motions to discern WDs from more distant main sequence dwarfs of identical colors. As such, we carried out a proper motion survey of the entire southern hemisphere, the SuperCOSMOS-RECONS (SCR) proper motion survey. In addition to finding several new WDs, we found the 24th nearest star system, which consists of a late type M dwarf and a brown dwarf. Using this proper motion information, we spectroscopically identified 43 new WD systems, both new and known proper motion objects. Of these, two are likely unresolved double degenerates, one is a very cool WD, and another is very metal-rich. Using CCD photometry to estimate distances, we target new WDs presumed to be within 25 pc for trigonometric parallax determinations. To date, we have 44 WDs on the Cerro Tololo Inter-American Observatory Parallax Investigation (CTIOPI) program, of which, 22 have preliminary parallaxes within 25 pc. This effort will significantly increase the number of WDs within 25 pc, and with the wealth of data we've collected, we're able to characterize these objects precisely. This effort will provide a more complete sample of nearby WDs that can be observed astrometrically from space in hopes of finding extrasolar planets as well as provide specimens for testing various aspects of astrophysical interest (i.e. star formation rates, Galactic disk age, dark matter constituents, etc.).