Finding the Lights in the Shadows: A Multiple Telescope Search for Unresolved Companions to Nearby Low-Mass Wide Binary Systems and Galactic Halo Stars

Wednesday, 28 June 2023 8 a.m. — 9 a.m. MST

AURA Lecture Hall

NOIRLab South Colloquia
Zachary Hartman (Gemini Observatory / NOIRLab)

Over the past two decades, the number of known multiple stellar systems in the solar neighborhood has increased dramatically.  The arrival of the Gaia data releases, high angular resolution imaging at multiple 4-m and up class telescopes and spectroscopic surveys, such as SDSS and LAMOST, have allowed for the identification of thousands of multiple systems.  Identifying these systems is critical as further follow-up and characterization of these systems can inform our understanding of various fields of astronomy, ranging from supernovae to star formation to exoplanets.  In this talk, I will discuss two ongoing surveys attempting to find unresolved companions to the widest nearby low-mass disk binaries and to nearby Galactic halo stars and determine the multiplicity, or high-order multiplicity, fractions for both groups.  These fractions are poorly known, with only a few studies conducted on each.  In order to better constrain this fraction and identify systems for further follow-up, we have obtained high angular resolution imaging observations from multiple telescopes, including speckle observations taken at Gemini North, Gemini South and WIYN.  Preliminary results show a lower fraction than expected for both cases although the surveys are far from complete and biases have not been fully taken into account.