# # Program information file # PROGRAM_ID 2023B045 PROGRAM_TITLE The Disk Eclipse of R Aqr PROGRAM_INV1 Kenneth Hinkle PROGRAM_INV2 Sean Brittain PROGRAM_INV3 Francis Fekel PROGRAM_INV4 Adwin Boogert PROGRAM_INV5 Thomas Lebzelter PROGRAM_SCICAT stellar PROGRAM_ABSTRACT_BEG The AGB/WD binary R Aqr is a mass transfer system with a dusty flow from the AGB star feeding an accretion disk around the WD. R Aqr is nearby, bright, and extensively studied. The system is a 'disk-eclipse' binary where the WD accretion disk/mass flow eclipses the AGB star every 44 years. An eclipse is currently underway. A feature of the R Aqr system is that the eclipse occurs near periastron. Due to orbital eccentricity, near periastron the WD Roche lobe becomes smaller than the disk and fuels the peculiar aspects of this system. In 2023 the eclipse will be ending with the trailing flow between the stars crossing in front of the AGB star. We propose to observe the trailing debris using high-resolution infrared spectroscopy of the M and K windows taken with iSHELL. Using lines of the CO fundamental and first overtone, velocities, temperatures, and column densities in the disk and mass flow will be measured. The data will be combined with archival spectra that span the eclipse to measure how the disk changes near periastron and to characterize the flow of gas and dust from the AGB star to the WD. PROGRAM_ABSTRACT_END