Collaborative Research: Variable Circumstellar Disks: Prevalence, Timescales, and Physical Mechanisms

Lowell Observatory, Flagstaff AZ

Investigators

Abstract

Stars many times more massive than our Sun are rare, but they are responsible for producing nearly all of the heavier elements found in nature. Through dramatic supernova explosions, they produce and shed this material throughout the galaxy, mixing it with material out of which the next generation of stars, and planets, are formed. One interesting class of stars, known as Be stars, rotate so rapidly that they somehow shed material that then forms in a disk around their equators. In order to better understand how these disks are formed and why they occasionally seem to disappear, researchers at the University of Oklahoma, Lowell Observatory, and the University of Toledo have formed a team to carry out an intensive study of these systems. They will use an array of ground-based telescopes to observe these events, and they are developing sophisticated computer codes to aid the interpretation of these observations. This program will support graduate students at the University of Oklahoma and at the University of Toledo, as well as undergraduate students at all three institutions. They will develop research-based planetarium shows that satisfy state education standards. Undergraduates will be trained to develop content and conduct outreach and to take these shows on the road to K-12 students using a portable planetarium and a digital projector. These shows will be freely released for use in other settings. This program will determine the timescales, relative prevalence, and physical mechanisms of disk-loss and disk rebuilding episodes of classical Be stars. These goals will be accomplished by carrying out a statistical assessment of the prevalence of disk-loss/renewal episodes of populations of Be stars in open clusters, as well as intensive multi wavelength studies of individual Be stars actively experiencing disk-loss/renewal episodes. Predictions of state-of-the-art radiation transfer and hydrodynamical modeling codes will be compared against the data obtained in this program, to test a range of scenarios that have been proposed to explain how circumstellar disks may be created and destroyed during the lifetime of the host star.