Author(s) :

Yiyang Zheng.

Volume/Issue :

Abstract :

During stellar evolution, some stars evolve into blue straggler stars (BSS), stars that are more blue and luminous compared to the main sequence turnoff point (MSTO) of the parent generation. Two main theories for BSS formation exist, stellar collision and binary mass transfer. One way to determine which theory led to BSS formation is by determining if there is a correlation between local stellar density and BSS frequency. A strong positive correlation suggests that collision is the main method, while a very weak or negative correlation suggests that binary mass transfer dominates BSS formation. While most previous research have focused on BSS formation within stellar clusters, this paper intends to find a trend between local stellar density and binary mass transfer in the field regions of a large spiral galaxy, Andromeda (M31). Data from the Panchromatic Hubble Andromeda Treasury (PHAT) was used, and BSS candidates were identified. Local stellar density was then plotted against BSS frequency for each star in a logistic regression, and the coefficient was recorded. Out of 11 fields, 8 fields showed a weak trend with a confidence interval containing zero for the coefficient, with coefficients ranging from -2.818 to 2.222, while 3 fields showed a negative correlation between BSS frequency and local stellar density with coefficients from -4.231 to -3.587. This supports the theory that binary mass transfer is the primary mechanism for BSS formation in field stars.