Stellar Multiplicity Statistics in APOGEEDaher, Christine Mazzola (2022) Stellar Multiplicity Statistics in APOGEE. Doctoral Dissertation, University of Pittsburgh. (Unpublished)
AbstractNearly every area of astrophysics is impacted by our knowledge of stellar multiplicity, though perhaps none more so than the life cycles of the stars within close binaries. This dissertation seeks to characterize these effects through statistical analyses of stellar parameters and multi-epoch radial velocities (RV) determined from the high-resolution spectra of the Apache Point Observatory Galactic Evolution Experiment (APOGEE). Given that the majority of APOGEE’s stars have sparsely-sampled RV curves, we utilize the maximum shift in the radial velocities, ∆RVmax, as an indicator for RV variability and the fraction of RV variable systems as a proxy for the close binary fraction. First, we select a sample of 41 363 dwarf and subgiant stars from APOGEE data release 14 and explore the observed trends across a variety of stellar parameters before focusing on the discovery of a complex anticorrelation between the close binary fraction and Fe, overall α, O, Mg, and Si abundances. The steeper trends between α-process abundances as compared to Fe indicate that dust and ices within protostellar discs are largely responsible for the disks’ opacity and likelihood of fragmentation. Second, we define a sample of 24 496 dwarfs and 2786 giants from APOGEE data release 14 with projected rotation speeds vsini determined by our pipeline and ages, distances, and masses taken from the Sanders et al. 2018 catalog. We demonstrate that rapid stellar rotation is overwhelmingly associated with close binaries and that rotation in close binaries diverges significantly from the predictions of gyrochronolgy. Finally, we expose further insights into low-mass binary formation by separately analyzing samples of G, K, and M dwarfs taken from APOGEE data release 17. Through an analysis of the cumulative distributions of [Fe/H], [M/H], and [α/H], we find that correlations between stellar abundances and the close binary fraction depend on spectral type. These preliminary results suggest that the metallicity-dependent protostellar disc fragmentation crucial to forming K dwarf primaries is less important than mass-dependent disc fragmentation for G dwarf primaries, and that M dwarf binary formation may be more sensitive to disc cooling promoted by gas enriched with dust and icy grains. Share
Details
MetricsMonthly Views for the past 3 yearsPlum AnalyticsActions (login required)
|
![[feed]](/images/feed-icon-32x32.png){kind=icon}