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Double Trouble: The Impact of Binarity on Large Stellar Rotation Datasets

Simonian, Gregory Vahag Aghabekian
http://orcid.org/0000-0002-4230-6732
http://rave.ohiolink.edu/etdc/view?acc_num=osu1563439631310165

Abstract Details

2019, Doctor of Philosophy, Ohio State University, Astronomy.
The Kepler satellite revolutionized our understanding of stellar rotation by providing tens of thousands of rotation periods for stars in the Kepler field, including a substantial fraction of rapid rotators. I explore the nature of the rapid rotators there both using Gaia parallazes and spectra from APOGEE. One expected source of rapid rotators in the Kepler field is a population of tidally-synchronized binaries. I test the binary nature of the Kepler rapid rotators using Gaia parallaxes to distinguish photometric binaries (PBs) from single stars on the unevolved lower main sequence, and compare their distribution of rotation properties to those of single stars both with and without APOGEE spectroscopic characterization. I find that 59% of stars with 1.5 day < P < 7 day lie 0.3 mag above the main sequence, compared with 28% of the full rotation sample. The fraction of stars in the same period range is 1.7 ± 0.1% of the total sample analyzed for rotation periods. Both the photometric binary fraction and the fraction of rapid rotators are consistent with a population of non-eclipsing short period binaries inferred from Kepler eclipsing binary data after correcting for inclination. This suggests that the rapid rotators are dominated by tidally-synchronized binaries rather than single-stars obeying traditional angular momentum evolution. This finding provokes caution against interpreting rapid rotation in the Kepler field as a signature of youth. Following up this new sample of 217 candidate tidally-synchronized binaries will help further understand tidal processes in stars. I also use the 5466 spectroscopic v sin i measurements of Kepler dwarfs and subgiants from the APOGEE survey to explore stellar rotation in late-type dwarfs. I find a detection threshold of 10 km/s, which also allows me to explore the spindown of intermediate-mass stars leaving the main sequence, merger products, young stars, and tidally-synchronized binaries. I use Gaia parallaxes and APOGEE temperatures to calculate radii and to search for photometric binaries. For the unevolved lower main sequence, I see the same concentration toward rapid rotation in photometric binaries as that observed in rotation period data, but at an enhanced rate. I attribute this difference to unresolved spectroscopic binaries with velocity displacements on the order of the APOGEE resolution, which can spuriously overestimate rotational broadening. Among cool, unevolved stars where rapid single star rotation is not expected, I find an excess detection rate of 4 ± 1%, which I argue is a measure of the impact of this phenomenon. For the subgiants, I use asteroseismic data to demonstrate that period and v sin i methods agree, indicating the v sin i measurements are less impacted by the presence of binaries for these targets. There is clear evidence for a transition between rapid and slow rotation on the subgiant branch in the domain predicted by modern angular momentum evolution models, with detections on the hot side much larger than the background from binary stars. I also find substantial agreement between the spectroscopic and photometric properties of KIC targets added by Huber et al. (2014) based on 2MASS photometry.
Marc Pinsonneault (Advisor)
Donald Terndrup (Committee Member)
Todd Thompson (Committee Member)
136 p.
Astronomy
stellar rotation; late-type stars; close binaries

Recommended Citations

Citations

  • Simonian, G. V. A. (2019). Double Trouble: The Impact of Binarity on Large Stellar Rotation Datasets [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1563439631310165

    APA Style (7th edition)

  • Simonian, Gregory. Double Trouble: The Impact of Binarity on Large Stellar Rotation Datasets . 2019. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1563439631310165.

    MLA Style (8th edition)

  • Simonian, Gregory. "Double Trouble: The Impact of Binarity on Large Stellar Rotation Datasets ." Doctoral dissertation, Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1563439631310165

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.