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Young Stars and Planet Formation

  • Author(s): Haney, Laura
  • Advisor(s): Zuckerman, Ben
  • et al.
Abstract

Young stars represent important laboratories for studying stellar and planet formation. Furthermore, low-mass stars are not only the most common product of star formation, but also provide appealing conditions for the direct imaging of exoplanets. Determining youth in solar-type stars and low-mass stars can be challenging. I have examined young stars and the planet formation processes that occur around them from several different perspectives. First, I examined one of the most commonly-used age determination methods for solar-type stars - chromospheric activity. I compiled a large (~2,800 star) sample of stars with known chromospheric activity levels, calculated their ages, and searched for evidence of an infrared excess (indicative of a circumstellar debris disk) using data from the Wide Field Infrared Survey Explorer (WISE). I found that, while the distribution of stars with a strong infrared excess peaks at young ages, there are a significant number of debris disks occurring at much later ages. I present 74 newly discovered debris disks. Following this work, I examined dust production mechanisms in debris disks by performing an in-depth analysis of 24 stars observed with the Herschel Space Observatory. I present 7 newly resolved stars, and characterize the dust formation mechanisms in 15 stars with confirmed infrared excesses. In addition, I identify four stars as potential targets for follow-up observations to search for previously unseen planets. Finally, I analyzed over 450 optical spectra of low-mass stars to identify young, nearby stars as targets for direct imaging observations. As a part of this project, I also identify 60 stars as bonafide members of nearby moving groups, 39 of which are presented for the first time. I also identify 41 stars with signatures of youth, but that do not appear to belong to any one particular moving group. I discovered 36 spectroscopic binaries, 30 of which are newly presented here. I used the UCAC4 catalog to search for wide binary companions to stars in my sample, and discovered 35 stars in common proper motion pairs, 32 of which are presented here for the first time. I also used my measurements of Li to re-calculate lithium depletion boundary ages for three nearby moving groups (beta Pic, Tuc Hor, and AB Dor). In an effort to characterize youth indicators in low-mass stars, I investigated the magnetic activity of stars in my sample using NUV, X-Ray, and H-alpha emission. I identify a new late-type (M4.9) debris disk host that shows some signatures of active accretion. This newly discovered debris disk host joins a very small population of late-type stars with dusty debris disks.

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