Discovery of Very-Low-Mass Binary Stars and Circumstellar Disks in the Infrared

Persistent Link:
http://hdl.handle.net/10150/194754
Title:
Discovery of Very-Low-Mass Binary Stars and Circumstellar Disks in the Infrared
Author:
Siegler, Nick
Issue Date:
2007
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
We present results from three infrared observational studies investigating different aspects of stellar evolution. The first survey, conducted in the near-infrared with adaptive optics, measures for the first time the stellar multiplicity properties of field M6-M7.5 dwarf stars. We report that their binary fraction, separation distribution, and mass ratio distribution are very similar to those of later spectral type stars and brown dwarfs while distinct from more massive stellar binaries. These differences, when coupled with age, shed light on possibly different formation mechanisms and kinematic evolution between binary systems of different primary masses. I incorporate these results with those from all known very-lowmass binary systems (M(tot) ≤ 0.2 M⊙) and present their statistical properties. We also present the discovery of a very tight (66 mas) brown dwarf companion to a mid-L dwarf demonstrating the capabilities of laser guide star adaptive optics. In the second study we present mid-infrared Spitzer observations of members of the ∼ 50 Myr open stellar cluster IC 2391 where, using photometric techniques, we report that about a third of the solar-like stars (spectral types FGK) likely possess debris disks. With respect to several other stellar groups of known age, we show for the first time the evolution of the debris disk fraction of solar-like stars. We conclude that, along with more massive late-B and A stars, the formation of planetesimals around solar-like stars appears to be a universal process of star formation. Lastly, we present preliminary near- and mid-infrared Spitzer observations of stars in the direction of the ∼ 6 Myr open cluster IC 2395. Using photometric techniques, we identify upper main sequence cluster members and lower-mass candidate members with evidence of circumstellar disks at different stages of disk evolution - primordial, transition, and debris. We present for the first time the evolution of the median IRAC flux ratios emitted from the inner ∼ 0.2 AU regions of classic T Tauri stars. These results are possibly consistent with the processes of grain growth and dust settling as a mechanism for planetesimal formation.
Type:
text; Electronic Dissertation
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Astronomy; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Young, Erick T.; Close, Laird M.
Committee Chair:
Young, Erick T.; Close, Laird M.

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleDiscovery of Very-Low-Mass Binary Stars and Circumstellar Disks in the Infrareden_US
dc.creatorSiegler, Nicken_US
dc.contributor.authorSiegler, Nicken_US
dc.date.issued2007en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractWe present results from three infrared observational studies investigating different aspects of stellar evolution. The first survey, conducted in the near-infrared with adaptive optics, measures for the first time the stellar multiplicity properties of field M6-M7.5 dwarf stars. We report that their binary fraction, separation distribution, and mass ratio distribution are very similar to those of later spectral type stars and brown dwarfs while distinct from more massive stellar binaries. These differences, when coupled with age, shed light on possibly different formation mechanisms and kinematic evolution between binary systems of different primary masses. I incorporate these results with those from all known very-lowmass binary systems (M(tot) ≤ 0.2 M⊙) and present their statistical properties. We also present the discovery of a very tight (66 mas) brown dwarf companion to a mid-L dwarf demonstrating the capabilities of laser guide star adaptive optics. In the second study we present mid-infrared Spitzer observations of members of the ∼ 50 Myr open stellar cluster IC 2391 where, using photometric techniques, we report that about a third of the solar-like stars (spectral types FGK) likely possess debris disks. With respect to several other stellar groups of known age, we show for the first time the evolution of the debris disk fraction of solar-like stars. We conclude that, along with more massive late-B and A stars, the formation of planetesimals around solar-like stars appears to be a universal process of star formation. Lastly, we present preliminary near- and mid-infrared Spitzer observations of stars in the direction of the ∼ 6 Myr open cluster IC 2395. Using photometric techniques, we identify upper main sequence cluster members and lower-mass candidate members with evidence of circumstellar disks at different stages of disk evolution - primordial, transition, and debris. We present for the first time the evolution of the median IRAC flux ratios emitted from the inner ∼ 0.2 AU regions of classic T Tauri stars. These results are possibly consistent with the processes of grain growth and dust settling as a mechanism for planetesimal formation.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineAstronomyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorYoung, Erick T.en_US
dc.contributor.advisorClose, Laird M.en_US
dc.contributor.chairYoung, Erick T.en_US
dc.contributor.chairClose, Laird M.en_US
dc.contributor.committeememberStrittmatter, Peteren_US
dc.contributor.committeememberWalker, Chrisen_US
dc.identifier.proquest2229en_US
dc.identifier.oclc752259904en_US
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