Abstract

Observational studies of star and planet formation represent a fundamental means to understand the origins of exoplanetary systems and our own solar system. In this dissertation I present a multiwavelength approach to study a wide range of stages of the evolution of protostars and pre-main sequence (pre-MS) stars. I have investigated, via an infrared and multi-epoch X-ray study of the L1630 dark cloud, whether and how X-ray variability in young stellar objects is related to protostellar evolutionary state. Among a subsample of 52 X-ray-emitting young stars in L1630, I find that the earliest stages of young stellar evolution show the highest levels of X-ray variability, indicative of high levels of magnetic activity during star formation. I also find evidence of active magnetospheric accretion in three L1630 stars with circumstellar disks.

I also present multiwavelength analyses of several phenomenologically interesting young stars at different stages of pre-MS stellar evolution. I investigate, via contemporaneous X-ray and optical/IR observations, the nearby, pre-main sequence star/disk systems T Chamaeleontis (T Cha) and TWA 30A and 30B. I analyze X-ray and optical emission signatures of accretion and magnetic activity in T Cha, and infer the X-ray absorbing properties of its circumstellar disk. Like T Cha, each component of the wide binary TWA 30A and 30B is viewed through a highly inclined circumstellar disk. Both TWA 30A and 30B display large near-IR variability, suggestive of (respectively) variable obscuration of the stellar photosphere and a possible disk-rim warp. In the case of T Cha and TWA 30A, I find a correlation of optical/near-IR and X-ray extinction consistent with that of photospheric obscuration from an intervening disk clump.

Library of Congress Subject Headings

Stars--Observations; Stars--Formation; Extrasolar planets

Publication Date

8-2014

Document Type

Dissertation

Student Type

Graduate

Degree Name

Astrophysical Sciences and Technology (Ph.D.)

Department, Program, or Center

School of Physics and Astronomy (COS)

Advisor

Joel Kastner

Advisor/Committee Member

John Kerekes

Advisor/Committee Member

Christopher O’Dea

Comments

Physical copy available from RIT's Wallace Library QB6 .P74 2014

2015 RIT Outstanding Ph.D. Dissertation Award

Campus

RIT – Main Campus

Plan Codes

ASTP-PHD

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