多波段觀測下恆星從誕生至死亡對周遭環境的影響研究

Abstract

本論文旨在探討恆星從誕生到死亡的各個演化階段中，如何透過不同型態的能量活動影響其周遭環境。我結合多波段觀測資料與時間變化分析，針對不同階段的恆星系統進行研究，藉此建立一個關於恆星環境影響之統一觀點。 第一項研究針對前主序（pre-main-sequence, PMS）M型恆星 DM Tau，分析其可見光與毫米波觀測資料。結果顯示，其光變曲線具有週期性，並伴隨空間上非對稱的游離氣體分布，推論其恆星表面存在一個巨大的冷斑，作為各向異性的紫外線與X射線輻射源，選擇性地照射圓盤特定區域，可能造成區域性化學與動力結構的變化。 第二項研究聚焦於 PMS 恆星在不同時間尺度上的吸積變異性。我利用來自可見光、紫外線與X射線的多波段時域觀測，探討週期性調制與長時間尺度的吸積爆發現象。爆發期間釋放出遠高於平常吸積狀態的能量，可能顯著改變圓盤的結構與輻射條件。透過顏色變化推估的溫度變動進一步支持吸積活動隨時間演化的假說。 第三項研究則探討大麥哲倫星系在OB 星協內的超新星遺骸（supernova remnants, SNRs）。我利用測光資料與恆星演化軌跡，估算其前身恆星的質，並探討超新星回饋對周圍星際介質與恆星形成環境的影響。 綜合上述三項研究，本論文展示了恆星如何透過吸積、放射與爆炸等多樣機制，在其生命不同階段對周遭環境產生深遠影響。這些結果提供了一個跨越恆星誕生與死亡階段、整合多波段與時域觀測的統一觀點，有助於深入理解恆星與其周遭環境之間的相互作用與共演化。

The evolution of the Universe is driven by complex interactions between stars and their surrounding environments. From the formation of stars within molecular clouds to their eventual demise in supernova explosions, stars exert a continuous influence on their environments through radiation, accretion, and dynamic feedback. This dissertation investigates such environmental impacts across multiple stellar evolutionary stages, using a combination of multi-wavelength and time-domain observations. The focus is placed on both the early (pre-main-sequence; PMS) and final (supernova) phases of stellar evolution, with an emphasis on their radiative and dynamical feedback onto the interstellar medium and circumstellar structures. The first study explores the M-type PMS star DM Tau, which exhibits strong magnetic activity. I identify periodic optical and infrared photometric variations and asymmetric ionized gas distributions, which can be coherently explained by a large cold spot acting as an anisotropic UV/X-ray source. This result provides observational evidence that localized stellar surface features can lead to spatially confined high-energy irradiation, introducing directional asymmetries in disk photochemistry and gas dynamics. The second study focuses on accretion variability in PMS stars across various timescales. Through optical, UV, and X-ray monitoring of DM Tau and similar targets, I detect both rotational modulations and sporadic accretion bursts. These bursts deliver significantly enhanced energy compared to the steady-state accretion, potentially altering disk temperature structures or driving disk dispersal via photoevaporation. Color-based temperature estimates support this scenario and suggest evolving accretion regimes over time. The third study examines five supernova remnants (SNRs) associated with OB associations in the Large Magellanic Cloud to estimate the progenitor masses. By combining photometric color-magnitude diagram analysis and evolutionary tracks, I assess progenitor mass and characterize how explosive feedback from massive stars influences the surrounding star-forming environment and interstellar medium. Collectively, these studies highlight the diverse and phase-dependent ways in which stars shape their surroundings—from influencing planet formation and disk evolution in their youth, to triggering star formation and chemically enriching the interstellar medium through their explosive deaths. This unified observational approach provides new insights into how individual stellar lives contribute to the broader, interconnected processes of cosmic evolution.