https://ir.lib.ncu.edu.tw/handle/987654321/23 Search the Channel s https://ir.lib.ncu.edu.tw/simple-search https://ir.lib.ncu.edu.tw/handle/987654321/99232 title: 利用 ePESSTO+資料探討 Ia 型超新星 光譜特徵及其宿主星系性質的關係;Spectroscopic Analysis of Type Ia Supernovae from ePESSTO+ and Their Connection with Host Galaxy Properties abstract: Ia 型超新星是重要的宇宙學距離指標，然而其前身星通道與爆炸機制至今 仍未被完全理解。為了對此進行限制，我們透過分析其宿主星系的性質，推測 有關前身星的重要資訊。本研究使用 ePESSTO+ 計畫於 2019 至 2023 年間所 觀測的 SNe Ia 最大光度時的光譜，探討 Si II λ6355 與 Si II λ5972 吸收線的 外殼膨脹速度及偽等效寬(pseudo equivalent width)與宿主星系物理性質(包 含恆星質量與比恆星形成率)之間的關係。我們同時比較不同的 SNe Ia 分類 方式與其宿主環境的相關性。結果顯示，傳統的分類在宿主星系性質上呈現出 最明顯的差異。此外，普通型 SNe Ia 可依宿主環境再區分為兩個亞型，可能 對應於不同的爆炸機制。對這些分類而言，Si II λ6355 吸收線的偽等效寬可作 為區分爆炸機制的良好指標。;Type Ia supernovae (SNe Ia) are important cosmological distance indicators; however, their progenitor channels and explosion mechanisms are not fully un- derstood. To constrain these aspects, we analyze the properties of their host galaxies, from which key information about the progenitors can be inferred. In this study, we examine the maximum-light spectra of SNe Ia obtained by the ePESSTO+ program from year 2019 to 2023. We investigate the relationships between the ejecta velocities and pseudo-equivalent widths (pEWs) of the Si II λ6355 and Si II λ5972 absorption lines and the physical properties of their host galaxies, including stellar mass and specific star formation rate. We also test how different SN Ia classification schemes correlate with their host environments. Our results show that the traditional subtype classification provides the clearest distinctions among host properties. Furthermore, normal SNe Ia can be divided into two subgroups based on their host environments, with one subgroup tend- ing to be High-Velocity (HV) and associated with older host galaxies, while the other tends to be Normal-Velocity (NV). For these subgroups, the pEW of the Si II λ6355 line serves as a strong indicator for distinguishing between their explo- sion mechanisms. These results suggest that 91bg-like SNe Ia and HV SNe Ia tend to favor double-degenerate progenitor systems. <br> Fri, 06 Mar 2026 10:23:35 GMT https://ir.lib.ncu.edu.tw/handle/987654321/99230 title: 利用宿主星系了解2002es-like 與 2003fg-like 超新星之前身系統;Understanding the progenitor systems of peculiar 2002es-like and 2003fg-like supernovae with their host galaxies abstract: 2002es-like 與 2003fg-like Ia 型超新星為 Ia 型超新星中的特殊類型。儘管其前身系統與爆炸機制尚未明確確定，但過去研究結果普遍認為兩者源自不同的環境。然而，近期針對其紫外光變曲線的分析顯示，兩者在紫外波段具有高度相似性，並推測可能擁有共同的起源。本研究旨在透過分析其宿主星系環境，深入探討這些特殊超新星的爆炸特性與前身系統。本研究將比較 2002es-like 與 2003fg-like Ia 型超新星的宿主星系性質，以辨識其環境上的差異與共通點。本研究樣本包含 13 個 2002es-like 與 42 個 2003fg-like Ia 型超新星的紫外光至紅外線影像，資料來源包含 GALEX、PS1、SDSS、SkyMapper、2MASS 與 WISE 巡天望遠鏡，並額外使用 SDSS 巡天望遠鏡資料中的 463 個一般 Ia 型超新星作為參考樣本。本研究提取宿主星系的整體光度，並推導其恆星質量、年齡、金屬量、恆星形成率與特徵恆星形成率。結果顯示，兩類型之間的宿主星系環境存在顯著差異：2002es-like Ia 型超新星通常位於質量較大、年齡較老、恆星形成活動較低的星系；相反地，2003fg-like 超新星則多出現在質量較小、年齡較年輕、且恆星形成較為活躍的星系。這些環境趨勢暗示其前身系統與爆炸機制可能有所不同。本研究結論指出，儘管兩類型皆可能被富含碳的環星物質所環繞，但 2002es-like Ia 型超新星較符合具有較長延遲時間的雙簡併模型中的暴力併合情境（violent merger）；而 2003fg-like Ia 型超新星則更符合延遲時間較短的核心簡併模型（core degenerate）。;The 2002es-like and 2003fg-like supernovae (SNe) are among the most peculiar members of the SNe Ia population. While their progenitor systems and explosion mechanisms remain uncertain, past observations believed that they originate from different channels. However, recent studies of their UV light curves indicate that they are remarkably similar in the UV and may even share a common origin. In this work, we investigate these peculiar explosions and their progenitor systems through an analysis of their host-galaxy environments. We examine and compare the host-galaxy properties of 2002es-like and 2003fg-like SNe Ia to identify their environmental differences and similarities. Our sample consists of UV-to-IR imaging for 13 2002es-like and 42 2003fg-like SNe Ia collected from the GALEX, PS1, SDSS, SkyMapper, 2MASS, and WISE surveys, along with an additional 463 normal SNe Ia from SDSS photometry used as a reference sample. We extract global host-galaxy photometry and derive their stellar masses, ages, metallicities, star-formation rates, and specific star-formation rates. Our results reveal clear environmental differences between the two subtypes: 2002es-like SNe Ia preferentially reside in more massive, older, and less star-forming galaxies, whereas 2003fg-like events are found in relatively lower-mass, younger, and more actively star-forming hosts. These environmental trends imply distinct progenitor systems and explosion mechanisms. We conclude that although the progenitor systems of both subtypes may be associated with a carbon-rich circumstellar medium, the 2002es-like SNe Ia are consistent with a longer-delay-time, double-degenerate violent merger scenario, while the 2003fg-like SNe Ia are more consistent with a shorter-delay-time, core-degenerate origin. <br> Fri, 06 Mar 2026 10:23:24 GMT https://ir.lib.ncu.edu.tw/handle/987654321/99229 title: Simultaneous Multi-site, Multi-wavelength, and Multi-messenger Monitoring of the Nearby Red Dwarf GJ 3147 abstract: 本研究針對距離地球約10秒差距的紅矮星 GJ 3147，進行多地點、多波段與多手段的聯合觀測，從 2021年11月11日至17日，共五座天文台的光度觀測（威海、興隆、麗江、南山、Maidanak）以及兩座天文台的光度偏振觀測（鹿林與ARIES）。在約100小時的總觀測時間內，成功捕捉到三次主要閃焰與多次次級閃焰。其中11月16日偵測到的大型閃焰，由三台望遠鏡在 R 波段，以不同取樣函數觀測成功，我們得以有效還原出閃焰的本質輪廓，推導其峰值亮度、能量注入時間尺度，以及冷卻衰減時間尺度。 藉由模擬閃焰光變模型，並與各台天文台的實測光變曲線進行比對，以簡化卡方值（reduced chi-square）評估擬合品質，最終找出最佳解，所對應之參數為閃焰峰值亮度超過恆星亮度 0.29--0.30 星等、峰時發生在當天 UT 22794.6--22794.7 秒 (約為 UT 06:19:54)，閃焰衰減時間常數為 4.9--5.0*10^{-4}，持續約 2 分 46 秒。 同樣的2021年11月16日事件也被鹿林望遠鏡在 g′、r′、i′ 波段以相同取樣函數觀測到，依此而估計閃焰溫度約為 6800+- 300K。 此外，偏振觀測顯示 GJ~3147 在非閃焰狀態具備顯著的線性偏振，分別是 g′波段為 5.8%、r′ 波段為 2%，而i′ 波段為 0.5%，指出該恆星大氣中存在不均勻的散射結構，可能與塵埃凝結或快速自轉造成的恆星形狀變形有關。;We present a multi-site, multi-wavelength, and multi-messenger observing campaign of the nearby (10 pc) flaring red dwarf GJ 3147, conducted from November 11 to 17 in 2021. We obtained approximately 100 hours of data from five observatories (Weihai, Xinglong, Lijiang, Nanshan, Maidanak) undertaking imaging photometry, and two observatories (Lulin and ARIES) doing photopolarimetry. Three major flares and several minor events were detected. We report here a prominent flare detected on November 16, which was: (1) observed in $R$ band by three telescopes, each acquiring the light curve with a distinct sampling function, hence enabling reconstruction of the intrinsic flare profile, including parameters such as the peak time, amplitude, and energizing/cooling timescales of the flare, and (2) detected in g′, r′, and i′ bands simultaneously, allowing us to estimate a flare temperature of 6800+-300 K. }By simulating flare models and comparing them with the observed light curves, we identified best-fit solutions, in an averaged reduced chi-square sense, with peak times near UT of 22794.6s (18:19:54, UTC), peak amplitudes of 0.29--0.30 mag, and a decay constant of 5.0 *10^{-4}, which leads to flare duration of 2 minutes and 46 s. Additionally, linear polarization was detected during the quiescent state of 5.8\% in g′, 2.0% in r′, and 0.5% in i′, suggesting scattering by an inhomogeneous atmosphere, likely due to dust condensation or rapid rotation. <br> Fri, 06 Mar 2026 10:23:09 GMT https://ir.lib.ncu.edu.tw/handle/987654321/98903 title: 躍進時域天文物理學前沿──以兩米望遠鏡參與LSST計畫( III );Jump-Start Time-Domain Astrophysics: Lsst Partnership with the Trans-Pacific 2-Meter Telescope( III ) abstract: 本計畫為基礎科學（天文學）之基礎建設，在世界上良好的觀測地點建置望遠鏡，一方面提升我國光學天文觀測之設備能力，另方面以此參與國際矚目的 LSST 巡天計畫，完成後也將部分時間提供國際學界使用，增加我國研究能見度與競爭力，也讓國人在本土鹿林天文台以外，有了認識宇宙的機會。 <br> Fri, 23 Jan 2026 08:05:22 GMT