中大及其他天文台

  • 鹿林天文台空拍
  • 鹿林天文台一米望遠鏡
    一米望遠鏡控制室
  • 鹿林天文台一米望遠鏡
  • 中大天文台(科一館)
  • 兩米望遠鏡
  • 兩米望遠鏡
  • GROWTH
  • Credit: LSST
  • Credit: LSST

Recent Research + more

  • Caption: Temporal mass accretion rates during unstable accretion bursts. The upper panel shows DL Tau, and the lower panel shows Haro 6-13. The left side of the figure displays the simultaneous accretion luminosity bursts observed by TESS, ZTF, or ASAS-SN. The horizontal axis represents time (in days), and the vertical axis represents normalized flux. The right side of the figure presents the derived temporal mass accretion rates. The horizontal axis represents time (in days), and the left vertical axis (black) represents accretion rates (in units of M☉/yr), while the right vertical axis (blue) represents accretion luminosity (in units of erg/s).

    PhD student Chia-Lung Lin: We have combined photometric and spectroscopic surveys from both space telescopes (TESS) and ground-based telescope (LAMOST, ZTF, and ASAS-SN) to study the mass accretion rates, flare activities, and variability characteristics of 16 Classical T Tauri Stars (CTTS) in Taurus. By calculating the flux of various spectral lines such as H-alpha, we derived an average mass accretion rate of 1.76×10-9 M☉/yr for these 16 CTTSs. Among them, two stars, DL Tau and Haro 6-13, exhibited temporary brightness increases in their TESS light curves due to bursts of unstable mass accretion rates. By analyzing simultaneous monitoring data from ZTF, ASAS-SN, and TESS, we estimated the time series variations in mass accretion rates for these two stars over a span of 50 days. If the results from spectral data reflect a stable accretion pattern, we concluded that the mass accretion behavior of these two stars is primarily driven by stable accretion. Additionally, we detected a total of 13 large flares across these 16 stars, with energy ranging from 2×1034 to 6×1035 erg, making their flare activity more than a hundred times more active than that of solar-like stars. We also found that the variability classes of these 16 stars change over time, with the timescales of these changes falling roughly between 1.6 to 4 years compared to results in the literature.

    This study has been published in Astronomical Journal in 2023, August: Lin, C.-L., Ip, W.-H., Hsiao, Y., et al. 2023, AJ, 166, 82 (Including Prof. Ip, Wing-Huen, master graduate Hsiao, Yao and Cheng, Tzu-Hueng in the IANCU)
    DOI: 10.3847/1538-3881/ace322

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  • Master student Yao-Wen Jhang and Prof. Yi Chou report the analysis results of X-ray light curves collected by Neutron star Interior Composition ExploreR (NICER) from June 2017 to July 2022 of the X-ray binary 4U 1820-30, located at the globular cluster NGC 6624. From the yearly orbital phases obtained by the orbital modulation light curves and historical records, we measured that the observed orbital period derivative is 1/P dP/dt = (-5.21±0.13)×10-8 yr-1 from a time span of 46.3 years database. No significant second order orbital period derivative can be found with 2σ upper limit of | d2P / dt2 | < 5.48×10-22s s-1. To explain the complete different orbital period evolution trends from theoretical prediction and observation result, we agreed that it is caused by the acceleration of the binary system in the gravitational field of globular cluster NGC 6624, as suggested by previous studies. However, we pointed out that it is improper to estimate the acceleration of 4U 1820-30 by observed orbital period derivative because there are too much uncertainties in the intrinsic orbital period derivative. Furthermore, we detected a modulation with a period of 691.6±0.7 s in the NICER X-ray light curves, which is consistent with the superhump period discovered in the far-ultraviolet band of Hubble Space Telescope. In addition to explaining how the superhump modulation can be detected in X-ray band, we also suggested that this periodic modulation may be induced by a hierarchical third star that orbits around the binary system. These results have been published in Chou & Jhang 2023 ApJ, 951, 42.

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  • Based on light curves data taken from ZTF and published distances, the team led by Prof. Chow-Choong Ngeow derived the gri-band period-luminosity (PL) relations for various types of pulsating stars located in the globular clusters. These include RR Lyrae, Type II Cepheids, and anomalous Cepheids. Many of these PL relations were derived for the first-time in gri filters, with potential applications in the era of Rubin Observatory’s LSST. These works are published in Ngeow et al (2022, AJ 163:239, AJ 164:154, and AJ 164:191).

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  • 博士生 Bhavana Lalchand 與陳文屏教授在恆星形成區指認稀有的年輕棕矮星。一般相信這種天體跟恆星與行星一樣，都在分子暗雲中誕生，但因為棕矮星質量比恆星小，不足以維持內部核反應，因此形成後光度與表面溫度很快降低，不容易偵測，傳統使用多波段紅外顏色來辨認，容易受遙遠背景光源受到紅化而誤判。我們團隊歷來在紅外線的水分子吸收波段，以特殊的濾光片觀測，挑選大氣中有水分子的候選棕矮星，然後利用紅外光譜驗證，證明非常有效率。這次發表的成果，在距離約1000光年的英仙座分子雲中，先以廣視野紅外影像，然後利用光譜驗證，成功找到棕矮星。圖左是利用 IRTF 的光譜儀取得的紅外光譜。圖右是以 Gaia 太空望遠鏡的數據，估計該區域不同分子雲（黑色字母）的距離（紅色數字表示週年視差角 milli-arcsecond）與運動狀況（箭頭表示自行運動 mas/year），以探討該區域不同分子雲的恆星形成活動。

    Lalchand et al. 2022, Astron. J., 164, 125
    https://doi.org/10.3847/1538-3881/ac8547

    點此看大圖: 左圖
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  • B. T. Bolin, GSFC, on behalf of the "Zwicky Transient Facility (ZTF) Collaboration", reports on observations of possible comet candidate ZTFt001 taken with the 1.2-m Schmidt telescope at Palomar Observatory. The object was flagged as having a possible cometary appearance in data taken on 2022 August 15 at 11:59:00 UTC and on 2022 August 16 at 12:04:10.071 by the Tails artificial intelligence pipeline (Duev et al. 2021, DOI: 10.3847/1538-3881/abea7b). The object’s appearance contained a coma ~4 arcsec wide and a broad tail ~20 arcsec long in ZTF images taken on 2022 August 15.499 and August 16.503 UTC. The comet was identified in ZTF images on subsequent nights by Tails and M. S. P. Kelley (U. Maryland). ZTF r-band photometry (5" radius aperture), measured by Quanzhi Ye (U. Maryland), was as follows: 2022 Aug 15.499, ~18.5; 2022 Aug 16.503, 17.8. The position angle of the comet’s tail was ~272 degrees.

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  • 博士生 Tanvi Sharma 與陳文屏教授研究大質量恆星誘發星團與恆星形成的過程。我們針對 Sh2-142 這個大質量恆星周圍的氫游離區，探討 DH Cep 這顆大質量恆星其恆星風以及輻射如何影響分子雲（上左圖紅色與藍色曲線為一氧化碳紅移與藍移的輻射強度的分布）、游離雲（上左圖底的可見光照片，黑灰色代表恆星或發射雲氣）、星團（NGC 7380），以及個別年輕恆星（我們利用紅外數據指認）。上圖右為交互作用的示意圖。

    Sharma et al. 2022, Astrophy. J., 928, 17，
    https://doi.org/10.3847/1538-4357/ac510b

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  • 碩士生林瀚堂與陳文屏教授研究紅矮星的爆發。這顆 Wolf 359 已知常有亮度爆發，一般認為來自表面磁場重組，有如在太陽表面觀察到的閃焰現象，但紅矮星因為內部對流旺盛，表面磁場更強，更好發閃焰，釋放能量規模也大得多。我們利用兩座望遠鏡同步監測目標，以估計閃焰的次數以及能量分布，尤其針對其中某巨大閃焰事件，利用兩個取樣不同的光變曲線（如上圖所示），我們推測出閃焰實際的強度，以及能量釋放的時間尺度，而這是單一望遠鏡所無法估計。以此閃焰來說，一共釋放 10^33 爾格，實際上爆發峰值達到恆星靜態亮度的1.6倍，而單一望遠鏡各觀測到的峰值都低估為0.4與0.8倍。

    Lin et al. 2022, Astron. J., 163, 164
    https://doi.org/10.3847/1538-3881/ac4e92

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  • 碩士生 Aashish Gupta 與陳文屏教授探討鄰近的 Rho Ophiuchi（蛇夫座）區域中的恆星形成過程。由於恆星來自星際雲氣重力塌縮，剛誕生的恆星周圍仍有大量雲氣，而隨著星球演化，不但周圍雲氣消散，原來環繞在恆星四周的盤狀雲氣也消失（或是誕生了行星）。我們利用位於夏威夷 的次毫米波望遠鏡JCMT取得低溫雲氣的分布（上圖灰色曲線標示範圍），並使用紅外波段數據指認不同演化階段的年輕恆星，以及蓋婭 (Gaia) 數據有關星球的距離與運動狀態，探討初生星球跟雲氣的關係。上圖中雲氣集中之處聚集了年輕恆星，而右方的紫色曲線代表雲核，以及剛從其中誕生、周圍仍有充分物質的（第二類）年輕天體，而最右方的紅色曲線則標示周圍物質已經消散的（第三類）年輕星球。已知在此圖以外右下方有個OB星協，我們的研究提供了大質量恆星誘發下一代恆星誕生（從紅色曲線，到紫色曲線，再到雲氣）的時間序列。

    Gupta & Chen, 2022, Astron. J., 163, 233
    https://doi.org/10.3847/1538-3881/ac5cc8 點此看大圖

  • 黃崇源教授和柯伊娜研究學者自2010年的泛星計畫（Pan-STARRS Project）與許多不同的天文學觀測資料中，選擇高紅移類星體作為目標。2020年透過光譜觀測與分析，希望能釐清該星體的紅移。在耗時兩年多的研究後，原本以為觀測對象只是電波類星體，然而透過電波及光譜分析和英國紅外線望遠鏡（UKIRT）觀測出其快速變化的特徵後，卻發現對象為紅移6.5的蝎虎座BL天體。然而，學界從未發現過如此遙遠的蝎虎座BL天體。
    目前兩人正與國際團隊合作，透過特長基線干涉測量法（VLBI），觀察此紅移6.5的蝎虎座BL天體和其他鄰近蝎虎座BL天體的差異。除此之外，兩人也希望能夠找到更多更遙遠的蝎虎座BL天體，在浩瀚的宇宙中發掘更多未解之謎。

  • Prof. Chow-Choong Ngeow: Using ZTF data, we derived the contact binaries period-luminosity relations in the gr-band for the first time. These contact binaries were located in the globular clusters (black filled circles), showing a remarkable good agreement with the contact binaries located in the Solar neighborhood (purple crosses, after transformed the BV-band to gr-band) in the period-luminosity relation. This work is published in Ngeow et al 2021, AJ, 162, 63

    DOI: 10.3847/1538-3881/ab930b

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Honor+ more

  • Congratulations to Academician Wing-Huen Ip for receiving the Presidential Science Prize of Taiwan, 2023.
    恭賀本所葉永烜教授榮獲2023年總統科學獎 (2023-09-15)
  • 恭賀本所 饒兆聰老師 通過112學年升等為教授 (2023-06-27)
  • 恭賀本所碩士班蔡沛均同學獲2023天文年會「最佳學生壁報獎」 (2023-05-22)
  • 恭賀本所潘彥丞老師榮獲 111學年度理學院教學優良獎 (2023-05-19)
  • 恭賀 陳文屏教授續聘本校天文講座教授(112-115) (2023-04-18)

Academic Event

Colloquium

  • Date: 2023-10-05
  • Time: 13:00
  • Location: S4-1013
  • Speaker: Hung-Hsu "James" Chan
  • Title: Lensed Quasar Search in Imaging Surveys

Journal Club

  • 近期無期刊導讀

    • Visiting Scholar + more

    • Mr. Fernando Abárzuza (2023-09-18~2024-06-30)