中大及其他天文台


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  • 2022年6月24日五星連珠
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Recent Research + more


  • 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

    點此看大圖 1
    點此看大圖 2

  • 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

    點此看大圖

  • 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

  • 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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  • Prof. Yen-Chen Pan: Ejecta velocity of SNe Ia is one powerful tool to differentiate between progenitor scenarios and explosion mechanisms. In this paper we investigate the relation between ejecta velocity (using photospheric Si II 6355 line) and host-galaxy properties with ∼280 SNe Ia. We find a significant trend that SNe Ia with faster ejecta velocities tend to explode in massive environments, whereas their slower counterparts can be found in both lower-mass and massive environments. We suggest this relation is likely caused by at least two populations of SNe Ia. We conclude metallicity is likely the dominant factor in forming high-velocity SNe Ia. This also implies their potential evolution with redshift and impact on the precision of SN Ia cosmology. This result has been published in Pan (2020), ApJL, 897, L5.

    DOI: 10.3847/2041-8213/ab8e47

  • Young Supernova Experiment, YSE, presents panchromatic observations of supernova SN 2020tlf at ~130 days from mass-loss episodes to the explosion, which involved Prof. Yen-Chen Pan at the graduate institute of astronomy in NCU. This project was led by Ph.D. student Wynn Jacobson-Galán at UC Berkeley to detect a supernova explosion in 2022, by using the Pan-STARRS telescope. SN 2020tlf is far from earth about one hundred million light-years. YSE detected “flash” spectroscopy about one days before its explosion, which is the first time revealed the light curve fluctuated before the explosion of a supernova. Astronomers considered it was due to the mass-loss episodes. So, the tiny changes can only be detected by a sensitive telescope. This may be the reason why it has never been revealed before. This observation can also help us understand the dying process of the massive star. Observations of SN 2020tlf were also obtained with the 1 m Lulin telescope located at Lulin Observatory, which contributed to BVgr bands before the explosion. Lulin observatory played a key role with its excellent location. It can contribute to those events in the future. This important result has been also reported by CNN. This result is published in Jacobson-Galán et al. 2022, ApJ, 924, 15 (Including Prof. Yen-Chen Pan).

    DOI: 10.3847/1538-4357/ac3f3a

  • [Image caption] The left and right images are GIT and LOT images that captured the JWST, marked with the green and red circles, respectively. The yellow circles are a reference star to compare the relative locations of JWST on these images.
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    The next generation space telescope, the James Webb Space Telescope (JWST), was successfully launched on Christmas Day of 2021. After nearly a month of journey, JWST finally reached its destination – the second Lagrange point L2. This location is about 1.5 million km away from the Earth, therefore using two distant telescopes on Earth it is possible to measure the parallax of JWST. On 08 February 2022, both the Lulin One-meter Telescope (LOT) and the 0.7m GROWTH India Telescope (GIT) imaged the sky where the JWST was expected to be located. Based on the relative locations of JWST on both images taken with LOT and GIT, we measured the parallax of JWST and hence derived its distance to be 1.54 million km. We thank the observing staff at Lulin Observatory for the assistance in carrying out the observations.

  • Dr. Zhong-Yi Lin: We observed Episodically Active Asteroid (6478) Gault in 2020 with multiple telescopes in Asia and North America and have found that it is no longer active after its recent outbursts at the end of 2018 and start of 2019. The inactivity during this apparition allowed us to constrain Gault’s rotation period using time-series photometric lightcurves taken over 17 h on multiple days in 2020 August, September and October. The photometric lightcurves have a repeating 0.05 magnitude feature suggesting that Gault has a rotation period of ∼2.5 hours and may have a semi-spherical or top-like shape, much like Near-Earth Asteroids Ryugu and Bennu. The rotation period of ∼2.5 hours is near to the expected critical rotation period for an asteroid with the physical properties of Gault suggesting that its activity observed over multiple epochs is due to surface mass shedding from its fast rotation spun up by the YORP effect.

  • Dr. Zhong-Yi Lin: We present visible and mid-infrared imagery and photometry of temporary Jovian co-orbital comet P/2019 LD2 taken between 2019 April and 2020 August. Our observations indicate that the nucleus of LD2 has a radius between 0.2-1.8 km assuming a 0.08 albedo. We measure CO/CO2 gas production of ≤1027 mol/s /≤1026 mol/s from our 4.5 μm Spitzer observations, g-r = 0.59±0.03, r-i = 0.18±0.05, i-z = 0.01±0.07 from GROWTH observations, H2O gas production of ≤80 kg/s scaling from our estimated C2 production of QC2 ≤7.5×1024 mol/s from Keck/LRIS spectroscopy. In the simulations, we find that the clones entered the Jovian region approximately 2.37 years ago, and are ejected from the region 8.70 years in the future. Using these transition object population estimates and our estimate of the radius of P/2019 LD2 of ∼1.8 km suggests there are ∼100 objects with the size of P/2019 LD2 in the transition region at any given time.

  • Caption: The mass-velocity dispersion relation (MVDR) on BCG-cluster scales

    Dr. Yong Tian: For the first time, we discovered a tight kinematic scaling relation on the BCG-cluster scale. In this figure, the vertical axis represents the total baryonic mass Mbar, while the horizontal axis represents the flat velocity dispersion σ. This relation strongly indicates Mbar α σ4, so called mass-velocity dispersion relation (MVDR). Moreover, the velocity dispersion profile of BCGs demonstrates a nearly flat tail, even in the innermost region. This result is published in Tian et al. 2021, ApJL, 917, L24 (Including Prof. Chung-Ming Ko and Han Cheng).

    DOI: 10.3847/2041-8213/ac1a18

Honor+ more


  • 恭喜 碩士班一年級許博智、張耀文、謝庫馬同學榮獲本所110年度第一學期學業優秀獎學金一萬元 (2022-03-01)
  • 恭喜本所碩士班鄭豫立同學榮獲2022物理年會佳作壁報獎
    陳文屏教授指導大氣系凌郁涵榮得2022物理年會優勝壁報獎 (2022-03-01)
  • 恭賀本所葉永烜教授榮獲 2021年物理學會特殊貢獻獎 (2022-01-25)
  • 恭賀本所饒兆聰副教授榮獲本校110學年度研究傑出獎 (2022-01-13)

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