91T/99aa类Ia型超新星2019vrq，第一部分：近标准烛光的光度测量、光谱和光谱偏振测量
The 91T/99aa-like Type Ia Supernova 2019vrq, Part I: Photometry, Spectroscopy, and Spectropolarimetry of a Nearly Standard Candle
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- Tsinghua University（清华大学）
- Florida State University（佛罗里达州立大学）
- University of Texas（德克萨斯大学）
- European Organisation for Astronomical Research in the Southern Hemisphere (ESO)（欧洲南方天文台）
- Texas A&M University（德克萨斯农工大学）
- Las Cumbres Observatory（拉西布朗观测站）
- University of California, Santa Barbara（加州大学圣塔芭芭拉分校）
- University of California, Berkeley（加州大学伯克利分校）
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中文总结 AI 辅助
本研究通过光谱、光度和偏振观测，发现过亮91T/99aa类Ia型超新星2019vrq具有球对称光球层和低偏振，结合其高光度和短形成时间，表明该子类可作为高红移标准烛光。
中文摘要 AI 辅助
在Ia型超新星（SNe）的各种主要子类型中，明亮的1991T-like（Filippenko等人1992年；Phillips等人1992年）和1999aa-like（Krisciunas等人2000年；Garavini等人2004年）事件对于约束爆炸机制尤为重要。它们的白矮星（WD）前身星被认为质量接近或超过钱德拉塞卡极限。我们展示了过亮Ia型超新星SN2019vrq的光谱光度测量和偏振测量时间序列观测。在光变曲线峰前9天到峰后12天之间，其连续谱偏振与零一致，这与大多数正常亮度SNe Ia中观察到的情况相同，尽管在向更长波长方向可能存在高达0.2%的上升，这在次光度SNe Ia中可见。主要光谱特征上的偏振是微弱的（≤0.3%），除了高速CaII近红外三重线，其达到约0.5%。这种低偏振表明电子散射光球层基本上是球对称的，并且抛射物的大尺度不对称性最小。早期光谱揭示了热的、双重电离的抛射物，以SiIII和混合铁族特征为主。中等质量元素谱线，如CaII和SiII，比在91T-like事件中更清晰可见，尽管这些谱线仍然比正常SNe Ia中的弱。过亮91T/99aa类SNe Ia固有更高的峰值光度（Yang等人2022年；Phillips等人2024年），它们相对较短的大质量WD前身星形成时间尺度——这一通道在高红移方向变得更常见，以及从其持续低偏振推断出的光谱光度特性对观测角度的中等依赖性，共同表明这一子类可能在高红移处作为有前景的标准烛光。
英文摘要
Among the various major subtypes of Type Ia supernovae (SNe), the luminous 1991T-like (Filippenko et al. 1992; Phillips et al. 1992) and 1999aa-like (Krisciunas et al. 2000; Garavini et al. 2004) events stand out as particularly important for constraining the explosion mechanism. Their white dwarf (WD) progenitors are thought to have masses close to or exceeding the Chandrasekhar limit. We present spectrophotometric and polarimetric time-series observations of the overluminous Type Ia SN2019vrq. Between -9 and +12 days relative to the light-curve peak, its continuum polarization is consistent with zero, as seen in most normal-bright SNeIa and despite a possible rise up to 0.2% toward longer wavelengths as seen in subluminous SNeIa. Polarization across major spectral features is marginal ($\lesssim$0.3%) with the exception of the high-velocity CaII near-infrared triplet, which reaches $\sim$0.5%. This low polarization indicates a substantially spherically symmetric electron-scattering photosphere and minimal large-scale ejecta asymmetry. Early-time spectra reveal hot, doubly ionized ejecta dominated by SiIII and blended iron-group features. Intermediate-mass-element lines, such as CaII and SiII, are more clearly seen than in 91T-like events, though these lines remain weaker than in normal SNeIa. The intrinsically higher peak luminosity of overluminous 91T/99aa-like SNeIa (Yang et al. 2022; Phillips et al. 2024), their comparatively short formation timescale for a massive WD progenitor - a channel that becomes more common toward high redshift, and the moderate viewing-angle dependence of their spectrophotometric properties as inferred from their persistently low polarization, together suggest that this subclass may serve as a promising standard candle at high redshift.
