Thorne–Żytkow objects are stars that have a neutron star core with an extended hydrogen-rich envelope. Massive Thorne–Żytkow objects are proposed to explode when the nuclear reactions sustaining their structure are terminated by the exhaustion of the seed elements. In this paper, we investigate the observational properties of the possible Thorne–Żytkow object explosions. We find that Thorne–Żytkow object explosions are observed as long-duration transients lasting for several years. If the accretion disc triggering the explosions does not last for a long time, Thorne–Żytkow object explosions have a luminosity plateau with about $10^{39}\, \mathrm{erg\, s^{-1}}$ lasting for a few years, and then they suddenly become faint. They would be observed as vanished stars after a bright phase lasting for a few years. If the accretion disc is sustained for long time, the Thorne–Żytkow object explosions become as bright as supernovae. They would be observed as supernovae with rise times of several hundred days. We found that their photospheric velocities are $2000\, \mathrm{km\, s^{-1}}$ at most, much smaller than those found in supernovae. Supernovae with extremely long rise times such as HSC16aayt and SN 2008iy may be related to the explosions of Thorne–Żytkow objects.

中文翻译：

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Thorne–Żytkow 物体爆炸的性质

Thorne-Żytkow 天体是具有中子星核心和扩展富氢包层的恒星。当维持其结构的核反应因种子元素耗尽而终止时，巨大的 Thorne-Żytkow 物体被提议爆炸。在本文中，我们研究了可能的 Thorne-Żytkow 天体爆炸的观测特性。我们发现 Thorne-Żytkow 天体爆炸被观察为持续数年的长时间瞬变。如果触发爆炸的吸积盘不会持续很长时间，Thorne–Żytkow 天体爆炸就会有一个光度平台，大约 $10^{39}\, \mathrm{erg\, s^{-1}}$ 持续几年，然后他们突然变得昏厥。在持续了几年的明亮阶段之后，它们将作为消失的恒星被观察到。如果吸积盘持续很长时间，Thorne-Żytkow 天体爆炸就会变得像超新星一样明亮。它们将作为超新星被观察到，上升时间为数百天。我们发现它们的光球速度最多为 $2000\, \mathrm{km\, s^{-1}}$，远小于超新星中的速度。HSC16aayt 和 SN 2008iy 等上升时间极长的超新星可能与 Thorne-Żytkow 天体的爆炸有关。