What Are The Properties of Thorne-Żytkow Object Explosions? (Planetary Science)

Takashi Moriya and Sergei Blinnikov investigated the outcomes of the potential TŻO explosions and shed light on their expected observational properties. Their study recently appeared in Arxiv.

Thorne-Żytkow objects are stars that have a neutron star core with an extended hydrogen-rich envelope. Previously, Takashi Moriya et al. suggested that the massive Thorne-Żytkow objects are proposed to explode when the nuclear reactions sustaining their structure are terminated by the exhaustion of the seed elements.

“We investigated the observational properties of the possible Thorne-Żytkow object explosions.”, told M. Takashi, Researcher at National Astronomical Observatory of Japan.

They showed that, Thorne-Żytkow object explosions are observed as long-duration transients lasting for several years.

They also showed that, if the accretion disk triggering the explosions does not last for a long time, Thorne-Żytkow object explosions have a luminosity plateau with about 1039 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.

Additionally, if the accretion disk 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.

Finally, it has been found that their photospheric velocities are 2000 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.

“While we only have a few SNe that have long-duration light curves similar to our synthetic light curves from TŻO explosions, many long-duration SNe will be found in the coming era of the Rubin Observatory’s Legacy Survey of Space and Time (LSST). Since the faintest TŻO explosions are expected to have luminosities that are similar to massive stars, they can be eventually found as disappeared stars.”, they concluded.

Reference: Takashi J. Moriya and Sergei I. Blinnikov, “Properties of Thorne-Żytkow object explosions”, Arxiv, 2021. https://arxiv.org/abs/2109.01250

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