Analysing The Origin Of The Supersoft X-ray Light Curve

Under the guidance of Ph.D. candidate Zhao Weitao and Prof. Meng Xiangcun, scientists from the Yunnan Observatories of the Chinese Academy of Sciences have recreated the quasi-periodic light curve of the supersoft X-ray source and put out a fresh theory to explain how it came to be.

This was done by simulating the white dwarf’s (WD) reaction to the periodic mass transfer brought on by the exposure of its partner to X-rays.

The Type La Supernova

In order to monitor cosmic parameters and study the development of the dark energy equation of state across time, type Ia supernovae are being utilised as standard candles. The most likely progenitor objects for type Ia supernovae are supersoft X-ray sources.

A huge main-sequence companion star and a WD make up a supersoft X-ray source. When the WD exceeds the Chandrasekhar mass limit and explodes as a type Ia supernova, it has accreted matter from its partner star and grown in mass.

Supersoft X-ray sources’ light curves exhibit a quasi-periodic fluctuation of lightness and blackness. It is currently unknown why the light curve of super-soft X-ray sources varies in such a quasi-periodic fashion.

The Unique Light Curves Of Supersoft X-ray

The light curves of super-soft X-ray sources show a quasi-periodic variation of brightness and darkness. The reason for the quasi-periodic variations in the light curve of super-soft X-ray sources is still unknown.

Previous assessments of this quasi-periodic light curve did not account for the effect of supersoft X-rays on the companion star. The X-ray radiation is expected to warm the companion star and change its effective surface boundary condition, which will reduce the rate of mass transfer in the binary system.

The companion star should be routinely exposed to supersoft X-rays to cause it to expand and contract, according to this study. As a result, the binary mass transfer rate fluctuates between increases and decreases.

What Was In The Observation?

In this study, it was suggested that the companion star be periodically exposed to supersoft X-rays to cause it to grow and contract. The binary mass transfer rate consequently oscillates between rises and falls.


In their 1D simulations, they adopted a periodic jagged accretion rate onto the WD rather of the periodic fluctuation in the mass transfer rate using the Modules for Experiments in Stellar Astrophysics (MESA) code.

The WD photosphere periodically expands and contracts as a result of the periodic variability in the mass accretion rate onto the WD, which accurately mimics the light curve of the supersoft X-ray source.

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