Annular distribution of SiC2 in circumstellar envelopes of carbon-rich asymptotic giant branch stars

The circumstellar envelopes (CSE) of asymptotic big department (AGB) stars include a lot of molecules, which account for about one-third of all molecules found in interstellar space.

Gasoline and dust are important parts of CSEs, and SiC₂ is among the important constituents of dust grains in carbon-rich AGB stars. Whether or not SiC₂ is a “mum or dad” molecule shaped within the photosphere or in the course of the high-temperature dust formation course of (exhibiting a “strong” spatial distribution), or a “daughter” molecule shaped by means of photodissociation of “mum or dad” molecules within the outer envelopes (exhibiting an annular distribution), is an ongoing debate.

Researchers led by Ph.D. candidate Feng Yanan and Prof. Li Xiaohu from the Xinjiang Astronomical Observatory (XAO) of the Chinese language Academy of Sciences have performed observational work on the SiC₂ molecule in circumstellar envelopes of three carbon-rich AGB stars (AI Vol, II Lup, and RAFGL 4211) utilizing the Atacama Massive Millimeter/Submillimeter Array (ALMA).

Their study was revealed in Frontiers in Astronomy and Area Sciences on Aug. 14.

They discovered that the spatial distribution of the 4 rotational transition spectral strains of SiC₂ molecules round these three sources exhibited an annular distribution, indicating the characteristic of a typical “daughter” species.

Then they in contrast the ALMA outcomes of SiC₂ and SiO molecules in AI Vol. The SiO molecule exhibited a “strong” distribution characteristic, indicating that it’s a “mum or dad” molecule, which is according to earlier research.

“In future research, we have to rethink the formation mechanism of SiC₂ within the CSEs of developed stars,” stated Prof. Li.