Using the Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST), Chinese researchers have discovered nine new undeveloped stars.
These newly discovered stars displays an unusually high abundance of lithium.
The discovery is reported in a paper published on the arXiv.org.
Although the abundance of lithium in most stars is quite low, some of them contain much more lithium (Li) than the meteorite's value of 3.3 dex.
Researchers believe that stars with unusually high lithium abundances must be experiencing lithium enrichment.
However, current models on such enhancement mechanisms are still debated, and none of them can explain those stars well enough.
To better understand the mechanism of lithium growth, studies of super lithium-rich underdeveloped stars are needed.
Given that only a few such objects have been discovered to date.
A new study by Taisheng Yan of the Chinese Academy of Sciences and his colleagues has detected nine new stars in this class.
Presently, there can be a breakthrough in this area.
The researchers wrote, We discovered nine super Li-rich underdeveloped stars with NLTE [non-local thermodynamic equilibrium].
'Li abundance A(Li) greater than 3.8 dx from LAMOST-MRS, which is the highest of such stars'. The largest specimen
The nine new stars exhibit unusually high levels of lithium abundance, which suggests that they may have experienced a history of lithium enrichment.
Eight of them have near-solar metallicity (between -0.4 and 0.4 Dex), while the most metal-poor one is UCAC4 646-05072, which has a metallicity at the level of -0.69 Dex.
In general, the stars reported in the study have radii between 0.89 and 2.51 solar radii, while their mass ranges from 0.78 to 1.6 solar masses.
Except for the hottest star UCAC4 629-030411, the effective temperature of these stars was measured to be between 5,100 K and 5,800 K, as it has an effective temperature of 6,807 K.
Four stars in the sample, namely UCAC4 440-009448, UCAC4 441-011058, UCAC4 451-011087 and UCAC4 606-009417, turned out to be young stellar objects (YSOs).
Their lithium abundance is above 3.8 Dex, which is about three times higher than the upper envelope value of young stars reported by a study published in 2021.
Given that these four YSOs and three other stars are fast-rotating, astronomers believe that the accretion of circumstellar matter may be the main contributor to their lithium enrichment.
'Assuming all of them as fast rotators (v sin i>15 km/s), the situation is most likely to be accretion of Li-rich matter' the researchers noted.
Further studies are necessary to confirm this scenario.
The paper's authors expect the ongoing LAMOST medium-resolution spectroscopic survey (MRS) to lead to more discoveries of super lithium-rich unwound stars.
Are there any hypotheses about where the circumstellar lithium came from?ReplyDelete