J0524-0336, surprisingly high Li concentration

[Astronuc]

This article caught my attention with the claims. It's not exactly a new star, but some folks paid more attention to it recently, and probably someone finally got around to analyzing the spectrum.

Astronomers have discovered a new star that is 30 times larger than the sun and could force a major rethink of stellar evolution theories. The star, designated J0524-0336 and located around 30,000 light-years from Earth, has a shockingly high concentration of the element lithium when compared to the sun at its current age or other stars of similarly advanced ages.

This is an issue for our understanding of how stars forge heavier elements via nuclear fusion because lithium is a light element; current models suggest light elements are lost through this process in favor of heavier elements like carbon and oxygen.

Not only is J0524-0336 rich in lithium, but it also has a corresponding lack of heavy elements.

Discovery of a Metal-Poor Red Giant Star with the Highest Ultra-Lithium Enhancement​

https://arxiv.org/abs/2209.02184#

We present the discovery of 2MASS J05241392-0336543 (hereafter J0524-0336), a very metal-poor ([Fe/H]=-2.43 +- 0.16), highly r-process-enhanced ([Eu/Fe]= +1.34 +- 0.10) Milky Way halo field red giant star, with an ultra high Li abundance of A(Li)(3D,NLTE)= 6.15 +- 0.25 and [Li/Fe]= +7.64 +- 0.25, respectively. This makes J0524-0336 the most lithium-enhanced giant star discovered to date. We present a detailed analysis of the star's atmospheric stellar parameters and chemical abundance determinations. Additionally, we detect indications of infrared excess, as well as observe variable emission in the wings of the H_alpha absorption line across multiple epochs, indicative of a potential enhanced mass-loss event with possible outflows. Our analysis reveals that J0524-0336 lies either between the bump and the tip of the Red Giant Branch (RGB), or on the early-Asymptotic Giant Branch (e-AGB). We investigate the possible sources of lithium enrichment in J0524-0336, including both internal and external sources. Based on current models and on the observational evidence we have collected, our study shows that J0524-0336 may be undergoing the so-called lithium flash that is expected to occur in low-mass stars when they reach the RGB bump and/or the early-AGB.

I was searching for more information and found the following article on Wikipedia about 'Chemically peculiar star(s)'
https://en.wikipedia.org/wiki/Chemically_peculiar_star

There is an interesting discussion here.
https://en.wikipedia.org/wiki/Chemically_peculiar_star#Cause_of_the_peculiarities

 

[Vanadium 50]

I've grumbled about the tendency of astronomers to take the most extreme element in a distribution and to argue it is a new class of object. I understand why this happens, but I don't like it.

Lithium is detected on the surface and destroyed in the core. So Li-rich stars tend to have less mixing than other stars. One can always follow this up the "but why?" chain until one gets to "we don't know" but that will always be the case. What I think is more interesting is that chemically peculiar stars (and there are a few percent of them) tend to be oddballs in other ways as well - rotation, magnetic fields and such.

 

[Vanadium 50]

I took a look at some of the star's parameters. It is quite old, probably 10-11 Gy, so it formed in times with more lithium and fewer metals. As a MS star it was somewhere around K0-K5 so it was never fully convective (nor did I expect it to have been).

In short, it's exactly the sort of star one expects to have the described chemistry - probably why the team selected it to shoot its spectrum in the first place.