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https://phys.org/news/2018-10-high-scandium-galaxy-giant-black.html

 

High levels of scandium near the galaxy's giant black hole were illusory, astronomers find

October 10, 2018, Lund University


Astronomers from Lund University in Sweden have now found the explanation to a recent mystery at the centre of the Milky Way galaxy: the high levels of scandium discovered last spring near the galaxy's giant black hole were in fact an optical illusion.

Last spring, researchers published a study about the apparent presence of astonishing and dramatically high levels of three different elements in red giant stars, located less than three light years away from the big black hole at the centre of our galaxy. Various possible explanations were presented, for example that the high levels were a result of earlier stars being disrupted as they fall into the black hole, or a result of debris from the collisions of neutron stars.

Now another group of astronomers from Lund University among others, in collaboration with UCLA in California, have found an explanation for the high levels of scandium, vanadium and yttrium. They argue that the so-called spectral lines presented last spring were actually an optical illusion. Spectral lines are used to find out which elements a star contains—by using its own light.



Read more at: https://phys.org/news/2018-10-high-scandium-galaxy-giant-black.html#jCp

the paper:

http://iopscience.iop.org/article/10.3847/1538-4357/aadb97/meta

Evidence against Anomalous Compositions for Giants in the Galactic Nuclear Star Cluster:

 

Abstract:

Very strong Sc i lines have recently been found in cool M giants in the Nuclear Star Cluster (NSC) in the Galactic center. Interpreting these as anomalously high scandium abundances in the Galactic center would imply a unique enhancement signature and chemical evolution history for NSCs, and a potential test for models of chemical enrichment in these objects. We present high resolution K-band spectra (NIRSPEC/Keck II) of cool M giants situated in the solar neighborhood and compare them with spectra of M giants in the NSC. We clearly identify strong Sc i lines in our solar neighborhood sample as well as in the NSC sample. The strong Sc i lines in M giants are therefore not unique to stars in the NSC and we argue that the strong lines are a property of the line formation process that currently escapes accurate theoretical modeling. We further conclude that for giant stars with effective temperatures below approximately 3800 K these Sc i lines should not be used for deriving the scandium abundances in any astrophysical environment until we better understand how these lines are formed. We also discuss the lines of vanadium, titanium, and yttrium identified in the spectra, which demonstrate a similar striking increase in strength below 3500 K effective temperature.

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