Heavy radioactive elements in a star

[Moontanman]

Przybylski's Star Appears to have to have short lived radioactive elements in it's spectral lines. no reasonable source of these elements is known. As well as short lived elements heavier than uranium and thorium, plutonium is also present.

 

https://en.wikipedia.org/wiki/Przybylski%27s_Star

 

In 1961, the Polish-Australian astronomer Antoni Przybylski (Polish pronunciation [ˈantɔɲi pʂɨˈbɨlski]) discovered that this star had a peculiar spectrum that would not fit into the standard framework for stellar classification.^[5] Przybylski's observations indicated unusually low amounts of iron and nickel in the star's spectrum, but higher amounts of unusual elements like strontium, holmium, niobium, scandium, yttrium, caesium, neodymium, praseodymium, thorium, ytterbium, and uranium. In fact, at first Przybylski doubted that iron was present in the spectrum at all. Modern work shows that the iron-group elements are somewhat below normal in abundance, but it is clear that the lanthanides and other exotic elements are highly overabundant. Lanthanide elements are from 1000 to 10,000 times more abundant than in the Sun. As a result of these peculiar abundances this star belongs firmly in the Ap star class.

Przybylski's Star also contains many different short-lived actinide elements with actinium, protactinium, neptunium, plutonium, americium, curium, berkelium, californium, and einsteinium being detected. Other radioactive elements discovered in this star include technetium and promethium.^[11]

 

 

How could such short lived elements be present in this star?

[Raider5678]

[StringJunky]

From one of your sublinks (ap star class):

They also have stronger magnetic fields than classical A- or B-type stars in the case of HD 215441, reaching 33.5 kG (3.35 T).[1] Typically the magnetic field of these stars lies in the range of a few kG to tens of kG. In most cases a field which is modelled as a simple dipole is a good approximation and provides an explanation as to why there is an apparent periodic variation in the magnetic field, as if such a field is not aligned with the rotation axis—the field strength will change as the star rotates. In support of this theory it has been noted that the variations in magnetic field are inversely correlated with the rotation velocity.[2] This model of a dipolar field, in which the magnetic axis is offset to the rotation axis, is known as the oblique rotator model.

The origin of such high magnetic fields in Ap stars is problematic and two theories have been proposed in order to explain them. The first is the fossil field hypothesis, in which the field is a relic of the initial field in the interstellar medium (ISM). There is sufficient magnetic field in the ISM to create such high magnetic fields—indeed, so much so that the theory of ambipolar diffusion has to be invoked to reduce the field in normal stars. This theory does require the field to remain stable over a long period of time, and it is unclear whether such an obliquely rotating field could do so. Another problem with this theory is to explain why only a small proportion of A-type stars exhibit these high field strengths. The other generation theory is dynamo action within rotating cores of Ap stars; however, the oblique nature of the field cannot be produced, as yet, by this model, as invariably one ends up with a field either aligned with the rotation axis, or at 90° to it. It is also unclear whether it is possible to generate such large dipole fields using this explanation, due to the slow rotation of the star. While this could be explained by invoking a fast rotating core with a high rotation gradient to the surface, it is unlikely that an ordered axisymmetric field would result.

Abundance spots[edit]

The spatial locations of the chemical overabundances have been shown to be connected with the geometry of the magnetic field. Some of these stars have shown radial velocity variations arising from pulsations of a few minutes. For studying these stars high-resolution spectroscopy is used, together with Doppler imaging which uses the rotation to deduce a map of the stellar surface. These patches of overabundances are often referred to as abundance spots.

Edited April 7, 2017 by StringJunky

[Moontanman]

On 4/7/2017 at 3:56 PM, StringJunky said:

From one of your sublinks (ap star class):

Ok, I see that I have posted this before, one thing to realise that ap stars except this one, AFAICT, is the only one that contains very short lived isotopes of heavy elements. In fact one of them, technetium  simply does not exist in nature in anything but microscopic amounts. On the earth technetium is so rare than an amount equal to the volume of a sugar cube is all that exists at any one time..