Explanation for the first spinning neutron star detected in the Andromeda galaxy?
In the article it notes that the partner has less mass than the sun, or possibly up to about twice the mass of the sun (quite a range of uncertainty there!) It's not clear, from the article how they made these calculations, measurement of doppler shifts to get orbital velocity I suppose.

The mass suggested there is not especially small, there are pulsar binary systems in which the secondary is one hundredth the mass of the sun, and could be considered to be planets.

However it does rule out a black hole companion, which would have a mass of 3 solar masses at the least, (and more likely more than 5). There is no need to hypothesis a black hole to explain the spin. 

The last few sentences in your question don't make any sense to me.