In Beauville, Narasimhan, Ramanan's *Spectral curves and the generalized theta divisor*, Remark 3.7, the following exact sequence is presented: 


$0 \rightarrow M(-\Delta) \rightarrow \pi^\* E \xrightarrow{\pi^\*\varphi - x} \pi^\*(L \otimes E) \rightarrow \pi^\*L \otimes M \rightarrow 0$


where $X$ is a smooth curve, $L$ is a line bundle on $X$, $(E, \varphi)$ is a $L$-twisted Higgs bundle on $X$, $\pi: X\_s \rightarrow X$ is the spectral curve associated to the characteristic polynomial of $\varphi$ (supposed to be integral), $x$ is the tautological section of $\pi^\*L$, $\Delta = \pi^\*L^{\deg\pi-1}$ is the ramification divisor of $\pi$, and $M$ is the unique torsion free sheaf of rank 1 on $X\_s$ such that $E=\pi\_\* M$.


Do you have any suggestion about how to prove the exactness of the sequence? The intuition is that $M(-\Delta)$ must be the eigenspace of $\pi^\*\varphi$ associated to the eigenvalue $x$, but it is not clear to me why it should be.



Exact sequence involving spectral data for Higgs bundles
There is an argument in the proof of Proposition 5.17 of <https://arxiv.org/abs/2101.08583>


