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Tweak the text and make the process clearer.
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fjankowsk committed Jun 28, 2024
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Expand Up @@ -37,8 +37,10 @@ should work fine. Maybe replace `pip3` by `pip` depending on your Python install

There are several ways to estimate a pulse or burst's true dispersion measure (DM). For instance, one can optimise the burst profile for the total band-averaged S/N (S/N-maximising DM) or profile structure (structure-maximising DM). Scattering introduces a typically single-sided exponential tail that interferes with the classical DM-estimation techniques by shifting the profile centres in a frequency and DM-dependent way. Hence, one needs to account for scattering by estimating a scattering-corrected DM, which usually differs from the above DM values, sometimes quite significantly.

`scatfit` blindly dedisperses the data at the fiducial DM you provide in its command line call. This behaviour is advantageous, as it gives the user the flexibility to measure the optimum DM using external software, such as `DM_phase`. `scatfit` then performs its sub-banded scattering fits, after which it analyses the fit residuals to determine a scattering-corrected DM.
`scatfit` blindly dedisperses the data at the fiducial DM you provide in its command line call. This behaviour is advantageous, as it gives the user the flexibility to measure the optimum DM using external software, such as `DM_phase` and do the scattering fit based on this. `scatfit` then performs its sub-banded scattering fits, after which it analyses the fit residuals to determine a scattering-corrected DM.

To measure the scattering-corrected DM reliably, one must run `scatfit` iteratively several times by inputting the last determined scattering-corrected DM in the new call until the output DM converges to a stable value. This occurs when the output DM changes less than its fit uncertainty or an externally pre-defined value. The leading edge of the burst profile should be as sharp as possible (in the absence of DM-smearing) and the tail well-described by the scattering model.
To measure the scattering-corrected DM reliably, one must run `scatfit` iteratively several times by inputting the last-determined scattering-corrected DM in the new call until the output DM converges to a stable value. Convergence occurs when the difference between input and output DM changes less than its fit uncertainty or an externally pre-defined value.

Three to four iterations should be enough to reach a stable scattering-corrected DM if the initial DM was already close to the corrected value. Something must be wrong if the DM does not stabilise after 5-6 iterations.
In other words, start by giving the initial DM (e.g. S/N-optimizing DM) in the first `scatfit` call. Copy the output scattering-corrected DM and run `scatfit` again with the output DM as input. Repeat this process until the difference between input DM and output scattering-corrected DM is less than the reported DM uncertainty or a pre-determined value.

The leading edge of the burst profile should be as sharp as possible (in the absence of DM-smearing), and the tail well-described by the scattering model. Three to four iterations should be enough to reach a stable scattering-corrected DM if the initial DM was already close to the corrected value. Something must be wrong if the DM does not stabilise after 5-6 iterations.

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