Update tstart and tseg when using Lightcurve.truncate()

[matteobachetti]

Resolve #751

[codecov]

Codecov Report

Merging #753 (70231cc) into main (5d633c1) will increase coverage by 0.00%.
The diff coverage is 100.00%.

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  Coverage   97.13%   97.13%           
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  Lines        7929     7932    +3     
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+ Hits         7702     7705    +3     
  Misses        227      227           

Files Changed	Coverage Δ
stingray/lightcurve.py	97.89% <100.00%> (+<0.01%)	⬆️

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[mgullik]

Hi @matteobachetti,
Thanks a lot for solving this issue!
I guess that apply_mask in the _truncate_by_index/time takes care of all the array attribute of the object light curve, however, we do not test countrate and the errors on the count and countrate. Do you think it's worth adding those checks?

More importantly, I'm not sure if the new implementation modifies the Lightcurve attribute meanrate, meancount and n (The number of data points in the light curve) after the truncation is applied. Can you check these couple of things?

Cheers!

[matteobachetti]

@mgullik Thanks, I think I addressed your comments