Incorporating exposure times for photometric data

[CheerfulUser]

Hello,

This looks like a fantastic package! My group is trying to model afterglow-like lightcurves in TESS where we have objects with time resolutions of 30min, 10min and 200s. Since TESS continuously observes targets, we have data on the rise, and near peak. With this data we’ve found that the exposure time makes a significant difference to the lightcurve shape and the best fitting model parameters. Do you think it would be possible to incorporate exposure times for photometric measurements in the VegasAfterglow fitting routine?

The process we are currently using for afterglowpy is to generate a lightcurve at a high temporal resolution of 2 seconds, then convolve that model lightcurve with a normalized window function that is the same relative size as the exposure time. The convolved lightcurve is then sampled at the TESS observation times to get the model lightcurve that would be observed by TESS with the input exposure time. We could add a similar wrapper to the outside of VegasAfterglow, but I suspect that won’t be as efficient as something incorporated into the package.

Looking forward to testing VegasAfterglow on our data!

[YihanWangAstro]

Hi Ryan,

Thank you for the feedback and for your interest in testing VegasAfterglow on TESS data. This feature makes sense, and I can implement it as an intrinsic option so you can handle exposure times more efficiently.

Would you prefer an interface like

model.specific_flux_series(times, frequencies, expo_time)

where expo_time is an array of exposure times for the given points, or would you want this feature integrated directly into the MCMC module?

Just to note: the current MCMC module does not yet support some of the more advanced features in VegasAfterglow (e.g. reverse shock, user-defined medium, custom jet structures). For that reason, many users treat VegasAfterglow as the model light-curve generator and then use their own MCMC sampler externally, which gives them access to all the features.

Best,
Yihan

[CheerfulUser]

Hi Yihan,

Thank you for the quick response! Your suggested interface with specific_flux_series would be ideal. It would easily allow multi instrument observations with different exposure times could be incorporated in the same input.

We'll follow your recommendation and implement our own MCMC wrapper.

Thanks again!
Ryan

[YihanWangAstro]

Hi Ryan,

We’ve implemented the exposure-averaged method in our new release (apologies for the delay, as we were working on other feature developments). You can find usage examples in the section 'Calculate flux with exposure time averaging' of the documentation.

If you encounter any bugs or inconveniences when using this interface, please let us know.

Thanks,
Yihan