merge

daschlab.lightcurves.merge(lcs: List[Lightcurve]) → Lightcurve

Merge multiple lightcurves under the assumption that they all contain data for the same source.

Parameters:

lcslist of Lightcurve

The lightcurves to be merged. The provided value must be iterable and indexable.

Returns:

merged_lcLightcurve

The merged lightcurve.

Notes

This function is intended to address the source splitting issue that can affect DASCH lightcurves. In some cases, detections of the same astronomical source end up split across multiple DASCH lightcurves. When this happens, for each exposure containing a detection of the source, the detection will be assigned to one of several lightcurves quasi-randomly, depending on factors like image defects and the local errors of the WCS solution for the exposure in question.

This function accomplishes the merger by unifying all of the input lightcurves as keyed by their exposure identifier. For each exposure where there is only one non-rejected detection among all the inputs, that detection is chosen as the “best” one for that particular exposure. These unique detections are used to calculate a mean magnitude for the source. For cases where more than one input lightcurve has a non-rejected detection for a given exposure, the detection with the magnitude closest to this mean value is selected. Finally, for any exposures where no lightcurves have a non-rejected detection, the data from the zero’th input lightcurve are used.

The returned lightcurve has columns matching those of the zero’th input lightcurve, plus the following:

• source_lc_index specifies which input lightcurve a particular row’s data came from. This index number is relative to the lcs argument, which does not necessarily have to align with reference catalog source numbers.

• source_lc_row specifies which row of the input lightcurve was the source of the output row.

• merge_n_hits specifies how many lightcurves contained a non-rejected detection for this exposure. When things are working well, most rows should have only one hit. You may wish to reject rows where this quantity is larger than one, since they may indicate that the source flux is split between multiple SExtractor detections.