HLSP_K2SC are high level science products contributed by Suzanne Aigrain. The MAST HLSP page is located at https://archive.stsci.edu/prepds/k2sc/. Not every K2 target has a K2SC lightcurve, for example, short cadence targets are not included in K2SC. The extracted, detrended lightcurves are stored in FITS files, one per K2 target. For each target, there are two different, detrended fluxes available. The first FITS extension contains a data table that has the time stamps and fluxes for the detrended PDCSAP fluxes. The second FITS extension contains a data table that has the time stamps and fluxes for the detrended SAP fluxes.
DataDelivery only requires an observation ID to uniquely identify the FITS file to read from disk. The HLSP_K2SC observation IDs are stored in a subdirectory path that has the following format:
subdir_path = c<##>/<####00000>/
In the above formula, the first part is the 2-digit campaign number, and the second part is the first four digits of the EPIC (target) ID. As an example, the observation ID "k2sc200004923-c03_lc" would lie in a subdirectory path of:
c03/200000000/
The names of the FITS files are given by the following formula:
"hlsp_k2sc_k2_llc_" + TRUNC_OBS_ID + "_kepler_v1_lc.fits"
In the above formula, TRUNC_OBS_ID is the observation ID without the "k2sc" or "_lc" substrings, e.g., "200004923-c03" for the observation ID "k2sc200004923-c03_lc". If there are ever any short cadence targets provided as part of HLSP_K2SC, the files will end with "sc.fits" instead of "lc.fits".
Once the FITS file is located on disk, the time stamps and corrected fluxes for each of the FITS extensions #1 and 2 are read. The time stamps are stored in a truncated BJD format, where the full barycentric Julian date is given by:
BJD[i] = TIME[i] + 2454833.0
In the above formula, "TIME" is the array of truncated BJD time stamps, stored as a column in the data tables in each FITS extension. Similarly, the detrended fluxes are stored as a column called "FLUX". No additional processing is performed on the fluxes, and no filtering based on quality flags or other selection criteria is performed.