kepstddev: calculate Combined Differential Photometric Precision for a time series light curve

pyke.kepstddev.kepstddev(infile, outfile=None, datacol='PDCSAP_FLUX', timescale=6.5, overwrite=False, verbose=False, logfile='kepstddev.log')

kepstddev – Calculate Combined Differential Photometric Precision for a time series light curve.


infile : str

The name of a MAST standard format FITS file containing Kepler light curve data within the first data extension. While the kepstddev task will perform a calculation upon any data column in the first FITS extension of the input file, the output is only meaningful if the data column has first been normalized to a time-dependent model or function. For example, the kepflatten task removes astrophysical and systematic features in a light curve by fitting and normalizing to a running polynomial. The data output of kepflatten is a column named DETSAP_FLUX and is a suitable input column for kepstddev.

outfile : str

Name of the output FITS file containing the results of kepstddev. The output file is a direct copy of infile except for the addition of a new column called CDPPnn, where nn refers to the CDPP timescale. If the column CDPPnn exists already in the input file, then it will be overwritten in the output file.

datacol : str

The name of the FITS data column upon which to calculate CDPP. datacol must be a column within the FITS table extension of the light curve - the first extension of the input file. The time-series within datacol must be normalized, by e.g. the task kepflatten.

timescale : float

The characteristic timescale over which to calculate CDPP. The units are hours.

overwrite : bool

Overwrite the output file? if overwrite = False and an existing file has the same name as outfile then the task will stop with an error.

verbose : bool

Print informative messages and warnings to the shell and logfile?

logfile : str

Name of the logfile containing error and warning messages.


After applying kepflatten to kplr002437145-2009350155506_llc.fits, one can input it to kepstddev:

$ kepstddev kplr002437145-2009350155506_llc.fits --datacol DETSAP_FLUX
KEPSTDDEV --  infile=kplr002437145-2009350155506_llc.fits
outfile=kplr002437145-2009350155506_llc-kepstddev.fits datacol=DETSAP_FLUX
timescale=6.5 overwrite=False verbose=True logfile=kepstddev.log

Standard deviation = 1295.0731328136349 ppm
Median 6.5hr CDPP = 313 ppm
   RMS 6.5hr CDPP = 329 ppm