kepprfphot: fit a PSF model to time series observations within a Target Pixel File¶

pyke.kepprfphot.
kepprfphot
(infile, prfdir, columns, rows, fluxes, border=0, background=False, focus=False, ranges='0, 0', xtol=0.0001, ftol=0.01, qualflags=False, outfile=None, plot=False, overwrite=False, verbose=False, logfile='kepprfphot.log')¶ kepprfphot – Fit a PSF model to time series observations within a Target Pixel File
Parameters: nfile : str
The name of a MAST standard format FITS file containing Kepler Target Pixel data within the first data extension.
columns : str or list
A starting guess for the CCD column position(s) of the source(s) that are to be fit. The model is unlikely to converge if the guess is too far away from the correct location. A rule of thumb is to provide a guess within 1 CCD pixel of the true position. If more than one source is being modeled then the column positions of each are separated by a comma. The same number of sources in the columns, rows and fluxes field is a requirement of this task.
rows : str or list
A starting guess for the CCD row position(s) of the source(s) that are to be fit. The model is unlikely to converge if the guess is too far away from the correct location. A rule of thumb is to provide a guess within 1 CCD pixel of the true position. If more than one source is being modeled then the row positions of each are separated by a comma. The same number of sources in the columns, rows and fluxes field is a requirement of this task.
fluxes : str or list
A starting guess for the flux(es) of the source(s) that are to be fit. Fit convergence is not particularly reliant on the accuracy of these guesses, but the fit will converge faster the more accurate the guess. If more than one source is being modeled then the row positions of each are separated by a comma. The same number of sources in the columns, rows and fluxes field is a requirement of this task.
prfdir : str
The full or relative directory path to a folder containing the Kepler PSF calibration. Calibration files can be downloaded from the Kepler focal plane characteristics page at the MAST here: http://archive.stsci.edu/missions/kepler/fpc/prf/.
border : int
If a background is included in the fit then it is modeled as a twodimensional polynomial. This parameter is the polynomial order. A zeroorder polynomial is generally recommended.
background : bool
Whether to include a background component in the model. If
True
the background will be represented by a twodimensional polynomial of order border. This functionality is somewhat experimental, with one eye upon potential background gradients across large masks or on those detectors more prone to pattern noise. Generally it is recommended to set background asFalse
.focus : bool
Whether to include pixel scale and focus rotation with the fit parameters of the model. This is also an experimental function. This approach does not attempt to deal with inter or intrapixel variations. The recommended use is currently to set focus as
False
.ranges : str
The user can choose specific time ranges of data on which to work. This could, for example, avoid removing known stellar flares from a dataset Time ranges are supplied as commaseparated pairs of Barycentric Julian Dates (BJDs). Multiple ranges are separated by a semicolon. An example containing two time ranges is:
'2455012.48517,2455014.50072;2455022.63487,2455025.08231'
If the user wants to correct the entire time series then providing ranges = ‘0,0’ will tell the task to operate on the whole time series.
xtol : float
The dimensionless, relative model parameter convergence criterion for the fit algorithm.
ftol : float
The dimensionless, relative model residual convergence criterion for the fit algorithm.
qualflags : bool
If qualflags is
False
, archived observations flagged with any quality issue will not be fit.outfile : str
kepprfphot creates two types of output file containing fit results and diagnostics.
outfile.png
contains a time series plot of fit parameters, residuals and chisquared.outfile.fits
contains a table of the same properties, consistent with Kepler archive light curve files. The FITS column PSF_FLUX contains the flux timeseries in units of e/s derived by integrating under the bestfit PRF model. PSF_BKG provides the bestfit background (if calculated) averaged over all mask pixels in units of e/s/pixel. PSF_CENTR1 provides the bestfit PSF centroid position in the CCD column direction, in CCD pixel units. Similarly, PSF_CENTR2 provides the bestfit PSF centroid position in the CCD row direction, in CCD pixel units. If calculated, PSF_FOCUS1 and PSF_FOCUS2 provide scale factors in the column and row dimensions by which the CCD pixel scale is adjusted to approximate focus variation. PSF_ROTATION provides the angle by which the scaled PSF model was rotated on the focal plane in order to yield a best fit. The table column PSF_RESIDUAL provides the sum of all mask pixels after the bestfit model has been subtracted from the data. PSF_CHI2 delivers the bestfit chisqured statistic for each observation.plot : bool
Plot fit results to the screen?
verbose : bool
Print informative messages and warnings to the shell and logfile?
logfile : str
Name of the logfile containing error and warning messages.
Examples
$ kepprfphot kplr0125575482012004120508_lpdtarg.fits.gz columns 95 rows 1020 fluxes 1.0 border 0 prfdir ../kplr2011265_prf xtol 1e7 ftol 1e7 plot verbose  KEPPRFPHOT  infile=kplr0125575482012004120508_lpdtarg.fits.gz columns=95 rows=1020 fluxes=1.0 border=0 background=False focus=False prfdir=../kplr2011265_prf ranges=0,0 xtol=1e07 ftol=1e07 qualflags=False plot=True overwrite=True verbose=True logfile=kepprfphot.log KEPPRFPHOT started at: Wed Jun 14 15:33:30 2017 KepID: 12557548 RA (J2000): 290.96622 Dec (J2000): 51.50472 KepMag: 15.692 SkyGroup: 4 Season: 1 Channel: 32 Module: 10 Output: 4 19% nrow = 740 t = 0.1 sec