FITS Files¶
The FITS files available in the everest catalog contain the de-trended
light curves, as well as information used by everest to do
customized post-processing. Each FITS file is composed of six extensions:
Note
It is highly recommended that users access the catalog through the everest user interface, as this allows for post-processing of the light curves with custom masks.
[0] Primary HDU¶
A header unit containing general information about the data collection for this target;
this info was copied directly from the original K2 target pixel files. The VERSION
and DATE tags were added to indicate the everest pipeline version and
creation date, respectively.
[1] Lightcurve HDU¶
The main data unit containing the de-trended light curve. Again, the header keywords
were taken from the equivalent extension in the original K2 target pixel files. The
following everest keywords were added:
| Keyword | Description |
| MISSION | The photometry mission name |
| VERSION | The EVEREST pipeline version |
| DATE | FITS file creation date (YYYY-MM-DD) |
| MODEL | The name of the everest model used to de-trend |
| APNAME | The name of the aperture used |
| BPAD | Light curve segment overlap in cadences for mending at breakpoints |
| BRKPTXX | Index/indices of light curve breakpoint(s) |
| CBVNUM | Number of CBV signals to regress on |
| CBVNITER | Number of CBV SysRem iterations |
| CBVWIN | Window size for smoothing CBVs |
| CBVORD | Filter order when smoothing CBVs |
| CDIVS | Number of cross-validation subdivisions |
| CDPP | Average de-trended CDPP |
| CDPPR | Raw light curve CDPP |
| CDPPV | Estimated average validation CDPP |
| CDPPG | Average GP-de-trended CDPP |
| CDPPXX | De-trended CDPP in light curve segment XX |
| CDPPRXX | Raw CDPP in light curve segment XX |
| CDPPVXX | Estimated validation CDPP in light curve segment XX |
| CVMIN | Cross-validation objective function |
| GITER | Number of GP optimiziation iterations |
| GPFACTOR | GP amplitude initialization factor |
| GPWHITE | GP white noise amplitude (e-/s) |
| GPRED | GP red noise amplitude (e-/s) |
| GPTAU | GP red noise timescale (days) |
| LAMXXYY | Cross-validation parameter for segment XX and PLD order YY |
| RECLXXYY | Cross-validation parameter for segment XX and PLD order YY (iPLD only) |
| LEPS | Cross-validation minimum-finding CDPP tolerance |
| MAXPIX | Maximum size of TPF aperture in pixels |
| NRBYXXID | Nearby source XX ID number |
| NRBYXXX | Nearby source XX X position (pixels) |
| NRBYXXY | Nearby source XX Y position (pixels) |
| NRBYXXM | Nearby source XX magnitude |
| NRBYXXX0 | Nearby source reference X (pixels) |
| NRBYXXY0 | Nearby source reference Y (pixels) |
| NEIGHXX | Neighboring star ID used to de-trend (nPLD only) |
| OITER | Number of outlier clipping iterations |
| OPTGP | GP optimization performed? |
| OSIGMA | Outlier tolerance (standard deviations) |
| PXXT0 | Masked planet transit time (days) |
| PXXPER | Masked planet period (days) |
| PXXDUR | Masked planet transit duration (days) |
| PLDORDER | PLD de-trending order |
| SATUR | Is target saturated? |
| SATTOL | Fractional saturation tolerance |
The data container of this extension contains the following arrays:
| Keyword | Description |
| TIME | The original timestamp. For K2, this is (BJD - 2454833) |
| CADN | The original cadence number |
| FLUX | The everest de-trended flux, same units as original SAP flux (e-/s) |
| FCOR | The CBV-corrected de-trended flux (e-/s) |
| FRAW | The original (raw) SAP flux |
| FRAW_ERR | The observing errors on the raw flux |
| QUALITY | An int64 array of quality flags for each cadence (see note below) |
| BKG | If present, the background flux subtracted from each cadence |
| CBVXX | The co-trending basis vectors used to produce the corrected flux FCOR |
Note
The QUALITY array uses the same bit flags as K2, with the addition of four everest flags that indicate a data point was masked when computing the model:
23 Data point is flagged in the raw K2 TPF 24 Data point is a NaN25 Data point was determined to be an outlier 26 Not used 27 Data point is during a transit/eclipse
As an example, to get the indices of all points that were flagged with bit 23 in Python, run
inds = np.where(QUALITY & 2 ** (23 - 1))[0]
Note, however, that the everest user interface provides easy access to
these masks via the Everest.badmask, Everest.nanmask,
Everest.outmask, and Everest.transitmask attributes.
[2] Pixels HDU¶
An extension containing the pixel-level light curve.
The data container stores two arrays:
| Keyword | Description |
| FPIX | The flux in each of the pixels in the aperture |
| X1N | The first order PLD vectors for the neighbors (nPLD only) |
[3] Aperture HDU¶
An extension containing the aperture mask used for PLD de-trending. Ones correspond to pixels that were included in the de-trending; zeros correspond to pixels that were ignored.
[4] Images HDU¶
Stores images of the full target postage stamp at three points in the light curve, for plotting purposes only.
| Keyword | Description |
| STAMP1 | The postage stamp at the first cadence |
| STAMP2 | The postage stamp at the midpoint |
| STAMP3 | The postage stamp at the last cadence |
[5] HiRes HDU¶
An image HDU containing a higher resolution image of the target. For K2, this is
obtained from the Palomar Observatory Sky Survey.