Mission Overview

EPIC Variability Extraction and Removal for Exoplanet Science Targets (EVEREST)

 

Primary Investigator: Rodrigo Luger

HLSP Authors: Rodrigo Luger

Released: 2016-07-07

Updated: 2019-04-19

Primary Reference(s): Luger et al. (2018) & Luger et al. (2016)

DOI: 10.17909/T9501J

Citations: See ADS Statistics

Read Me

 
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An example of the uncorrected fluxes from K2 (black) and the corrected EVEREST version (blue).

Overview

EVEREST is an open-source pipeline for removing instrumental systematics from K2 light curves, using a combination of pixel-level decorrelations to remove spacecraft pointing error and Gaussian processes to capture astrophysical variability. Corrected light curves have precision comparable to the original Kepler mission for targets brighter than Kp = 13, and within a factor of 2 for fainter targets. Transit injection and recovery tests have been performed to validate the pipeline, and comparisons with other K2 detrended HLSPs is performed (consult Luger et al. 2016 for further details).

NOTE: Since EVEREST performs least-squares fits to reduce the noise in K2 light curves, astrophysical features such as transits and eclipses can sometimes be slightly shallower in the de-trended dataset. In order to prevent this, EVEREST automatically masks outliers prior to computing the fits. However, low signal-to-noise transits are likely to be missed in this step. The EVEREST software (available on Github) makes it easy to generate light curves with unbiased transit depths if the locations of the transits are known.

Source code is available on GitHub. Documentation is available at MAST (applicable to data archived here) and externally (updated by the team as their software evolves).

Latest Update (April 19, 2019): Version 2.0 files for Campaigns 14-18 are now available.

Previous Update: Version 2.0 files have replaced version 1.0. The previous version 1.0 files were available, but were removed from access on Nov. 15th 2017.

Data Products

Each target is organized into a subdirectory structure, based on its EPIC ID, with the following format: 

c<##>/<####00000>/<#####>/

where:

  • c<##> is normally the 2-digit, zero-padded Campaign number the target was observed in. There are exceptions: some campaigns, like Campaign 10, were split into two sub-campaigns designated as "c101" and "c102". There are EVEREST light curves for c102 only, and in this case the campaign number is a 3-digit field. Others have light curves for both, e.g., "c111" and "c112" for Campaign 11.
  • <####00000> are the first FOUR digits of the target's EPIC ID
  • <#####> are the last FIVE digits of the target's EPIC ID

For example, the star EPIC 202059070 was observed in Campaign 0. It's subdirectory path is therefore: 

<...>/c00/202000000/59070/

Several files are available for each target. Each file has the same prefix ("hlsp_everest_k2_llc_{EPICID}-c##_kepler_v2.0"), followed by an extension. Short cadence light curves are designated by "sc". The extensions and types for these files are:

The FITS file has 5 extensions: the primary HDU with just a header, the data extension with the de-trended light curve, an extension containing the pixel-level light curve, an extension containing the aperture mask used, an extension that stores images of the full target postage stamp at three points in the light curve, and an extension that has a higher resolution image of the target from the Palomar Observatory Sky Survey. The data extension (first extension) consists of the following columns:

_lc.fits | _sc.fits The FITS file has 5 extensions: the primary HDU with just a header, the data extension with the de-trended light curve, an extension containing the pixel-level light curve, an extension containing the aperture mask used, an extension that stores images of the full target postage stamp at three points in the light curve, and an extension that has a higher resolution image of the target from the Palomar Observatory Sky Survey.  Long and short cadences are denoted by "lc" and "sc", respectively.
_dvs.pdf | _dvs_sc.pdf The data validation summary (DVS) figures consist of PDF documents with two pages for each de-trended target. The first page shows three panels: the final, PLD-detrended and CBV-corrected flux (top), the uncorrected detrended flux (center), and the raw SAP flux (bottom). In the center plot, the red curve is the CBV fit. Miscellaneous information is displayed at the top (the K2 campaign number, the Kepler magnitude, the photometric precision, etc.). The second page shows the detailed PLD de-trending summary, showing the progression of the light curve as higher PLD orders are included in the de-trending. Snapshots of the postage stamp are shown at the top right, with a high resolution POSS image of the target. Below these, the cross-validation curves for each PLD order are plotted. More information on these summary files can be found in the EVEREST documentation.  Short cadence are denoted by the presence of an "_sc" in the file names.
_dvs-0.png, _dvs-1.png | _dvs_sc-0.png, _dvs_sc-1.png PNG versions of page 1 and 2 of the respective "dvs.pdf" file. Short cadence are denoted by the presence of an "_sc" in the file names.

 

The data extension (first extension) of the _lc.fits and _sc.fits files consists of the following columns:

  • CADN - The original cadence number.
  • FLUX - The de-trended flux, (e-/s). "De-trended" light curve in the middle panel of the preview plots.
  • FRAW - The original, raw SAP flux. "Raw" light curve in the bottom panel of the preview plot.
  • FRAW_ERR - The observing errors on the raw flux.
  • QUALITY - A 64-bit integer array of quality flags for each cadence.
  • TIME - The original timestamp (BJD - 2454833.0).
  • FCOR - The CBV-corrected, de-trended flux, (e-/s). "Corrected" light curve in top panel of preview plots.
  • CBV01 - First co-trending basis vector.
  • CBV02 - Second co-trending basis vector.
  • CBV03 - Third co-trending basis vector.
  • CBV04 - Fourth co-trending basis vector.
  • CBV05 - Fifth co-trending basis vector.
  • BKG - If present, the background flux subtracted from each cadence.

Data Access

EVEREST light curves are available in the MAST Portal (web-based, cross-mission search interface) and Astroquery (Python package to search for and download files from Python scripts you write), and a MAST Classic Search Form (web-based form with mission-specific metadata available).  For those who want to download all EVEREST light curves for a given Campaign, we provide tar bundles in the table below.

Link to the MAST Portal Webpage

MAST Portal

A web-based interface for cross-mission searches of data at MAST or the Virtual Observatory. Download EVEREST light curves for a few targets.

MAST Astroquery

Search for, and retrieve, EVEREST data products programmatically based on a list of coordinates or target names.
Link to EVEREST MAST Classic Search Form

EVEREST Classic Form

A web-based form to search based on target, coordinate, or metadata. Specify output format: HTML table, CSV files, or download scripts.

In addition to the services above, bundles of EVEREST files are available as tar files.

Tar Bundles
c00 c01 c02 c03
c04 c05 c06 c07
c08 c102 c111 c112
c12 c13 c14 c15
c16 c17 c18

Citations

Please remember to cite the appropriate paper(s) below and the DOI if you use these data in a published work. 

Note: These HLSP data products are licensed for use under CC BY 4.0.

References