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Kepler Previews

The Kepler previews display a variety of information about the input dataset:
  • Files Online - The local directories are searched for both the light curve file and the target pixel file. If a file is found, right clicking the "online" link(s) will allow the user to download that file.

  • Available Data - A database query is used to determine in which quarters observations were made of the same target; for both long and short cadence. Since up to three short cadence light curves may be available in one quarter, they are shown with an added a, b, or c. If one of the list of quarters is clicked, a new preview is displayed for that light curve. The quarter for the plotted light curve is shown in black.

  • DV Files - The Kepler Data Release 25 Data Validation process produces several files for stars with at least one Threshold-crossing event (TCE). One TCE is defined as three transit-like signals detected with a consistent period. If a TCE was detected for the input target, links will appear to the following files:
    • A single-page summary PDF file for each TCE,
    • an extensive multi-page PDF report,
    • the DV time series files in FITS format (right-click to download).

  • Target Search Results - Clicking this link will display the Kepler target catalog information for the input Kepler ID.

  • Display primary header - Clicking this button displays the primary header from the light curve FITS file which contains most of the parameters from the Kepler Input Catalog (KIC). Clicking it again will hide the FITS header.

  • Display Aperture Image - Both the light curve file and the Target Pixel file store an image of the aperture which can be displayed by clicking the 2 buttons.


Plotting

The previews use the HTML5 Canvas API for drawing graphics. Canvas is supported by the latest versions of all popular browsers including IE 9, but it is NOT directly supported by IE 6,7 or 8.

With Canvas and javascript, most of the plotting options can be run locally on the users computer and therefore can be executed fairly quickly. Reloading the page or clicking the "Start again" button will retrieve the data from the MAST web server, which takes a little longer, but allows you to return to the original display.

Note: to reset parameters to their initial values, click the shift key which clicking the reload button. Clicking "Start again" will re-display the original spectra, but some javascript-based options may remain unchanged.

  • Zoom - To zoom in on a particular region, click the mouse button and drag it across the desired region. You can drag the mouse right to left or vice versa. As you drag the mouse, a box will be drawn showing the region to be displayed. Releasing the mouse button will display the selected region and the min and max values shown above the plot will be updated. The zoomed-in region will be displayed in histogram mode to more accurately described the digitized data whereas the inital plot is drawn by just connecting points with straight lines. Note zooming with the cursor may not work properly if any part of the plotted data is on the edge or outside the plot window. Slightly increasing the min/max y values will help alleviate the problem. Also, if no points appear, click "Start again" to redraw the original plot.

  • Changing plot limits - Besides zooming, the min and max X and Y axes limits can be specified manually by entering new values in the boxes provided. Unlike zooming with the mouse, one can zoom in or OUT by specifying new limits. To make a change, type in a new value and click return. The new plot range will appear without the page refreshing.

  • Reading Cursor Positions - Moving the mouse across the plot window will display the X any Y positions of the cursor (in data units) just below the plot window.

Tips

  • Clicking "Start again" will replot the data and reset all parameters to their default values except for Kepler light curves for which the data type remains unchanged. Write down scale factors if you want to save them.
  • For Kepler previews, clicking "Back to previous quarter" will display the previous page displayed in the same browser window.
  • For spectra dominated by a few bright emission lines, it may be hard to zoom in on the continuum if it lies close to the minimum flux value. To make it easier to zoom in, first decrease the "Min Flux" value.
  • To save a plot, either click the "Create png image" button, or do a screen capture of the original page. Note the png image appears to have a black background but it will appear gray when you save it to disk. When printing, the background color will not appear.

Source of Data

Plotted data and displayed FITS headers are extracted from the online (public) FITS light curve files produced by the Kepler project. Both the PDCsap and the Sap Flux vectors are plotted by default. All long cadence data is now from data release 25 (DR25). The short cadence data is currently DR24, but should be reprocessed by the end of summer 2016.

The (DR25) DV files were obtained from NExScI. If no file files are listed, it probably means the target had no TCE.