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Kepler Data Photometry

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WBY
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Joined: 2010-07-24

I have been downloading Kepler data from the MAST search page for the Kepler mission http://archive.stsci.edu/Kepler/data_search/search.php . For several Variable stars. When I display the data in VStar I always get single digit values for Kp magnitude of the variable no matter the Kepler average magnitude given for the season's measurements. The Kp season mean values are sensible in relation to the values shown for the variable in VSX (VSX  lists some magnitudes in Kp but even if not, the Kepler season mean magnitudes seem reasonable in relation to V magnitudes) . Several questions arise:

1. What is the best way to convert that to the Actual Kp. Do I take the mean of the data for the season's observations in VStar and add an offset that converts the value to the mean Kp value in the summary data for that season of that star?

2. Another way I thought of doing it was to take a Kepler secondary standard star of similar magnitude and color that has a known constant Kp for the season and find the offset between its Kp season mean magnitude and the VStar mean magnitude and add the offset to the VStar magnitudes of the variable. The problem with this is that I haven't found a list of the Kepler IDs for the secondary standards established for the field. I can find mention of the secondary standards in several places in the Kepler manuals, but I haven't discovered how I can identify them.

3. Is there a generally accepted method for transforming The SAP flux used by VStar into one of the Johnson-Cousins photometric bands? If  transformations exist, over what color ranges ranges do they apply and what are the estimated errors?

Brad Walter, WBY

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484