Skip to main content

Converting PPM to magnitudes - Kepler Data

WBY's picture
WBY
Offline
Joined: 2010-07-24

I have been doing some research on KOI-13 in preparation. The Extra solar Planet Encyclopaedia. Exoplanets.org data base and several recent papers list a transet depth of 0.008 magnitudes. The Kepler project Planet Candidate Data Explorer lists the transit depth as 4646 parts per million. If I am converting correctly this works out to be about 0.005 magnitudes, which makes me suspect that I am not doing the conversion correctly.

I am using the following conversion delta mag =-2.5*LOG(1-4646/1000000) = 0.00506. Can anyone confirm that this is the correct calculation.

If that is correct then there are very significant differences between reference sites one normally uses for exoplanet information. There are other significant differences between the kepler site data and the other sources concerning KOI-13, relating to things such as error limtis on transit epochs and periods. Does anyone know whether the Kepler Planet Candidate Date Explorer has the best data for Kepler objects? I would assume it does, but I have been surprised many times in the past by seemingly obvious conclusions that turned out to be bad assumptions, particularly concerning the merits of data sources.  It may be possible that this site doesn't contain updates from follow on observations but the smaller error limits on the Kepler site argue for the Kepler site being more current.

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