observed ingress/egress BJD times don't match predicted

Posted by james.lowenthal on Apr 04, 2022; 10:26pm
URL: http://astroimagej.170.s1.nabble.com/observed-ingress-egress-BJD-times-don-t-match-predicted-tp1871.html

At Smith College Observatory we got a nice light curve for the Hot Jupiter K2-34b on the night of 3 Mar 2022 (UT 4 mar 2022).  We took the UT start/mid/end times from the ETD, and converted them to BJD using the AIJ Coordinate Converter.  In AIJ, we reduced the data and plotted the curve in BJD_TDB, and plotted the predicted ingress/egress BJD times.  The transit is very clearly visible.  But the timing is off: the transit is about 30 min late compared to the predicted start/mid/end times.

We also observed a similar offset in our light curve of XO-2b on the night of 4 Mar 2022 (UT 5 Mar 2022): there, the transit came early compared to the prediction.

Any suggestions?