WASP-1b Transit Parameters

Affiliation
American Association of Variable Star Observers (AAVSO)
Mon, 09/04/2017 - 23:20

I recently had a chance to observe a transit of WASP-1b.  I compared my observations to the predicted times in ETD, exoplanets.org and VSX.  I found much more variation in the prediction parameters (Epoch of mid trans, period and duration) than I have seen for most other exoplanets.  As I did the calculation for the night in question, I found ETD and exoplanets.org differed by 3-6 minutes.  However, VSX differed by more than an hour.  I found the transit model I derived from my observations differed by less than a minute from the ETD prediction.

It seems to me that VSX needs to be corrected for this exoplanet.  Does anyone else see similar results?

Attached is the preditions I see.

best regards,

Cliff

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Affiliation
American Association of Variable Star Observers (AAVSO)
I often have difference in

I often have difference in minutes, but there might be two reasons. Sometimes there are exoplanets that need orbital period to be updated. The O-C graph would show a trend when the difference is getting larger on later years. And the other reason might be the prediction time shown in JD without HJD correction.