Apologies if this is the incorrect forum. I dont post here often.
A couple of nights ago I was observing an exoplanet transit. Then yesterday I decided to check the 'light curves' of some other stars in the same dataset. Most are just noisy flat lines (see end of post below), however one stood out to my eye. See below. I checked VSX and there is no variable star for these coordinates. I also checked the sloan dss and the star listed there does not have any info suggesting its a variable.
I was wondering how to determine if this is really a pattern or if its just noise.
For reference here is my exoplanet transit. I missed a chunk of the start of transit due to weather.
And for to get a better idea of the noise, here are a couple of other stars in the same dataset.
Hi Derek,
While the variation could well be real, I'd recommend examining the underlying images for focus changes and variable sky conditions. Another possibility would be image drift across flat-field artifacts or bad pixels. For example, the dips could occur if the candidate star's maximum pixel intensity briefly entered your CCD's non-linear regime -- as might happen if the focus was very sharp and the seeing and transparency were both excellent during the dips. If any of those conditions degraded, the maximum pixel intensity might then return to your CCD's linear regime, causing the star to appear to brighten. Likewise, if the candidate star drifted across an imperfectly corrected dust shadow, it could produce a spurious signal in the light curve.
Does the star have an extreme color?
Best,
Colin
Colin,
Thanks for your ideas. I totally forgot to check for saturation and the star's peak pixel values are not only out of the linear range but are totally saturated. Such a beginner mistake to make :-)
Great thinking for checking the flat too. It did not coencide with any dust doughnuts but was fairly close to the edge of the field in the area where my off-axis pickoff mirror causes a slight shadow in my flat frames.
Derek