If you have observed a KELT exoplanet candidate, the request for data submission is a bit different from AAVSO/CBA.
One difference is that they request us to use ~8 comparison stars that are close in brightness to the target star. This is to mitigate the effects of CCD nonlinearly and Residual Bulk Image (RBI; i.e. image retention from one exposure to the next) on the differential photometry. If none are available, try to select some brighter and some fainter comp stars such that the average number of counts within the comp star apertures is close to the target star counts. If possible, choose comp stars that are near the target and distributed around the target star to help mitigate the effects of atmospheric gradients on your differential photometry.
One of the issues with KELT is that it has very poor angular resolution, and so stars can get blurred together. A star of constant brightness blurred with an eclipsing binary star can look like a transiting exoplanet. So, if you don't see a clear transit in your star of interest, take a look at the other nearby stars of similar brightness. Do any of these stars show dramatic dips in their light curves? If so, note this in your email (along with the dipping star's name). Also include the dipping star in your light curve plot.
Once you have carried out your photometry, you will submit via email to the KELT follow-up email list (kelt-followup@googlegroups.com) and cc Laura in your email. Please send one email per KELT target per observing night. Your email should include:
- In the subject line, please include the full target name, the UT date, the filter, and the observatory.
ex: Source: KC22C08640, UTC: 2018-03-26 03:54, Filter: V, Obs: Michigan State Campus Observatory
- The email body doesn’t need to contain much, just a description of the observations and any relevant comments about the observing conditions and results. Include a description of any movement of the field on the the detector (e.g. due to bad tracking and/or guiding) of more than ~3 pixels from the start to finish of observations.
ex: Hello,
The pixel scale is 0.55''/pixel. We caught the ingress just barely, and observed well past the egress; the posted start/mid/end times of the transit are UTC 2018-03-26 04:03/ 2018-03-26 05:14/ 2018-03-26 06:25 (or BJD 8203.669/8203.719/8203.769 ) with an error of +/- 0:35. The star was continuously moving throughout the night over 10s of pixels due to issues with guiding; that has since been fixed and should not be an issue in more recent observations.
Thanks,
x
- Attach a plot of the lightcurve, preferably in jpeg or png format. Always include the raw differential target star lightcurve at the top of the plot. If you plot the light curves of comparison stars, offset these so they are below the target star light curve. Please do NOT paste the plot into the body of the email. The example in the following image shows a plot created by AstroImageJ. The plots you probably created following the instructions on the "KELT Image Photometry" page do not make plots like this. If you followed the "KELT Image Photometry" instructions, attach ALL of your lightcurve plots.
- Do the same with a finder chart from the observations, with the position of the target and comparison stars marked. A finder chart that includes sky orientation and pixel scale markers is strongly preferred (AstroImageJ provides this capability).
Finder Chart Example You can make this in Astro Image J. After you finish making the measurements file, go back to your first image (or the image you made the aperature selections on) & click the button with the blue pen over the double circles. This will load all your aperatures on the image. Zoom in so that the x/y scales and the orientation compass are on the image & then use the Snipping Tool to capture that. Use this as your finder chart.
- Finally, include a space or tab-delimited ASCII table of the lightcurve, which should include the time, out-of-transit (OOT) normalized differential target star flux, normalized target star error, airmass, and any other parameters you found useful for detrending. The brightness may be provided in magnitudes or millimagnitudes, but OOT normalized flux is preferred. Often times folks just attach the output from AstroImageJ.
ex: the measurements file output from AIJ will work fine.
After observations are acquired, the observer should reduce them and send them on to the appropriate KELT follow-up email list quickly - within 1-2 days is preferred. Results can be provided after a longer wait time, but the longer the wait, the less useful they may prove to be.
.