The Monitor project: data processing and light curve production

Jonathan Irwin, Mike Irwin, Suzanne Aigrain, Simon Hodgkin, Leslie Hebb, Estelle Moraux

Research output: Contribution to journalArticlepeer-review

68 Citations (Scopus)


We have begun a large-scale photometric survey of nearby open clusters and star-forming regions, the Monitor project, aiming to measure time-series photometry for > 10 000 cluster members over > 10 deg(2) of sky, to find low-mass eclipsing binary and planet systems. We describe the software pipeline we have developed for this project, showing that we can achieve peak rms accuracy over the entire data set of better than similar to 2 mmag using aperture photometry, with rms < 1 per cent over similar to 4 mag, in data from 2- and 4-m class telescopes with wide-field mosaic cameras. We investigate the noise properties of our data, finding correlated 'red' noise at the similar to 1-1.5 mmag level in bright stars, over transit-like time-scales of 2.5 h. An important source of correlated noise in aperture photometry is image blending, which produces variations correlated with the seeing. We present a simple blend index based on fitting polynomials to these variations, and find that subtracting the fit from the data provides a method to reduce their amplitude, in lieu of using techniques, such as point spread function fitting photometry, which tackle their cause. Finally, we use the SYSREM algorithm to search for any further systematic effects.

Original languageEnglish
Pages (from-to)1449-1462
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Publication statusPublished - 11 Mar 2007


  • methods : data analysis
  • techniques : photometric
  • surveys


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