Machine learning for transient discovery in Pan-STARRS1 difference imaging

D. E. Wright*, S. J. Smartt, K. W. Smith, P. Miller, R. Kotak, A. Rest, W. S. Burgett, K. C. Chambers, H. Flewelling, K. W. Hodapp, M. Huber, R. Jedicke, N. Kaiser, N. Metcalfe, P. A. Price, J. L. Tonry, R. J. Wainscoat, C. Waters

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

39 Citations (Scopus)


Efficient identification and follow-up of astronomical transients is hindered by the need for humans to manually select promising candidates from data streams that contain many false positives. These artefacts arise in the difference images that are produced by most major ground-based time-domain surveys with large format CCD cameras. This dependence on humans to reject bogus detections is unsustainable for next generation all-sky surveys and significant effort is now being invested to solve the problem computationally. In this paper, we explore a simple machine learning approach to real-bogus classification by constructing a training set from the image data of similar to 32 000 real astrophysical transients and bogus detections from the Pan-STARRS1 Medium Deep Survey. We derive our feature representation from the pixel intensity values of a 20 x 20 pixel stamp around the centre of the candidates. This differs from previous work in that it works directly on the pixels rather than catalogued domain knowledge for feature design or selection. Three machine learning algorithms are trained (artificial neural networks, support vector machines and random forests) and their performances are tested on a held-out subset of 25 per cent of the training data. We find the best results from the random forest classifier and demonstrate that by accepting a false positive rate of 1 per cent, the classifier initially suggests a missed detection rate of around 10 per cent. However, we also find that a combination of bright star variability, nuclear transients and uncertainty in human labelling means that our best estimate of the missed detection rate is approximately 6 per cent.

Original languageEnglish
Pages (from-to)451-466
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Early online date17 Mar 2015
Publication statusPublished - 01 May 2015


  • methods: data analysis
  • methods: statistical
  • techniques: image processing
  • surveys
  • supernovae: general
  • 1ST


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