Now showing items 1-8 of 8

    • Correcting CCD photometry of stars for seeing effects 

      Koen, Chris (Oxford Univeristy Press, 2009)
      Systematic variability in stellarmagnitudes, as derived from profile fitting to CCD images,may in some instances be due to variable seeing. It is suggested that this happens in cases where the stars are unresolved pairs, ...
    • An extensive search for rapid optical variability in ultracool dwarfs 

      Koen, Chris (Oxford University Press, 2013)
      In this paper, a summary of optical time-series photometry of 125 ultracool dwarfs is given. The observing strategy was to monitor each object continuously for 2–3 h in order to ascertain whether itwas rapidly variable. ...
    • HELP: The Herschel Extragalactic Legacy Project 

      Jarvis, M.J.; Shirley, R; Duncan, K; Campos Varillas, M.C.; Hurley, P.D.; Malek, K; Roehlly, Y; Oliver, S.J. (Oxford University Press, 2021)
      We present the Herschel Extragalactic Legacy Project (HELP). This project collates, curates, homogenizes and creates derived data products for most of the premium multiwavelength extragalactic data sets. The sky boundaries ...
    • Improved SAAO–2MASS photometry transformations 

      Koen, Chris; Marang, F.; Kilkenny, David; Jacobs, C. (Oxford University Press, 2007)
      Near-infrared photometry of 599 stars is used to calculate transformations from the South African Astronomical Observatory (SAAO) JHK system to the Two-Micron All-Sky Survey (2MASS) JHKS system. Both several-term formal ...
    • JHKs time-series observations of a few ultracool dwarfs 

      Koen, Chris; Tanabe, T.; Tamura, M.; Kusakabe, N. (Oxford University Press, 2005)
      The M8.5 object SSSPM J0109−5101 has recently been shown to be both a periodic and a flaring variable, based on optical observations in the extreme red. More than 16 h of monitoring in the near-infrared (NIR) reported ...
    • Linking multi-epoch CCD photometry of partially overlapping fields 

      Koen, Chris (Oxford University Press, 2013)
      A common problem in CCD photometry is to combine measurements obtained at different epochs. This is especially challenging if the fields only overlap partially, and are sparse, so that not all calibrating stars are ...
    • UBV(RI)C photometry of transiting planet hosting stars 

      Maxted, P.F.L.; Koen, Chris; Smalley, B. (Oxford University Press, 2011)
      We present new UBV(RI)C photometry of 22 stars that host transiting planets, 19 of which were discovered by the Wide Angle Search for Planets (WASP) survey. We use these data together with Two Micron All Sky Survey (2MASS) ...
    • Unsupervised machine learning for transient discovery in deeper, wider, faster light curves 

      Lochner, Michelle; Webb, Sara; Muthukrishna, Daniel (Oxford University Press, 2020)
      Identification of anomalous light curves within time-domain surveys is often challenging. In addition, with the growing number of wide-field surveys and the volume of data produced exceeding astronomers’ ability for manual ...