Now showing items 1-7 of 7

    • Estimation of the coherence time of stochastic oscillations from modest samples 

      Koen, Chris (Oxford University Press, 2012)
      ‘Quasi-periodic’ or ‘solar-like’ oscillations can be described by three parameters – a characteristic frequency, a coherence time (or ‘quality factor’) and the variance of the random driving process. This paper is concerned ...
    • HE 0230−4323 revisited: a new rapidly pulsating sdB star 

      Kilkenny, David; Koen, Chris; Worters, H. (Oxford University Press, 2010)
      HE 0230−4323 is a hot sdB star in a binary system. An earlier work demonstrated that the light curve of the system shows a strong (∼4 per cent) reflection effect and also appears to exhibit photometric variations of the ...
    • HE0230–4323: an unusual pulsating hot subdwarf star 

      Koen, Chris (Oxford University Press, 2007)
      HE 0230−4323 is a known binary, consisting of a subdwarf star and a companion which is not observable in the optical. Photometric measurements reported in this paper have shown it to be both a reflection-effect and a ...
    • JL 82: a slowly pulsating hot subdwarf star in a close binary system 

      Koen, Chris (Oxford University Press, 2009)
      JL 82 is a known binary, consisting of an sdB star and a companion which is not directly observable in the optical. Photometric measurements reported in this paper show it to variable with both the binary period (∼0.75 ...
    • KPD 0629–0016, a slowly pulsating hot subdwarf star 

      Koen, Chris; Green, E.M. (Oxford University Press, 2007)
      The results of nine CCD photometric observing runs on KPD 0629–0016 are presented. During six of the runs measurements were obtained alternately through B and V filters. Four periodicities, for which there is good agreement ...
    • Statistical tests for changes in the amplitude, frequency or phase of a sinusoidal variation 

      Koen, Chris (Oxford University Press, 2009)
      The problem considered is that of testing for small changes over time in the properties of a sinusoidal signal contaminated by noise. Two test statistics are proposed. The first is a frequency domain statistic based on ...
    • Two new variable sdB stars, HE 0218−3437 and LB 1516 

      Koen, Chris; Kilkenny, David; Pretorius, M.L.; Frew, D.J. (Oxford University Press, 2010)
      We present photometry which shows that two known hot subdwarf stars, HE 0218−3437 and LB 1516, are variable. LB 1516 exhibits several frequencies in the range 12–25 cycles d−1 (periods of about 1–2 h) with amplitudes ...