Desperately Seeking Non-Gaussianity

The Light Curve of 0957+561
  • W. H. Press
  • G. B. Rybicki
Part of the Astrophysics and Space Science Library book series (ASSL, volume 218)


“Non-Gaussian” is the casual explanation often given for anything unexpected in an astronomical time series. What better place to look for non-Gaussianity, therefore, than in the light curve of 0957+561, the gravitational lens that, until recently, had yielded frustratingly inconsistent determinations of its lag. We discuss the difficulties in measuring deviations from Gaussianity in weakly nonstationary processes (such as 1/f noise or random walk) and define a restricted set of “well-behaved” three-point statistics. An important special case of such a well-behaved statistic is the skew of a linear combination of the data, with coefficients summing to zero. Analytic and Monte Carlo calculations evaluate the performance of such a statistic in the case of a non-Gaussian “wedge model” (shot noise, with each shot having a rapid rise and slow decay). We find that even for as well studied an object as 0957+561, the detectability of any deviation from Gaussian is problematical at best. At present, one can rule out a wedge model only if the individual shots are as infrequent as one in 10–20 days.


Gaussian Process Light Curve Shot Noise Important Special Case High Order Statistic 
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  1. Kundie, T., Colley, W.N., Gott, J.R., Malhotra, S., Pen, U., Rhoads, J.E., Stanek, K.Z, and Turner, E.L. (1995) Astrophys. J. (Lett.), 455, L5.Google Scholar
  2. Kundié, T., Turner, E.L., Colley, W.N., Gott, J.R., Rhoads, J.E., Wang, Y., Bergeron, L.E., Gloria, K.A., Long, D.C., Malhotra, S., and Wambsganss, J. (1996) preprint astro-ph/9610162 [K96].Google Scholar
  3. Pelt, J., Kayser, R., Refsdal, S., and Schramm, T. (1996) Astron. Astrophys., 305, 97106.Google Scholar
  4. Press, W.H., Rybicki, G.B., and Hewitt, J.N. (1992) Astrophys. J., 385, 404CrossRefGoogle Scholar
  5. Press, W.H., Rybicki, G.B., and Hewitt, J.N. (1992) Astrophys. J., 385, 416CrossRefGoogle Scholar
  6. Rybicki, G.B. and Press, W.H. (1992) Astrophys. J., 398, 169CrossRefGoogle Scholar
  7. Vanderriest, C., Schneider, J., Herpe, G., Chevreton, M., Moles, M., and Wlerick, G. (1989) Astron. Astrophys., 215, 1–13.Google Scholar
  8. Weisskopf, M.C., Sutherland, P.G., Katz, J.I., and Canizares, C.R. (1978) Astrophys. J. (Lett.), 223, L17 — L20.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media Dordrecht 1997

Authors and Affiliations

  • W. H. Press
    • 1
  • G. B. Rybicki
    • 1
  1. 1.Harvard-Smithsonian Center for AstrophysicsCambridgeUSA

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