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Issue A&A Volume 391, Number 1, August III 2002 Page(s) 369 - 377 Section Instruments, observational techniques and data processing DOI 10.1051/0004-6361:20020802

A&A 391, 369-377 (2002)
DOI: 10.1051/0004-6361:20020802

A box-fitting algorithm in the search for periodic transits

G. Kovács¹, S. Zucker² and T. Mazeh<sup>2

1</sup>  Konkoly Observatory, PO Box 67, 1525, Budapest, Hungary
²  Wise Observatory, Tel Aviv University, Tel Aviv, 69978, Israel
    e-mail: shay@wise.tau.ac.il, mazeh@wise1.tau.ac.il

(Received 28 February 2002 / Accepted 4 April 2002 )

Abstract
We study the statistical characteristics of a box-fitting algorithm to analyze stellar photometric time series in the search for periodic transits by extrasolar planets. The algorithm searches for signals characterized by a periodic alternation between two discrete levels, with much less time spent at the lower level. We present numerical as well as analytical results to predict the possible detection significance at various signal parameters. It is shown that the crucial parameter is the effective signal-to-noise ratio - the expected depth of the transit divided by the standard deviation of the measured photometric average within the transit. When this parameter exceeds the value of 6 we can expect a significant detection of the transit. We show that the box-fitting algorithm performs better than other methods available in the astronomical literature, especially for low signal-to-noise ratios.

Key words: methods: data analysis -- stars: variables: general -- stars: planetary systems -- occultations

Offprint request: G. Kovács, kovacs@konkoly.hu

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