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A&A 420, 789-797 (2004)
DOI: 10.1051/0004-6361:20034220
Searching for periods in X-ray observations using Kuiper's test
Application to the ROSAT PSPC archive
S. PaltaniLaboratoire d'Astrophysique de Marseille, BP 8, 13376 Marseille cedex 12, France
(Received 21 August 2003 / Accepted 28 February 2004 )
Abstract
We use Kuiper's test to detect periodicities in X-ray and
gamma-ray observations. Like Rayleigh's test, it uses the individual
photon arrival times, and is therefore well suited to the analysis
of faint sources. Our method makes it possible to take into account
the discontinuities in the observation, and to completely get rid of
the contamination that results from them. This makes it particularly
adapted to the search of periods long compared to the total
observation duration. We propose a semi-analytical approach to
determine the effective number of trial frequencies when searching
for unknown periods over a frequency range. This approach can be
easily adapted to other tests. We show that, using Kuiper's test, we
can recover periods in frequency domains where other tests are
completely confused by contamination. We finally search the entire
ROSAT Position-Sensitive Proportional Counter (PSPC) archive for
long periods, and find 28 new periodic-source candidates.
Key words: methods: data analysis -- methods: statistical -- stars: pulsars: general -- X-ray: stars
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