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Paper: Detection of negative superhumps in a LMXRB -- an end to the long debate on the nature of V1405 Aql (X 1916--053)
Volume: 261, The Physics of Cataclysmic Variables and Related Objects
Page: 527
Authors: Retter, A.; Chou, Y.; Bedding, T.
Abstract: Two similar periodicities (3001 and 3028 s) are known from the X-ray and optical light curves of V1405 Aql, a low mass X-ray Binary (LMXRB). Two competing models have been offered for this system. According to the first, V1405 Aql is a triple system. The second model invokes the presence of an accretion disc that precesses in the apsidal plane, suggesting that the shorter period is the orbital period while the longer is a positive superhump. Re-examination of previously published X-ray data on V1405 Aql reveals an additional periodicity of 2979 s. The periods in V1405 Aql fit well within a newly found relation where the ratio between the negative superhump deficit (over the orbital period) and the positive superhump excess is a function of orbital period in cataclysmic variables that show both types of superhumps. Therefore, the 2979 s period is naturally interpreted as a negative superhump. The recently found 4.8-d period in the X-ray light curve of V1405 Aql is consequently understood as the precession of the accretion disc in the nodal direction. This is the first firm detection of negative superhumps and nodal precession in a LMXRB. Our results thus confirm the classification of V1405 Aql as a permanent superhump system. The 13-year argument on the nature of this intriguing object has thus finally come to an end.
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