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Title:
The unstable long-term periodicity of Aquila X-1
Authors:
Kitamoto, Shunji; Tsunemi, Hiroshi; Miyamoto, Sigenori; Roussel-Dupre, Diane
Affiliation:
AA(Osaka Univ., Toyonaka, Japan), AB(Osaka Univ., Toyonaka, Japan), AC(Osaka Univ., Toyonaka, Japan), AD(Los Alamos National Lab., NM)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 403, no. 1, p. 315-321. (ApJ Homepage)
Publication Date:
01/1993
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
Accretion Disks, Neutron Stars, Periodic Variations, X Ray Binaries, Light Curve, Sky Surveys (Astronomy), Spaceborne Astronomy, Stellar Flares
DOI:
10.1086/172204
Bibliographic Code:
1993ApJ...403..315K

Abstract

We present the results of the periodicity analysis of 4.5 yr of data observed with the All Sky Monitor (ASM) on-board Ginga and of 10 yr of data accumulated by the Vela 5b satellite. ASM observed three outbursts from Aql X-1 which indicate a 309 day periodicity, but Vela 5b data instead show a 125 day periodicity. This result indicates that the Aql X-1 long-term periodicity is not stable and therefore, cannot be due to some regular mechanism such as orbital motion or precession. This long-term periodicity may be related to some unstable mechanism such as the activity of the companion star or some instability of the accretion disk. However, no models proposed so far can completely explain the observed behavior.

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