On the Dynamics of Ultra Compact X-ray Binaries: 4U 1850-087, 4U 0513-40 and M15 X-2

Abstract

In this work we extend our dynamical study of Ultra Compact X-ray Binaries (UCXB) 4U 1820-30 from Prodan and Murray 2012 to three more UCXBs in globular clusters: 4U 1850-087, 4U 0513-40 and M15 X-2. These three UCXBs have orbital periods < 20 mins. Two of them, 4U 1850-087 and 4U 0513-40, have suspected luminosity variations of order of ~ 1yr. There is insufficient observational data to make any statements regarding the long periodicity in the light curve of M15 X-2 at this point. The properties of these three systems are quite similar to 4U 1820-30, which prompt us to model their dynamics in the same manner. As in the case of 4U 1820-30, we interpret the suspected long periods as the period of small oscillations around a stable fixed point in the Kozai resonance. We provide a lower limit on the tidal dissipation factor Q which is in agreement with results obtained for the case of 4U 1820-30.

ApJ accepted, 11 pages, 13 figures

References in corpus (3)

• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• Hot Jupiters in binary star systems
• The superorbital variability and triple nature of the X-ray source 4U 1820-303

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• Ultra-compact binary pulsars as continuous dual-line gravitational wave sources
• Connecting the m-dots: accretion rates and thermonuclear burst recurrence times on neutron stars and white dwarfs
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