The superorbital variability and triple nature of the X-ray source 4U 1820-303

Details The superorbital variability and triple nature of the X-ray source 4U 1820-303 The superorbital variability and triple nature of the X-ray source 4U 1820-303

2007-01-16

arxiv.org/abs/astro-ph/0701470v2

Mon.Not.Roy.Astron.Soc.377:1006-1016,2007

Astronomy and Astrophysics

Astrophysics

MNRAS, in press

Scientific paper

10.1111/j.1365-2966.2007.11686.x

We perform a comprehensive analysis of the superorbital modulation in the ultracompact X-ray source 4U 1820-303, consisting of a white dwarf accreting onto a neutron star. Based on RXTE data, we measure the fractional amplitude of the source superorbital variability (with a 170-d quasi-period) in the folded and averaged light curves, and find it to be by a factor of about 2. As proposed before, the superorbital variability can be explained by oscillations of the binary eccentricity. We now present detailed calculations of the eccentricity-dependent flow through the inner Lagrangian point, and find a maximum of the eccentricity of about 0.004 is sufficient to explain the observed fractional amplitude. We then study hierarchical triple models yielding the required quasi-periodic eccentricity oscillations through the Kozai process. We find the resulting theoretical light curves to match well the observed ones. We constrain the ratio of the semimajor axes of the outer and inner systems, the component masses, and the inclination angle between the inner and outer orbits. Last but not least, we discover a remarkable and puzzling synchronization between the observed period of the superorbital variability (equal to the period of the eccentricity oscillations in our model) and the period of the general-relativistic periastron precession of the binary.

Affiliated with

Also associated with

No associations

Rating

The superorbital variability and triple nature of the X-ray source 4U 1820-303 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with The superorbital variability and triple nature of the X-ray source 4U 1820-303, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The superorbital variability and triple nature of the X-ray source 4U 1820-303 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-188324