Analysis of X-ray bursts in 4U 1636-53

Greenwell, Oscar (2018) Analysis of X-ray bursts in 4U 1636-53. Bachelor's Thesis, Astronomy.

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Abstract

I investigated the spectral properties of millihertz quasi-periodic oscillations (mHz QPOs) in the neutron star low-mass X-ray binary (NS LMXB) system 4U 1636-53 using observations taken by the Rossi X-ray Timing Explorer (RXTE). The analysis of all X-ray bursts from this source show that all the type 1 X-ray bursts that were associated with a mHz QPO had a short rising time, were energetic, and also had a short duration. Kolmogorov-Smirnov testing showed to a high degree of certainty that X-ray bursts associated with a mHz QPO are from a different parent population than X-ray bursts that are not associated with a mHz QPO. The features of the X-ray bursts associated with a mHz QPO suggest a link between mHz QPOs and helium rich X-ray bursts. It was also found that in all 39 cases that a mHz QPO was associated to an X-ray burst, the burst had positive convexity. Kolmogorov-Smirnov testing showed to a high degree of certainty that this was not an anomalous result. According to recent models, convexity is related to the ignition site of an X-ray burst on the neutron star surface. My research suggests that in 4U 1636-53 the 39 bursts associated with a mHz QPO, and the marginally stable nuclear burning process responsible for their generation, both happen at the equator of the neutron star. This finding reconciles the disparity between the necessary high mass accretion rate needed to trigger mHz QPOs in theoretical models and the low mass accretion rate that is derived from observations.

Item Type:	Thesis (Bachelor's Thesis)
Supervisor name:	Mendez, R.M.
Degree programme:	Astronomy
Thesis type:	Bachelor's Thesis
Language:	English
Date Deposited:	13 Jul 2018
Last Modified:	18 Jul 2018 12:53
URI:	https://fse.studenttheses.ub.rug.nl/id/eprint/17873

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