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The Cooling of The Neutron Star in The Cassiopeia A Supernova Remnant Open Access


Other title
High Energy Astrophysics
Cooling Neutron Stars
Type of item
Degree grantor
University of Alberta
Author or creator
Elshamouty, Khaled
Supervisor and department
Heinke, Craig
Examining committee member and department
Heinke, Craig (Physics)
Sivakoff, Gregory (Physics)
Morsink, Sharon (Physics)
Sanchez-Azofeifa, Arturo (Earth and Atmospheric Sciences)
Department of Physics

Date accepted
Graduation date
Master of Science
Degree level
A young neutron star cools mainly via neutrino emission from the star's core. Thus, the thermal evolution of neutron stars reflects changes in their core, constraining temperature-sensitive properties such as the composition of the core and the envelope of the neutron star. The neutron star in the Cassiopeia A supernova remnant (Cas A NS) is the youngest known, at only 330 years old. Heinke & Ho (2010) reported a drop of 3.6\% in its surface temperature (21\% drop in observed flux) from Chandra ACIS-S X-ray data on the Cas A NS between 2000 and 2009. This is the only young neutron star to have been observed to cool over time, permitting a clearer picture of its thermal evolution. This drop was interpreted as enhanced neutrino emission due to a superfluid transition in the core (Page et al. 2011), Shternin et al. (2011)). Here I present analysis of data from another Chandra detector (HRC-S) over the same time period to test the cooling rate. I used the best current estimates of the effective area of this detector and the spectrum of the Cas A NS to infer the countrates corresponding to various NS temperatures, and thus to compute the temperature drop from the countrate change. The temperature drop inferred from HRC-S observations is more uncertain, but is significantly less than the temperature drop inferred from ACIS-S. Observations using Chandra's other detectors suffer a variety of systematic uncertainties. The result suggests that the temperature drop could be half as large as originally suggested, but that the Cas A NS's temperature is indeed decreasing.
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