TY - JOUR
T1 - Simulating the Collapse of a Thick Accretion Disk due to a Type i X-Ray Burst from a Neutron Star
AU - Fragile, P. Chris
AU - Ballantyne, David R.
AU - Maccarone, Thomas J.
AU - Witry, Jason W.L.
N1 - Publisher Copyright:
© 2018. The American Astronomical Society. All rights reserved..
PY - 2018/11/10
Y1 - 2018/11/10
N2 - We use two-dimensional, general relativistic, viscous, radiation hydrodynamic simulations to study the impact of a Type I X-ray burst on a hot and geometrically thick accretion disk surrounding an unmagnetized, non-rotating neutron star. The disk is initially consistent with a system in its low/hard spectral state, and is subject to a burst that rises to a peak luminosity of 1038 erg s-1 in 2.05 s. At the peak of the burst, the temperature of the disk has dropped by more than three orders of magnitude and its scale height has gone down by more than one order of magnitude. The simulations show that these effects predominantly happen due to Compton cooling of the hot plasma, and clearly illustrate the potential cooling effects of bursts on accretion disk coronae. In addition, we demonstrate the presence of Poynting-Robertson drag, though it only enhances the mass accretion rate onto the neutron star by a factor of ∼3-4 compared to a simulation with no burst. Simulations such as these are important for building a general understanding of the response of an accretion disk to an intense X-ray impulse, which, in turn, will be crucial for deciphering burst spectra. Detailed analysis of such spectra offers the potential to measure neutron star radii, and hence constrain the neutron star equation of state, but only if the contributions coming from the impacted disk and its associated corona can be understood.
AB - We use two-dimensional, general relativistic, viscous, radiation hydrodynamic simulations to study the impact of a Type I X-ray burst on a hot and geometrically thick accretion disk surrounding an unmagnetized, non-rotating neutron star. The disk is initially consistent with a system in its low/hard spectral state, and is subject to a burst that rises to a peak luminosity of 1038 erg s-1 in 2.05 s. At the peak of the burst, the temperature of the disk has dropped by more than three orders of magnitude and its scale height has gone down by more than one order of magnitude. The simulations show that these effects predominantly happen due to Compton cooling of the hot plasma, and clearly illustrate the potential cooling effects of bursts on accretion disk coronae. In addition, we demonstrate the presence of Poynting-Robertson drag, though it only enhances the mass accretion rate onto the neutron star by a factor of ∼3-4 compared to a simulation with no burst. Simulations such as these are important for building a general understanding of the response of an accretion disk to an intense X-ray impulse, which, in turn, will be crucial for deciphering burst spectra. Detailed analysis of such spectra offers the potential to measure neutron star radii, and hence constrain the neutron star equation of state, but only if the contributions coming from the impacted disk and its associated corona can be understood.
KW - X-rays: binaries
KW - X-rays: bursts
KW - accretion, accretion disks
KW - stars: neutron
UR - http://www.scopus.com/inward/record.url?scp=85056716658&partnerID=8YFLogxK
U2 - 10.3847/2041-8213/aaeb99
DO - 10.3847/2041-8213/aaeb99
M3 - Article
AN - SCOPUS:85056716658
SN - 2041-8205
VL - 867
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 2
M1 - L28
ER -