210
D. K. Galloway and L. Keek
5.9 Nuclear Experimental Physics . .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. 249
5.10 Summary and Outlook . .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. 251
References . .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. 252
Abstract Type-I X-ray bursts arise from unstable thermonuclear burning of
accreted fuel on the surface of neutron stars. In this chapter we review the
fundamental physics of the burning processes, and summarise the observational,
numerical, and nuclear experimental progress over the preceding decade. We
describe the current understanding of the conditions that lead to burst ignition,
and the influence of the burst fuel on the observational characteristics. We provide
an overview of the processes which shape the burst X-ray spectrum, including
the observationally elusive discrete spectral features. We report on the studies of
timing behaviour related to nuclear burning, including burst oscillations and mHz
quasi-periodic oscillations. We describe the increasing role of nuclear experimental
physics in the interpretation of astrophysical data and models. We survey the
simulation projects that have taken place to date, and chart the increasing dialogue
between modellers, observers, and nuclear experimentalists. Finally, we identify
some open problems with prospects of a resolution within the timescale of the next
such review.
5.1 Overview
Thermonuclear (type-I) bursts are triggered by unstable ignition of accreted fuel
on the surface of neutron stars (e.g. [68]). The first such events were detected in
1975 from the ultracompact binary 3A 1820−30 (in the globular cluster NGC 6624)
with the Small Astronomy Satellite 3 (SAS-3) and the Astronomical Netherlands
Satellite (ANS; [26, 59]). Since then, a growing population of bursters (currently
numbered at 115 1 ) has been observed by almost every major X-ray satellite,
sometimes for a substantial fraction of their mission duration. These events remain
a high observational priority, as a key diagnostic of the nature of newly-discovered
transient X-ray binaries. In addition, thermonuclear bursts have been increasingly
exploited to constrain the fundamental properties of the host neutron stars, and to
probe the accretion environment of the binary system.
In this chapter we focus on the research areas that have been of highest priority
to both observers and theorists in the previous decade. These areas include the
fundamentals of ignition of different types of bursts; the study of “long” bursts,
both intermediate-duration (He) bursts and superbursts (the latter thought to burn
carbon, rather than the H/He fuel for short bursts); the study of burst oscillations;
the physics of the formation of the burst spectra, and the focus on deriving neutronstar parameters from them; the searches for, and theoretical predictions of, discrete
1 http://burst.sci.monash.edu/sources.
D. K. Galloway and L. Keek
5.9 Nuclear Experimental Physics . .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. 249
5.10 Summary and Outlook . .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. 251
References . .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. 252
Abstract Type-I X-ray bursts arise from unstable thermonuclear burning of
accreted fuel on the surface of neutron stars. In this chapter we review the
fundamental physics of the burning processes, and summarise the observational,
numerical, and nuclear experimental progress over the preceding decade. We
describe the current understanding of the conditions that lead to burst ignition,
and the influence of the burst fuel on the observational characteristics. We provide
an overview of the processes which shape the burst X-ray spectrum, including
the observationally elusive discrete spectral features. We report on the studies of
timing behaviour related to nuclear burning, including burst oscillations and mHz
quasi-periodic oscillations. We describe the increasing role of nuclear experimental
physics in the interpretation of astrophysical data and models. We survey the
simulation projects that have taken place to date, and chart the increasing dialogue
between modellers, observers, and nuclear experimentalists. Finally, we identify
some open problems with prospects of a resolution within the timescale of the next
such review.
5.1 Overview
Thermonuclear (type-I) bursts are triggered by unstable ignition of accreted fuel
on the surface of neutron stars (e.g. [68]). The first such events were detected in
1975 from the ultracompact binary 3A 1820−30 (in the globular cluster NGC 6624)
with the Small Astronomy Satellite 3 (SAS-3) and the Astronomical Netherlands
Satellite (ANS; [26, 59]). Since then, a growing population of bursters (currently
numbered at 115 1 ) has been observed by almost every major X-ray satellite,
sometimes for a substantial fraction of their mission duration. These events remain
a high observational priority, as a key diagnostic of the nature of newly-discovered
transient X-ray binaries. In addition, thermonuclear bursts have been increasingly
exploited to constrain the fundamental properties of the host neutron stars, and to
probe the accretion environment of the binary system.
In this chapter we focus on the research areas that have been of highest priority
to both observers and theorists in the previous decade. These areas include the
fundamentals of ignition of different types of bursts; the study of “long” bursts,
both intermediate-duration (He) bursts and superbursts (the latter thought to burn
carbon, rather than the H/He fuel for short bursts); the study of burst oscillations;
the physics of the formation of the burst spectra, and the focus on deriving neutronstar parameters from them; the searches for, and theoretical predictions of, discrete
1 http://burst.sci.monash.edu/sources.