High-Energy Astrophysics American and Soviet Perspectives/Proceedings from the U.S.-U.S.S.R. Workshop on High-Energy Astrophysics (1991) / Chapter Skim
Currently Skimming:
NEUTRON STARQUAKE MODEL FOR GAMMA-RAY BURSTS
NEUTRON STARQUAKE MODEL FOR GAMMA-RAY BURSTS
Pages 28-38
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 28... ...
Some observational implications are mentioned. INTRODUCTION This is a report on an interpretation of Gray bursts, a phenomenon studied intensively by space scientists in the United States and the Soviet Union, as neutron starquakes.
|
From page 29... ...
It was therefore implicitly assumed that the nuclei would be able to exchange nucleons freely in order to attain this lowest energy state. Under normal conditions, nucleon exchange amongst high Z nuclei requires thermonuclear reactions at a temperature of > 4 x 109K (e.g., BisnovaWi-Kogan and Chechetkin 1979, 1986; Thielemann 1989)
|
From page 30... ...
The crustal composition clearly depends subtly on the detailed history of the star. SLOW ACCRETION AND CRUSTAL LOADING Isolated, old, cold neutron stars moving through the interstellar medium Secrete interstellar gas at a mean rate M ~ 10~0g s~i (e.g., Ostriker e' al.
|
From page 31... ...
For example, at a pressure of p ~ 7 x 1026 dyne cm~2 and a density p ~ 1.5 x 109 dyne cm~3, 56Fe will undergo electron capture to form 56MU which will rapidly capture a second electron to form 56Cr, with an overall energy release of 2.1MeV, of which ~ 1.2MeV will be camed off in neutrinos. The remaining ~ O.9MeV per nucleus is released too slowly to produce significant heating of the interior.
|
From page 32... ...
SEISMIC WAVES There is however, a much faster way for the energy released to reach the surface and this is seismically. There are two types of high frequency waves that can propagate through the crust, pressure waves and shear waves.
|
From page 33... ...
If we consider shear waves in the WE approximation, then in the part of the crust supported by the degeneracy pressure of relativistic electrons, a vertically propagating wave's wavelength will decrease or Zi/2, wee its horizontal displacement will increase or Z-7/4. However, the amplitude cannot increase indefinitely.
|
From page 34... ...
If this is the location of Me ~y-ray emission then only a small fraction of the ,-rays would be re-radiated from the stellar surface as X-rays as me observations seem to require. EMISSION OF GAMMA RAYS We now turn to the component of the whole problem where there is the greatest prospect for confronting present and future observations, and where I have least to suggest!
|
From page 36... ...
OBSERVATIONAL IMPLICATIONS In this report, I have outlined some studies of a particular model for gamma ray bursts involving neutron starquakes. The model, as described, is fairly fragile especially on energetic and demographic grounds.
|
From page 37... ...
A clearer understanding of radio and X-ray pulsar magnetic fields would have immediate implications for the study of gamma ray bursts. We eagerly await the launch and successful deployment of HST, GRO, GRANAT and SPEKTRUM-y which should provide answers to some of these pressing questions.
|
From page 38... ...
Prod Enrico Fermi Summer School in Physics. Academic Press, Ned York Muslimov, JUG., and AI.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.