1997 Fiscal Year Final Research Report Summary
Studies on the Anomalous Rotation Observed in Millisecond Pulsars
| Project/Area Number |
07640358
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Astronomy
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| Research Institution | RIKKYO UNIVERSITY |
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Principal Investigator |
SHIBAZAKI Noriaki RIKKYO UNIV..DEPT.of SCIENCE・ASSIST.PROF., 理学部, 助教授 (50206124)
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| Co-Investigator(Kenkyū-buntansha) |
HOUSHI Reiun RIKKYO UNIV..DEPT.of SCIENCE・PROF, 理学部, 教授 (70062601)
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| Project Period (FY) |
1995 – 1996
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| Keywords | neutron stars / pulsars / superfluid / frictional instability / braking index |
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| Research Abstract |
The millisecond pulsar 1620-26 in the globular cluster M4 exhibits an unusually large second derivative of the pulse frequency, which togethr with the other pulse timing parameters yields a braking index of 4*10^7. Shibazaki and Mochizuki (1995, ApJ 438,288) have suggested a frictional instability in the crust-superfluid coupling, which sets in below a critical temperature, as a possible cause for this extreme behavior of the pulsar rotation. We have conducted numerical calculations for the thermal and rotational evolution of old neutron stars after being recycled in order to examine this suggestion. We confirm that the rapid growth in internal friction between the crust and the superfluid, caused by frictional instability, can produce an extremely large second derivative in the crust-rotation rate, as observed in PSR 1620-26. We obtain omega_<cr>-10 rad s^<-1> and I_s-3.6*10^<43> g cm^2 respectively for the critical angular-velocity difference and the moment of inertia of the inner crust superfluid from a comparison of our results with the timing parameters observed in PSR 1620-26. These values for omega_<cr> and I_s are in the range expected in current models. We find that a strong pinning region is required in the inner crust in order to explain OMEGA_c of PSR 1620-26.
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