Hostname: page-component-cd9895bd7-gxg78 Total loading time: 0 Render date: 2024-12-12T16:44:44.707Z Has data issue: false hasContentIssue false

On the Dramatic Spin-Up/Spin-Down Torque Reversals in BATSE Observations of Accretion Powered Pulsars

Published online by Cambridge University Press:  12 April 2016

Robert W. Nelson
Affiliation:
Space Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125
Brian A. Vaughan
Affiliation:
Space Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125
Lars Bildsten*
Affiliation:
Space Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125
Deepto Chakrabarty*
Affiliation:
Space Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125
Danny T. Koh
Affiliation:
Space Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125
Thomas A. Prince
Affiliation:
Space Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125
Mark H. Finger
Affiliation:
Space Science Laboratory, NASA/Marshall Space Flight Center, Huntsville, AL 35812
Robert B. Wilson
Affiliation:
Space Science Laboratory, NASA/Marshall Space Flight Center, Huntsville, AL 35812
Bradley C. Rubin
Affiliation:
Space Science Laboratory, NASA/Marshall Space Flight Center, Huntsville, AL 35812
*
2 Current address: Department of Physics and Department of Astronomy, University of California, Berkeley, CA 94720
3 Current address: Center for Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

X-ray pulsars are the only accreting magnetic stars where rotation torques induced by accretion are large enough to be measured on short timescales ~ days. They are thus unique laboratories for studying the interaction between an accretion disk and a stellar magnetosphere. We describe 5 years of continuous pulsar timing observations by the BATSE instrument on GRO which paint a strikingly different picture of pulsar spin behavior than understood from the previous 20 years of sparse observations. In particular, we find that more than half of the persistent pulsars we observe undergo dramatic torque reversals, switching suddenly between extended periods of steady spin-up and steady spin-down. Moreover, variations in pulsed flux are anticorrelated with torque in at least one system undergoing secular spin-down, GX1+4. This behavior contradicts standard accretion torque theory (Ghosh and Lamb 1979). A simple – albeit unconventional – hypothesis which naturally explains these observations is that the disks in these systems somehow alternate between epochs of prograde and retrograde rotation.

Type
Part 6. Disk-Star-Magnetosphere Interaction
Copyright
Copyright © Astronomical Society of the Pacific 1997

Footnotes

1

Theoretical Astrophysics, California Institute of Technology, Pasadena, CA 91104

2

Universities Space Research Association

References

Campbell, C.G. MNRAS, 229, 405 Google Scholar
Chakrabarty, D. et al. 1997a, ApJ, 474, in pressGoogle Scholar
Chakrabarty, D. et al. 1997b, ApJ, in preparationGoogle Scholar
Elsner, R.F., & Lamb, F.K. 1977, ApJ, 215, 897 Google Scholar
Finger, M.H., Wilson, R.B. & Fishman, G.J. 1994, in Compton Gamma-Ray Observatory: AIP Conference Proceedings 280, NY, AIP Press, 304 Google Scholar
Fryxell, B.A., & Taam, R.E. 1988, ApJ, 335, 862 CrossRefGoogle Scholar
Ghosh, P 1995, MNRAS, 272, 763 Google Scholar
Ghosh, P, & Lamb, F.K. 1979, ApJ, 234, 296 Google Scholar
Konigl, A 1991, ApJ, 370, L39 Google Scholar
Makishima, K. et. al. 1988 Nature, 333, 746 CrossRefGoogle Scholar
Pringle, J.E. & Rees, M.J. 1972 A&A, 21, 1 Google Scholar
Rappaport, S. & Joss, P. 1977 Nature, 266, 683 CrossRefGoogle Scholar
Rubin, et al. 1997, ApJ, in preparationGoogle Scholar
Wang, Y.-M. 1987, A&A, 183, 257 Google Scholar
Wang, Y.-M. 1995, ApJ, 449, L153 Google Scholar
Warner, B 1990, Ap&SS, 164, 79 Google Scholar
White, N. 1988, Nature, 266, p 708 CrossRefGoogle Scholar
Vaughan, et al. 1997, ApJ, in preparationGoogle Scholar