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Hard X-Ray Detection and Timing of Accretion-Powered Pulsars with BATSE


Chakrabarty, Deepto (1996) Hard X-Ray Detection and Timing of Accretion-Powered Pulsars with BATSE. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/6K2P-2A91.


The BATSE all-sky monitor on the Compton Gamma Ray Observatory is a superb tool for the study of accretion-powered pulsars. In the first part of this thesis, I describe its capabilities for hard X-ray observations above 20 keV, present techniques for timing analysis of the BATSE data, and discuss general statistical issues for the detection of pulsed periodic signals in both the time and frequency domains. BATSE's 1-day pulsed sensitivity in the 20-60 keV range is ≈ 15 mCrab for pulse periods 2 s ≲ Ppulse ≲ 400 s, covering most of the known accreting pulsars. Its sensitivity degrades substantially outside of this range.

In the second part of this thesis, I present the results of several science investigations applying these techniques. Half the 42 known accreting pulsars have been detected with BATSE and are monitored whenever they are active. Except for a few which lie outside of BATSE's sensitivity range, the rest are all transient sources which may eventually be detected in outburst. The detected systems include four new transients discovered by BATSE, one of which is discussed in detail. A new technique used to localize this source, GRO J1948+32, is described.

Observations of the 38-s pulsar OAO 1657-415 discovered that it is in a 10.4-d eccentric orbit and undergoes regular X-ray eclipses by its massive companion, making it only the seventh known eclipsing X-ray pulsar. Constraints placed by the pulsar mass function and the eclipse duration indicate that the undetected binary companion must be an OB supergiant. If the companion can be identified and its orbital velocity measured, the neutron star mass can be determined.

The 7.7-s pulsar 4U 1626-67 was found to be in an extended spin-down state, ending over a decade of rapid, steady spin-up. It is only the second steady-state disk accreter known to have undergone a torque reversal. The other, the 2-min pulsar GX 1+4, underwent two torque reversals during our observations and is detected up to 160 keV. During spin-down, we find that pulsed flux and torque in GX 1+4 are anticorrelated, the opposite of what is predicted by the usual theories of magnetic accretion torques.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Neutron Stars, Pulsars
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Prince, Thomas A.
Group:Space Radiation Laboratory, Astronomy Department
Thesis Committee:
  • Prince, Thomas A. (chair)
  • Blandford, Roger D.
  • Schmidt, Maarten
  • Soifer, B. Thomas
Defense Date:21 December 1995
Non-Caltech Author Email:deepto (AT)
Funding AgencyGrant Number
NASA Graduate Student Research Program FellowshipNGT-51184
NASA Compton Observatory Guest Observer ProgramNAG 5-1458
NASA Long-Term Space Astrophysics ProgramNAGW-4517
Record Number:CaltechETD:etd-09022008-132322
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Chapter 4. adapted for Chapter 5 and Appendix G.
Chakrabarty, Deepto0000-0001-8804-8946
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3313
Deposited By: Imported from ETD-db
Deposited On:10 Sep 2008
Last Modified:10 Mar 2020 23:09

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