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Rapid Spin-Up Episodes in the Wind-Fed Accreting Pulsar GX 301-2

Koh, Danny T. and Bildsten, Lars and Chakrabarty, Deepto and Nelson, Robert W. and Prince, Thomas A. and Vaughan, Brian A. and Finger, Mark H. and Wilson, Robert B. and Rubin, Bradley C. (1997) Rapid Spin-Up Episodes in the Wind-Fed Accreting Pulsar GX 301-2. Astrophysical Journal, 479 . pp. 933-947. ISSN 0004-637X. doi:10.1086/303929.

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The accreting pulsar GX 301-2 (P = 680 s) has been observed continuously by the large-area detectors of the Burst and Transient Source Experiment (BATSE) instrument on the Compton Gamma Ray Observatory since 1991 April 5. Orbital parameters determined from these data are consistent with previous measurements, with improved accuracy in the current orbital epoch. The most striking features in the pulsar frequency history are two steady and rapid spin-up episodes, with ν˙~(3-5)×10^(-12) Hz s^(-1), each lasting for about 30 days. They probably represent the formation of transient accretion disks in this wind-fed pulsar. Except for these spin-up episodes, there are virtually no net changes in the neutron star spin frequency on long timescales. We suggest that the long-term spin-up trend observed since 1984 (ν˙~2×10^(-13) Hz s^(-1)) may be due entirely to brief (~20 days) spin-up episodes similar to those we have discovered. We assess different accretion models and their ability to explain the orbital phase dependence of the observed flux. In addition to the previously observed preperiastron peak at orbital phase 0.956 +/- 0.022, we also find a smaller peak close to apastron at orbital phase 0.498 +/- 0.057. We show that if the companion star's effective temperature is less than 22,000 K, then it must have a mass M_c < 70 M_⊙ and a radius R_c < 85 R_⊙ so as not to overfill the tidal lobe at periastron. In order not to overflow the Roche lobe at periastron, the corresponding values are M_c < 55 M_⊙ and R_c < 68 R_⊙. These constraints are nearly at odds with the reclassification by Kaper et al. of the companion as a B1 Ia + hypergiant.

Item Type:Article
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URLURL TypeDescription
Chakrabarty, Deepto0000-0001-8804-8946
Prince, Thomas A.0000-0002-8850-3627
Additional Information:© 1997 American Astronomical Society. Received 1996 September 13; accepted 1996 November 13. We thank Dong Lai for helpful discussions, Colleen Wilson for analyzing occultation data for pulsed fraction determination, and the anonymous referee for insightful comments. This work was funded in part by NASA grants NAG 5-1458 and NAGW-4517. L. B. was supported by Caltech's Lee A. DuBridge Fellowship, funded by the Weingart Foundation and the Alfred P. Sloan Foundation. D. C. was supported by a NASA GSRP Graduate Fellowship under grant NGT-51184. The NASA Compton Postdoctoral Fellowship program has supported L. B. (NAG 5-2666), D. C. (NAG 5-3109), and R. N. (NAG 5-3119).
Group:Space Radiation Laboratory
Funding AgencyGrant Number
NASANAG 5-1458
Lee A. DuBridge FellowshipUNSPECIFIED
Weingart FoundationUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
NASA Compton FellowshipNAG 5-2666
NASA Compton FellowshipNAG 5-3109
NASA Compton FellowshipNAG 5-3119
Subject Keywords:binaries: close; pulsars: individual (GX 301–2); stars: rotation; X-rays: stars
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Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory1997-03
Record Number:CaltechAUTHORS:20140703-224332587
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46853
Deposited By: Deborah Miles
Deposited On:14 Jul 2014 16:04
Last Modified:10 Nov 2021 17:30

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