COMMON PATTERNS IN THE EVOLUTION BETWEEN THE LUMINOUS NEUTRON STAR LOW-MASS X-RAY BINARY SUBCLASSES
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Fridriksson-2015-COMMON PATTERNS IN T.pdf
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Author(s)
Homan, Jeroen
Fridriksson, Joel Karl
Remillard, Ronald A
Date Issued
August 2015
Journal
The Astrophysical Journal
Publisher
IOP Publishing
Citation
Fridriksson, Joel K., Jeroen Homan, and Ronald A. Remillard. “COMMON PATTERNS IN THE EVOLUTION BETWEEN THE LUMINOUS NEUTRON STAR LOW-MASS X-RAY BINARY SUBCLASSES.” The Astrophysical Journal 809, no. 1 (August 10, 2015): 52. © 2015 The American Astronomical Society
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Final published version
Abstract
The X-ray transient XTE J1701–462 was the first source observed to evolve through all known subclasses of low-magnetic-field neutron star low-mass X-ray binaries (NS-LMXBs), as a result of large changes in its mass accretion rate. To investigate to what extent similar evolution is seen in other NS-LMXBs we have performed a detailed study of the color–color and hardness–intensity diagrams (CDs and HIDs) of Cyg X-2, Cir X-1, and GX 13+1—three luminous X-ray binaries, containing weakly magnetized neutron stars, known to exhibit strong secular changes in their CD/HID tracks. Using the full set of Rossi X-ray Timing Explorer Proportional Counter Array data collected for the sources over the 16 year duration of the mission, we show that Cyg X-2 and Cir X-1 display CD/HID evolution with close similarities to XTE J1701–462. Although GX 13+1 shows behavior that is in some ways unique, it also exhibits similarities to XTE J1701–462, and we conclude that its overall CD/HID properties strongly indicate that it should be classified as a Z source, rather than as an atoll source. We conjecture that the secular evolution of Cyg X-2, Cir X-1, and GX 13+1—illustrated by sequences of CD/HID tracks we construct—arises from changes in the mass accretion rate. Our results strengthen previous suggestions that within single sources Cyg-like Z source behavior takes place at higher luminosities and mass accretion rates than Sco-like Z behavior, and lend support to the notion that the mass accretion rate is the primary physical parameter distinguishing the various NS-LMXB subclasses.
MIT Department
MIT Kavli Institute for Astrophysics and Space Research
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DOI of Published Version
https://doi.org/10.1088/0004-637x/809/1/52
