SPECTRAL STATES OF XTE J1701 – 462: LINK BETWEEN Z AND ATOLL SOURCES
We have analyzed 866 Rossi X-ray Timing Explorer observations of the 2006–2007 outburst of the accreting neutron star XTE J1701 −462, during which the source evolves from super-Eddington luminosities to quiescence. The X-ray color evolution first resembles the Cyg X-2 subgroup of Z sources, with fre...
| Main Authors: | , , |
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| Other Authors: | |
| Format: | Article |
| Language: | en_US |
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IOP Publishing
2015
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| Online Access: | http://hdl.handle.net/1721.1/96027 |
| _version_ | 1826195218730319872 |
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| author | Lin, Dacheng Homan, Jeroen Remillard, Ronald A |
| author2 | MIT Kavli Institute for Astrophysics and Space Research |
| author_facet | MIT Kavli Institute for Astrophysics and Space Research Lin, Dacheng Homan, Jeroen Remillard, Ronald A |
| author_sort | Lin, Dacheng |
| collection | MIT |
| description | We have analyzed 866 Rossi X-ray Timing Explorer observations of the 2006–2007 outburst of the accreting neutron star XTE J1701 −462, during which the source evolves from super-Eddington luminosities to quiescence. The X-ray color evolution first resembles the Cyg X-2 subgroup of Z sources, with frequent excursions on the horizontal and normal branches (HB/NB). The source then decays and evolves to the Sco X-1 subgroup, with increasing focus on the flaring branch (FB) and the lower vertex of the "Z." Finally, the FB subsides, and the source transforms into an atoll source, with the lower vertex evolving to the atoll soft state. Spectral analyses suggest that the atoll stage is characterized by a constant inner disk radius, while the Z stages exhibit a luminosity-dependent expansion of the inner disk, which we interpret as effects related to the local Eddington limit. Contrary to the view that the mass accretion rate ([dot over m]) changes along the Z, we find that changes in [dot over m] are instead responsible for the secular evolution of the Z and the subclasses. Motion along the Z branches appears to be caused by three different mechanisms that may operate at roughly constant . For the Sco X-1-like Z stage, we find that the FB is an instability track that proceeds off the lower vertex when the inner disk radius shrinks from the value set by the X-ray luminosity toward the value measured for the atoll soft state. Excursions up the NB occur when the apparent size of the boundary layer increases while the disk exhibits little change. The HB is associated with Comptonization of the disk emission. The Z branches for the Cyg X-2-like stage are more complicated, and their origin is unclear. Finally, our spectral results lead us to hypothesize that the lower and upper Z vertices correspond to a standard thin disk and a slim disk, respectively. |
| first_indexed | 2024-09-23T10:09:16Z |
| format | Article |
| id | mit-1721.1/96027 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T10:09:16Z |
| publishDate | 2015 |
| publisher | IOP Publishing |
| record_format | dspace |
| spelling | mit-1721.1/960272022-09-30T19:12:14Z SPECTRAL STATES OF XTE J1701 – 462: LINK BETWEEN Z AND ATOLL SOURCES Lin, Dacheng Homan, Jeroen Remillard, Ronald A MIT Kavli Institute for Astrophysics and Space Research Lin, Dacheng Remillard, Ronald Alan Homan, Jeroen We have analyzed 866 Rossi X-ray Timing Explorer observations of the 2006–2007 outburst of the accreting neutron star XTE J1701 −462, during which the source evolves from super-Eddington luminosities to quiescence. The X-ray color evolution first resembles the Cyg X-2 subgroup of Z sources, with frequent excursions on the horizontal and normal branches (HB/NB). The source then decays and evolves to the Sco X-1 subgroup, with increasing focus on the flaring branch (FB) and the lower vertex of the "Z." Finally, the FB subsides, and the source transforms into an atoll source, with the lower vertex evolving to the atoll soft state. Spectral analyses suggest that the atoll stage is characterized by a constant inner disk radius, while the Z stages exhibit a luminosity-dependent expansion of the inner disk, which we interpret as effects related to the local Eddington limit. Contrary to the view that the mass accretion rate ([dot over m]) changes along the Z, we find that changes in [dot over m] are instead responsible for the secular evolution of the Z and the subclasses. Motion along the Z branches appears to be caused by three different mechanisms that may operate at roughly constant . For the Sco X-1-like Z stage, we find that the FB is an instability track that proceeds off the lower vertex when the inner disk radius shrinks from the value set by the X-ray luminosity toward the value measured for the atoll soft state. Excursions up the NB occur when the apparent size of the boundary layer increases while the disk exhibits little change. The HB is associated with Comptonization of the disk emission. The Z branches for the Cyg X-2-like stage are more complicated, and their origin is unclear. Finally, our spectral results lead us to hypothesize that the lower and upper Z vertices correspond to a standard thin disk and a slim disk, respectively. High Energy Astrophysics Science Archive Research Center (Goddard Space Flight Center) 2015-03-16T14:13:44Z 2015-03-16T14:13:44Z 2009-04 2008-09 Article http://purl.org/eprint/type/JournalArticle 0004-637X 1538-4357 http://hdl.handle.net/1721.1/96027 Lin, Dacheng, Ronald A. Remillard, and Jeroen Homan. “SPECTRAL STATES OF XTE J1701 – 462: LINK BETWEEN Z AND ATOLL SOURCES.” The Astrophysical Journal 696, no. 2 (April 23, 2009): 1257–1277. © 2009 The American Astronomical Society. en_US http://dx.doi.org/10.1088/0004-637x/696/2/1257 Astrophysical Journal Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf IOP Publishing American Astronomical Society |
| spellingShingle | Lin, Dacheng Homan, Jeroen Remillard, Ronald A SPECTRAL STATES OF XTE J1701 – 462: LINK BETWEEN Z AND ATOLL SOURCES |
| title | SPECTRAL STATES OF XTE J1701 – 462: LINK BETWEEN Z AND ATOLL SOURCES |
| title_full | SPECTRAL STATES OF XTE J1701 – 462: LINK BETWEEN Z AND ATOLL SOURCES |
| title_fullStr | SPECTRAL STATES OF XTE J1701 – 462: LINK BETWEEN Z AND ATOLL SOURCES |
| title_full_unstemmed | SPECTRAL STATES OF XTE J1701 – 462: LINK BETWEEN Z AND ATOLL SOURCES |
| title_short | SPECTRAL STATES OF XTE J1701 – 462: LINK BETWEEN Z AND ATOLL SOURCES |
| title_sort | spectral states of xte j1701 462 link between z and atoll sources |
| url | http://hdl.handle.net/1721.1/96027 |
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