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          Institute: MPI für Astrophysik     Collection: High Energy Astrophysics at MPA     Display Documents

ID: 12126.0, MPI für Astrophysik / High Energy Astrophysics at MPA
Hiding in plain sight: Chandra observations of the quiescent neutron star 4U 2129+47 in eclipse
Authors:Nowak, M. A.; Heinz, S.; Begelman, M. C.
Date of Publication (YYYY-MM-DD):2002
Title of Journal:The Astrophysical Journal
Journal Abbrev.:Astrophys. J.
Issue / Number:2
Start Page:778
End Page:788
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:During a previous outburst phase, the neutron star 4U 2129+47 exhibited evidence for a spatially extended accretion disk corona via broad, partial X-ray eclipses occurring periodically on the 5.24 hr orbit. Since 1983, however, 4U 2129+47 has entered a quiescent state several orders of magnitude fainter. We have performed a 37 ks (approximate totwo binary orbits) Chandra observation of 4U 2129+47 to determine whether an extended coronal structure also exists in quiescence. Total eclipses are found, and the rapidity of the eclipse ingress and egress is used to place upper limits on the size of the X-ray source. The spectrum is found to be comprised of a soft component plus a fairly hard power-law tail. The former is seen to be sinusoidally modulated over the orbital period in a manner consistent with neutral column variations, possibly due to the interaction of an accretion stream with a (small) disk about the neutron star. We fit realistic neutron star atmosphere models to the soft spectra and comment on the consistency of the spectra with cooling neutron star models. It has been previously suggested that the 4U 2129+47 system is a hierarchical triple, with the outer body being an F star. We use differential astrometry to show that the X-ray point source and F star are spatially coincident to within 0."1. We further compare newly determined upper limits for the extrinsic neutral column to the reddening of the F star. Finally, we discuss how future X-ray observations can further constrain models of quiescent neutron star emission as well as directly verify the triple hypothesis.
Free Keywords:aaccretion; accretion disks; stars : individual (4U 2129+47); stars : neutron; X-rays : stars
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astrophysik
External Affiliations:MIT, Ctr Space Res, 77 Massachusetts Ave, Cambridge, MA 02139; USA; MIT, Ctr Space Res, Cambridge, MA 02139 USA; Max Planck Inst Astrophys, D-85740 Garching, Germany; Univ Colorado, JILA, Boulder, CO 80309 USA; Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA; Yale Astron Dept, New Haven, CT USA
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