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UV and X-ray observations of the neutron star LMXB EXO 0748-676 in its quiescent state
- Source :
- MNRAS 501, 1453 (2021, original manuscript) and MNRAS 502, 2826 (2021, erratum)
- Publication Year :
- 2021
-
Abstract
- The accretion behaviour in low-mass X-ray binaries (LMXBs) at low luminosities, especially at <E34 erg/s, is not well known. This is an important regime to study to obtain a complete understanding of the accretion process in LMXBs, and to determine if systems that host neutron stars with accretion-heated crusts can be used probe the physics of dense matter (which requires their quiescent thermal emission to be uncontaminated by residual accretion). Here we examine ultraviolet (UV) and X-ray data obtained when EXO 0748-676, a crust-cooling source, was in quiescence. Our Hubble Space Telescope spectroscopy observations do not detect the far-UV continuum emission, but do reveal one strong emission line, Civ. The line is relatively broad (>3500 km/s), which could indicate that it results from an outflow such as a pulsar wind. By studying several epochs of X-ray and near-UV data obtained with XMM-Newton, we find no clear indication that the emission in the two wavebands is connected. Moreover, the luminosity ratio of Lx/Luv >100 is much higher than that observed from neutron star LMXBs that exhibit low-level accretion in quiescence. Taken together, this suggests that the UV and X-ray emission of EXO 0748-676 may have different origins, and that thermal emission from crust-cooling of the neutron star, rather than ongoing low-level accretion, may be dominating the observed quiescent X-ray flux evolution of this LMXB.<br />Comment: 10 pages, 1 table, 4 figures, published in MNRAS. This arXiv version includes the changes described in the paper erratum
- Subjects :
- Astrophysics - High Energy Astrophysical Phenomena
Subjects
Details
- Database :
- arXiv
- Journal :
- MNRAS 501, 1453 (2021, original manuscript) and MNRAS 502, 2826 (2021, erratum)
- Publication Type :
- Report
- Accession number :
- edsarx.2103.06278
- Document Type :
- Working Paper
- Full Text :
- https://doi.org/10.1093/mnras/staa3734,