MS 1603.6+2600: an accretion disc corona source? |
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Authors: | P G Jonker M van der Klis C Kouveliotou M Méndez W H G Lewin T Belloni |
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Institution: | Institute of Astronomy, Madingley Road, Cambridge CB3 0HA;Astronomical Institute "Anton Pannekoek", University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, the Netherlands;SD 50, Space Science Research Center, National Space Science and Technology Center, 320, Sparkman Drive, Huntsville, AL 35805, USA;Nasa's Marshall Space Flight Center, AL 35812, USA;SRON, National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, the Netherlands;Department of Physics and Center for Space Research, Massachusetts Institute of Technology, Cambridge, MA 02138, USA;INAF, Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate, Italy |
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Abstract: | We have observed the eclipsing low-mass X-ray binary MS 1603.6+2600 with Chandra for 7 ks. The X-ray spectrum is well fit with a single absorbed power law with an index of ~2. We find a clear sinusoidal modulation in the X-ray light curve with a period of 1.7 ± 0.2 h , consistent with the period of 1.85 h found before. However, no (partial) eclipses were found. We argue that if the X-ray flare observed in earlier X-ray observations was a type I X-ray burst, then the source can only be an accretion disc corona source at a distance of ~11–24 kpc (implying a height above the Galactic disc of ~8–17 kpc). It has also been proposed in the literature that MS 1603.76+2600 is a dipper at ~75 kpc. We argue that, in this dipper scenario, the observed optical properties of MS 1603.6+2600 are difficult to reconcile with the optical properties one would expect on the basis of comparisons with other high-inclination, low-mass X-ray binaries, unless the X-ray flare was not a type I X-ray burst. In that case, the source can be a nearby soft X-ray transient accreting at a quiescent rate, as was proposed by Hakala et al., or a high-inclination source at ~15–20 kpc. |
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Keywords: | accretion accretion discs stars: individual: MS 1603 6+2600 stars: neutron X-rays: stars |
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