MS 1603.6+2600: an Accretion Disc Corona source?

Abstract

We have observed the eclipsing low-mass X-ray binary MS1603.6+2600 with Chandra for 7 ksec. The X-ray spectrum is well fit with a single absorbed powerlaw with an index of ~2. We find a clear sinusoidal modulation in the X-ray lightcurve with a period of 1.7+-0.2 hours, consistent with the period of 1.85 hours 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 between ~11-24 kpc (implying a height above the Galactic disk of ~8-17 kpc). It has also been proposed in the literature that MS1603.76+2600 is a dipper at ~75 kpc. We argue that in this dipper scenario the observed optical properties of MS1603.6+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.(1998) or a high inclination source at ~15-20 kpc.

6 pages, 3 figures, accepted by MNRAS

References in corpus (9)

• The USNO-B Catalog
• Photospheric radius expansion X-ray bursts as standard candles
• The X-ray Spectra of Black Hole X-ray Novae in Quiescence as Measured by Chandra
• An XMM-Newton study of the 401 Hz accreting pulsar SAX J1808.4-3658 in quiescence
• Discovery of an X-ray pulsar in the low-mass X-ray binary 2A 1822-371
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• Chandra follow-up of bursters with low persistent emission
• Hiding in Plain Sight: Chandra Observations of the Quiescent Neutron Star 4U 2129+47 in Eclipse
• ASCA Observation of MS 1603.6+2600 (=UW Coronae Borealis): a Dipping Low-Mass X-ray Binary in the Outer Halo?

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• Delimiting the black hole mass in the X-ray transient MAXI J1659-152 with H$\alpha$ spectroscopy
• Discovery of Optical Bursts from MS1603.6+2600 = UW CrB
• The X-ray Pulsar 2A 1822-371 as a Super Eddington source
• Light Curve Morphology Study of UW CrB -- Evidence for a 5 d Superorbital Period