2005A&A...438..963B -
Astronomy and Astrophysics, volume 438, 963-972 (2005/8-2)
Further evidence for the presence of a neutron star in 4U 2206+54. INTEGRAL and VLA observations.
BLAY P., RIBO M., NEGUERUELA I., TORREJON J.M., REIG P., CAMERO A., MIRABEL I.F. and REGLERO V.
Abstract (from CDS):
The majority of High Mass X-ray Binaries (HMXBs) behave like X-ray pulsars, revealing that they contain a magnetised neutron star. Among the four HMXBs showing neither pulsations nor the characteristics of accreting black holes, there is the unusual HMXB
4U 2206+54. Here we present contemporaneous high-energy and radio observations of this system conducted with INTEGRAL and the VLA, in order to unveil its nature. The high-energy spectra show clear indications of the presence of an absorption feature at ∼32keV. This is the third high-energy observatory to reveal marginal evidence of this feature, giving strong support to the existence of a cyclotron resonance scattering feature, which implies a magnetic field of 3.6x10
12G. On the other hand, the source is not detected at centimetre radio wavelengths with a 3σ upper limit of 0.039mJy. The expected radio emission for an accreting black hole in the low/hard state, inferred from X-ray flux measurements, would be at least 60 times greater than the measured upper limit. Both results firmly indicate that, in spite of the absence of pulsations,
4U 2206+54 hosts a magnetic accreting neutron star, the first one not to be observed as an X-ray pulsar.
Abstract Copyright:
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Journal keyword(s):
stars: individual: 4U 2206+54 - X-rays: binaries - radio continuum: stars - accretion, accretion disks - magnetic fields - stars: binaries: close
Simbad objects:
12
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