2017MNRAS.468.4018P -
Mon. Not. R. Astron. Soc., 468, 4018-4024 (2017/July-2)
A test of the neutron star hypothesis for Fomalhaut b.
POPPENHAEGER K., AUCHETTL K. and WOLK S.J.
Abstract (from CDS):
Fomalhaut b is a directly imaged object in the debris disc of the star Fomalhaut. It has been hypothesized to be a planet; however, there are issues with the observed colours of the object that do not fit planetary models. An alternative hypothesis is that the object is a neutron star in the near fore- or background of Fomalhaut's disc. We test if Fomalhaut b could be a neutron star using X-ray observations with Chandra's HRC-I instrument in the energy range of 0.08-10 keV. We do not detect X-ray emission from either Fomalhaut b or the star Fomalhaut itself. Our non-detection corresponds to an upper limit on the X-ray flux of Fomalhaut b of FX < 1.3 x 10–14 erg cm–2 s–1 in the energy range 0.08-10 keV. For the A-type central star Fomalhaut, we derive an X-ray upper limit of LX < 2.0 x 1025 erg s–1 in the energy range 0.08-10 keV. Fomalhaut b's X-ray non-detection constrains the parameter space for a possible neutron star significantly, implying surface temperatures lower than 91 000 K and distances closer than 13.3 pc to the Solar system. In addition, we find that reflected starlight from the central star fits the available optical detections of Fomalhaut b; a smaller planet with a large ring system might explain such a scenario.
Abstract Copyright:
© 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
Journal keyword(s):
stars: individual: Fomalhaut - stars: neutron - planetary systems - X-rays: individual: Fomalhaut b - X-rays: individual: Fomalhaut b
Simbad objects:
10
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