# A Test of the Neutron Star Hypothesis for Fomalhaut b

Source: [A Test of the Neutron Star Hypothesis for Fomalhaut b](<https://www.sota2.com/research/paper/68fa35531e209131ce8a0808>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2025-10-24T21:11:13.349Z

Authors: K. Poppenhaeger, K. Auchettl, S.J. Wolk

Published: 2017-03-09T15:01:54.000Z

## Abstract

Fomalhaut b is a directly imaged object in the debris disk 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 disk. 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 nondetection corresponds to an upper limit on the X-ray flux of Fomalhaut b of F\_X \< 1.3e-14 erg/cm/s^2 in the energy range 0.08-10 keV. For the A-type central star Fomalhaut, we derive an X-ray upper limit of L\_X \< 2e25 erg/s 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 91000 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.

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## Original sources and implementation

[Original paper](<https://arxiv.org/abs/1703.03279>)

[PDF](<https://arxiv.org/pdf/1703.03279.pdf>)