New paper: Testing if Fomalhaut b is a neutron star ?>

New paper: Testing if Fomalhaut b is a neutron star

Different scenarios for what Fomalhaut b might be: planet hypothesis in grey, limiting neutron star model in black (temperature ca. 90000 K, distance ca. 13 pc, i.e. located in the background of the Fomalhaut disk), reflected starlight model from a large planetary ring system in green. Emission from the star Fomalhaut for comparison in blue. Reflected starlight is the most likely of the hypotheses. From Poppenhaeger et al. (2017).

Happy to report that our paper has also been picked for presentation on the Astrobites blog:

Here’s the abstract of the paper:

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 FX < 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 LX < 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.

“A Test of the Neutron Star Hypothesis for Fomalhaut b”, published in MNRAS stx565, 04 March 2017, Poppenhaeger, K.; Auchettl, K.; Wolk, S. J.

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