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Old 2020-02-23, 13:18   #2707
Dr Sardonicus
 
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It is also possible that, assuming the neutron stars formed in situ (rather than the binary system being formed by orbital capture), the nebula from two supernovas occurring at different times but spatially nearby might have some distinctive properties.
Unfortunately that is not very likely to occur. The production of the first SN releases so much gravitational energy that the system becomes unbound, often to the extent that the remaining star takes off at high velocity. A number of so-called "runaway stars" have been identified and their high space velocities attributed to this process.
A hot and fast ultra-stripped supernova that likely formed a compact neutron star binary
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Abstract
Compact neutron star binary systems are produced from binary massive stars through stellar evolution involving up to two supernova explosions. The final stages in the formation of these systems have not been directly observed. We report the discovery of iPTF 14gqr (SN 2014ft), a type Ic supernova with a fast-evolving light curve indicating an extremely low ejecta mass (≈ 0.2 solar masses) and low kinetic energy (≈ 2 × 1050 ergs). Early photometry and spectroscopy reveal evidence of shock cooling of an extended helium-rich envelope, likely ejected in an intense pre-explosion mass-loss episode of the progenitor. Taken together, we interpret iPTF 14gqr as evidence for ultra-stripped supernovae that form neutron stars in compact binary systems.
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Old 2020-02-23, 13:38   #2708
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Thanks for the reference.
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Old 2020-02-26, 17:46   #2710
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I would have thought Silbo to be somewhat tricky, especially across the distances in which it was often used.
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Old 2020-03-05, 07:16   #2712
Uncwilly
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There has been a push the last few years for the return of LORAN (with enhancements). This would be a good back-up to GPS. It is supposed to be less susceptible to jamming.
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