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Old January 13th 19, 05:35 PM posted to sci.astro.research
Thomas 'PointedEars' Lahn
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Default LIGO sensitivity compared with the human eye

Michael Asherman wrote:
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a) LIGO can (easily) see a source at one billion light years
distance which emits the energy of 3 solar masses in 1 second
(like the black hole mergers!)


Does the figure of 3 solar masses include only gravitational energy, or is
it total energy including electromagnetic?


By contrast to the merger of neutron stars (e.g. GW170817), there is no
electromagnetic (EM) energy coming from the merger of black holes (BHs).

*That* they do NOT emit EM radiation is why they are called *black* holes.

The result of such a merger is also a BH whose mass is necessarily
larger than each of the progenitor masses; therefore its Schwarzschild
radius is larger, too (râ=9B = 2 G M/c²), and any EM radiation produced
in the merger is then already beyond the event horizon of the resulting
BH.

The number of 3 Mâ probably refers to the first event detected by
Advanced LIGO, GW150914, where two BHs of masses 29 M_sun and 36 M_sun
merged to form a BH of 62 M_sun (instead of 65 M_sun), emitting the
*equivalent* of 3 M_sun (this is a *mass*, NOT an energy) in gravitational
energy (the energy is E = 3 M_sun c² instead). But that was NOT emitted
in 1 s, but in \_a fraction of a second_/, precisely 20 ms = 0.02 s.

https://www.ligo.caltech.edu/page/press-release-gw150914
https://arxiv.org/abs/1602.03837

https://www.ligo.caltech.edu/page/press-release-gw170817

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