OP May 20119
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A.E.I.O.U. - Antarticae est imperare orbi universo
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Article: Black hole may have swallowed neutron star, say astronomers
Scientists analyse whether gravitational wave detectors picked up signs of collision
Astronomers may have spotted a neutron star being swallowed by a black hole for the first time, marked by a belch of gravitational waves rippling across the cosmos.
If confirmed, the detection by the twin Ligo detectors in the US and the Virgo detector in Italy would be the first evidence that black holes and neutron stars can pair up in binary systems. The observations could also reveal new details about the nature of such dramatic mergers, including whether the neutron star was ripped apart before crossing the black hole's threshold or whether it slid seamlessly into oblivion.
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Article: Gravitational waves hint at detection of black hole eating star
LIGO and Virgo observatories have spotted ripples from what could be the first-ever detection of this long-sought event.
Gravitational waves might have just delivered the first sighting of a black hole devouring a neutron star. If confirmed, this would be the first evidence of the existence of such binary systems. The news came just a day after astronomers detected gravitational waves from a merger of two neutron stars for only the second time.
At 15:22:17 UTC on 26 April, the twin detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO)in the United States and the Virgo observatory in Italy reported a burst of waves of an unusual type. Astronomers are still analysing the data and performing computer simulations to interpret them.
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Article: Gravitational-wave Detectors Come Online, Find Possible Black Hole-Neutron Star Crash
By: Monica Young | May 3, 2019
143
Only a month into a new observing run, gravitational-wave observatories have announced five new signals — one of which could turn out to be a black hole swallowing a neutron star.
This image from a simulation shows a neutron star merging with a black hole. Most matter falls into the black hole, but some is left outside the event horizon — ripe for follow-up observations.
F. Foucart (U. of New Hampshire) / SXS Collaboration / Classical and Quantum Gravity, 34, 4 (2017)
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It wasn't so long ago that scientists announced the very first detection of gravitational waves. Now, only three years later, major improvements to both the Laser Interferometer Gravitational-wave Observatory (LIGO) in the U.S. and the Virgo observatory near Pisa, Italy, are promising to make those discoveries commonplace.
In the first month of their third observing run, which runs from April 2019 to April 2020, LIGO and Virgo have already detected five gravitational wave signals, ripples in spacetime that began their journey in cataclysmic crashes billions of light-years away. These are candidate events, which means they're not fully vetted yet. Indeed, one of these candidates might turn out to be a fluke, but two others appear to be bona fide black hole mergers, while a fourth appears to be a neutron star crash. The most tantalizing, though, is the fifth and most recent mashup: a black hole swallowing a neutron star.
Designation (based on date detected) Likely Source False alarm rate*
S190408an Two black holes one in 100 years
S190412m Two black holes one in 2 x 1019years
S190421ar Two black holes one in 2 years
S190425z Two neutron stars one in 70,000 years
S190426c Black hole and neutron star one in 1 year, 7 months
* The false alarm rate describes how often we'd expect to see a similar signal by chance, rather than due to a real event. Gravitational-wave detectors have been running for just over a year total, between three observing runs, so events with equivalent false alarm rates may turn out to be flukes.
LIGO / Virgo / NASA / Leo Singer (Milky Way image: Axel Mellinger)
Unlike the previous discoveries, which were carefully vetted and confirmed as real sources before being announced to the public, we're hearing about these new events right away. That's because finding electromagnetic radiation (i.e., light) from these gravitational-wave sources is crucial to understanding them. Immediate announcements means that telescopes on the ground and in space can set to observing the sky near these gravitational-wave sources at once.
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This image from a simulation shows a neutron star merging with a black hole. Most matter falls into the black hole, but some is left outside the event horizon — ripe for follow-up observations. 
The LIGO and Virgo teams estimate that S190425z, a signal likely from two merging neutron stars, originated from the region outlined on the sky map. Because only LIGO Livingston and Virgo saw the signal (LIGO Hanford was offline at the time), its localization was not very precise, covering about 18 percent of the sky. 
