Scientists spot a 'kilonova' flash so bright they can barely explain it

rod

Oct 22, 2019
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The arXiv paper cited says "The NIR counterpart, revealed by our HST observations at a rest-frame time of ≈2.3 days, has a luminosity of ≈(1.3−1.7)×10^42 erg s−1. This is substantially lower than on-axis short GRB afterglow detections, but is a factor of ≈8-17 more luminous than the kilonova of GW170817, and significantly more luminous than any kilonova candidate for which comparable observations exist.", https://arxiv.org/abs/2008.08593

Considering some 10^42 erg s^-1 released, that is still some blast. I am glad the Earth is not orbiting in this location :)
 
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Nov 12, 2020
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The arXiv paper cited says "The NIR counterpart, revealed by our HST observations at a rest-frame time of ≈2.3 days, has a luminosity of ≈(1.3−1.7)×10^42 erg s−1. This is substantially lower than on-axis short GRB afterglow detections, but is a factor of ≈8-17 more luminous than the kilonova of GW170817, and significantly more luminous than any kilonova candidate for which comparable observations exist.", https://arxiv.org/abs/2008.08593

Considering some 10^42 erg s^-1 released, that is still some blast. I am glad the Earth is not orbiting in this location :)
That's nothing...
Back in my days, 10^77 erg s−1 was pretty common.
 
Nifty video, explaining the artist's conception, here: https://www.sciencealert.com/we-may-have-just-witnessed-the-birth-of-a-magnetar-from-colliding-neutron-stars .

I am glad the Earth is not orbiting in this location :)
:)

A similar context here:

An international team of researchers led by Dr. Diederik Kruijssen at the Center for Astronomy at the University of Heidelberg (ZAH) and Dr. Joel Pfeffer at Liverpool John Moores University has now managed to infer the Milky Way's merger history and reconstruct its family tree, using only its globular clusters.
[ https://phys.org/news/2020-11-family-tree-milky-deciphered.html ]

From the paper Conclusions:

Focusing on the assembly history of the Milky Way, our results add to a growing body of evidence that the Milky Way experienced an unusual path to adolescence. Not only did it assemble unusually quickly for its mass, but it also experienced a striking paucity of major accretion events, with only a handful of minor mergers shaping the Galactic stellar halo. The fact that it grew most of its stellar mass through secular processes and in-situ star formation implies that it may not be the most representative example for understanding the evolution and assembly of the galaxy population, but is a correspondingly more pleasant environment to live in.
By the way, I recommend reading the somewhat technical abstract and then looking at the more detailed figure 9 of the merger tree to get a quick look-see on the putative merger history. Paper here: https://arxiv.org/pdf/2003.01119.pdf .
 
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FWIW, this is just in on an interesting application of kilonova research to improve the method of multimesssenger observation of the universe expansion rate:

We’re not quite sure how old we are — cosmologically, that is. The main methods scientists use to measure the age of the universe don’t agree with each other. Many physicists hope a newly applicable technique that incorporates gravitational-wave observations will solve this age discrepancy once and for all.

But this new technique may not be as straightforward as researchers hoped. A new paper by Hsin-Yu Chen, a postdoc at the MIT Kavli Institute for Astrophysics and Space Research, describes a potential problem ...
Using telescopes, it is easy to measure how fast these galaxies move away from us, but it's difficult to measure their distance. But when observing gravitational-waves signals, it is the other way around: We can measure distance directly from the gravitational-wave observation, but it’s hard to measure how fast these gravitational-wave sources are flying away from us. For that part, we need help from traditional telescopes; we need to capture the light produced by the gravitational-wave sources.

To measure the age of the universe in this newer way, you need these two components: gravitational waves and light. It is actually a very straightforward method that astronomers consider rather clean.
If we don't know what the geometry of the emission is, then we might preferentially observe one specific viewing angle and lead to a bias in our measurement.
... the gravitational waves give us some idea of the viewing angle of the sources we observe. By combining observation of the kilonova with this viewing angle constraint from the gravitational-wave side, it’s possible that after many, many observations we could figure out whether there is a bias or not.
[ https://news.mit.edu/2020/3-questions-hsin-yu-chen-treading-lightly-when-dating-universe-1113 ]

It's not all that bad. The paper abstract discuss systematic biases that are 2-3 % or so, much less than the current 9 % tension between expansion rate measurements.
 
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rod

Oct 22, 2019
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Torbjorn, interesting posts and info. I have a number of reports showing H0 ranging from recent measurements, 67.9 to 82 km/s/Mpc which changes the Hubble time calculation too.
 

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