[HN Gopher] Photons, neutrinos, and gravitational-wave astronomy
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Photons, neutrinos, and gravitational-wave astronomy
Author : ninocan
Score : 44 points
Date : 2025-04-03 04:00 UTC (3 days ago)
(HTM) web link (www.as.arizona.edu)
(TXT) w3m dump (www.as.arizona.edu)
| MeteorMarc wrote:
| Figure 3 is really nice!
| perihelions wrote:
| _" Made with Emacs 28.1 - Org mode 9.5.2"_
| joshvm wrote:
| Unless I'm missing something - do the notes cover neutrino
| astronomy somewhere else? Aside from the general discussion on
| stellar evolution. Shame, because the detection of pre-optical
| neutrino emission from 1987A by Kamiokande (and others) was a
| fantastic theoretical confirmation. Essentially when the core
| collapses, the environment around the surroundings are optically
| opaque, but the neutrinos sail on through so you'd expect to see
| them before the photons.
|
| https://ui.adsabs.harvard.edu/abs/1987ApJ...318L..63B/abstra...
|
| I would recommend Telescope in the Ice as one of the best
| introductions to modern neutrino detectors - why and where
| they're built. Also provides a good insight into how a big
| collaboration is formed, funded and operates. I've worked for
| IceCube so I'm somewhat biased, but the book is great just for
| the history.
|
| IceCube has an entire processing pathway (on ice) that is
| specifically designed to trigger on a supernova detection. One of
| the very few science results that would page us, and why uptime
| is absolutely critical to the experiment. On the one hand, we
| can't point the detector and we don't know where the signal will
| come from, so it's not predictable (and it's highly transient).
| On the other, becuase the burst happens shortly before the
| optical, we can use neutrinos to trigger optical observations as
| fast as possible - pretty much the whole observing community will
| drop what they're doing if a star blows up.
|
| I believe we'd expect the whole flux through the detector to bump
| up above the background, at least at IceCube. PDF:
| https://iopscience.iop.org/article/10.1088/1742-6596/309/1/0...
| pfdietz wrote:
| > Essentially when the core collapses, the environment around
| the surroundings are optically opaque, but the neutrinos sail
| on through so you'd expect to see them before the photons.
|
| Also, the source, the hot nascent neutron star, is optically
| thick to neutrinos, so it radiates them very fiercely. Almost
| all the energy of the collapse goes into neutrino radiation.
| mathren wrote:
| These are my notes for a course in stellar physics that I am
| teaching, the full set of lecture notes is here
| https://www.as.arizona.edu/~mrenzo/courses/lectures.html and
| includes some more on neutrino cooling in evolved stars, core
| collapse physics, and a guest lecture (also with notes that I
| am NOT the author of) on high energy neutrinos, but if you want
| to learn specifically about neutrino astrophysics this is
| certainly not the most comprehensive resource.
|
| Re neutrinos, I would also mention KM3NET which looks for
| Cherenkov flashes in the Mediterranean sea used as a detector,
| which recently detected some extremely high energy neutrinos,
| e.g.:
|
| https://www.nature.com/articles/s41586-024-08543-1
| throwawaymaths wrote:
| After so many observations why is multi messenger still n=1?
| magicalhippo wrote:
| Hopefully an expert can chime in, but from what I've gathered
| we were fairly lucky to catch that one.
|
| First off, it needs to happen when enough detectors are
| operational to get a good localization. Back then there were
| just three and all happened to be operational during the event.
| Just two won't cut it, as you can see from this[1] using just
| LIGO data versus this[2] which also includes VIRGO data for
| GW170817[3].
|
| Next the detectors have a limited mass window they're sensitive
| to, with low frequencies (high mass) limited by seismic
| isolation and high frequencies (low mass) due to quantum
| effects. And the noise floor at peak sensitivity limits the
| maximum range to the objects.
|
| Current sensitivity means we're at the edge of the binary-
| neutron star population, so we wouldn't expect to see many of
| those.
|
| With more detectors coming online soon and existing ones
| getting further upgraded, presumably it'll not be such a rare
| event in the future.
|
| A nice recent talk which touches on this was given at PIRSA
| here[4].
|
| [1]:
| https://dcc.ligo.org/public/0146/G1701985/001/bayestar_no_vi...
|
| [2]: https://dcc.ligo.org/public/0146/G1701985/001/bayestar.png
|
| [3]: https://dcc.ligo.org/LIGO-P170817/public
|
| [4]: https://pirsa.org/25030061
| mathren wrote:
| Author here: this are my notes on what I mean to say in class,
| the website contain my whole course.
|
| This particular lecture is still "in prep", in fact the section
| "the problem" is just a bullet point and a figure. All other
| lectures are a bit more polished.
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