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Review the #JWSTbit.ly/3z3qhHR

Promotional image for AAS244: The 244th meeting of the American Astronomical Society, Madison, Wisconsin, 9-13 June 2024
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KLkellylepo.bsky.social

Goodbye #AAS244#AAS245!

Statue of the University of Wisconsin–Madison badger mascot, in front of lake Mendota at sunset. There is a line of patchy clouds in the sky.
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KLkellylepo.bsky.social

Final plenary of the conference: Scanning the X-ray Sky for Dark Matter by Kerstin Perez, Columbia University. What is dark matter? A new kind of particle? Using the annoying stray light in NuStar to search for signals of sterile neutrinos, a dark matter candidate. Only upper limits so far #AAS244

The (challenge is crossed out) FUN of astroparticle searches! Common challenge = minimize/constrain astrophysical background, maximize predicted dark matter signal. No matter what, measuring something new about the universe! A schematic graph shows flux vs energy. A blue line slopes downward. It is labeled "Background (choice of target, particle signature)". A red line is flat and then peaks to the left, above the blue line. It is labeled "Dark Matter annihilation". The distance above the blue line is labeled "σν, dark matter profile/density, boost factors, galactic/solar propagation...". This shows a signal from dark matter above the background.
The sky as a laboratory Three scenarios are depected. 1) Two dark matter particles collide in a box labeled "New (BSM) physics". It produces stable particles. Charged particles follow a circuitous path to us. Choose particle signature with low or well-constrained predicted background, need precise modelling of cosmic-ray propagation, interaction cross sections, etc. 2) A dark matter particle enters a box labeled "New (BSM) physics". It produces a photon which goes in a straight line to us. Choose observational target with high DM density (Galactic center, dwarf galaxies), low or well-constrained predicted astrophysical background. 3) Dark matter streams out of a star. It interacts with interstellar material/fields. Uncertainties due to stellar model, inter- stellar material/fields
Adapting NuSTAR as a large-aperture DM telescope. • "0-bounce" photons that bypass the optics are typically a major background. • Novel analysis exploits >10x increase in efficiency for slowly-varying, diffuse signa.l Image of the full NuStar field of view with an orange shaded area that looks like a pacman. It has a 3.5 deg radius. Image of the NuStar telescope, which looks a little like a dog bone, with the mirrors on one end, a long mast, and the instruments on the other end. Arrow points to mirrors: "High-resolution, small field-of-view (0.05deg²), snapshots of the sky"
Towards fully probing the sterile neutrino dark matter window? Many points on a map of the sky. "Full-sky" analyses: 332 (!) Ms of NuSTAR data + 547 (!!) Ms of XMM-Newton data Foster et al. 2102.02207 (2021) Roach et al. 2207.04572 (2023) New! Krivonos et al. 2405.17861 (2024) Graph showing possible mixing of neutrinos vs neutrino mass. Most of the area is shaded in, ruling out those areas. Limits reach the edge of theoretical predictions of simplest models, leaving only a small room left to explore.
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KLkellylepo.bsky.social

Justin Vandenbroucke: Do novae produce neutrinos? Probably, but searches of IceCube neutrino data don't find anything. Jessie Thwaites: Preparing for the expected T CrB nova. It's closer, in a more sensitive area of the sky for IceCube, and has a short eruption, so they are optimistic. #AAS244

The IceCube Neutrino Observatory * Sensitive to neutrinos at MeV, GeV, TeV, PeV, EeV scales * >99% up time * Full sky (both hemispheres) capability * Better sensitivity in North than South (at TeV scale) * Bi-directional real-time observatory Diagram of a spherical IceCube detector Diagram of the full observatory showing a cut-away view of the ice top, through the Antarctic ice, down to the bedrock. The bedrock is 2820 m below the ice. There are 80 stings, arranged in a hexagon pattern that contain sensors. They go from the ice top to the bedrock.
Neutrinos from novae? • It is likely that all novae are gamma-ray sources • The gamma-ray emission is likely hadronic • Therefore, novae are likely neutrino sources • And likely also cosmic-ray sources • "I have enough faith in the hadronic model that [neutrinos are] a pretty sure bet." - Brian Metzger, March 6, 2020 email • Protons colliding with photons or other protons produce pions • Neutral pions decay to gamma rays • Charged pions decay to neutrinos • High-energy neutrinos are a smoking gun of high-energy hadrons
Prospects for T CrB neutrino search. Graph showing the sensitivity of the IceCube detectors vs change in time. A map of sky coordinates and the sensitivity of the detector. IceCube is more sensitive to T CrB than the nova RS Oph.
Summary and looking forward * Novae are an exciting potential transient neutrino source class * Neutrinos from nearby Galactic novae are able to be probed by IceCube, to investigate hadronic particle acceleration in nova shocks. * T Coronae Borealis is nearby, bright, and predicted to erupt any time now. Photo of the IceCube building at the south pole during the Antarctic night, with the Milky Way and an aurora.
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KLkellylepo.bsky.social

First session: The Powerful Shocks in Novae V: Revisiting Novae with a Multi-messenger Approach Kirill Sokolovsky: NuSTAR observations of classical novae show depleted iron (or enhanced CNO). X-ray light curves don't have periodic changes like in visible light -> X-rays are made further out #AAS244

NuSTAR lightcurves and shock location • Some variability on ~10 hour timescale • No periodic modulation (orbital/WD rotation) • No obvious correlation with optical Shocked region is large compared to the binary? Not directly related to optical - below the photosphere?
Summary • NuSTAR spectra of all detected novae look alike • Consistent with single-temperature CNO-enriched plasma • Heavily absorbed - shocks are deep within ejecta • But no fast variability, so not too close to the WD Lx/Ly <<1, defying explanation
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