Rubin-LSST

Abstract:

We present ultraviolet to infrared observations of the extraordinary Type IIn supernova 2023zkd (SN 2023zkd). Photometrically, it exhibits persistent and luminous precursor emission spanning ∼4 yr preceding discovery (Mr ≈ −15 mag, 1500 days in the observer frame), followed by a secondary stage of gradual brightening in its final year. Post-discovery, it exhibits two photometric peaks of comparable brightness (Mr ≲ −18.7 mag and Mr ≈ −18.4 mag, respectively) separated by 240 days. Spectroscopically, SN 2023zkd exhibits highly asymmetric and multicomponent Balmer and He I profiles that we attribute to ejecta interaction with fast-moving (1000–2000 km s−1) He-rich polar material and slow-moving (∼400 km s−1) equatorially distributed H-rich material. He II features also appear during the second light curve peak and evolve rapidly. Shock-driven models fit to the multiband photometry suggest that the event is powered by interaction with ∼5–6 M⊙ of CSM, with 2–3 M⊙ associated with each light curve peak, expelled during mass-loss episodes ∼3–4 yr and ∼1–2 yr prior to explosion. The observed precursor emission, combined with the extreme mass-loss rates required to power each light curve peak, favors either super-Eddington accretion onto a black hole or multiple long-lived eruptions from a massive star to luminosities that have not been previously observed. We consider multiple progenitor scenarios for SN 2023zkd, and find that the brightening optical precursor and inferred explosion properties are most consistent with a massive (MZAMS ≥ 30 M⊙) and partially stripped He star undergoing an instability-induced merger with a black hole companion.

Abstract:

We describe updated scientific goals for the wide-field, millimeter-wave survey that will be produced by the Simons Observatory (SO). Significant upgrades to the 6-meter SO Large Aperture Telescope (LAT) are expected to be complete by 2028, and will include a doubled mapping speed with 30,000 new detectors and an automated data reduction pipeline. In addition, a new photovoltaic array will supply most of the observatory's power. The LAT survey will cover about 60% of the sky at a regular observing cadence, with five times the angular resolution and ten times the map depth of the Planck satellite. The science goals are to: (1) determine the physical conditions in the early universe and constrain the existence of new light particles; (2) measure the integrated distribution of mass, electron pressure, and electron momentum in the late-time universe, and, in combination with optical surveys, determine the neutrino mass and the effects of dark energy via tomographic measurements of the growth of structure at redshifts z ≲ 3; (3) measure the distribution of electron density and pressure around galaxy groups and clusters, and calibrate the effects of energy input from galaxy formation on the surrounding environment; (4) produce a sample of more than 30,000 galaxy clusters, and more than 100,000 extragalactic millimeter sources, including regularly sampled AGN light-curves, to study these sources and their emission physics; (5) measure the polarized emission from magnetically aligned dust grains in our Galaxy, to study the properties of dust and the role of magnetic fields in star formation; (6) constrain asteroid regoliths, search for Trans-Neptunian Objects, and either detect or eliminate large portions of the phase space in the search for Planet 9; and (7) provide a powerful new window into the transient universe on time scales of minutes to years, concurrent with observations from the Vera C. Rubin Observatory of overlapping sky.

Abstract:

This paper presents searches for the direct pair production of charged light-flavour sleptons, each decaying into a stable neutralino and an associated Standard Model lepton. The analyses focus on the challenging “corridor” region, where the mass difference, Δ𝑚, between the slepton (𝑒˜ or 𝜇˜) and the lightest neutralino (𝜒˜ 0 1 ) is less or similar to the mass of the 𝑊 boson, 𝑚(𝑊), with the aim to close a persistent gap in sensitivity to models with Δ𝑚 ≲ 𝑚(𝑊). Events are required to contain a high-energy jet, significant missing transverse momentum, and two same-flavour opposite-sign leptons (𝑒 or 𝜇). The analysis uses 𝑝 𝑝 collision data at √ 𝑠 = 13 TeV recorded by the ATLAS detector, corresponding to an integrated luminosity of 140 fb−1 . Several kinematic selections are applied, including a set of boosted decision trees. These are each optimised for different Δ𝑚 to provide expected sensitivity for the first time across the full Δ𝑚 corridor. The results are generally consistent with the Standard Model, with the most significant deviations observed with a local significance of 2.0 𝜎 in the selectron search, and 2.4 𝜎 in the smuon search. While these deviations weaken the observed exclusion reach in some parts of the signal parameter space, the previously present sensitivity gap to this corridor is largely reduced. Constraints at the 95% confidence level are set on simplified models of selectron and smuon pair production, where selectrons (smuons) with masses up to 300 (350) GeV can be excluded for Δ𝑚 between 2 GeV and 100 GeV.