Overview of the EUSO-SPB2 Target of Opportunity program using the Cherenkov Telescope

During the Extreme Universe Space Observatory on a Super Pressure Balloon 2 (EUSO-SPB2) mission, we planned Target of Opportunity (ToO) operations to follow up on possible sources of $\gtrsim 10 \, {\rm PeV}$ neutrinos. The original plan before flight was to point the onboard Cherenkov Telescope (CT) to catch the source's path on the sky just below Earth's horizon. By using the Earth as a tau-neutrino to tau-lepton converter, the CT would then be able to look for optical extensive air shower signals induced by tau-lepton decays in the atmosphere. The CT had a field of view of $6.4^\circ$ vertical $\times$ $12.8^\circ$ horizontal. Possible neutrino source candidates include gamma ray bursts, tidal disruption events and other bursting or flaring sources. In addition, follow-ups of binary neutron star mergers would have been possible after the start of the O4 observation run from LIGO-Virgo-KAGRA. The resulting exposure is modeled using the NuSpaceSim framework in ToO mode. With the launch of the EUSO-SPB2 payload on the 13th May 2023, this summarizes the ToO program status and preliminary data, as available

EUSO-SPB2 Fluorescence Telescope Calibration and Field Tests

The Extreme Universe Space Observatory on a Super Pressure Balloon 2 (EUSO-SPB2), successfully launched from Wanaka, New Zealand on May 13, 2022, is a precursor for a space-based astroparticle observatory such as the Probe Of Extreme Multi-Messenger Astrophysics (POEMMA). EUSO-SPB2 flew two custom telescopes. Both have UV/UV-visible sensitivity and feature Schmidt optics. The Fluorescence Telescope (FT) measures ultra-high energy cosmic rays by looking down. The \v{C}erenkov Telescope (CT) searches for neutrino signatures by looking toward Earth's limb. The two telescopes each have a 1 m diameter entrance pupil and segmented glass mirrors that collect light from extensive air showers at the PeV and EeV-scale. Here we describe the FT telescope optics together with the results of the FT field tests at the Utah Telescope Array (TA) site from August/September 2022. The FT recorded the night sky background, lasers, and artificial point sources. The field tests included an absolute photometric calibration of the FT telescope that is compared to a piece-wise laboratory calibration

Neutrino propagation in the Earth and emerging charged leptons with nuPyProp\texttt{nuPyProp}

Ultra-high-energy neutrinos serve as messengers of some of the highest energy astrophysical environments. Given that neutrinos are neutral and only interact via weak interactions, neutrinos can emerge from sources, traverse astronomical distances, and point back to their origins. Their weak interactions require large target volumes for neutrino detection. Using the Earth as a neutrino converter, terrestrial, sub-orbital, and satellite-based instruments are able to detect signals of neutrino-induced extensive air showers. In this paper, we describe the software code $\texttt{nuPyProp}$ that simulates tau neutrino and muon neutrino interactions in the Earth and predicts the spectrum of the $\tau$-lepton and muons that emerge. The $\texttt{nuPyProp}$ outputs are lookup tables of charged lepton exit probabilities and energies that can be used directly or as inputs to the $\texttt{nuSpaceSim}$ code designed to simulate optical and radio signals from extensive air showers induced by the emerging charged leptons. We describe the inputs to the code, demonstrate its flexibility and show selected results for $\tau$-lepton and muon exit probabilities and energy distributions. The $\texttt{nuPyProp}$ code is open source, available on github.Comment: 42 pages, 21 figures, code available at https://github.com/NuSpaceSim/nupypro

Neutrino Target-of-Opportunity Sky Coverage and Scheduler for EUSO-SPB2

International audienceVery-high-energy neutrinos can be observed by detecting air shower signals. Detection of transienttarget of opportunity (ToO) neutrino sources is part of a broader multimessenger program. TheExtreme Universe Space Observatory on a Super Pressure Balloon 2 (EUSO-SPB2) Mission,launched on May 12, 2023, was equipped with an optical Cherenkov Telescope (CT) designed todetect up-going air showers sourced by Earth-skimming neutrinos that interact near the Earth’slimb. Presented here is an overview of the sky coverage and ToO scheduler software for EUSO-SPB2. By using the balloon trajectory coordinates and setting constraints on the positions of theSun and Moon to ensure dark skies, we can determine if and when a source direction is slightlybelow the Earth’s limb. From a source catalog, CT scheduling and pointing is performed tooptimize the search for high energy neutrinos coming from astrophysical sources. Using historicalsuper pressure balloon trajectories and the EUSO-SPB2 trajectory, sample schedules are described

The Targets of Opportunity Source Catalog for the EUSO-SPB2 Mission

International audienceThe Extreme Universe Space Observatory on a Super Pressure Balloon 2 (EUSO-SPB2) mission was designed to take optical measurements of extensive air showers (EASs) from suborbital space. The EUSO-SPB2 payload includes an optical Cherenkov Telescope (CT), which searches above and below the Earth’s limb. Above the limb, the CT measures Cherenkov light from PeV-scale EASs induced by cosmic rays. Below the limb, the CT searches for upwards-going Cherenkov emission from PeV-scale EASs induced by tau neutrinos, to follow up on astrophysical Targets of Opportunity (ToO). ​​Target candidates include gamma-ray bursts, tidal disruption events, and - after the start of the O4 observation run from Ligo-Virgo-Kagra - binary neutron star mergers. Reported here is the selection and prioritization of relevant ToOs from alert networks such as the General Coordinates Network, Transient Name Server, and Astronomer Telegrams, and the translation to a viewing schedule for EUSO-SPB2. EUSO-SPB2 launched on a NASA super pressure balloon in May of 2023 from Wanaka, NZ

Cardiovascular Outcome of Pediatric Patients With Bi- Allelic (Homozygous) Familial Hypercholesterolemia Before and After Initiation of Multimodal Lipid Lowering Therapy Including Lipoprotein Apheresis

Twenty-four patients with bi-allelic familial hypercholesterolemia commencing chronic lipoprotein apheresis (LA) at a mean age of 8.5 +/- 3.1 years were analysed retrospectively and in part prospectively with a mean follow-up of 17.2 +/- 5.6 years. Mean age at diagnosis was 6.3 +/- 3.4 years. Untreated mean LDL-C concentrations were 752 mg/di +/- 193 mg/di (19.5 mmol/l +/- 5.0 mmol/l). Multimodal lipid lowering therapy including LA resulted in a mean LDL-C concentration of 184 mg/di (4.8 mmol/l), which represents a 75.5% mean reduction. Proprotein convertase subtilisin/kexin type 9-antibodies contributed in 3 patients to LDL-C lowering with 5 patients remaining to be tested. After commencing chronic LA, 16 patients (67%) remained clinically stable with only subclinical findings of atherosclerotic cardiovascular disease (ASCVD), and neither cardiovascular events, nor need for vascular interventions or surgery. In 19 patients (79%), pathologic findings were detected at the aortic valve (AV), which in the majority were mild. AV replacement was required in 2 patients. Mean Lipoprotein(a) concentration was 42.4 mg/dl, 38% had >50 mg/dl. There was no overt correlation of AV pathologies with other ASCVD complications, or Lipoprotein(a) concentration. Physicochemical elimination of LDL particles by LA appears indispensable for patients with bi-allelic familial hypercholesterolemia and severe hypercholesterolemia to maximize the reduction of LDL-C. In conclusion, in this rare patient group regular assessment of both the AV, as well as all arteries accessible by ultrasound should be performed to adjust the intensity of multimodal lipid lowering therapy with the goal to prevent ASCVD events and aortic surgery. (C) 2020 Elsevier Inc. All rights reserved

The EUSO-SPB2 Fluorescence Telescope for the Detection of Ultra-High Energy Cosmic Rays

International audienceThe Extreme Universe Space Observatory on a Super Pressure Balloon 2 (EUSO-SPB2) flew on May 13$^{\text{th}}$ and 14$^{\text{th}}$ of 2023. Consisting of two novel optical telescopes, the payload utilized next-generation instrumentation for the observations of extensive air showers from near space. One instrument, the fluorescence telescope (FT) searched for Ultra-High Energy Cosmic Rays (UHECRs) by recording the atmosphere below the balloon in the near-UV with a 1~$\mu$s time resolution using 108 multi-anode photomultiplier tubes with a total of 6,912 channels. Validated by pre-flight measurements during a field campaign, the energy threshold was estimated around 2~EeV with an expected event rate of approximately 1 event per 10 hours of observation. Based on the limited time afloat, the expected number of UHECR observations throughout the flight is between 0 and 2. Consistent with this expectation, no UHECR candidate events have been found. The majority of events appear to be detector artifacts that were not rejected properly due to a shortened commissioning phase. Despite the earlier-than-expected termination of the flight, data were recorded which provide insights into the detectors stability in the near-space environment as well as the diffuse ultraviolet emissivity of the atmosphere, both of which are impactful to future experiments

The EUSO-SPB2 Fluorescence Telescope for the Detection of Ultra-High Energy Cosmic Rays

International audienceThe Extreme Universe Space Observatory on a Super Pressure Balloon 2 (EUSO-SPB2) flew on May 13$^{\text{th}}$ and 14$^{\text{th}}$ of 2023. Consisting of two novel optical telescopes, the payload utilized next-generation instrumentation for the observations of extensive air showers from near space. One instrument, the fluorescence telescope (FT) searched for Ultra-High Energy Cosmic Rays (UHECRs) by recording the atmosphere below the balloon in the near-UV with a 1~$\mu$s time resolution using 108 multi-anode photomultiplier tubes with a total of 6,912 channels. Validated by pre-flight measurements during a field campaign, the energy threshold was estimated around 2~EeV with an expected event rate of approximately 1 event per 10 hours of observation. Based on the limited time afloat, the expected number of UHECR observations throughout the flight is between 0 and 2. Consistent with this expectation, no UHECR candidate events have been found. The majority of events appear to be detector artifacts that were not rejected properly due to a shortened commissioning phase. Despite the earlier-than-expected termination of the flight, data were recorded which provide insights into the detectors stability in the near-space environment as well as the diffuse ultraviolet emissivity of the atmosphere, both of which are impactful to future experiments