Session F02: The 2023 NASA Astrophysics MIDEX/MO Phase A Studies: A glimpse of the pending future

MoonBEAM: A Beyond Earth-orbit Gamma-ray Burst Detector for Multi-Messenger Astronomy

Multi-messenger observations of both gravitational wave and neutrino events critically depend upon identifying and localizing gamma-ray transients. At present, these types of observations are largely performed by satellites in low Earth-orbit whose capabilities are constrained by Earth blockage and highly variable particle backgrounds. The Moon Burst Energetics All-sky Monitor (MoonBEAM) is a gamma-ray mission that solves these limitations by using a cislunar orbit to observe the entire sky instantaneously. I will present an overview of the MoonBEAM mission and describe how it can provide the observations needed to construct a comprehensive picture of compact mergers and energetic phenomena, which addresses a key goal of the Astro2020 decadal survey.   

LEAP – The LargE Area burst Polarimeter on the ISS

The LargE Area burst Polarimeter (LEAP) is proposed as an International Space Station external payload, launching in 2027, and was selected by NASA for a Phase A concept study. LEAP will make the fist high-fidelity polarization and spectroscopic measurements of gamma-ray bursts (GRBs). GRBs are highly luminous explosions, involving relativistic, jetted outflows and play an important role in the multimessenger era. Basic questions about the physics of GRBs have yet to be answered. These include: 1.) The jet composition: Is the energy in the jet carried by magnetic fields or baryons? 2.) The structure of the magnetic fields in the emission region: Are they ordered or oriented randomly? 3.) What is the emission mechanism: Is it synchrotron radiation or some modified thermal process? We argue that past spectral and temporal observations have been maximally exploited for addressing these questions and a fundamentally different approach is needed to achieve significant progress. Sensitive polarization measurements will open up a new dimension for GRBs and will naturally address the above questions. LEAP’s baseline mission requires observation of at least 65 GRBs with a sensitivity defined by a minimum detectable polarization (MDP) of 30%. The current LEAP design is expected to trigger on approximately 400 GRBs, with about 86 of those having an MDP < 30%. The LEAP design enables a broad range of secondary science such as polarization sensitive observations of short GRBs jointly with gravitational waves, magnetar bursts, accreting pulsars and Solar flares. LEAP will open a new window into the nature of the most energetic phenomena in the universe with gamma-ray polarization.   

Exploring the Dynamic Ultraviolet Universe with UVEX

The Ultraviolet Explorer (UVEX) is a Medium Class Explorer (MIDEX) mission, currently undergoing a competitive Phase A study, that will explore the Ultraviolet Universe. UVEX is built on three scientific pillars: (1) Exploring the low-mass, low-metallicity galaxy frontier; (II) Providing new views of the dynamic universe, and (III) Leaving a broad legacy of modern, deep synoptic surveys adding to the panchromatic richness of 21st century astrophysics. Exploring the low-mass galaxy frontier is forefront because low-mass galaxies dominate the local (z < 0.3) population, and the processes taking place in their low-metallicity, actively star-forming environments are largely unexplored. UVEX observations will provide crucial templates for understanding the high-redshift population of low-mass, low-metallicity systems discovered by ALMA and JWST. UVEX opens new views on the dynamic universe by discovering and diagnosing the early UV aftermaths of gravitational-wave-discovered neutron star mergers. Through rapid spectroscopy, it will probe the evolutionary history of massive stars in the moments before their demise, and provide a resource for the entire community for target of opportunity UV spectroscopic follow up of transients. The UVEX deep, synoptic allsky surveys will likely be its most important legacy, replacing GALEX with a survey that: is cadenced; includes the Galactic Plane and Magellanic Clouds; provides rapid transient alerts to the community; and achieves depths and resolution matching modern optical/IR surveys with Rubin, Roman and Euclid. We will describe the UVEX science goals and objectives, and provide an overview of the mission and its implementation.

    

Studying the Fast, Furious and Forming Universe in the X-ray and UV with STAR-X

STAR-X is a MIDEX mission that was proposed to NASA HQ in December 2021 and that was selected for a competitive Phase A study in August 2022.  Comprising an X-ray Telescope (XRT) provided by GSFC and MIT, a UV Telescope (UVT) provided by the University of Colorado, and a spacecraft provided by Ball Aerospace, STAR-X is designed to conduct time-domain surveys and to respond rapidly to transient events discovered by other observatories such as LIGO, Rubin/LSST, Roman/WFIRST, and SKA.   STAR-X is a timely response to Astro2020’s recommendation for a space-based, sustaining time-domain and multi-messenger program.    The science theme for the mission is “to study the fast, furious and forming Universe.” The “Fast” theme covers transients such as supernova shock breakouts,  electromagnetic radiation from neutron star-neutron star mergers detected by ground-based gravitational wave detectors and stellar flares that affect exoplanet atmospheres.  The “Furious” theme covers large and rapid amounts of accretion onto black holes, so as to understand rapid black hole growth at earlier times in our Universe, and involves study of Tidal Disruption Events of stars around black holes and time-domain reverberation studies of accretion disk geometry.   The third pillar, “Forming”, concerns the growth of large scale structure in the Universe, covering the growth of massive galaxy clusters from their epoch of formation at z>3 to their ongoing growth from the filaments of the cosmic web at the current time.  This talk will cover the mission architecture, performance, and the science case.    More information on STAR-X, including the full team list, is available at http://star-x.xraydeep.org/