ASCENT: a balloon-borne hard x-ray imaging spectroscopy telescope using transition edge sensor microcalorimeter detectors

Abstract

Core collapse supernovae are thought to be one of the main sources in the galaxy of elements heavier than iron. Understanding the origin of the elements is thus tightly linked to our understanding of the explosion mechanism of supernovae and supernova nucleosynthesis. X-ray and gamma-ray observations of young supernova remnants, combined with improved theoretical modeling, have resulted in enormous improvements in our knowledge of these events. The isotope 44 Ti is one of the most sensitive probes of the innermost regions of the core collapse engine, and its spatial and velocity distribution are key observables. Hard X-ray imaging spectroscopy with the Nuclear Spectroscopic Telescope Array (NuSTAR) has provided new insights into the structure of the supernova remnant Cassiopeia A (Cas A), establishing the convective nature of the supernova engine. However, many questions about the details of this engine remain. We present here the concept for a balloon-borne follow-up mission called ASCENT (A SuperConducting ENergetic x-ray Telescope). ASCENT uses transition edge sensor gamma-ray microcalorimeter detectors with a demonstrated 55 eV Full Width Half Maximum (FWHM) energy resolution at 97 keV. This 8-16-fold improvement in energy resolution over NuSTAR will allow high resolution imaging and spectroscopy of the 44 Ti emission. This will allow a detailed reconstruction of gamma-ray line redshifts, widths, and shapes, allowing us to address questions such as: What is the source of the neutron star "kicks"? What is the dominant production pathway for 44 Ti? Is the engine of Cas A unique?

Multimessenger Diagnostics of the Engine behind Core-collapse Supernovae

“…The current and funded suite of gamma-ray telescopes, including Fermi (Atwood et al 2009), Integral (Ubertini et al 2003) and COSI (Tomsick et al 2019), are all capable of these transient observations and will detect nearby supernova events, but not out to this distance. A number of mission concepts have been proposed to increase the distance of detection of radioactive decay emission from supernovae: AMEGO-X (Caputo et al 2022), LOX (Miller et al 2019;Miller et al 2023), and ASCENT (Kislat et al 2023). Similarly, detectors such as the UltraSAT (Ben-Ami et al 2022) and CASTOR (Ménesguen et al 2017) satellites are designed to increase the number of shock-breakout detections in the UV.…”

511-CAM mission: a pointed 511 keV gamma-ray telescope with a focal plane detector made of stacked transition edge sensor microcalorimeter arrays

“…34 This setup draws from the designs of the XL-Calibur hard x-ray polarimetry mission scheduled for launches in summer 2022 and 2024, as well as the ASCENT mission proposed to the 2020 Pioneers opportunity. 62,63 ASCENT employs a single but larger area SLEDGEHAMMER-type focal plane detector to map the 44 Ti hard x-ray lines from supernova remnants, such as Cas-A.…”

Metal-metal attachment of absorbers for Gamma-Ray TES

“…For the focal plane instrumentation, ASCENT will use TES microcalorimeter gamma-ray detectors similar to the system 'Spectrometer to Leverage Extensive Development of Gamma-ray TESs for Huge Arrays using Microwave Multiplexed Enabled Readout' (SLEDGEHAMMER) which comprises of an array of 256 detectors with an energy resolution of 55eV FWHM at 97keV [1].…”

“…The presence of this a-thermal tail poses a challenge to accurately analyze the pulses riding on the tail of prior pulses, also affecting the pulse arrival time measurements [1] (Fig. 2).…”

“…A Super-Conducting ENergetic x-ray Telescope (ASCENT) (Fig. 1) [1] is a concept for a future balloonborne high energy X-ray telescope to study gamma ray emissions from supernova remnants with the aim to achieve an energy resolution ~ 50eV in the energy range 60-85keV, about 15 times better than NuSTAR which had a spectral resolution of 900eV at 68keV.…”