HERMES: Gamma-ray burst and gravitational wave counterpart hunter^⋆

¹ INAF – Osservatorio Astronomico di Brera, via E. Bianchi 46, I-23807 Merate (LC), Italy
² INFN – Sezione di Milano-Bicocca, piazza della Scienza 3, I-20126 Milano, Italy
³ INAF – Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, I-34143 Trieste, Italy
⁴ IFPU – Institut for Fundamental Physics of the Universe, Via Beirut 2, I-34014 Trieste, Italy
⁵ INAF – OAS, Via Piero Gobetti 101, Bologna I-40129, Italy
⁶ INFN – Sezione di Bologna, Viale Berti Pichat 6/2, Bologna I-40127, Italy
⁷ INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano, Via A. Corti 12, 20133 Milano, Italy
⁸ Dipartimento di Fisica, Università degli Studi di Cagliari, SP Monserrato–Sestu km 0.7, 09042 Monserrato, Italy
⁹ Dipartimento di Fisica, Università di Trento, Sommarive 14, 38122 Povo (TN), Italy
¹⁰ INAF – Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere 100, I-00133 Roma (RM), Italy
¹¹ INFN – Sezione di Roma Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Roma (RM), Italy
¹² Agenzia Spaziale Italiana, Via del Politecnico snc, 00133 Roma, Italy
¹³ Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, D-72076 Tübingen, Germany
¹⁴ School of Physics, University of Melbourne, Parkville Vic 3010, Australia
¹⁵ Australian Research Council Centre of Excellence for All-Sky Astrophysics in 3-Dimensions, Stromlo, Australian Capital Territory
¹⁶ Physics Department, Federico II University, via Cintia 21, I-80126 Napoli, Italy
¹⁷ Politecnico di Milano - Department of Aerospace Science and Technology, Milan, Italy
¹⁸ Fondazione Bruno Kessler, Center for Sensors and Devices, Trento, Italy
¹⁹ Politecnico di Milano - Department of Electronics, Information and Bioengineering, Como, Italy
²⁰ Dipartimento di Matematica e Informatica, Università degli Studi di Cagliari, SP Monserrato–Sestu km 0.7, 09042 Monserrato, Italy
²¹ Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
²² INAF - IASF Palermo, Via Ugo La Malfa 153, 90146 Palermo, Italy
²³ Dipartimento di Fisica e Chimica, Università degli Studi di Palermo, via Archirafi 36, I-90123 Palermo, Italy
²⁴ SkyLabs d.o.o., Zagrebška c. 104, 2000 Maribor, Slovenia
²⁵ Center for Astrophysics and Cosmology, University of Nova Gorica, Vipavska 13, 5000 Nova Gorica, Slovenia
²⁶ Department of Electrical, Computer and Biomedical Engineering, University of Pavia, Pavia I-27100, Italy
²⁷ Department of Theoretical Physics and Astrophysics, Faculty of Science, Masaryk University, Brno, Czech Republic
²⁸ INAF – Osservatorio Astronomico di Roma, Via Frascati 33, I-00078 Monte Porzio Catone (RM), Italy
²⁹ Department of Mathematical, Informatics, and Physics University of Udine, Udine I-33100, Italy
³⁰ INAF - OAPA, piazza del Parlamento 1, 90134 Palermo, Italy

Received: 16 March 2024
Accepted: 22 May 2024

Abstract

Gamma-ray bursts (GRBs) bridge relativistic astrophysics and multimessenger astronomy. Space–based γ- and X-ray wide-field detectors have proven essential for detecting and localizing the highly variable GRB prompt emission, which is also a counterpart of gravitational wave events. We studied the capability of detecting long and short GRBs with the High Energy Rapid Modular Ensemble of Satellites (HERMES) Pathfinder (HP) and SpIRIT, namely a swarm of six 3U CubeSats to be launched in early 2025, and a 6U CubeSat launched on December 1 2023. We also studied the capabilities of two advanced configurations of swarms of more than eight satellites with improved detector performances (HERMES Constellations). The HERMES detectors, sensitive down to ∼2–3 keV, will be able to detect faint and soft GRBs, which comprise X-ray flashes and high-redshift bursts. By combining state-of-the-art long- and short-GRB population models with a description of the single module performance, we estimate that HP will detect ∼195₋₂₁⁺²² long GRBs (3.4_−0.8^+0.3 at redshift z > 6) and ∼19₋₃⁺⁵ short GRBs per year. The larger HERMES Constellations under study can detect between ∼1300 and ∼3000 long GRBs per year and between ∼160 and ∼400 short GRBs per year, depending on the chosen configuration, with a rate of long GRBs above z > 6 of between 30 and 75 per year. Finally, we explored the capability of HERMES to detect short GRBs as electromagnetic counterparts of binary neutron star (BNS) mergers detected as gravitational signals by current and future ground–based interferometers. Under the assumption that the GRB jets are structured, we estimate that HP can provide up to ∼1 (14) yr⁻¹ joint detections during the fifth LIGO–Virgo–KAGRA observing run (Einstein Telescope single triangle 10 km arm configuration). These numbers become ∼4 (100) yr⁻¹, respectively, for the HERMES Constellation configuration.