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arXiv · 2310.09683

Detection of the 2021 Outburst of RS Ophiuchi with the LST-1

Yukiho Kobayashi·Arnau Aguasca-Cabot·María Isabel Bernardos Martín·David Green·Rubén López-Coto
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Abstract

Novae are luminous explosions in close binaries which host a white dwarf and a companion donor star. They are triggered by a thermonuclear runaway when the white dwarf accretes a critical amount of matter from the secondary. Though novae are established as high-energy gamma-ray emitters through observations by the Fermi Large Area Telescope (LAT), the origin of the gamma-ray emission, whether it is hadronic or leptonic, had been under intense debate until very recently. RS Ophiuchi (RS Oph) is a well-known recurrent symbiotic nova with a recurrence time scale of 15 years. The most recent outburst of RS Oph in 2021 brought the first detection of very-high-energy (VHE) gamma rays from a nova ever. The first Large-Sized Telescope prototype (LST-1) of the Cherenkov Telescope Array observed this historic event along with H.E.S.S. and MAGIC. The LST-1 observations in the first days after the burst onset show a clear VHE gamma-ray signal from RS Oph. The low energy threshold of LST-1 allows us to reconstruct the RS Oph gamma-ray spectrum down to $\sim$30 GeV, providing the best connection of the VHE gamma-ray data to the Fermi LAT energy range. The results from the analysis of the LST-1 observations are consistent with those obtained with H.E.S.S. and MAGIC, and also support a hadronic origin for the observed gamma-ray fluxes. In this contribution, we will present the analysis results of the LST-1 observations of the 2021 outburst of RS Oph.

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Yukiho Kobayashi, Arnau Aguasca-Cabot, María Isabel Bernardos Martín, David Green, Rubén López-Coto. 2023-10-14. Detection of the 2021 Outburst of RS Ophiuchi with the LST-1. https://arxiv.org/abs/2310.09683

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