2024/05/02 by Bradley E. Schaefer, Schaefer, Bradley E. · 1 citation
Physics and Astronomy · #FOS: Physical sciences #Gamma-ray bursts and supernovae #High Energy Astrophysical Phenomena (astro-ph.HE) #History and Developments in Astronomy #Solar and Stellar Astrophysics (astro-ph.SR) #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2405.01210
openalex publication_date 2024/05/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
V2487 Ophiuchi (V2487 Oph) is a recurrent nova with classical nova eruptions in 1900 and 1998, and it is also the most extreme known superflare star. These superflares are roughly-hour-long flares with amplitudes and optical energies reaching up to 1.10 mag and 1039.21 ergs, with the superflares recurring once-a-day. The V2487 Oph superflares are certainly operating with the same mechanism as all the other types of superflare stars, where magnetic loops are twisted and stretched until reconnection occurs, whereupon ambient electrons are accelerated to relativistic energies and then emitted bremsstrahlung radiation from X-ray to radio. V2487 Oph is unique among known superflare stars in that one of the loop footprints is in an accretion disk. This exact mechanism was theoretically predicted by M. R. Hayashi and colleagues in 1996. Now, I have found two superflares recorded on Harvard archival photographs from the years 1941 and 1942. These two superflares have B magnitude amplitudes of >1.83 and >2.00 mag and total radiated energies of 1042.4 and 1042.5 ergs with bolometric corrections. Each has emitted energies of ∼30-billion Carringtons, in units of the most energetic solar flare. Further, I find superflares in the Zwicky Transient Factory light curves, so V2487 Oph has been superflaring from 1941 to 2023. For the observed number distribution of dN/dE=4E-2 superflares per year, for E in units of 1041 ergs, the emitted energy in superflare light is 1042.1 erg in each year, or 1044.1 ergs from 1941 to 2023.