Jordan Forman | Searcharxiv

arXiv2025

Einstein Probe Discovery of an X-ray Flare from K-type Star PM J23221-0301

Stellar flares are an intense stellar activity that can significantly impact the atmospheric composition of the surrounding planets and even the possible existence of life. During such events, the radiative energy of the star is primarily concentrated in the optical and X-ray bands, with the X-ray flux potentially increasing by tens or even hundreds of times. Einstein Probe (EP) detected a new X-ray transient EP J2322.1-0301 on 27 September 2024. Its spatial localization shows a high positional coincidence with the nearby high proper motion K-type star PM J23221-0301. Follow-up X-ray observations confirmed the flux enhancement of the source, while optical spectroscopic monitoring revealed time-variable features, particularly the disappearance of the H-alpha emission line. This X-ray flare is consistent with a characteristic fast-rise-exponential-decay (FRED) light curve, with a rise timescale of 1.4 ks, a decay timescale of 5.7 ks, and a total duration of about 7.1 ks. The peak luminosity in the 0.5-4.0 keV energy band reached about 1.3 x 10^31 erg s^-1, with a total energy release of about 9.1 x 10^34 erg, consistent with the empirical energy correlations observed in magnetic-reconnection-driven stellar flares, as inferred from the multitemperature plasma structure and H-alpha-X-ray energy correlation. This discovery underscores EP's capability in understanding stellar magnetic activity via observing stellar transients.

astro-ph.HE↗

arXiv2024

Multi-Messenger Emission Characteristics of Blazars

Multi-Messenger observations and theory of astrophysical objects is fast becoming a critical research area in the astrophysics scientific community. In particular, point-like objects like that of BL Lac, flat spectrum radio quasars (FSRQ), and blazar candidates of uncertain type (BCU) are of distinct interest among those who look at the synchrotron, Compton, neutrino, and cosmic ray emissions sourced from compact objects. Notably, there is also much interest in the correlation between multi-frequency observations of blazars and neutrino surveys on source demographics. In this review we look at such multi-frequency and multi-physics correlations of the radio, X-ray, and $\gamma$-ray fluxes of different classes of blazars from a collection of survey catalogues. This multi-physics survey of blazars shows that there are characteristic cross-correlations in the spectra of blazars when considering their multi-frequency and multi-messenger emission. Accompanying this will be a review of cosmic ray and neutrino emissions from blazars and their characteristics.

astro-ph.HE↗