Publication details

Discovery of extraordinary X-ray emission from magnetospheric interaction in the unique binary stellar system ϵ Lupi

Authors	DAS B. PETIT V. NAZE Y. CORCORAN M. F. COHEN D. H. BISWAS A. CHANDRA P. DAVID-URAZ A. LEUTENEGGER M. A. NEINER C. PABLO H. PAUNZEN Ernst SHULTZ M. E. UD-DOULA A. WADE G. A.
Year of publication	2023
Type	Article in Periodical
Magazine / Source	Monthly Notices of the Royal Astronomical Society
MU Faculty or unit	Faculty of Science
Citation
Web	https://arxiv.org/abs/2304.12882 https://doi.org/10.1093/mnras/stad1276
Doi	http://dx.doi.org/10.1093/mnras/stad1276
Keywords	magnetic reconnection; stars: binaries: general; stars: early-type; stars: magnetic fields; X-rays: binaries; Xrays: stars
Description	We report detailed X-ray observations of the unique binary system ? Lupi, the only known short-period binary consisting of two magnetic early-type stars. The components have comparably strong, but anti-aligned magnetic fields. The orbital and magnetic properties of the system imply that the magnetospheres overlap at all orbital phases, suggesting the possibility of variable inter-star magnetospheric interaction due to the non-negligible eccentricity of the orbit. To investigate this effect, we observed the X-ray emission from ? Lupi, both near and away from periastron passage, using the Neutron Star Interior Composition Explorer mission (NICER) X-ray Telescope. We find that the system produces excess X-ray emission at the periastron phase, suggesting the presence of variable inter-star magnetospheric interaction. We also discover that the enhancement at periastron is confined to a very narrow orbital phase range (??5 per cent of the orbital period), but the X-ray properties close to periastron phase are similar to those observed away from periastron. From these observations, we infer that the underlying cause is magnetic reconnection heating the stellar wind plasma, rather than shocks produced by wind–wind collision. Finally, by comparing the behavior of ? Lupi with that observed for cooler magnetic binary systems, we propose that elevated X-ray flux at periastron phase is likely a general characteristic of interacting magnetospheres irrespective of the spectral types of the constituent stars.