astro-ph.HE; astro-ph.SR; Space and Planetary Science; Astronomy and Astrophysics
Abstract :
[en] We report detailed X-ray observations of the unique binary system $\epsilon$
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
$\epsilon$ 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 ($\approx 5\%$ 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
$\epsilon$ 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.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Das, B. ; Department of Physics and Astronomy, Bartol Research Institute, University of Delaware , 104 The Green, Newark, DE 19716, USA
Petit, V. ; Department of Physics and Astronomy, Bartol Research Institute, University of Delaware , 104 The Green, Newark, DE 19716, USA
Nazé, Yaël ; Université de Liège - ULiège > Département d'astrophysique, géophysique et océanographie (AGO) > Groupe d'astrophysique des hautes énergies (GAPHE)
Corcoran, M. F.; CRESST and X-ray Astrophysics Laboratory, NASA/Goddard Space Flight Center, Code 662 , Greenbelt, MD 20771, USA ; Institute for Astrophysics and Computational Sciences, The Catholic University of America , 620 Michigan Avenue , N.E. Washington, DC 20064, USA
Cohen, D. H. ; Department of Physics and Astronomy, Swarthmore College , 500 College Ave, Swarthmore, PA 19081, USA
Biswas, A. ; Department of Physics, Engineering Physics & Astronomy, Queen’s University , 99 University Ave, Kingston, ON K7L 3N6, Canada ; Department of Physics and Space Science, Royal Military College of Canada , 13 General Crerar Crescent, Kingston, ON K7K 7B4, Canada
Chandra, P. ; National Radio Astronomy Observatory , 520 Edgemont Road , Charlottesville VA 22903, USA
David-Uraz, A. ; CRESST and X-ray Astrophysics Laboratory, NASA/Goddard Space Flight Center, Code 662 , Greenbelt, MD 20771, USA ; Department of Physics and Astronomy, Howard University , 2355 6th St NW, Washington, DC 20059, USA
Leutenegger, M. A. ; X-ray Astrophysics Laboratory, NASA/GSFC , 8800 Greenbelt Road, Greenbelt, MD 20771, USA
Neiner, C. ; LESIA, Paris Observatory, PSL University, CNRS, Sorbonne University, Université Paris Cité , 5 place Jules Janssen, 92195 Meudon, France
Pablo, H. ; American Association of Variable Star Observers , 185 Alewife Brook Pkwy , Cambridge, MA 02138, USA
Paunzen, E. ; Department of Theoretical Physics and Astrophysics, Masaryk University , Kotlářská 2 , 611 37 Brno, Czechia
Shultz, M. E.; Department of Physics and Astronomy, Bartol Research Institute, University of Delaware , 104 The Green, Newark, DE 19716, USA
ud-Doula, A. ; Penn State Scranton , 120 Ridge View Drive , Dunmore, PA 18512, USA
Wade, G. A.; Department of Physics and Space Science, Royal Military College of Canada , 13 General Crerar Crescent, Kingston, ON K7K 7B4, Canada
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