2026-06-01T07:36:11Zhttps://docta.ucm.es/rest/oai/request

oai:docta.ucm.es:20.500.14352/332912024-07-11T16:25:08Zcom_20.500.14352_14col_20.500.14352_15

XMM-Newton monitoring of the close pre-main-sequence binary AK Sco. Evidence of tide-driven filling of the inner gap in the circumbinary disk Gómez De Castro, Ana Inés López Santiago, Javier Talavera, A. Sytov, A. Y. Bisikalo, D. 52 Binaries: spectroscopic Magnetic fields Stars: pre-main sequence T-tauri stars X-ray-emission System kh 15d Wavelength dependence Accretion shocks mg-ii Scorpii Polarization Simulations Extinction Astronomía (Matemáticas) 21 Astronomía y Astrofísica AK Sco stands out among pre-main-sequence binaries because of its prominent ultraviolet excess, the high eccentricity of its orbit, and the strong tides driven by it. AK Sco consists of two F5-type stars that get as close as 11 R-* at periastron passage. The presence of a dense (n(e) similar to 10(11) cm(-3)) extended envelope has been unveiled recently. In this article, we report the results from an XMM-Newton-based monitoring of the system. We show that at periastron, X-ray and UV fluxes are enhanced by a factor of similar to 3 with respect to the apastron values. The X-ray radiation is produced in an optically thin plasma with T similar to 6.4 x 10(6) K and it is found that the N-H column density rises from 0.35 x 10(21) cm(-2) at periastron to 1.11 x 10(21) cm(-2) at apastron, in good agreement with previous polarimetric observations. The UV emission detected in the Optical Monitor band seems to be caused by the reprocessing of the high-energy magnetospheric radiation on the circumstellar material. Further evidence of the strong magnetospheric disturbances is provided by the detection of line broadening of 278.7 km s(-1) in the Nv line with Hubble Space Telescope/Space Telescope Imaging Spectrograph. Numerical simulations of the mass flow from the circumbinary disk to the components have been carried out. They provide a consistent scenario with which to interpret AK Sco observations. We show that the eccentric orbit acts like a gravitational piston. At apastron, matter is dragged efficiently from the inner disk border, filling the inner gap and producing accretion streams that end as ring-like structures around each component of the system. At periastron, the ring-like structures come into contact, leading to angular momentum loss, and thus producing an accretion outburst. Ministerio de Ciencia, Innovación y Universidades (España) Russian Foundation for Basic Research grant Russian Federation President grant Unidad Deptal. de Astronomía y Geodesia Fac. de Ciencias Matemáticas Instituto de Matemática Interdisciplinar (IMI) TRUE pub 2023-06-19T13:21:34Z 2023-06-19T13:21:34Z 2013-03 journal article https://hdl.handle.net/20.500.14352/33291 0004-637X 10.1088/0004-637X/766/1/62 eng AYA2008-06423-C03-01/03 open access application/pdf IOP Publishing