A persistent ultraviolet outflow from an accreting neutron star binary transient
N. Castro Segura, C. Knigge, K. S. Long, D. Altamirano, M. Armas Padilla, C. Bailyn, D. A. H. Buckley, D. J. K. Buisson, J. Casares, P. Charles, J. A. Combi, V.… 展开作者
N. Castro Segura, C. Knigge, K. S. Long, D. Altamirano, M. Armas Padilla, C. Bailyn, D. A. H. Buckley, D. J. K. Buisson, J. Casares, P. Charles, J. A. Combi, V. A. Cúneo, N. D. Degenaar, S. del Palacio, M. Díaz Trigo, R. Fender, P. Gandhi, M. Georganti, C. Gutiérrez, J. V. Hernandez Santisteban, F. Jiménez-Ibarra, J. Matthews, M. Méndez, M. Middleton, T. Muñoz-Darias, M. Özbey Arabacı, M. Pahari, L. Rhodes, T. D. Russell, S. Scaringi, J. van den Eijnden, G. Vasilopoulos, F. M. Vincentelli, P. Wiseman
All disc-accreting astrophysical objects produce powerful outflows. In binaries containing neutron stars (NS) or black holes, accretion often takes place during violent outbursts. The main disc wind signatures during these eruptions are blue-shifted X-ray absorption lines, which are preferentially seen in disc-dominated "soft states". By contrast,optical wind-formed lines have recently been detected in "hard states", when a hot corona dominates the luminosity. The relationship between these signatures is unknown, and no erupting system has revealed wind-formed lines between the X-ray and optical bands yet, despite the many strong resonance transitions in this ultraviolet (UV) region. Here, we show that the transient NS binary Swift J1858.6-0814 exhibits wind-formed, blue-shifted absorption associated with C IV, N V and He II in time-resolved UV spectroscopy during a luminous hard state. This represents the first evidence for a warm, moderately ionized outflow component in this state. Simultaneously observed optical lines also display transient blue-shifted absorption. Decomposing the UV data into constant and variable components, the blue-shifted absorption is associated with the former. This implies that the outflow is not connect to the luminous flares in the data. The joint presence of UV and optical wind features reveals a multi-phase and/or stratified outflow from the outer disc. This type of persistent mass loss across all accretion states has been predicted by radiation-hydrodynamic simulations and helps to explain the shorter-than-expected outbursts duration.
Almost all accreting black hole and neutron star X-ray binary systems (XRBs) exhibit prominent brightness variations on a few characteristic time-scales and their harmonics. These quasi-periodic oscillations (QPOs) are thought to be associated with the precession of a warped accretion disc, but the physical mechanism that generates the precessing warp remains uncertain. Relativistic frame dragging (Lense-Thirring precession) is one promising candidate, but a misaligned magnetic field is an alternative, especially for neutron star XRBs. Here, we report the discovery of 5 accreting white dwarf s…
A persistent bow shock in a diskless magnetised accreting white dwarf
Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences(尼古拉·哥白尼天文学中心,波兰科学院);Centre for Extragalactic Astronomy, Department of Physics, Durham University(杜伦大学物理系河外天文中心);INAF-Osservatorio Astronomico di Capodimonte(意大利国家天体物理研究所卡波迪蒙特天文台);School of Physics and Astronomy, University of Southampton(南安普顿大学物理与天文学院);INAF-Osservatorio Astronomico di Brera(意大利国家天体物理研究所布雷拉天文台);University of Oxford, Department of Physics, Astrophysics(牛津大学物理系天体物理学);Institute of Space Sciences (ICE, CSIC)(空间科学研究所(欧洲空间科学中心,西班牙高等科学研究委员会));Institut d’Estudis Espacials de Catalunya (IEEC)(加泰罗尼亚太空研究研究所);South African Astronomical Observatory(南非天文台);Department of Astronomy, University of Cape Town(开普敦大学天文系);Department of Physics, University of the Free State(自由州大学物理系);Department of Physics, University of Warwick(华威大学物理系);Department of Astrophysics/IMAPP, Radboud University(拉德堡德大学天体物理学/IMAPP系)
Roche lobe overflow from a donor star onto a black hole or neutron star binary companion can evolve to a phase of unstable runaway mass-transfer, lasting as short as hundreds of orbits ($\lesssim 10^{2}$ yr for a giant donor), and eventually culminating in a common envelope event. The highly super-Eddington accretion rates achieved during this brief phase ($\dot{M} \gtrsim 10^{5}\dot{M}_{\rm Edd})$ are accompanied by intense mass-loss in disk winds, analogous but even more extreme than ultra-luminous X-ray (ULX) sources in the nearby universe. Also in analogy with observed ULX, this expanding …
We perform magnetohydrodynamic simulations of accreting, equal-mass binary black holes in full general relativity focusing on the effect of spin and minidisks on the accretion rate and Poynting luminosity variability. We report on the structure of the minidisks and periodicities in the mass of the minidisks, mass accretion rates, and Poynting luminosity. The accretion rate exhibits a quasi-periodic behavior related to the orbital frequency of the binary in all systems that we study, but the amplitude of this modulation is dependent on the existence of persistent minidisks. In particular, syste…
Optical time-domain surveys can unveil and characterize exciting but less-explored non-accreting and/or non-beaming neutron stars (NS) in binaries. Here we report the discovery of such a NS candidate using the LAMOST spectroscopic survey. The candidate, designated LAMOST J112306.9+400736 (hereafter J1123), is in a single-lined spectroscopic binary containing an optically visible M star. The star's large radial velocity variation and ellipsoidal variations indicate a relatively massive unseen companion. Utilizing follow-up spectroscopy from the Palomar 200-inch telescope and high-precision phot…
We investigate the aperiodic variability for a relatively large sample of accreting neutron stars and intermediate polars, focusing on the properties of the characteristic break commonly observed in power spectra of accreting objects. In particular, we investigate the relation of the break frequency and the magnetic field strength, both of which are connected to the size of the magnetosphere. We find that for the majority of objects in our sample the measured break frequency values indeed agree with estimated inner radii of the accretion disc, which allows to use observed break frequencies to …
Roaring to softly whispering: Persistent X-ray emission at the location of the Fast Blue Optical Transient AT2018cow $\sim$3.7 yrs after discovery and implications on accretion-powered scenarios
We report on the fast Nova Sgr 2016 N.4 being surprisingly trapped in a long-lasting and bright plateau (Delta I >= 10 mag above quiescence) six years past the nova eruption. Very few other novae experience a similar occurrence. We carried out an intensive observing campaign collecting daily BVRI photometry and monthly high-resolution optical spectroscopy, and observed the nova in ultraviolet and X-rays with Swift satellite at five distinct epochs. The bolometric luminosity radiated during the plateau is ~4200 Lsun (scaled to the distance of the Galactic Bulge), corresponding to stable nuclear…