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We use a global magnetohydrodynamic simulation of a geometrically thin accretion disk to investigate the locality and detailed structure of turbulence driven by the magnetorotational instability (MRI). The model disk has an aspect ratio $H…

高能天体物理现象 · 物理学 2015-05-28 Kris Beckwith , Philip J. Armitage , Jacob B. Simon

We developed a new technique for measuring the thermodynamic entropy as a function of the magnetic field angle. This technique enables high-resolution angle-resolved measurements of the entropy in an unprecedentedly short measuring time.…

强关联电子 · 物理学 2018-06-15 Shunichiro Kittaka , Shota Nakamura , Hiroaki Kadowaki , Hiroshi Takatsu , Toshiro Sakakibara

We have computed models of rotating relativistic stars with a toroidal magnetic field and investigated the combined effects of magnetic field and rotation on the apparent shape (i.e. the surface deformation), which could be relevant for the…

广义相对论与量子宇宙学 · 物理学 2014-02-14 Joachim Frieben , Luciano Rezzolla

The observed abrupt torque reversals in X-ray pulsars, 4U 1626-67, GX 1+4, and OAO 1657-415, can be explained by transition in accretion flow rotation from Keplerian to sub-Keplerian, which takes place at a critical accretion rate, $\sim…

天体物理学 · 物理学 2009-10-30 Insu Yi , J. Craig Wheeler

By performing 2.5-dimensional general relativistic radiation magnetohydrodynamic simulations, we demonstrate supercritical accretion onto a non-rotating, magnetized neutron star, where the magnetic field strength of dipole fields is…

高能天体物理现象 · 物理学 2017-08-23 Hiroyuki R. Takahashi , Ken Ohsuga

We numerically investigate the hydrodynamics of accretion disk reversal and relate our findings to the observed spin-rate changes in the accreting X-ray pulsar GX~1+4. In this system, which accretes from a slow wind, the accretion disk…

天体物理学 · 物理学 2009-10-31 James R. Murray , Martijn de Kool , Jianke Li

We investigate angular momentum transport and accretion properties in a sample of protoplanetary discs with dynamical measurements of stellar masses, disc masses, and scale radii. From these data we infer effective $\alpha$-viscosities,…

地球与行星天体物理 · 物理学 2025-12-11 Cristiano Longarini , Cathie Clarke

We perform three-dimensional magnetohydrodynamic simulations of magnetospheric accretion in a T Tauri star to study the accretion and wind structures in the close vicinity of the star. The gas accreting onto the star consists of the gas…

太阳与恒星天体物理 · 物理学 2022-12-21 Shinsuke Takasao , Kengo Tomida , Kazunari Iwasaki , Takeru K. Suzuki

We study the evolution of magnetic fields in accretion flows around six different sink particles in a global star formation simulation. Using the adaptive mesh refinement capabilities of \ramses, the vicinity of the sinks is resolved with a…

太阳与恒星天体物理 · 物理学 2017-11-01 Michael Kuffmeier , Farrukh Nauman

We improved the discless accretion models of Wynn \& King, considering the effects of the changing aspect due to the white dwarf spin and the variable feeding intensity caused by the asynchronism, and set up a more general spot model which…

太阳与恒星天体物理 · 物理学 2020-12-02 Qishan Wang , Shengbang Qian , Zhongtao Han , Xiaohui Fang , Lei Zang , Wei Liu

We show that the irradiated accretion disk model can account for all the optical and infrared observations of the anomalous X-ray pulsars in the persistent state. Model fits do not constrain the outer disk radii, while placing an upper…

天体物理学 · 物理学 2015-06-24 Unal Ertan , Sirin Caliskan

We show results of global 3D MHD simulations of accretion onto stars with superposition of the dipole and octupole fields, where we vary the ratio between components. Simulations show that if octupolar field strongly dominates at the…

高能天体物理现象 · 物理学 2015-05-14 Min Long , Marina M. Romanova , Frederick K. Lamb

Disk accretion to rotating stars with complex magnetic fields is investigated using full three-dimensional magnetohydrodynamic (MHD) simulations. The studied magnetic configurations include superpositions of misaligned dipole and quadrupole…

天体物理学 · 物理学 2009-11-13 M. Long , M. M. Romanova , R. V. E. Lovelace

We analyze the configuration of a thin rotating accretion disk, which is embedded in a magnetic field inducing a backreaction in the gravitating plasma. The aim of this study is to determine the conditions under which the gaseous accretion…

太阳与恒星天体物理 · 物理学 2015-06-05 Giovanni Montani , Nakia Carlevaro

The phenomenology of anomalous X-ray pulsars is usually interpreted within the paradigm of very highly magnetized neutron stars, also known as magnetars. According to this paradigm, the persistent emission of anomalous X-ray pulsars (AXPs)…

高能天体物理现象 · 物理学 2020-11-25 Victor Doroshenko , Andrea Santangelo , Valery Suleimanov , Sergey Tsygankov

We report a systematic analysis of the spin, orbital, and superorbital modulations of 4U 0114+650, a high-mass X-ray binary consists of one of the slowest spinning neutron stars. Utilizing the dynamic power spectrum, we found that the spin…

高能天体物理现象 · 物理学 2017-07-26 Chin-Ping Hu , Yi Chou , C. -Y. Ng , Lupin Chun-Che Lin , David Chien-Chang Yen

Context: Observations suggest that magnetic fields of disk-bearing stars may have non-dipolar configurations. However, the influence of these configurations on magnetospheric accretion remains poorly understood. Aims: We aim to simulate…

太阳与恒星天体物理 · 物理学 2025-11-05 A. Moranchel-Basurto , D. Kocakova , M. Cemeljic , R. O. Chametla , F. J. Sanchez-Salcedo , I. Bermejo-Lozano

We formulate a general, steady-state model for the torque on a magnetized star from a surrounding accretion disc. For the first time, we include the opening of dipolar magnetic field lines due to the differential rotation between the star…

天体物理学 · 物理学 2009-11-10 Sean Matt , Ralph E. Pudritz

It is thought that neutron stars in low-mass binary systems can accrete matter and angular momentum from the companion star and be spun-up to millisecond rotational periods. During the accretion stage, the system is called a low-mass X-ray…

This paper continues the analysis of a set of general relativistic 3D MHD simulations of accreting tori in the Kerr metric with different black hole spins. We focus on bound matter inside the initial pressure maximum, where the…

天体物理学 · 物理学 2009-11-10 Julian H. Krolik , John F. Hawley , Shigenobu Hirose