Luca NASO: Magnetic field structure and torque in accretion discs

Magnetic field structure and torque in accretion discs around millisecond pulsars

Speaker: Luca Naso (NAOC)
Time: Nov 8, 3pm~5pm
Place: NAOC, A508 

 

Abstract:
Millisecond pulsars are rather weakly-magnetized neutron stars which are thought to have been spun up by disc accretion, with magnetic linkage between the star and the disc playing a key role. Their spin history depends sensitively on details of the magnetic field structure, but idealized models from the 1980s and 1990s are still commonly used for calculating the magnetic field components.
We will present results obtained from a step-by-step analysis which we are making of the problem, starting with very simple models and then progressively including additional features one at a time, with the aim of gaining new insights into the mechanisms involved.
In our previous papers, the magnetic field structure in the disc was calculated for a standard Shakura and Sunyaev model, by solving the magnetic induction equation numerically in the stationary limit within the kinematic approximation; here we consider a more general velocity field in the disc, including backflow.
We find that the profiles of the poloidal and toroidal components of the magnetic field are fairly similar in the two cases but that they can be very different from those in the models mentioned above, giving important consequences for the torque exerted on the central object. In particular we find that, contrary to what is usually thought, some regions of the disc outward of the co-rotation point (rotating more slowly than the neutron star) may nevertheless contribute to spinning up the neutron star on account of the detailed structure of the magnetic field in those parts of disc.
 
Reference:
Naso et al. MNRAS, 435, 2633-2649 (2013)

Next Teeminars

Time Plan 2018/2017

2018
Time and Place: 3:00 - 5:00 p.m., NAOC (unless noted otherwise); tbc = to be confirmed
  • Dec. 25: (note unusual Tuesday!): Sambaran Banerjee (Argelander Inst., Univ. Bonn, Germany): Stellar-mass black holes in open clusters: implications for gravitational-wave generation
  • Dec. 21: no tea seminar, MIDAS meeting
  • Dec. 11 (note unusual Tuesday!): Kohei Inayoshi (KIAA): Black hole accretion in the present-day and early universe; and general discussion on supercomputing in China
  • Dec. 7: no tea seminar, KCK10 at Suzhou
  • Nov. 30: no tea seminar
  • Nov. 23: Agostino Leveque (CAMK, Poland): The C MOCCA version: a step toward AMUSE
  • Nov. 16: Discussion with Mirek Giersz (CAMK, Poland)
  • Nov. 9: Sergey Khoperskov (Moscow/Garching)
  • Oct. 19/Nov. 2: no tea seminar
  • Oct. 12:
  • Oct. 5: vacation?
  • Sep. 28:Jongsuk Hong (KIAA): Stellar Evolution in Star Clusters: Applications
  • Sep. 21: Rainer Spurzem (NAOC): Discussion Meeting on Status of Stellar Evolution in NBODY simulations
  • Sep. 14: Planning Session and Reports
  • May 18: Shuo Li (NAOC): Multi-mass galaxy merger simulations

 

2017

 

  • Dec. 15: note location and changed speaker: at KIAA Room 208: Shu Qi: Dynamic evolution of free-floating comets in star cluster / Taras Panamarev: N-body model of galactic center
  • Dec. 8: Li Shuo: Tidal disruption in galaxy mergers with Multi-mass and stellar evolution model.
  • Nov. 17: Verónica Vázquez: The merger of two quarks stars. A SPH Newtonian simulation
  • Oct. 27: Mirek Giersz (CAMK Warsaw, Poland): MOCCA - Survey Data Base - Projects (Black Holes and Gravitational Waves from Star Clusters)
  • Oct. 25 Lunch Seminar at KIAA (12:00 p.m.): Holger Baumgardt (Queensland Univ., Australia): The formation of the smallest galaxies
  • Oct. 20: Bohdan Novosyadlyj & Valerii Shulga (Ivan Franko Natl. Univ. of Lviv, Ukraine and Jilin Univ. China): Dark matter and dark energy probes: from Dark Ages to Giant Voids
  • Sep. 15: Xiaoying Pang: Open clusters from SDSS DR 14 | Bai Jing: Short Report on Galev Work | Rainer Spurzem: Short Status Report and Discussion of DRAGON Data Project
    • Sep. 7: Yohai Meiron (Eötvös University, Budapest, Hungary):  Relaxation and mixing of constants of motion in globular clusters
  • Sep. 1: Planning Meeting (Tea Seminar, Conferences, Travel)
      • Next Seminars:

  • Dec. 22: No tea seminar (KCK9)
  • Dec. 29:?

 

———Summer Break——————————————————

  • May 5: no tea seminar (Lazenby KIAA colloquium overlaps)
  • May 12: Alexandr Zhuk (Odessa  National University, Ukraine and Jilin University, China):  Cosmic screening of the gravitational interaction in the Universe (Abstract)
  • May 19: Xian Chen (DoA, PKU):   Retrieving the rest mass of GW150914  and Rainer Spurzem (Silk Road NAOC): News on NBODY6++GPU and Galactic Center DRAGON

     

    ———2016:—————————————————————————————————————

  • Oct. 28: no tea seminar (EANAM7)
  •     Nov. 4: no tea seminar (CAS2016 Wuhan)
  •     Nov. 11: no tea seminar (KIAA Astro Forum)
  •     Nov. 14: DoA/PKU Lunch Talk: Abbas Askar: Monte Carlo Models
  •     Nov. 18: Li Shuo: Binary Black Holes in Merging Galaxies
  •     Nov. 25/Dec. 2: no tea seminar (China/South Africa workshop)
  •     Dec. 9: Matthias Kühtreiber: Galaxy Evolution Models
  •     Dec. 16: Shu Qi: Comets and Planets in Star Clusters/Taras Panamarev: N-Body models of Galactic Center
  •     Dec. 23: Jongsuk Hong: Multiple Populations in star clusters
  •     Dec. 28: Shuo Li: postponed to next year

 

Past Seminars in this period:

 

  • Sep. 16 Discussion Meeting with Guests
    1.) Thijs Kouwenhoven, Xian Jiaotong/Liverpool Univ. at Suzhou:
    Disk fragmentation and brown dwarfs in the Galactic field
     2.) Xiaoying Pang, Shanghai Inst. of Technology, on open clusters
     3.) Yohai Meiron, Eoetvoes Univ. Budapest, Hungary, on stellar disks in AGN
  • Sep. 23 at Room 410, Morningside Center of Mathematics near AMSS/CAS (location see link), 4:00 p.m.: Yohai Meiron, Eötvös University (Budapest, Hungary)Triple companion in gravitational wave signals (Abstract) (notice: postponed: Fabian Klein on Initial Models for AGN Disks using pluto)

 

 

Past Seminars