Radio Emission from Sgr A*: Pulsar Transits Through the Accretion Disc

Abstract

Radiatively inefficient accretion flow models have been shown to accurately account for the spectrum and luminosity observed from Sgr A* in the X-ray regime down to mm wavelengths. However, observations at a few GHz cannot be explained by thermal electrons alone but require the presence of an additional non-thermal particle population. Here, we propose a model for the origin of such a population in the accretion flow via means of a pulsar orbiting the supermassive black hole in our Galaxy. Interactions between the relativistic pulsar wind with the disc lead to the formation of a bow shock in the wind. During the pulsar's transit through the accretion disc, relativistic pairs, accelerated at the shock front, are injected into the disc. The radio-emitting particles are long-lived and remain within the disc long after the pulsar's transit. Periodic pulsar transits through the disc result in regular injection episodes of non-thermal particles. We show that for a pulsar with spin-down luminosity $L_{\mathrm{sd}}\sim 3\times 10^{35}$ erg s${}^{-1}$ and a wind Lorentz factor of ${\gamma }_{\mathrm{w}}\sim 10^4$ a quasi-steady synchrotron emission is established with luminosities in the $1-10$ GHz range comparable to the observed one.

arXiv comment5 pages, 3 figures

References in corpus (27)

• The ATNF Pulsar Catalogue
• Monitoring stellar orbits around the Massive Black Hole in the Galactic Center
• The ATNF Pulsar Catalogue
• The Galactic Center Massive Black Hole and Nuclear Star Cluster
• Advection-Dominated Accretion: Self-Similarity and Bipolar Outflows
• Chandra X-ray Spectroscopic Imaging of Sgr A* and the Central Parsec of the Galaxy
• Nonthermal Electrons in Radiatively Inefficient Accretion Flow Models of Sagittarius A*
• A strong magnetic field around the supermassive black hole at the centre of the Galaxy
• Convection-Dominated Accretion Flows
• Particle Acceleration in Relativistic Magnetized Collisionless Pair Shocks: Dependence of Shock Acceleration on Magnetic Obliquity
• Variable Infrared Emission from the Supermassive Black Hole at the Center of the Milky Way
• NuSTAR discovery of a 3.76-second transient magnetar near Sagittarius A*
• The old nuclear star cluster in the Milky Way: dynamics, mass, statistical parallax, and black hole mass
• The simultaneous spectrum of Sgr A* from 20cm to 1mm and the nature of the mm-excess
• Hybrid Thermal-Nonthermal Synchrotron Emission from Hot Accretion Flows
• Probing the Spacetime Around Sgr A* with Radio Pulsars
• Disrupted Globular Clusters Can Explain the Galactic Center Gamma Ray Excess
• Multiwavelength Constraints on Pulsar Populations in the Galactic Center
• Relativistic MHD simulations of pulsar bow-shock nebulae
• How to hide large scale outflows: size constraints on the jets of Sgr A*
• Finding Radio Pulsars in and Beyond the Galactic Center
• Pulsar bow-shock nebulae. II. Hydrodynamical simulation
• Jet-lag in Sgr A*: What size and timing measurements tell us about the central black hole in the Milky Way
• The Galactic centre pulsar population
• Radio light curves during the passage of cloud G2 near Sgr A*
• Modelling Accretion Disk and Stellar Wind Interactions: the Case of Sgr A*
• Flares from Galactic centre pulsars: a new class of X-ray transients?

Cited by in corpus (1)

• X-ray mapping of the stellar wind in the binary PSR J2032+4127/MT91 213