A Stellar Wind Origin for the G2 Cloud: Three-Dimensional Numerical Simulations

Abstract

We present 3D, adaptive mesh refinement simulations of G2, a cloud of gas moving in a highly eccentric orbit towards the galactic center. We assume that G2 originates from a stellar wind interacting with the environment of the Sgr A* black hole. The stellar wind forms a cometary bubble which becomes increasingly elongated as the star approaches periastron. A few months after periastron passage, streams of material begin to accrete on the central black hole with accretion rates $\dot{M}\sim 10^{-8}$ M${}_{\odot }$ yr${}^{-1}$. Predicted Br$\gamma$ emission maps and position-velocity diagrams show an elongated emission resembling recent observations of G2. A large increase in luminosity is predicted by the emission coming from the shocked wind region during periastron passage. The observations, showing a constant Br$\gamma$ luminosity, remain puzzling, and are explained here assuming that the emission is dominated by the free-wind region. The observed Br$\gamma$ luminosity ($\sim 8\times 10^{30}$ erg s${}^{-1}$) is reproduced by a model with a $v_w=50$ km s${}^{-1}$ wind velocity and a $10^{-7}$ M${}_{\odot }$ yr${}^{-1}$ mass loss rate if the emission comes from the shocked wind. A faster and less dense wind reproduces the Br$\gamma$ luminosity if the emission comes from the inner, free wind region. The extended cometary wind bubble, largely destroyed by the tidal interaction with the black hole, reforms a few years after periastron passage. As a result, the Br$\gamma$ emission is more compact after periastron passage.

6 pages, 5 figures, submitted to the Astrophysical Journal Letters

References in corpus (28)

• Measuring Distance and Properties of the Milky Way's Central Supermassive Black Hole with Stellar Orbits
• Nonthermal Electrons in Radiatively Inefficient Accretion Flow Models of Sagittarius A*
• A gas cloud on its way towards the super-massive black hole in the Galactic Centre
• Physics of the Galactic Center Cloud G2, on its Way towards the Super-Massive Black Hole
• The dynamics, appearance and demographics of relativistic jets triggered by tidal disruption of stars in quiescent supermassive black holes
• Simulations of the Origin and Fate of the Galactic Center Cloud G2
• Keck Observations of the Galactic Center Source G2: Gas Cloud or Star?
• Pericenter passage of the gas cloud G2 in the Galactic Center
• New observations of the gas cloud G2 in the Galactic Center
• The Galactic Center Cloud G2 -- a Young Low-Mass Star with a Stellar Wind
• Gamma-Ray Burst Dynamics and Afterglow Radiation from Adaptive Mesh Refinement, Special Relativistic Hydrodynamic Simulations
• Three-Dimensional Moving-Mesh Simulations of Galactic Center Cloud G2
• Hydrodynamical simulations of a compact source scenario for the Galactic Center cloud G2
• Radio light curves during the passage of cloud G2 near Sgr A*
• Radio Synchrotron Emission from a Bow Shock around the Gas Cloud G2 Heading toward the Galactic Center
• Possible Origin of the G2 Cloud from the Tidal Disruption of a Known Giant Star by Sgr A*
• MHD simulations of radiative jets from young stellar objects: Halpha emission
• Dust-enshrouded star near supermassive black hole: predictions for high-eccentricity passages near low-luminosity galactic nuclei
• A nova origin of the gas cloud at the Galactic Center ?
• Flaring up of the Compact Cloud G2 during the Close Encounter with Sgr A*
• A star disrupted by a stellar black hole as the origin of the cloud falling toward the Galactic center
• The Properties and Fate of the Galactic Center G2 Cloud
• Location of the bow shock ahead of cloud G2 at the Galactic Center
• Radio Synchrotron Emission from the Bow Shock of G2
• The dynamics of internal working surfaces in MHD jets
• Simulating the effect of the Sgr A* accretion flow on the appearance of G2 after pericenter
• Signatures of an Encounter Between the G2 Cloud and a Jet from Sgr A*
• Colliding with G2 near the Galactic Centre: a geometrical approach

Cited by in corpus (21)

• The Galactic Center cloud G2 and its gas streamer
• Unprecedented variability of Sgr A* in NIR
• Fifteen years of XMM-Newton and Chandra monitoring of Sgr A*: Evidence for a recent increase in the bright flaring rate
• Monitoring the Dusty S-Cluster Object (DSO/G2) on its Orbit towards the Galactic Center Black Hole
• The Post-Pericenter Evolution of the Galactic Center Source G2
• Clump formation through colliding stellar winds in the Galactic Centre
• Nature of the Galactic centre NIR-excess sources. I. What can we learn from the continuum observations of the DSO/G2 source?
• 3D adaptive mesh refinement simulations of the gas cloud G2 born within the disks of young stars in the Galactic Center
• Effect of an isotropic outflow from the Galactic centre on the bow-shock evolution along the orbit
• No asymmetric outflows from Sagittarius A* during the pericenter passage of the gas cloud G2
• The evolution of circumstellar discs in the Galactic Centre: an application to the G-clouds
• The G2+G2t complex as a fast and massive outflow?
• Survival of the Fittest: Numerical Modeling of Supernova 2014C
• Probing the Gas Density in our Galactic Center: Moving Mesh Simulations of G2
• 3D AMR hydrosimulations of a compact source scenario for the Galactic Centre cloud G2
• Investigating dusty Red Supergiant outflows in Westerlund 1 with 3D Hydrodynamic simulations
• MOLsphere and pulsations of the Galactic Center's red supergiant GCIRS 7 from VLTI/GRAVITY
• G2 and Sgr A*: A Cosmic Fizzle At The Galactic Center
• Tidal phenomena in the Galactic Center: The curious case of X7
• Black Hole Survival Guide: Searching for Stars in the Galactic Center That Endure Partial Tidal Disruption
• 3D AMR simulations of G2 as an outflow