Low angular momentum accretion-outflow model of flares from Sgr A$^*$

Abstract

We employ a low angular momentum accretion-outflow scenario to model the flares emanating out from the central region of Sgr A$^*$. The primary donor for matter accreting onto the central SMBH of Sgr A$^*$ is assumed to be the WR star ISR 13 E3. We analytically calculate the specific energy and angular momentum density of stellar wind originating from ISR 13 E3 and study the dynamics of that wind down to the very close vicinity of the central SMBH of Sgr A$^*$. We show that on the way to the Galactic centre, such wind-fed accretion may encounter standing shocks and such shock drives outflow from the close vicinity of the SMBH. Matter content of such outflow is computed and it is argued that such outflow is responsible for production of the Galactic centre flares. We then self-consistently compute the luminosity ${\cal L}_j$ and the duration time scale $τ$ of such flares, as a function of fundamental accretion parameters. Our theoretical calculation of ${\cal L}_j$ and $τ$ are in good agreement with observational results.