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# Regulation of accretion by its outflow in a symbiotic star: the 2016 outflow fast state of MWC 560

Lucy, A. B., Sokoloski, J. L., Munari, U., Roy, N., Kuin, N. Paul M., Rupen, M. P., Knigge, C., Darnley, M. J., Luna, G. J. M., Somogyi, P., Valisa, P., Milani, A., Sollecchia, U. and Weston, J. H. S. (2020) Regulation of accretion by its outflow in a symbiotic star: the 2016 outflow fast state of MWC 560. Monthly Notices of the Royal Astronomical Society, 492 (3), 3107-3127.

Record type: Article

## Abstract

The symbiotic binary MWC 560 (=V694 Mon) is a laboratory for the complex relationship between an accretion disk and its outflow. In 2016, at the peak of a slow rise in optical flux, the maximum velocity of the broad absorption line outflow abruptly doubled to at least 2500 km s$^{-1}$. The sudden onset of high-velocity Balmer absorption coincided with remarkable developments indicating an increase in outflow power:optically-thin thermal radio emission began rising by about 20$\mu$Jy/month, and soft X-ray flux increased by an order of magnitude. Comparison to historical data suggests that both high-velocity and low-velocity optical outflow components must be simultaneously present to yield a large soft X-ray flux, which may originate in a shock where these fast and slow absorbers collide. Balmer absorption and the enduring Fe II ultraviolet absorption curtain demonstrate that the absorption line-producing outflow was consistently fast and dense($\gtrsim10^{6.5}$ cm$^{-3}$) throughout the 2016 outflow fast state, steadily feeding a lower-density ($\lesssim10^{5.5}$ cm$^{-3}$) region of radio-emitting gas. Persistent optical and near-ultraviolet flickering indicates that the accretion disk remained intact, and that the increase in optical brightness was due to an increase in the rate of accretion through the disk. The stability of all these properties in 2016 stands in marked contrast to dramatic variations during the 1990 optical brightening event of MWC 560, despite reaching a similar accretion luminosity. We propose that accretion state changes in MWC560, such as evacuation of the inner disk, are sometimes prevented by the self-regulatory effect of the disk's outflow.

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pdf - Accepted Manuscript

Submitted date: 8 May 2019
Accepted/In Press date: 20 December 2019
e-pub ahead of print date: 3 January 2020
Published date: March 2020
Keywords: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics

## Identifiers

Local EPrints ID: 430972
URI: http://eprints.soton.ac.uk/id/eprint/430972
ISSN: 0035-8711
PURE UUID: 15c9556e-2075-48e4-8f71-1eb9dab52547

## Catalogue record

Date deposited: 20 May 2019 16:30

## Contributors

Author: A. B. Lucy
Author: J. L. Sokoloski
Author: U. Munari
Author: N. Roy
Author: N. Paul M. Kuin
Author: M. P. Rupen
Author: C. Knigge
Author: M. J. Darnley
Author: G. J. M. Luna
Author: P. Somogyi
Author: P. Valisa
Author: A. Milani
Author: U. Sollecchia
Author: J. H. S. Weston