Mass-transfer Outburts reborn: Modeling the light curve of the dwarf nova EX Draconis

Abstract

EX Draconis is an eclipsing dwarf nova that shows outbursts with moderate amplitude ($\simeq 2$ mag) and a recurrence timescale of $\simeq 20$-30 d. Dwarf novae outbursts are explained in terms of either a thermal-viscous instability in the disc or an instability in the mass transfer rate of the donor star (MTIM). We developed simulations of the response of accretion discs to events of enhanced mass transfer, in the context of the MTIM, and applied them to model the light curve and variations in the radius of the EX Dra disc throughout the outburst. We obtain the first modeling of a dwarf nova outburst by using ${\chi }^2$ to select, from a grid of simulations, the best-fit parameters to the observed EX Dra outbursts. The observed time evolution of the system brightness and the changes in the radius of the outer disc along the outburst cycle are satisfactorily reproduced by a model of the response of an accretion disc with a viscosity parameter $\alpha =4.0$ and a quiescent mass transfer rate ${\dot{M}}_2(\text{quiescence})=4.0\times 10^{16}$ g/s to an event of width $\Delta t=6.0\times 10^5$ s ($\sim 7$ d) where the mass-transfer rate increases to ${\dot{M}}_2(\text{outburst})=1.5\times 10^{18}$ g/s.

arXiv comment18 pages, 12 figures, prepared with AASLatex; to appear in The Astrophysical Journal

References in corpus (25)

• The Gaia mission
• Gaia Data Release 3: Summary of the content and survey properties
• The disc instability model of dwarf-novae and low-mass X-ray binary transients
• The disc instability model for X-ray transients: evidence for truncation and irradiation
• A review of the disc instability model for dwarf novae, soft X-ray transients and related objects
• 3D numerical simulation of gaseous flows structure in semidetached binaries
• Strong disc winds traced throughout outbursts in black-hole X-ray binaries
• On the physical nature of accretion disc viscosity
• Two and Three Dimensional Numerical Simulations of Accretion Discs in a Close Binary System
• Structure and properties of transition fronts in accretion discs
• The nature of dwarf nova outbursts
• Eclipse mapping of the flickering sources in the dwarf nova V2051 Ophiuchi
• The Detection of 13CO and Other Apparent Abundance Anomalies in the Secondary Stars of Long-Period Cataclysmic Variables
• Eclipse studies of the dwarf-nova Ex Draconis
• Dwarf Nova Outbursts with Magnetorotational Turbulence
• Changes in the structure of the accretion disc of EX Draconis through the outburst cycle
• Anomalous Z Cam stars: a response to mass-transfer outbursts
• The V-EUV Delay for Dwarf Nova Outbursts: A Case Study for VW Hydri, U Geminorum, and SS Cygni
• Abundance Derivations for the Secondary Stars in Cataclysmic Variables from Near-Infrared Spectroscopy
• A study of the evolution of the accretion disk of V2051 Oph through two outburst cycles
• V4140 Sgr: a short period dwarf nova with a peculiar behavior
• EX Draconis: Using Eclipses to Separate Outside-In and Inside-Out Outbursts
• SOAR observations of the high-viscosity accretion disc of the dwarf nova V4140 Sagitarii in quiescence and in outburst
• Challenging the disk instability model: I -- The case of YZ LMi
• The Influence of Parameters on the Flow Structure in Semidetached Binary Systems: 3D Numerical Simulation

Cited by in corpus (1)

• Modeling the high-brightness state of the recurrent nova T CrB as an enhanced mass-transfer event