Cool and luminous transients from mass-losing binary stars

[摘要] Motivated by the recently established link between luminous red novae (LRN) and catastrophic phases of binary star evolution, we perform smoothed particle hydrodynamic calculations of outflows from binary stars with realistic equation of state and opacities. We focus on the case of mass loss from the outer Lagrangian point (L2), where the resulting spiral stream experiences tidal torques from the binary and becomes unbound. As the individual spiral arms merge and collide near the binary, the outflow thermalizes about 5% of its kinetic energy. For reasonable binary parameters, the outflow can produce luminosities up to 106Lowith effective temperatures between 500 and 6000 K, depending on the optical depth through the outflow. This is compatible with many examples of the LRN such as V838 Mon and V1309 Sco. The luminosity and the expansion velocity are correlated, as is roughly observed in the known LRN. The outflow readily forms dust, leading to great variations of the appearance of the transient as a function of the viewing angle. Our results are relevant for a more general class of equatorial outflows with asymptotic velocity and heating rate near the binary proportional to its orbital speed.

[发布机构] Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton; NJ; 08540, United States^1;Columbia Astrophysics Laboratory, Columbia University, New York; NY; 10027, United States^2;Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Osaka, Toyonaka; 560-0043, Japan^3

[效力级别] 天文学 [学科分类] 天文学(综合)

[关键词] Binary parameters;Effective temperature;Equation of state;Expansion velocity;General class;Lagrangian points;Optical depth;Smoothed particle hydrodynamics