3D Radiative Transfer Modeling of the Red Supergiant NML Cyg

Abstract

Red supergiants are bright but cool massive stars that have depleted their core hydrogen supply and have started fusing heavier elements. These evolved stars ex perience a strong mass loss through a slow moving stellar wind that results in an extended circumstellar envelope with a rich chemistry. The circumstellar envelopes of red supergiants will eventually enrich the interstellar medium, influencing the formation and evolution of the next generation of stars and planets. Understanding the mass loss of massive evolved stars is a key component in understanding both the evolution of individual stars and the chemical evolution of the universe. We analyze carbon monoxide emission around the red supergiant NML Cyg ob served with the ground based JCMT 15 meter and Onsala 20 meter telescopes, as well as the HIFI instrument aboard the Herschel Space Observatory. The line pro files have complex shapes, suggestive of multiple components in the stellar outflow. 3D radiative transfer modeling is used to recreate the observed line profiles. We con clude that it is possible to recreate the observed line profiles by using one spherical component and three directed outflows.