Tidal Distortion of the Envelope of an AGB Star IRS 3 near Sgr A*

Yusef-Zadeh, F.; Wardle, M.; Cotton, W.; Schödel, R.; Royster, M. J.; Roberts, D. A.; Kunneriath, D.
eprint arXiv:1702.02196


We present radio and mm continuum observations of the Galactic center taken with the VLA and ALMA at 44 and 226 GHz, respectively. We detect radio and mm emission from IRS 3, lying ~4.5" NW of Sgr A*, with a spectrum that is consistent with the photospheric emission from an AGB star at the Galactic center. Millimeter images reveal that the envelope of IRS 3, the brightest and most extended 3.8$\mu$m Galactic center stellar source, consists of two semi-circular dust shells facing the direction of Sgr A*. The outer circumstellar shell at the distance of 1.6$\times10^4$ AU, appears to break up into "fingers" of dust directed toward Sgr A*. These features coincide with molecular CS (5-4) emission and a near-IR extinction cloud distributed between IRS 3 and Sgr A*. The NE-SW asymmetric shape of the IRS 3 shells seen at 3.8 micron and radio are interpreted as structures that are tidally distorted by Sgr A*. Using the kinematics of CS emission and the proper motion of IRS 3, the tidally distorted outflowing material from the envelope after 5000 years constrains the distance of IRS 3 to $\sim$0.7 pc in front of or $\sim$0.5 pc behind Sgr A*. This suggests that the mass loss by stars near Sgr A* can supply a reservoir of molecular material near Sgr A*. We also present dark features in radio continuum images coincident with the envelope of IRS 3. These dusty stars provide examples in which high resolution radio continuum images can identify dust enshrouded stellar sources embedded an ionized medium.