Stellar Systems Group

Eckart, A.; Horrobin, M.; Britzen, S.; Zamaninasab, M.; Mužić, K.; Sabha, N.; Shahzamanian, B.; Yazici, S.; Moser, L.; García-Marin, M.; Valencia-S., M.; Borkar, A.; Bursa, M.; Karssen, G.; Karas, V.; Zajaček, M.; Bronfman, L.; Finger, R.; Jalali, B.; Vitale, M.; Rauch, C.; Kunneriath, D.; Moultaka, J.; Straubmeier, C.; Rashed, Y. E.; Markakis, K.; Zensus, A.
Proceedings of the International Astronomical Union, Volume 303, pp. 269-273 (2014).
05/2014

ABSTRACT

A fast moving infrared excess source (G2) which is widely interpreted as a core-less gas and dust cloud approaches Sagittarius A* (Sgr A*) on a presumably elliptical orbit. VLT K_s -band and Keck K'-band data result in clear continuum identifications and proper motions of this ˜19 ^m Dusty S-cluster Object (DSO). In 2002-2007 it is confused with the star S63, but free of confusion again since 2007. Its near-infrared (NIR) colors and a comparison to other sources in the field speak in favor of the DSO being an IR excess star with photospheric continuum emission at 2 microns than a core-less gas and dust cloud. We also find very compact L'-band emission (<0.1″) contrasted by the reported extended (0.03″ up to ˜0.2″ for the tail) Brγ emission. The presence of a star will change the expected accretion phenomena, since a stellar Roche lobe may retain a fraction of the material during and after the peri-bothron passage.