Contributed Talk - Splinter Historical

Friday, 25 September 2020, 16:55   (virtual room E)

Discovery of an emission nebula in the Galactic globular cluster M22

F. Göttgens (1), P. Weilbacher (2), M. M. Roth (2), S. Dreizler (1) et al.
(1) Institut für Astrophysik, Universität Göttingen, (2) Leibniz-Institut für Astrophysik Potsdam

We present the discovery of an emission nebula in the Galactic globular cluster M22 in observations made the with the MUSE instrument at the VLT. We extract the spectrum of the nebula and use emission-line ratios to determine a nebula mass of 10^-5 to 10^-4 solar masses which is in the range of nova remnants. The radial velocity measured from the emission lines confirm that the nebula is part of M22. The position of M22 coincides with the reported location of a 'guest star' observed by Chinese astronomers in May 48 BCE. Using Gaia proper motion data for the reference star mentioned in the ancient text, we show that the positions agree to ~2 degrees. In my talk, I will discuss possible origins of the nebula. While its mass and the proximity to the ancient 'guest star' suggest that the nebula is a nova remnant, other properties such as the current expansion velocity are more typical for planetary nebulae. I will also discuss a possible connection to the known planetary nebula in M22.