S62 on a 9.9 year orbit around the supermassive black hole in the center of our galaxy

ATel #12979; Florian Peissker (Ph1, Cologne), Andreas Eckart (Ph1, Cologne), Marzieh Parsa (Ph1, Cologne)
on 1 Aug 2019; 20:21 UT
Credential Certification: Florian Peissker (peissker@ph1.uni-koeln.de)

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Based on our forthcoming publication (Peißker et al., submitted to ApJ), we report the detection of the S-star S62 on its 9.9 years highly eccentric orbit around the supermassive black hole SgrA*. This makes S62 the star with the shortest orbital period. We trace this star consistently in our high-quality NACO and SINFONI (both VLT/Paranal, Chile) data-sets. Between 2003 and 2012, a detection of this star was possible without confusion by neighboring bright stars like S2. Because of the periapse passage of S2 in 2018, blending with S2 hindered a direct observation of S62 between 2013 and 2018. Now that the S2 periapse passage has passed, S62 can closely be followed entering its very close periapse section. We expect a gravitational periapse shift of almost 10 degrees. From the maximized likelihood method, we derive an enclosed mass of (4.15 +- 0.6) x 10^6 M_sun. Until now this is the enclosed mass measurement closest to a supermassive black hole carried out with a stellar object. The closest approach of this star is at 5.2 AU (after inclination correction). The next periapse of S62 will be towards the end of 2022. From the mass-luminosity relation, we determine the mass of S62 to 2.2 M_sun which is in line with other S-stars. We derive a K-band magnitude of around 16 mag. Observations densely spaced in time are essential to further refine the orbit.