The fastest star around a super massive black hole
ATel #13935; Florian Peissker (Ph1, Cologne), Andreas Eckart (Ph1, Cologne), Michal Zajacek (cft, Warsaw), Basel Ali (Ph1, Cologne), Marzieh Parsa (Ph1, Cologne)
on 11 Aug 2020; 16:00 UT
Credential Certification: Florian Peissker (peissker@ph1.uni-koeln.de)
Subjects: Black Hole, Star
We are excited to announce the detection of a new member of the S-cluster, S4711. This B8/9-V star orbits SgrA* in the center of our Galaxy in around 7.6 years. We found this star during the analysis of S62 (doi: 10.3847/1538-4357/ab5afd, see also ATel #12979). Furthermore, we find indications for a population of fast-moving stars that are at least temporarily inside the orbit of S2.
In the related publication (accepted and published via ApJ, doi: 10.3847/1538-4357/ab9c1c, arxiv version will be online soon), we update several values for S62 and establish a method to calculate the mass of a S-cluster member purely on photometric results.
All newly discovered stars S4711-S4715 are close to the detection limit and have a calculated mass between 2.0-2.8 M_sun. For S62, we find with this new method a mass of 6.1 M_sun. The star S4714 shows the highest relativistic parameter (r_s/r_p) with 64 compared to 46 of S62. S4711 has a relativistic parameter of 5.6.
We are using BONNSAI simulations based on the spectral analysis to derive several parameters for S4711 like e.g., the rotational velocity of 260 +- 25 km/s. We relate the finding of the stars S4711-S4715 to our recent publication about the two disks in the GC (Ali et al. 2020) and confirm, that the major axis is a function of the eccentricity.
For S62, we find a pericenter velocity of ~20000 km/s (6.7% of c), for S4711 ~6700 km/s (2.2% of c), and for S4714 ~24000 km/s (8% of c).
