On the nature of the fast moving star S2 in the Galactic Center

Abstract

We analyze the properties of the star S2 orbiting the supermassive black hole at the center of the Galaxy. A high quality SINFONI H and K band spectrum obtained from coadding 23.5 hours of observation between 2004 and 2007 reveals that S2 is an early B dwarf (B0-2.5V). Using model atmospheres, we constrain its stellar and wind properties. We show that S2 is a genuine massive star, and not the core of a stripped giant star as sometimes speculated to resolve the problem of star formation so close to the supermassive black hole. We give an upper limit on its mass loss rate, and show that it is He enriched, possibly because of the presence of a magnetic field.

4 pages, 5 figures, ApJ letters accepted

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• The Galactic Center cloud G2 and its gas streamer
• The nuclear cluster of the Milky Way: Our primary testbed for the interaction of a dense star cluster with a massive black hole
• Event-Horizon-Telescope Evidence for Alignment of the Black Hole in the Center of the Milky Way with the Inner Stellar Disk
• Origin of the S Stars in the Galactic Center
• The Anisotropic Spatial Distribution of Hypervelocity Stars
• The S-Star Cluster at the Center of the Milky Way: On the nature of diffuse NIR emission in the inner tenth of a parsec
• HVS7: a chemically peculiar hyper-velocity star
• Star Formation in Quasar Disk
• Clocks around Sgr A*
• Sculpting the Stellar Cusp in the Galactic Center
• Locating the VHE source in the Galactic Centre with milli-arcsecond accuracy
• LIINUS/SERPIL: a design study for interferometric imaging spectroscopy at the LBT
• LIINUS/SERPIL: a design study for interferometric imaging spectroscopy at the LBT