2002/05/13 by S. Gezari, A. M. Ghez, E. E. Becklin +3 · 8 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Pulsars and Gravitational Waves Research #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/341807
19 pages, 8 figures, 2 tables. Accepted for publication in ApJ
arxiv created 2002/05/13 · openalex publication_date 2002/09/10 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We present K -band λ/Δλ ~ 2600 spectroscopy of five stars ( K ~ 14-16 mag) within 0 5 of Sgr A*, the radio source associated with the compact massive object suspected to be a 2.6 × 10 6 M ☉ black hole at the center of our Galaxy. High spatial resolution of ~0 09 and good Strehl ratios of ~0.2 achieved with adaptive optics on the 10 m Keck telescope make it possible to measure moderate-resolution spectra of these stars individually for the first time. Two stars (S0-17 and S0-18) are identified as late-type stars by the detection of CO band head absorption in their spectra. Their absolute K magnitudes and CO band head absorption strengths are consistent with early K giants. Three stars (S0-1, S0-2, and S0-16) with r proj < 0.0075 pc (~0 2) from Sgr A* lack CO band head absorption, confirming the results of earlier lower spectral and lower spatial resolution observations that the majority of the stars in the Sgr A* cluster are early-type stars. The absolute K magnitudes of the early-type stars suggest that they are late O, early B main-sequence stars of ages less than 20 Myr. The presence of young stars in the Sgr A* cluster so close to the central supermassive black hole poses the intriguing problem of how these stars could have formed or could have been brought within its strong tidal field.