Massive Stars and the Creation of our Galactic Center

Abstract

Our Galactic Center hosts over 10% of the known massive stars in the Galaxy. The majority of these stars are located in three particularly massive clusters that formed within the past 5 Myr. While these clusters are extraordinary, their formation repesents about half of the total inferred star formation rate in the Galactic Center. There is mounting evidence that the clusters are just present-day examples of the hundreds of such similar clusters that must have been created in the past, and whose stars now comprise the bulk of all stars seen in the region. I discuss the massive stellar content in the Galactic Center and present a new analysis that suggests that effects of continuous star formation in the Galactic Center can be seen in the observed luminosity functions newly-obtained HST/NICMOS and Gemini AO data.

Monitoring the activity of the Be star OT Geminorum

“…However the indications in the Atlas are qualitative estimates, at best on a year-to-year basis, without precise dates, which is obviously not suited to the present study of the short-term variations. Thus, the only clearly confirmed correlation between an increase of the spectroscopic activity and an increase of the light output is the one mentioned by Figer (1981b) and already described in Sect. 3.…”

“…The total event lasted 150−200 days. The 45% light increase has been correlated with simultaneous spectroscopy showing the Balmer discontinuity in emission (Figer 1981b), which indicates a very violent atmospheric event. The corresponding light curve slopes are about −4 mmag/day for the light increase (lasting about 60 days), and +2.5 mmag/day for the decrease (lasting about 90 days), i.e.…”

“…The GEOS 1977 to 1981 observations published by Figer (1981b) show that the star had remained at a visual magnitude m v around 6.4 for three years (JD 2443500 to 2444700). Then a 0.4 magnitude light increase (from m v = 6.4 to 6.0) was detected in november 1980, followed by a rather rapid return to the previous light level, in the first months of 1981.…”

“…d'Observation Stellaire) during 1977 -1980 and reported by Figer (1981b). Since that time, OT Gem has been followed by the GEOS as a part of a Be stars campaign, and professionals were alerted when they visually detected and confirmed the new light increase at JD 2449980−2450010 (i.e.…”

The Stellar and Sub-Stellar Initial Mass Function of Simple and Composite Populations

“…Such a steep IMF may be the true mass-distribution if unresolved multiple systems are corrected for, but an affirmation of this and thus the negation of the physical stellar mass limit awaits a detailed investigation of this issue. Figer (2005) followed by performing the same analysis with his HST data on the Arches cluster confirming the same physical mass limit, and Oey & Clarke (2005) published a statistical analysis of a number of OB associations and clusters again confirming that a physical mass limit exists in the mass range 120 − 200 M ⊙ . Thus, stellar masses are limited near 0.072 M ⊙ (Chabrier 2003a) and near 150 M ⊙ .…”