The compact and, with about 4.3+-0.3 million solar masses, very massive object located at the center of the Milky Way is currently the very best candidate for a supermassive black hole (SMBH) in our immediate vicinity.
The presentation will conclude with an outlook to the near future about how the upcoming astrometric and off-axis phase-referencing capabilities of the Keck and VLT Interferometers, nicknamed ASTRA and PRIMA, will greatly extend the currently existing capabilities to observe astrophysical phenomena in the Galactic center at the borderline to General relativity in a yet uninvestigated regime. The feasibility of phase-referencing to the supergiant GCIRS 7, located only 5" away from SgrA*, to increase the sensitivity and spectral resolution of the observations, is discussed, and supported by the first real data. An overview over the currently available IF-technology is given, biased towards the GC science case. We show that the highest angular resolution only available through interferometric techniques is necessary to observe the GC ISM production in the making and distinguish individual sources from its dusty surroundings. We achieved first IR-IF fringes in both available IR science regimes of the VLTI (MIDI: 10 mum) and (AMBER: 2 mum), demonstrating the new capabilities provided by large aperture telescope arrays to the Galactic center research. The current results of our ongoing Galactic Center (GC) observations with optical long baseline interferometry (OLB-IF) are presented. Comment: accepted by A&A, now in press 19 pages, 22 figures, 5 tables Our findings suggest further studies of the composition of interstellar dust and the shape of the 10um silicate feature at this outstanding region. We have demonstrated that optical long baseline interferometry at infrared wavelengths is an indispensable tool to investigate sources at the Galactic Center. This indicates physically and chemically distinct conditions of the local dust, changing with the distance to IRS3. The silicate absorption most probably takes place in the outer diffuse dust, which is mostly ignored by MIDI measurements. Despite observed deep silicate absorption towards IRS3 we favor a carbon rich chemistry of the circumstellar dust shell. The IF data resolve the innermost area of dust formation. The coinciding interpretation of multiple datasets confirm dust emission at several spatial scales. The luminosity and size estimates show that IRS3 is probably a cool carbon star enshrouded by a complex dust distribution.
ENIGMA PROPERTIES FULL
Photometry data were added to enable simple SED- and full radiative transfer-models of the data. The VLTI/MIDI instrument was used to measure visibilities at 10mas resolution of that compact 10um source, still unresolved by a single VLT.
VISIR imaging separates a compact source from diffuse, surrounding emission. We initiated an interferometric experiment to understand IRS3 and investigate its properties as spectroscopic and interferometric reference star at 10um. The properties of extreme individual objects of the central stellar cluster contribute to our knowledge of star and dust formation close to a supermassive black hole. NIR spectroscopy failed to solve the enigma of its nature.
ENIGMA PROPERTIES PC
GCIRS3 is the most prominent MIR source in the central pc of the Galaxy.
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