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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 559173.0, MPI für Astronomie / Publikationen_mpia
Signatures of strong gravity with GRAVITY
Authors:Eckart, A.; Zamaninasab, M.; Straubmeier, C.; Fischer, S.; Araujo-Hauck, C.; Garcia-Marin, M.; Wiest, M.; Witzel, G.; Buchholz, R. M.; Sabha, N.; Muzic, K.; Eisenhauer, F.; Paumard, T.; Yazici, S.; Perrin, G.; Brandner, W.; Perraut, K.; Amorim, A.; Schöller, M.
Date of Publication (YYYY-MM-DD):2010
Title of Proceedings:Optical and Infrared Interferometry II
Start Page:77340X-77340X
End Page:11
Volume (in Series):7734
Name of Conference/Meeting:Optical and Infrared Interferometry II
Audience:Not Specified
Abstract / Description:The dynamics of stars and gas undoubtedly shows the existence of a 4 million solar mass black hole at the center of the Milky Way: Sagittarius A* (SgrA*). Violent flare emission allows us to probe the immediate environment of the central mass. Near-infrared polarimetry now shows signatures of strong gravity that are statistically significant against randomly polarized red noise. Using these signatures we can derive spin and inclination information of SgrA*. A combined synchrotron self Compton (SSC) and adiabatic expansion model with source components peaking in the sub-mm domain can fully account for the observed flare flux densities and the time delays towards the (sub-)mm flares that have been reported in some cases. We discuss the expected centroid paths of the NIR images and summarize how the geometrical structure of the emitting region (i.e. spot shape, presence of a torus or spiral-arm pattern etc.) affects this centroid tracks. While most of the mentioned geometries are able to fit the observed fluxes, future NIR interferometry with GRAVITY at the VLT will break some of the degeneracies between different emission models. In this contribution we summarize several GRAVITY science cases for SgrA*. Our simulations propose that focusing GRAVITY observations on the polarimetry mode could reveal a clear centroid track of the spot(s). A non-detection of centroid shifts cannot rule out the multi-component model or spiral arms scenarios. However, a clear wander between alternating centroid positions during the flares will prove the idea of bright long-lived spots occasionally orbiting the central black hole.
Comment of the Author/Creator:Date: 2010, July 1, 2010
External Publication Status:published
Document Type:Conference-Paper
Communicated by:N. N.
Affiliations:MPI für Astronomie
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