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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 660645.0, MPI für Astronomie / Publikationen_mpia
Disentangling confused stars at the Galactic Center with long-baseline infrared interferometry
Authors:Stone, J. M.; Eisner, J. A.; Monnier, J. D.; Woillez, J.; Wizinowich, P.; Pott, J. -. U.; Ghez, A. M.
Date of Publication (YYYY-MM-DD):2012
Journal Abbrev.:The Astrophysical Journal
Issue / Number:2
Start Page:id. 151
Audience:Not Specified
Abstract / Description:We present simulations of Keck Interferometer ASTRA and VLTI GRAVITY observations of mock star fields in orbit within ~50 mas of Sgr A*. Dual-field phase referencing techniques, as implemented on ASTRA and planned for GRAVITY, will provide the sensitivity to observe Sgr A* with long-baseline infrared interferometers. Our results show an improvement in the confusion noise limit over current astrometric surveys, opening a window to study stellar sources in the region. Since the Keck Interferometer has only a single baseline, the improvement in the confusion limit depends on source position angles. The GRAVITY instrument will yield a more compact and symmetric point-spread function, providing an improvement in confusion noise which will not depend as strongly on position angle. Our Keck results show the ability to characterize the star field as containing zero, few, or many bright stellar sources. We are also able to detect and track a source down to mK ~ 18 through the least confused regions of our field of view at a precision of ~200 μas along the baseline direction. This level of precision improves with source brightness. Our GRAVITY results show the potential to detect and track multiple sources in the field. GRAVITY will perform ~10 μas astrometry on an mK = 16.3 source and ~200 μas astrometry on an mK = 18.8 source in 6 hr of monitoring a crowded field. Monitoring the orbits of several stars will provide the ability to distinguish between multiple post-Newtonian orbital effects, including those due to an extended mass distribution around Sgr A* and to low-order general relativistic effects. ASTRA and GRAVITY both have the potential to detect and monitor sources very close to Sgr A*. Early characterizations of the field by ASTRA, including the possibility of a precise source detection, could provide valuable information for future GRAVITY implementation and observation.
Free Keywords:astrometry; Galaxy: center; instrumentation: interferometers; techniques: interferometric
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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