EDP Sciences
Press Release
Free Access

Fig. 1.


Monitoring the S2 orbit around Sgr A with the three VLT(I) instruments NACO (AO-assisted, single UT imaging), GRAVITY (interferometric astrometry-imaging with all four UTs of the VLT) and SINFONI (AO-assisted integral field spectroscopy). Upper left: Deconvolved NACO K-band image of the Galactic centre a few weeks before the 2018 pericentre passage. The source S2 appears slightly elongated because of confusion with Sgr A. Upper right: Nearly simultaneous GRAVITY image of S2 and Sgr A. The image shows the central 150 mas (0.0059 pc ≈ 1.4 × 104RS) after self-calibration and CLEANing with AIPS. The image is reconstructed from 34 integrations of 5 min each from several nights at the end of March 2018. Sgr A was (on average) K = 16.6 mag and the rms noise level of the background after cleaning is ≈20 mag. Both Sgr A and S2 are unresolved. Here and in the other GRAVITY images, the elongation is due to the shape of the interferometric clean beam. Bottom: S2 – Sgr A GRAVITY images (coaddition of several days) from July 2017 (bottom left) and May / June 2018, a few days after pericentre (bottom right). The inset in the bottom left panel shows the instantaneous interferometric beam, which is 2.2 mas × 4.7 mas without Earth rotation. The inset in the middle left shows a co-added SINFONI K-band spectrum of the star S2, taken from Habibi et al. (2017).

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.