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Monitoring the Dusty S-cluster Object (DSO/G2) on its orbit towards the Galactic Center Black Hole: Periapse not yet reached

ATel #6285; A. Eckart (Universitaet zu Koeln), M. Valencia-S. (Universitaet zu Koeln), F. Peissker (Universitaet zu Koeln), N. Grosso (Observatoire astronomique de Strasbourg), E. Mossoux (Observatoire astronomique de Strasbourg), D. Porquet (Observatoire astronomique de Strasbourg), V. Karas (Astronomical Institute Academy of Sciences Prague), M. Dovciak (Astronomical Institute Academy of Sciences Prague), S. Smajic (Universitaet zu Koeln), S. Yazici (Universitaet zu Koeln), L. Moser (Universitaet zu Koeln), B. Shahzamanian (Universitaet zu Koeln), M. Garcia-Marin (Universitaet zu Koeln), M. Zajacek (Charles University in Prague), G. D. Karssen (Universitaet zu Koeln), M. Bursa (Astronomical Institute Academy of Sciences Prague), D. Kunneriath (Astronomical Institute Academy of Sciences Prague), C. Straubmeier (Universitaet zu Koeln)
on 30 Jun 2014; 22:34 UT
Credential Certification: Monica Valencia-S. (mvalencias@ph1.uni-koeln.de)

Subjects: Infra-Red, AGN, Black Hole, Transient

We report new near-infrared (1.45 - 2.45 microns) observations of the Dusty S-cluster Object (DSO/G2) during its approach to the black hole at the center of the Galaxy, that were carried out with ESO VLT/SINFONI between February and April 2014. We detect spatially compact Brackett-gamma and Paschen-alpha line emission from the DSO/G2 at about 30-40mas east of SgrA*. This is in agreement with the position reported by A. M. Ghez et al. (ATel #6110) from L-band observations in March 2014. The velocity of the source, measured from the red-shifted emission, is approx. 2700 km/s. No blue-shifted emission above the noise level is detected at the position of SgrA* or upstream the presumed orbit. The full width at half maximum of the Brackett-gamma line is ~50 Angstroms, i.e. no significant line broadening with respect to last year is observed. This is a further indication for the compactness of the source. For the moment, the flaring activity of the black hole in the near-infrared regime has not shown any statistically significant increment. We conclude that the DSO/G2 source has not yet reached its periapse, and that the increased accretion activity of SgrA* is still upcoming.