Astrophys. J., 800, 125 (2015/February-3)
Monitoring the dusty s-cluster object (DSO/G2) on its orbit toward the Galactic Center black hole.
VALENCIA-S. V., ECKART A., ZAJACEK M., PEISSKER F., PARSA M., GROSSO N., MOSSOUX E., PORQUET D., JALALI B., KARAS V., YAZICI S., SHAHZAMANIAN B., SABHA N., SAALFELD R., SMAJIC S., GRELLMANN R., MOSER L., HORROBIN M., BORKAR A., GARCIA-MARIN M., DOVCIAK M., KUNNERIATH D., KARSSEN G.D., BURSA M., STRAUBMEIER C. and BUSHOUSE H.
Abstract (from CDS):
We analyze and report in detail new near-infrared (1.45-2.45 µm) 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 the ESO Very Large Telescope/SINFONI between 2014 February and September. Before 2014 May we detect spatially compact Brγ and Paα line emission from the DSO at about 40 mas east of Sgr A*. The velocity of the source, measured from the redshifted emission, is 2700±60 km/s. No blueshifted emission above the noise level is detected at the position of Sgr A* or upstream of the presumed orbit. After May we find spatially compact Brγ blueshifted line emission from the DSO at about 30 mas west of Sgr A* at a velocity of -3320±60 km/s and no indication for significant redshifted emission. We do not detect any significant extension of the velocity gradient across the source. We find a Brγ line FWHM of 50±10 Å before and 15±10 Å after the peribothron transit, i.e., no significant line broadening with respect to last year is observed. Brγ line maps show that the bulk of the line emission originates from a region of less than 20 mas diameter. This is consistent with a very compact source on an elliptical orbit with a peribothron time passage in 2014.39±0.14. For the moment, the flaring activity of the black hole in the near-infrared regime has not shown any statistically significant increment. Increased accretion activity of Sgr A* may still be upcoming. We discuss details of a source model according to which the DSO is a young accreting star rather than a coreless gas and dust cloud.
astrometry - black hole physics - Galaxy: center - line: identification - line: profiles - techniques: imaging spectroscopy
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