A. Borkar

Monitoring the Dusty S-cluster Object (DSO/G2) on its Orbit toward the Galactic Center Black Hole

We analyze and report in detail new near-infrared (1.45-2.45 ?m) 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 Br? and Pa? 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?1. 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 Br? blueshifted line emission from the DSO at about 30 mas west of Sgr A* at a velocity of ?3320???60 km s?1 and no indication for significant redshifted emission. We do not detect any significant extension of the velocity gradient across the source. We find a Br? line FWHM of 50???10 ? before and 15???10 ? after the peribothron transit, i.e., no significant line broadening with respect to last year is observed. Br? 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.

Polarized light from Sagittarius A* in the near-infrared Ks-band

We present a statistical analysis of polarized near-infrared (NIR) light from Sgr A*, the radio source associated with the supermassive black hole at the center of the Milky Way. The observations have been carried out using the adaptive optics instrument NACO at the VLT UT4 in the infrared

Star formation in the vicinity of nuclear black holes: young stellar objects close to Sgr A*

K_\mathrm{s}

Monitoring the Galactic Centre with the Australia Telescope Compact Array

-band from 2004 to 2012. Several polarized flux excursions were observed during these years. Linear polarization at 2.2

The Multifrequency Behavior of Sagittarius A

\mu m

The Center of the Milky Way from Radio to X-rays

, its statistics and time variation, can be used constrain the physical conditions of the accretion process onto this supermassive black hole. With an exponent of about 4 for the number density histogram of fluxes above 5~mJy, the distribution of polarized flux density is closely linked to the single state power-law distribution of the total

Experimental Indicators of Accretion Processes in Active Galactic Nuclei

K_\mathrm{s}

Nuclear Activity and the Conditions of Star-formation at the Galactic Center

-band flux densities reported earlier. We find typical polarization degrees of the order of 20\%

Submillimeter and radio variability of Sagittarius A* - A statistical analysis

\pm

Sgr A West in the light of molecules: cold and dense gas east of the circumnuclear disk

10\% and a preferred polarization angle of 13