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Context: The supermassive black hole at the Galactic center, SgrA*, showsfrequent radiation outbursts, often called 'flares'. In the near-infrared someof these flares were reported as showing intrinsic quasi-periodicities. Theflux peaks associated with the quasi-periodic behavior were found to be highlypolarized. Aims: The aim of this work is to present new evidence to supportprevious findings of the properties of the polarized radiation from SgrA* andto again provide strong support for the quasi-periodicity of ~18+-3 minreported earlier. Methods: Observations were carried out at the EuropeanSouthern Observatory's Very Large Telescope on Paranal, Chile. We used theNAOS/CONICA adaptive optics/near-infrared camera instrument. By fitting thepolarimetric lightcurves with a hot-spot model, we addressed the question ofwhether the data are consistent with this model. To fit the observed data weused a general relativistic ray-tracing code in combination with a simplehot-spot/ring model. Results: We report on new polarization measurements of aK-band flare from the supermassive black hole at the Galactic center. The dataprovide very strong support for a quasi-periodicity of 15.5+-2 min. The meanpolarization of the flare is consistent with the direction of the electricfield vector that was reported in previous observations. The data can bemodeled successfully with a combined blob/ring model. The inclination i of theblob orbit must be i > 20 deg on a 3sigma level, and the dimensionless spinparameter of the black hole is derived to be a > 0.5.Comment: accepted by A&A Letters for publication; 5 pages, 9 figure

K-band polarimetry of an Sgr A* flare with a clear sub-flare structure