A 600 minute near-infrared lightcurve of Sagittarius A*

L. Meyer(1), T. Do(1), A. Ghez(1), M. R. Morris(1), G. Witzel(2), A. Eckart(2), G. Bélanger(3), R. Schödel(4)

(1) Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547
(2) Universität zu Köln, Zülpicher Str. 77, 50937 Köln
(3) ESA/ESAC, PO Box 78, 28691 Villanueva de la Ca\ nada, Spain
(4) Instituto de Astrofísica de Andalucía, Camino Bajo de Huétor 50, 18008 Granada, Spain

Paper: ApJL, accepted


We present the longest, by a factor of two, near-infrared lightcurve from Sgr A* - the supermassive black hole in the Galactic center. Achieved by combining Keck and VLT data from one common night, which fortuitously had simultaneous Chandra and SMA data, this lightcurve is used to address two outstanding problems. First, a putative quasi-periodicity of 20 min reported by groups using ESO's VLT is not confirmed by Keck observations. Second, while the infrared and mm-regimes are thought to be related based on reported time lags between lightcurves from the two wavelength domains, the reported time lag of 20 min inferred using the Keck data of this common VLT/Keck night only is at odds with the lag of 100 min reported earlier. With our long lightcurve, we find that (i) the simultaneous 1.3 millimeter observations are in fact consistent with a 100 min time lag, (ii) the different methods of NIR photometry used by the VLT and Keck groups lead to consistent results, (iii) the Lomb-Scargle periodogram of the whole NIR lightcurve is featureless and follows a power-law with slope -1.6, and (iv) scanning the lightcurve with a sliding window to look for a transient QPO phenomenon reveals for a certain part of the lightcurve a 25 min peak in the periodogram. Using Monte Carlo simulations and taking the number of trials into account, we find it to be insignificant.

Preprints available from the authors at leo@astro.UCLA.EDU , or the raw TeX (no figures) if you click here.

Back to the gcnews home-page.