English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We present the results of near-infrared (2 and 3 microns) monitoring of SgrA*-IR with 1 min time sampling using the natural and laser guide star adaptiveoptics (LGS AO) system at the Keck II telescope. Sgr A*-IR was observedcontinuously for up to three hours on each of seven nights, between 2005 Julyand 2007 August. Sgr A*-IR is detected at all times and is continuouslyvariable, with a median observed 2 micron flux density of 0.192 mJy,corresponding to 16.3 magnitude at K'. These observations allow us toinvestigate Nyquist sampled periods ranging from about 2 minutes to an hour.Using Monte Carlo simulations, we find that the variability of Sgr A* in thisdata set is consistent with models based on correlated noise with power spectrahaving frequency dependent power law slopes between 2.0 to 3.0, consistent withthose reported for AGN light curves. Of particular interest are periods of ~20min, corresponding to a quasi-periodic signal claimed based upon previousnear-infrared observations and interpreted as the orbit of a 'hot spot' at ornear the last stable orbit of a spinning black hole. We find no significantperiodicity at any time scale probed in these new observations for periodicsignals. This study is sensitive to periodic signals with amplitudes greaterthan 20% of the maximum amplitude of the underlying red noise component forlight curves with duration greater than ~2 hours at a 98% confidence limit.

A near-IR variability study of the Galactic black hole: a red noise source with no detected periodicity