A 600 minute near-infrared lightcurve of Sagittarius A*

Abstract

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.

12 pages, 3 figures; accepted by ApJ Letters for publication

References in corpus (9)

• Polarimetry of near-infrared flares from Sagittarius A*
• Flaring Activity of Sgr A* at 43 and 22 GHz: Evidence for Expanding Hot Plasma
• A Constant Spectral Index for Sagittarius A* During Infrared/X-ray Intensity Variations
• A polarised infrared flare from Sagittarius A* and the signatures of orbiting plasma hotspots
• Simultaneous Chandra, CSO and VLA Observations of Sgr A*: The Nature of Flaring Activity
• Near-infrared polarimetry setting constraints on the orbiting spot model for Sgr A* flares
• Polarized NIR and X-ray Flares from SgrA*
• K-band polarimetry of an Sgr A* flare with a clear sub-flare structure
• General Relativistic Flux Modulations from Disk Instabilities in Sagittarius A*

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• Time Dependent Models of Flares from Sagittarius A*
• Stellar transits across a magnetized accretion torus as a mechanism for plasmoid ejection
• Magnetic Reconnection as a Mechanism for Energy Extraction from Rotating Black Holes
• The X-ray Flux Distribution of Sagittarius A* as Seen by Chandra
• A power-law break in the near-infrared power spectrum of the Galactic center black hole
• A formal method for identifying distinct states of variability in time-varying sources: SgrA* as an example
• Simultaneous Monitoring of X-ray and Radio Variability in Sagittarius A*
• On More Sensitive Periodogram Statistics
• Global resistive MHD accretion flows around spinning AGNs: impact of resistivity on MAD state
• A Red-Noise Eigenbasis for the Reconstruction of Blobby Images
• SgrA* emission at 7mm: variability and periodicity