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2001ApJ...547L..29Z - Astrophys. J., 547, L29-L32 (2001/January-3)

Radio variability of Sagittarius A*–a 106 day cycle.

ZHAO J.-H., BOWER G.C. and GOSS W.M.

Abstract (from CDS):

We report the presence of a 106 day cycle in the radio variability of Sagittarius A* based on an analysis of data observed with the Very Large Array over the past 20 years. The pulsed signal is most clearly seen at 1.3 cm with a ratio of cycle frequency to frequency width f/Δf=2.2±0.3. The periodic signal is also clearly observed at 2 cm. At 3.6 cm the detection of a periodic signal is marginal. No significant periodicity is detected at both 6 and 20 cm. Since the sampling function is irregular, we performed a number of tests to ensure that the observed periodicity is not the result of noise. Similar results were found for a maximum entropy method and a periodogram with a CLEAN method. The probability of false detection for several different noise distributions is less than 5% based on Monte Carlo tests. The radio properties of the pulsed component at 1.3 cm are a spectral index α∼1.0±0.1 (for S∝να), an amplitude ΔS=0.42±0.04 Jy, and a characteristic timescale ΔtFWHM~25±5 days. The lack of a VLBI detection of a secondary component suggests that the variability occurs within Sgr A* on a scale of ∼5 AU, suggesting an instability of the accretion disk.

Abstract Copyright:

Journal keyword(s): Accretion, Accretion Disks - Black Hole Physics - Galaxies: Active - Galaxy: Center - Radio Continuum: Galaxies

CDS comments: Calibrator J1751-253 = RORF 1748-253

Simbad objects: 8

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2020.09.18-11:14:00

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