Statistical Analysis of Optical and Radio Variability of MWC349A

Details Statistical Analysis of Optical and Radio Variability of MWC349A Statistical Analysis of Optical and Radio Variability of MWC349A

Jan 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21541717f&link_type=abstract

American Astronomical Society, AAS Meeting #215, #417.17; Bulletin of the American Astronomical Society, Vol. 42, p.273

Astronomy and Astrophysics

Astronomy

Scientific paper

Several possible periods were previously suggested for the variability of MWC349A: 9.1±0.3 and 3.0±0.3 years for optical variability (Jorgenson et al. 2000; Stortz et al. 2004) and 125±15 and 84±3 days for the variations of the intensity ratio in the double-peak spectrum of the masing H30α radio recombination line (Thum et al. 1992; Moringello et al. 1998).
We undertook a statistical analysis of the results of the 12-year monitoring of the star in the optical R band, 2-year monitoring with an interference Hα filter, and 3-year monitoring in the H30α line. PERANSO software, utilizing the CLEANest algorithm for the Fourier spectrum and the discrete correlation function method of Edelson and Krolik (1988) were used for the analysis. No peaks stronger than 2σ were detected in the Fourier spectra of the optical (R and Hα) or radio (H30α "red” to "blue” component ratio) variations. The suspected (<2σ) peaks are: 96.6±2.7, 199±3, 218±7, 338±5, and 455±18 days for R; 620±6, 194±3, and 1000±10 days for Hα and 238±8 and 44.4±0.7 days for the H30α component ratio. None of the previously suggested periods were confirmed. Autocorrelation analysis indicates a few months as the characteristic time of variability for all three data sets. The weakness of the Fourier peaks suggests that both optical and radio variability of the star may be purely chaotic. Fitting the power law to the Fourier spectra gives the power indices of the noise-type variability between 0 and -0.5. More observations, both in optical and radio domains, are needed to verify these conclusions. This project was supported by NSF/REU grant AST-0851892 and the Nantucket Maria Mitchell Association.

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