[Automatic recognition of M-star spectral subtype based on fractal coding].

According to the local fractal feature in an astronomical spectrum, the data in the spectrum were coded in three bands 400-510, 600-700 and 780-900 nm. In the present paper, using the position of the matching data block and the minimum matching error, the fractal coding method was used to recognize the subtypes of astronomical spectra for the first time. The experimental results show that the fractal coding method has certain noise immunity and cannot be affected by the calibration error and the effective curves of LAMOST. The fractal method can effectively recognize the subtype of M stars of LAMOST and SDSS.

[A fractal denoising method for astronomical spectral signal].

To restore the continuum and the spectral lines from a noisy astronomical spectrum, then to measure the equivalent widths of the spectral lines, the fractal denoising method was firstly used in astronomical spectra in the present paper. The method is based on the distinguishing features, that is the local self-similarities exist in an astronomical spectrum, while not in a random white noise signal. The experimental results show that the fractal denoising method is efficient in parameter measurements, such as equivalent widths for spectral lines, redshift of galaxies, and so on. In addition, the method can achieve data compression. The fractal method can be used in the mass spectra of LAMOST.