Gravitational radiation detectability of supernova 1987A's remnant fully matched filter for double resonant gravitational detector
Part I There is some observational evidence of the presence of a pulsating light source in the remnant of the supernova (SN) 1987A [1]. This source is considered to be a rotating neutron star. Fourier analysis of the light intensity of this source reveals a main narrow frequency peak and side bands that are understood as a modulation of the main sinusoidal signal. A particular model of the neutron star invokes a precessing object to explain the modulation. From the Fourier spectrum of the source and changes in the frequency value, we can determine important parameters of the spinning neutron star as rotation frequency, precession frequency and spin-down rate. The neutron star is believed to spin down due to the emission of gravitational waves. We give a precise calculation of the strain value of the gravitational waves reaching earth and discuss the possibility of detection of this radiation by existing and soon on line gravitational waves detectors. Our conclusion is that just a few days of integration time will be sufficient to detect the signal using the next generation detectors as LIGO II. Part II Historically, in the search for burst signals, the ALLEGRO Gravitational Group used a matched filter constructed in the time domain, and with the particular characteristic of separating the information from the two resonant modes of the bar. The information from the two resonant modes is treated separately until the end when the total energy of the response of the bar is estimated, summing each mode output (we call this filter partially matched). We developed a filter (called fully matched) that doesn't separate the two resonant modes and treats the two modes system as a whole. This filter is constructed in the Fourier domain. We compared the performance of partially matched filter with the fully matched filter applying both filters to simulated and real data. The main conclusion is that even in the one mode case, but particularly in the two modes case, the fast filter is more efficient than the slow filter. In addition, we attempt also to explain why the fully matched is a better filter than the partially matched filter.
data analysis, neutron star, gravitational waves
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