Spectroscopic monitoring of SS 433: A search for long-term variations of kinematic model parametersстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:Between 1994 and 2006, we obtained uniform spectroscopic observations of SS 433 in the region of H alpha. We determined Doppler shifts of the moving emission lines, H alpha(+) and H alpha(-), and studied various irregularities in the profiles for the moving emission lines. The total number of Doppler shifts measured in these 13 years is 488 for H alpha(-) and 389 for H alpha(+). We have also used published data to study possible long-term variations of the SS 433 system, based on 755 Doppler shifts for H alpha(-) and 630 for H alpha(+) obtained over 28 years. We have derived improved kinematic model parameters for the precessing relativistic jets of SS 433 using five- and eight-parameter models. On average, the precession period was stable during the 28 years of observations (60 precession cycles), at 162.250(d) +/- 0.003(d). Phase jumps of the precession period and random variations of its length with amplitudes of approximate to 6% and approximate to 1%, respectively, were observed, but no secular changes in the precession period were detected. The nutation period, P(nut) = 6.2876(d) +/- 0.00035(d), and its phase were stable during 28 years (more than 1600 nutation cycles). We find no secular variations of the nutation cycle. The ejection speed of the relativistic jets, v, was, on average, constant during the 28 years, beta = v/c = 0.2561 +/- 0.0157. No secular variation of beta is detected. In general, SS 433 demonstrates remarkably stable long-term characteristics of its precession and nutation, as well as of the central "engine" near the relativistic object that collimates the plasma in the jets and accelerates it to v = 0.2561c. Our results support a model with a "slaved" accretion disk in SS 433, which follows the precession of the optical star's rotation axis.