![]() This research is supported by NSF/RUI Grant 00-71260 and by the Undergraduate Summer Research Assistance Program Grant from the Delaware Space Grant College Consortium. We discuss the results of the modeling of the optical and x-ray observations and present an integrated model of the system in which the light enhancements observed near 0.3 phase appear to arise from the impact of the stellar wind on the accretion disk. Also we have carried out an analysis of the light curves using the Wilson-Devinney Binary Code to compute refined values of the orbital inclination and mass ratio. We have downloaded ongoing X-ray observations of Cyg X-1 made by RXTE to search for correlations. We use soft X-ray data from the All Sky Monitor on board of Rossi X-ray Timing Explorer, hard. We study long-term cross-correlations between its X-ray and radio fluxes, searching for lags of the peak of the correlation. Its X-ray emission originates most likely in the accretion flow, while the radio emission is from a magnetized jet. The Hα photometry reveals a weak variation of Hα emission/absorption as a function of orbital phase. Cygnus X-1 is a Galactic black-hole binary and a microquasar. These most likely arise from small light variations (non-radial pulsations) of the O9 supergiant. Also present are apparently random light variations of ≈ 0.01mag. The least active orbital phases occur near 0.45 - 0.65P. However, near phase 0.20P to 0.35P persistent brightness enhancements of 0.02 mag are frequently observed. Light curves have been formed from the photometry, and show an show the underlying the 5.60 day low amplitude ( y-amp = 0.045mag) light variations expected to arise from the tidal and rotational distortion of the luminous supergiant. The observations started in September 2000 and are continuing through the Fall 2001. We report on Stromgren uvby and Hα narrow and intermediate band photometry of Cyg X-1 that is being carried out with the Four College Consortium 0.8m Automatic Photometric Telescope (FFCAPT). Some of the long-term x-ray and radio variations appear to be related to the semi-periodic changes in the accretion disk and also may arise from a precessing disk and jet. Long-term X-ray and radio observations of the system show it to change on times scales of seconds (flickering), minutes-hours (flares), days (orbital), months-years (low/hard states and high/soft x-ray states). This binary system shows complicated, low amplitude ellipsoidal light variations and consists of a O9.7 Iab star and a probable 7-10 M sun black hole companion with an x-ray emitting accretion disk. Using this phenomenon, many Xray telescopes today look for the Xray glows from the accretion disks surrounding compact objects believed to be black holes. ago this strong X-ray source was identified with a 9th mag spectroscopic binary (HDE 226868) having an orbital period of P = 5.60 days. While a typical black hole formed from a collapsing star ranges from 3 to 10 solar masses, this one is an estimated 21 solar masses making it the most. Cygnus X-1 is one of the best studied variable X-ray sources. ![]()
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