Predoctoral Projects, 2015

Project Title: A Multi-Wavelength Study of the Relativistic Jet Source Cygnus X-3

Project Advisor: Dr. Michael L. McCollough

Background: Cygnus X-3 is one of the most enigmatic X-ray binaries to have been studied. Its X-ray flux shows a 4.79 hr modulation associated with its orbital period. While the period is typical of a low mass system IR observations have shown that the mass donating companion is a massive Wolf-Rayet star. Cygnus X-3 has two major X-ray states (low/hard and high/soft), shows correlative activity between the radio and hard X-ray, and relativistic jets have been observed in the system (~0.9c).

Scientific Questions: Among the issues we are seeking to address in this study are:

Hard X-Ray/Gamma-Ray Continuum: We seek to understand the nature of the hard X-ray/gamma-Ray continuum associated with major radio flares. Is it due to synchrotron or inverse Compton? Are the processes producing this emission nonthermal or thermal in nature?

Annihilation Lines: The major radio flares in Cygnus X-3 have been linked to relativistic jets. The composition of these jets is a major point of interest. Are they a pair plasma (electrons and positrons) or do baryons play major role in their makeup? The detection of annihilation lines make help answer this question.

Timing Properties: Do the major flares have a distinctive timing signature? The RXTE observations probe times very close to the creation of these major flares.

Properties of Cygnus X-3's Wind: The Chandra observations (supported by the RXTE) observations will allow a detailed (phased resolved) measurement of the parameters and nature of the wind associated with Cygnus X-3.

Multi-Wavelength Correlations: We will look for and study the correlations between the different wavelenghts (radio, X-ray, Gamma-Ray, IR). These will be examined relative to previously discovered correlations.

Scientific Methodology: Since early 2002 Cygnus X-3 had been in an unusually long quiescent state (~ 1300 days). At the start of 2006 Cygnus X-3 transitioned from a radio quiescent (low/hard) state to a flaring (high/soft) state. Among the activities that have been observed are an extended quenched state (high X-ray, very low radio, and very low hard X-ray emission), rapid (< 1 day) bright flares (~ 3 Jy), and three major radio flares (~ 14 Jy).

During this active state, a major international multi-wavelength observing campaign has been undertaken. This campaign includes observations in the radio (Ryle, RATAN-600), IR (PAIRITEL), UV/Optical (Swift), X-ray (Chandra, RXTE, INTEGRAL, Swift), hard X-ray (RXTE, INTEGRAL, Swift), and Gamma-ray (INTEGRAL, Whipple).

This project involves the analysis of these various data sets with particular emphasis on the spacecraft data (Chandra, INTEGRAL, RXTE, and Swift). We will be using XSPEC, FTOOLS, CIAO, and OSA (INTEGRAL Data Analysis) software to analyze the various data sets.

Other links related to this project


Clay Fellow Warren Brown