The overall goal of this project is to understand the physics, populations and origins of black hole X-ray binaries - particularly those systems known as "microquasars" - and the physical conditions/processes which lead to the formation of relativistic jets in some of them. While astronomers have studied relativistic outflows from black hole systems for several decades, the details of the mechanism which accelerates and collimates such a jet at nearly the speed of light out of the black hole potential well remains a mystery. The scientific path taken here employs multi-wavelength studies of the physics of compact objects (particularly microquasars) and the populations and origins of compact objects in our Galaxy and beyond. With the addition of more than 2000 new X-ray sources recently discovered in the Galactic Center there is an opportunity to expand the sample size of accreting compact objects in general, and black hole binaries in particular, by an order of magnitude, enabling the use of population statistics to constrain the origin and evolution of even rare classes of X-ray binary such as microquasars. Furthermore, it is now possible to study the environment in which many of these systems form, to examine the feedback process between X-ray binaries and their environment. This combination of both detailed studies of individual sources and broader investigation of their origins and properties via population studies provides a powerful synergistic approach to addressing both problems.
Towards this end, several programs will be carried out by Drs. Eikenberry and Bandyopadhyay, including a search for new microquasars and other compact systems using 13 nights of guaranteed time with FLAMINGOS-2 on Gemini South. The resulting spectra of approximately 2000 candidate infrared counterparts to new X-ray sources in the Galactic center are expected to yield between 200 to 300 new binaries with compact object secondaries. Also included in this work will be the development of an infrared extinction map of the Galactic center using data from the UKIDSS Galactic Plane Survey (which will be necessary to accurately reddening-correct the photometry of stars observed with FLAMINGOS-2). Multiwavelength studies of the black hole candidate GRS1915+105 will be carried out and used to develop/refine Dr. Eikenberry's "magnetic bomb" model of relativistic jet formation and its relation to the Accretion Ejection Instability model. Dr. Eikenberry's multi-wavelength program to find X-ray sources in young clusters (in which the cluster properties are used to constrain the progenitor characteristics) will also be continued.
This program will enable the education and training of four graduate students who will be involved in the project. The project will also support an ongoing hands-on outreach program at local Title 1 public schools with large minority populations.
The primary focus of this research is to use a range of observational astronomical techniques to identify and study exotic "compact object" systems -- neutron stars and black holes -- and the extreme physical conditions and behaviors around them. Highlights of our achievements under the current 3-year award include: We have developed new observational insights into and phenomenological models for near-light-speed "jet" outflows from black hole systems known as "microquasars". This has led us to the point where we can begin detailed comparisons between our multiwavelength observations and the extreme physical processes involved in these behaviors. We have also identified a number of new black hole and neutron star systems in the Galactic Center region (see infrared image in Figure 1) - to the point that the majority of the identifications in these region are now attributed to our group. This grant supported 4 graduate students, three of whom successfully defended their PhD theses between 2008-2011 and moved on to postdoctoral positions in astronomy. (The 4th is still in graduate school). It also supported the research of 2 undergraduate students, including one Hispanic female student who is planning on pursuing graduate studies in astrophysics. Our outreach component, targeting under-represented minorities in the Gainesville area, has been highly successful, featuring the largest non-athletic university event in East Gainesville, as well as a minority-focused summer camp. The estimated total number of attendees at all outreach events supported by just the current 3-year grant exceeds 6,000, including more than 600 children participating in grant-developed astronomy curricular activities in schools.
