Supervisor: Gregory Sivakoff Email: email@example.com Office: CCIS 2-100 Mailing Address: CCIS 4-181 Department of Physics University of Alberta Edmonton Alberta T6G 2E1 CANADA Website Last Updated: Sep. 2016
I am an astrophysics graduate student, working with Gregory Sivakoff, studying the Galactic black hole X-ray binary Population.
All stellar mass black holes ever discovered have been in binary systems. If the companion is a typical star in a close orbit, that star's material can spiral onto an accretion disc around the black hole, in a process called accretion. These black hole X-ray binaries allow us to study stellar-mass black holes and provide unique insight into how binary stars evolve and how matter accretes. My research focuses on studying black hole X-ray binaries in our Galaxy.
The vast majority of black hole X-ray binaries vary on timescales of days to years. They cycle between periods of quiescence, when material from the disc falls onto the black hole at a slow rate, and outburst, when the infall rate can increase by factors of a million. This leads to bright X-ray emission, which astronomers have used to identify ~80 likely black hole X-ray binaries in our Galaxy. We use X-ray observations to measure outburst properties that we then connect to physical models of how the black hole is accreting. We also have observed some of these systems in the fainter quiescent state. Here, optical/infrared observations reveal orbital properties of the binary system and properties of the nearby companion star. These data provide one of the most reliable means of measuring the mass of a black hole.
To constrain how black hole X-ray binaries are formed and evolve, we ideally would observe these systems over their entire lifetimes. However, since their million-year lifetimes are out of reach, my first research area focuses on how the known population of black hole X-ray binaries behaves as a whole. To that end, I created WATCHDOG, an X-ray study cataloguing the behaviour over the last ~20 years of all known black hole X-ray binaries. WATCHDOG replaces decade-old catalogs, and implements first-of-their-kind comprehensive algorithms to discover, track, and quantitatively classify black hole X-ray binary outburst behaviour. This provides an unprecedented view of this ever-varying population in our Galaxy. See the WATCHDOG tab for more details.
My second research area focuses on detecting new black hole X-ray binaries and measuring their fundamental properties (like their mass). While the size of the total Galactic black hole X-ray binary population is uncertain, my team and I recently discovered that it is much larger than we previously thought. Combining radio, X-ray and optical data, we discovered a black hole X-ray binary using a new technique. Our discovery implies that there are more than 26,000 black hole X-ray binaries in our Galaxy. This was surprising because theoretical estimates based on the previously known sample of black hole X-ray binaries predicted much fewer sources. This implies that we have been missing a whole class of black hole X-ray binaries. This has motivated me to begin three projects using new observational methodologies to probe both this under-represented sample and the large fraction of black hole candidates in the known sample which lack dynamical mass estimates and binary parameter information: (i) a multi-wavelength campaign aimed at the discovery/study of faint black hole X-ray binaries in our Galaxy, (ii) an infrared program, aimed at rapidly identifying companion stars and black hole masses in the known sample of black hole X-ray binaries, and (iii) a project aimed at deriving fundamental binary parameters through the modelling and analysis of the X-ray light curves of known candidate black hole X-ray binaries.
These projects involve the analysis and use of data from a multitude of telescopes across many different wavelengths, including: the (i) Rossi X-ray Timing Explorer (RXTE), (ii) Swift X-ray Observatory, (iii) Chandra X-ray Observatory, (iv) XMM-Newton telescope, (v) Monitor of All-Sky X-ray Image (MAXI) telescope, (vi) INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) telescope, (vii) Gemini Observatory, (viii) Very Large Telescope (VLT), and (ix) Karl G. Jansky Very Large Array (VLA).
Undergraduate Physics Labs Useful Links for Students: Excused Absence Form Lab Schedule Lab Template Info Sheet (**info may be outdated as these documents are from a previous semester) Courses I am currently teaching: I will not be teaching in the Fall 2016/Winter 2017 Semesters
Master Of Science Thesis:
"The Definitive Observational Study of Accretion Disc Physics in Black Hole X-ray Binaries (BHXBs)" (read it HERE)
My Chandra Press Release for the first stellar-mass BH discovered in a quiescent low-mass X-ray binary, outside a globular cluster.
Taking advantage of the current suite of X-ray instruments, which have allowed the transient Universe to be probed in greater depth than ever before, we have established a comprehensive database of BH (and BH candidate) X-ray binary activity between 1996 and present day as revealed to us by a total of 7 separate all-sky, scanning surveys, and narrow-field instruments aboard the INTEGRAL, MAXI, RXTE, and Swift telescopes.
We call this resource the Whole-sky Alberta Time-resolved Comprehensive black-Hole Database Of the Galaxy or WATCHDOG.
Built to operate as an interactive online interface, WATCHDOG is meant to act as an multi-purpose, easy to use resource for the widespread X-ray binary community. Our overall goals for WATCHDOG is for it to not only replace decade-old catalogs, but also provide a resource that enables us to probe X-ray binary outburst behaviour over decades of both energy and time. Currently, the database itself includes the most up-to-date compilation of information on 77 BHs and BH candidates.
The online interface is located at: here. Please see the information pages at this location for an overview of the extensive array of features available in WATCHDOG.