| Description |
Out of the numerous high-mass X-ray binaries, only 6 are detected above 100 GeV, all of which host a massive Be/O type star and a compact star. The nature of the compact star in majority of these TeV binaries is unknown. The emission mechanisms in these systems may hold key information about their population scarcity in our galaxy. VERITAS has been instrumental in unraveling the physics of TeV binaries. This dissertation takes a closer look at the well-known TeV binary LS I +61 303 and a TeV binary candidate SS 433. LS I +61° 303 has a compact star revolving around a giant optical Be star which is rapidly losing mass due to its fast rotational speeds. The binary exhibits modulated emission from radio to TeV wavelengths dependent on its orbital and superorbital periods. This dissertation presents three new key aspects of this TeV binary, a correlation between X-ray and TeV emission from the source over multiple orbits that is sampled over 3 y, quiescent TeV emission around the entire orbit and probable subtle spectral changes dependent on the positions of the binary components in the 26.5-day orbit. The X-ray/TeV correlation hints at the origin of emission at these two wavebands from a single particle population. The TeV base emission and spectral variations may be indicative of a neutron star in the system which flip-flops between its accretor and propeller phases along the orbit. SS 433 is a high-mass X-ray binary consisting a stellar microquasar with dual relativistic jets orbiting a massive star once every 13.1 days. The binary is embedded in the W50 nebula and the precessing jets are shaping the morphology of the surrounding medium. The eastern and western jet termination regions have long been predicted to be potential sources of high-energy gamma rays, produced due to the interaction of the jets with surrounding interstellar medium. SS 433 is not detected at TeV energies from ~70 h of VERITAS data, 99% confidence level flux upper limits are calculated on multiple regions along the jets and at the location of the blackhole that were selected based on previous X-ray observations. The upper limits can be used to constrain the energetics in this microquasar system. |
