The following article is about a class of extraterrestrial sources, named Ultra-Luminous X-ray Sources (ULXS). ULXS were first discovered at the Einstein X-ray Telescope in 1980s. On average, every galaxy hosts one ULXS. The interesting fact about ULXS is that their Eddington ratio is larger than 1, meaning that their luminosity exceeds the Eddington luminosity of neutron stars and even stellar black holes. There are models that describe the possible sources that can power ULXS. The most important of these models are accreting intermediate-mass black holes, beamed emission of stellar mass objects, and super-Eddington emission. Observations of one ULXS in the M82 galaxy suggest that ULXS may be accreting intermediate-mass black holes. However, observations of another ULXS in the same galaxy suggest that ULXS may be pulsars instead of black holes. Observations of another ULXS in the M101 galaxy support the accreting intermediate-mass black holes by showing that this source might be an x-ray binary. Even though all these observations support the accreting intermediate-mass black hole model, the other models have not yet been ruled out, and more observations are necessary in order to confirm one model or another. Additionally, different astrophysicists may interpret a certain observation very differently based on their data analysis algorithms.
WC = 205
Reader’s Profile: I imagine a reader who is biased towards the super-Eddington luminosity, and is leaning towards accreting intermediate- mass black holes, even though the observations do not fully support that model or reject other models.
Reader’s response: Well, accreting intermediate-mass black holes sound reasonable. Plus, if super-Eddington accreting black holes are to exist, we have to use smaller cross sections rather than the Thompson’s cross section that we use for the Eddington limit. This would mean that we are neglecting some physical processes for particle acceleration.
WC = 205
Reader’s Profile: I imagine a reader who is biased towards the super-Eddington luminosity, and is leaning towards accreting intermediate- mass black holes, even though the observations do not fully support that model or reject other models.
Reader’s response: Well, accreting intermediate-mass black holes sound reasonable. Plus, if super-Eddington accreting black holes are to exist, we have to use smaller cross sections rather than the Thompson’s cross section that we use for the Eddington limit. This would mean that we are neglecting some physical processes for particle acceleration.