Curated by RSF Research Staff
Spectral Signatures of a Black Hole spinning at almost the speed of light
Fig 1 below shows the initial signals detected by the MAXI missions. These spectra are further analyzed, decomposed and fitted in order to obtain the final results published here.With the independent modeling of the broadband data spectra obtained by the three missions, and using the Markov chain Monte Carlo simulations on fitted spectral parameters, they find a range of the black hole spin parameter depicted in Fig. 2, amounting to 0.88–0.96 within a 3σ deviation, which indicates the presence of a rapidly spinning black hole in 4U 1630–47. This is the fifth occasion that a spinning black hole has been so firmly characterized, and the reason for such a few numbers of cases compared to the number of BH detected so far, relies on the fact that spinning black holes are very difficult to detect, as Dr. Pahari explains below.
Among the interesting features that the emission spectra reveals, one of most important one is the chemical elements surrounding the BH. For instance, the Chandra/HEG (High Energy Grating) spectrum shows two strong absorption lines at 6.705 keV and 6.974 keV (see Fig 3), which are produced by the element iron (Fe) in different oxidation states (Fe XXV and Fe XXVI) in a low-velocity ionized disk wind. The corresponding outflow velocity is determined to be 366±56 km/s.
Detecting signatures that allow us to measure spin is extremely difficult. The signature is embedded in the spectral information which is very specific to the rate at which matter falls into the black hole. The spectra, however, are often very complex mostly due to the radiation from the environment around the black hole.
By: Inés Urdaneta, RSF research Scientist
Illustration credit: CXC/M. Weiss and Figures taken from original IOP article.
AstroSat and Chandra View of the High Soft State of 4U 1630–47 (4U 1630–472): Evidence of the Disk Wind and a Rapidly Spinning Black Hole