After a two years analysis of the emission spectra from a
2016 X-ray transient outburst in the black hole system U4 1630-47, obtained by
three different independent space missions; Chandra/HEG, AstroSat, and MAXI, the
leader of the project Dr. Mayukh Pahari and collaborators could determine the
spinning and mass of the BH. The estimated spinning rate is 92-95% at the speed of
light, with a mass of 5-10 M (million solar masses).
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.
Fig.1: 2016 X-ray outburst of 4U 1630–47 as observed by MAXI
and Swift/BAT.
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.
Figure 2: spin parameter for three different joint spectral
fits.
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.
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. – Dr. Mayukh Pahari
Among the interesting features that the emission spectra reveal, one of the most important ones 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.
Fig. 3: Absorption lines from Chandra grating spectra,
showing two strong absorption lines visible at ∼6.7 and ∼6.97 keV, which are due to the ionized Fe XXV and Fe XXVI
absorption features, fitted with Gaussian absorption profiles.
In view of the model
proposed by Haramein, spin is at the origin of energy and mass, through the
vorticial nature or torque inherent to the structure of space-time – or vacuum
– itself (see here). For this reason, everything in the universe is spinning, from
sub-atomic particles to planets, galaxies, and beyond. The fact that all BH is
spinning is difficult to realize due to the difficulties measuring the effect
No comments