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Young Ninja Group (ages 3-5)

공개·회원 10명
Parker Thomas
Parker Thomas

FE Black Hole


European astronomers succeeded for the first time to confirm the signatures predicted near black holes by Albert Einstein's theory of Relativity in the light of the cosmic X-ray background. The group of scientists led by Günther Hasinger, director at the Max-Planck-Institute for extraterrestrial Physics in Garching near Munich, could identify the spectral fingerprint of iron atoms. They observed a strong, relativistically smeared iron line in the average spectrum of roughly 100 active galaxies, whose X-ray light had been emitted when the Universe was less than half of its current age.




FE Black Hole


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The whole sky is filled with a diffuse, high energy glow: the cosmic X-ray background. In the last years the astronomers could show, that this radiation can almost completely be associated with individual objects. Similarly, Galileo Galilei in the beginning of the 17th century resolved the light of the Milky Way into individual stars. The X-ray background originates in hundreds of millions of supermassive black holes, which feed from matter in the centres of distant galaxy systems. Because the black holes are accreting mass, we observe them in the X-ray background during their growth phase. In today's Universe, massive black holes are found in the centres of practically all nearby galaxies.


Figure 2: The average X-ray spectrum of active galaxies in the X-ray background. The light of about 100 distant active galaxies was first corrected to the rest frame of our Milky Way and then added together. Then a simple spectral model without lines was subtracted. The residual spectrum shows a strong, relativistically broadened iron line, which must originate from matter in the immediate vicinity of the black holes. Copyright: MPE


Now the researchers around Günther Hasinger of the Max-Planck-Institute for extraterrestrial Physics, jointly with the group of Xavier Barcons at the Spanish Instituto de Física de Cantabria in Santander and Andy Fabian at the Institute of Astronomy in Cambridge, UK have uncovered the relativistically smeared fingerprint of iron atoms in the average X-ray light of about 100 distant black holes of the X-ray background (see Figure 2). The astrophysicists utilized the X-ray observatory XMM-Newton of the European Space Agency ESA. They pointed the instrument to a field in the Ursa Major constellation for more than 500 hours and discovered several hundred weak X-ray sources. Because of the expansion of the Universe the galaxies move away from us with a speed increasing with their distance and thus their spectral lines all appear at different wavelength; the astronomers had first to correct the X-ray light of all objects into the rest frame of the Milky Way. The necessary distance measurements for more than 100 objects were obtained with the American Keck-Telescope. After having co-added the light from all objects, the researchers were very surprised about the unexpectedly large signal and the characteristically broadened shape of the iron line.


From the strength of the signal they deduced the fraction of iron atoms in the accreted matter. Surprisingly, the chemical abundance of iron in the "nutrition" of these relatively young black holes is about three times higher than in our Solar system, which had been created significantly later. The centres of galaxies in the early Universe therefore must have had a particularly efficient method to produce iron, possibly because violent star forming activity "breeds" the chemical elements rather quickly in active galaxies. The width of the line indicated that the iron atoms must radiate rather close to the black hole, consistent with rapidly spinning black holes. This conclusion is also found indirectly by other groups, who compared the energy in the X-ray background with the total mass of "dormant" black holes in nearby galaxies.


We measure the spin of XTE J1550-564 using the two leading methods: (i) modelling the thermal continuum spectrum of the accretion disc; and (ii) modelling the broad red wing of the reflection fluorescence Fe Kα line. We find that these two independent measurements of spin are in agreement. For the continuum-fitting analysis, we use a data sample consisting of several dozen Rossi X-ray Timing Explorer spectra, and for the Fe Kα analysis, we use a pair of ASCA spectra from a single epoch. Our spin estimate for the black hole primary using the continuum-fitting method is -0.11


To this date, nobody can explain how gravity works inside of a black hole because the are extremely dense and inescapable gravity-wise. Interestingly, Ghez also said that most galaxies have a huge black hole in the middle of them.


One of the largest black holes ever recorded has been discovered using a new technique that could spot thousands more of the insatiable celestial monsters in the coming years, according to astronomers.


It is the first black hole ever observed using a phenomenon called gravitational lensing, in which light travelling towards us from a distant galaxy appears to magnify and bend inwards, giving away the presence of a dark giant.


For the study of black holes, it is essential to have an accurate disk-reflection model with a proper treatment of the relativistic effects that occur near strong gravitational fields. These models are used to constrain the properties of the disk, including its inner radius, the degree of ionization of the gas, and the elemental abundances. Importantly, reflection models are the key to measuring black hole spin via the Fe-line method. The code XILLVER calculates the solution of the reflected intensity of the radiation field is calculated for each photon energy, position in the slab, and viewing angle.


A complete library of synthetic spectra has been calculated formodeling the component of emission that is reflected from anilluminated accretion disk. The spectra were computed using anupdated version of our code XILLVER that incorporates newroutines and a richer atomic data base. We offer in the form of atable model an extensive grid of reflection models that cover a widerange of parameters.These tables cover the physical parameterstypically inferred from observations of active galactic nuclei, andalso stellar-mass black holes in the hard state. These models areintended for use when the thermal disk flux is faint compared to theincident power-law flux.


Chandra spectroscopy of transient stellar-mass black holes in outburst has clearly revealed accretion disk winds in soft, disk-dominated states, in apparent anti-correlation with relativistic jets in low/hard states. These disk winds are observed to be highly ionized, dense, and to have typical velocities of 1000 km s-1 or less projected along our line of sight. Here, we present an analysis of two Chandra High Energy Transmission Grating spectra of the Galactic black hole candidate IGR J17091-3624 and contemporaneous Expanded Very Large Array (EVLA) radio observations, obtained in 2011. The second Chandra observation reveals an absorption line at 6.91 0.01 keV associating this line with He-like Fe XXV requires a blueshift of 9300+500 -400 km s-1 (0.03c, or the escape velocity at 1000 R Schw). This projected outflow velocity is an order of magnitude higher than has previously been observed in stellar-mass black holes, and is broadly consistent with some of the fastest winds detected in active galactic nuclei. A potential feature at 7.32 keV, if due to Fe XXVI, would imply a velocity of 14, 600 km s-1 (0.05c), but this putative feature is marginal. Photoionization modeling suggests that the accretion disk wind in IGR J17091-3624 may originate within 43,300 Schwarzschild radii of the black hole and may be expelling more gas than it accretes. The contemporaneous EVLA observations strongly indicate that jet activity was indeed quenched at the time of our Chandra observations. We discuss the results in the context of disk winds, jets, and basic accretion disk physics in accreting black hole systems.


"It is closer to the sun than any other known black hole, at a distance of 1,550 light years," Dr. Sukanya Chakrabarti, the Pei-Ling Chan Endowed Chair in the Department of Physics at UAH, a part of the University of Alabama System, said in a statement. "So, it's practically in our backyard."


To find the black hole, which is a mammoth task, Chakrabarti and a national team of scientists dug deep into a treasure trove of data comprising nearly 200,000 binary stars - that was released over the summer from the European Space Agency's Gaia satellite mission.


The professor explained that analyzing the line-of-sight velocities of the visible star, which is similar to our sun, can help explain how enormous the black hole companion is, along with the period of rotation and the orbit.


The majority of the black holes in binary systems are bright and visible in X-rays due to interaction with the black hole. This mostly happens when the black hole swallows the other star. "As the stuff from the other star falls down this deep gravitational potential well, we can see X-rays," Chakrabarti said.


We present the results of spectral analysis of the galactic black hole binary MAXI J1659-152 in the rising phase of the outburst that lasted for about 65 days starting on 2010 September 25. The presence of a broad Fe line, verified by Monte Carlo simulations, and coverage of a wide energy band by utilizing the combined spectral capabilities of XMM-Newton/EPIC-pn and RXTE/PCA allowed us to use a combination of reflection spectroscopy and continuum fitting methods to estimate the spin of the black hole. We explored the entire parameter range allowed by the present uncertainties on black hole mass, inclination, and distance as well as the accretion rate. We show that for about 95% of parameter space and very reasonable upper limits on ALT="$\dotM$" SRC="apjlab629eieqn1.gif"/, the spin of the black hole has to be negative. This is the first clear detection of negative spin in a galactic black hole binary. 041b061a72


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