Abstract
There is a hope that looking into the early Universe with next-generation telescopes, one will be able to observe the early accretion growth of supermassive black holes (BHs) when their ...masses were ∼104–106M⊙. According to the standard accretion theory, the bulk of the gravitational potential energy released by radiatively efficient accretion of matter onto a BH in this mass range is expected to be emitted in the extreme UV–ultrasoft X-ray bands. We demonstrate that such a ’miniquasar’ at z ∼ 15 should leave a specific, localized imprint on the 21 cm cosmological signal. Namely, its position on the sky will be surrounded by a region with a fairly sharp boundary of several arcmin radius, within which the 21 cm brightness temperature quickly grows inwards from the background value of ∼−250 mK to ∼+30 mK. The size of this region is only weakly sensitive to the BH mass, so that the flux density of the excess 21 cm signal is expected to be ∼0.1–0.2 mJy at z ∼ 15 and should be detectable by the Square Kilometer Array. We argue that an optimal strategy would be to search for such signals from high-z miniquasar candidates that can be found and localized with a next-generation X-ray mission such as Lynx. A detection of the predicted 21 cm signal would provide a measurement of the growing BH’s redshift to within Δz/(1 + z) ≲ 0.01.
This is the first paper in a series of studies of the Coma cluster using the SRG/eROSITA X-ray data obtained in the course of the calibration and performance verification observations. The data cover ...a ~3° × 3° area around the cluster with a typical exposure time of more than 20 ks. The stability of the instrumental background and operation of the SRG observatory in the scanning mode provided us with an excellent data set for studies of the diffuse emission up to a distance of ~1.5
R
200
from the Coma center. In this study, we discuss the rich morphology revealed by the X-ray observations (also in combination with the SZ data) and argue that the most salient features can be naturally explained by a recent (ongoing) merger with the NGC 4839 group. In particular, we identify a faint X-ray bridge connecting the group with the cluster, which is convincing proof that NGC 4839 has already crossed the main cluster. The gas in the Coma core went through two shocks, first through the shock driven by NGC 4839 during its first passage through the cluster some gigayear ago and, more recently, through the “mini-accretion shock” associated with the gas settling back to quasi-hydrostatic equilibrium in the core. After passing through the primary shock, the gas should spend much of the time in a rarefaction region, where radiative losses of electrons are small, until the gas is compressed again by the mini-accretion shock. Unlike “runway” merger shocks, the mini-accretion shock does not feature a rarefaction region downstream and, therefore, the radio emission can survive longer. Such a two-stage process might explain the formation of the radio halo in the Coma cluster.
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FMFMET, NUK, UL, UM, UPUK
The halo of the Milky Way provides a laboratory to study the properties of the shocked hot gas that is predicted by models of galaxy formation. There is observational evidence of energy injection ...into the halo from past activity in the nucleus of the Milky Way
; however, the origin of this energy (star formation or supermassive-black-hole activity) is uncertain, and the causal connection between nuclear structures and large-scale features has not been established unequivocally. Here we report soft-X-ray-emitting bubbles that extend approximately 14 kiloparsecs above and below the Galactic centre and include a structure in the southern sky analogous to the North Polar Spur. The sharp boundaries of these bubbles trace collisionless and non-radiative shocks, and corroborate the idea that the bubbles are not a remnant of a local supernova
but part of a vast Galaxy-scale structure closely related to features seen in γ-rays
. Large energy injections from the Galactic centre
are the most likely cause of both the γ-ray and X-ray bubbles. The latter have an estimated energy of around 10
erg, which is sufficient to perturb the structure, energy content and chemical enrichment of the circumgalactic medium of the Milky Way.
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FZAB, GEOZS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Using a spectral analysis of bright Chandra X-ray sources located in 27 nearby galaxies and maps of star-formation rate (SFR) and interstellar medium surface densities for these galaxies, we ...constructed the intrinsic X-ray luminosity function (XLF) of luminous high-mass X-ray binaries (HMXBs), taking into account absorption effects and the diversity of HMXB spectra. The XLF per unit SFR can be described by a power-law dN/dlog L
X,unabs ≈ 2.0(L
X,unabs/1039 erg s−1)−0.6 (M⊙ yr−1)−1 from L
X,unabs = 1038 to 1040.5 erg s−1, where L
X,unabs is the unabsorbed luminosity at 0.25–8 keV. The intrinsic number of luminous HMXBs per unit SFR is a factor of ∼2.3 larger than the observed number reported before. The intrinsic XLF is composed of hard, soft and supersoft sources (defined here as those with the 0.25–2 keV to 0.25–8 keV flux ratio of <0.6, 0.6–0.95 and >0.95, respectively) in ∼ 2:1:1 proportion. We also constructed the intrinsic HMXB XLF in the soft X-ray band (0.25–2 keV). Here, the numbers of hard, soft and supersoft sources prove to be nearly equal. The cumulative present-day 0.25–2 keV emissivity of HMXBs with luminosities between 1038 and 1040.5 erg s−1 is ∼5 × 1039 erg s−1(M⊙ yr−1)−1, which may be relevant for studying the X-ray preheating of the early Universe.
Abstract
Using a sample of 200 luminous (LX, unabs > 1038 erg s−1, where LX, unabs is the unabsorbed 0.25–8 keV luminosity) high-mass X-ray binary (HMXB) candidates found with Chandra in 27 nearby ...galaxies, we have constructed the collective X-ray spectrum of HMXBs in the local Universe per unit star formation rate, corrected for observational biases associated with intrinsic diversity of HMXB spectra and X-ray absorption in the interstellar medium. This spectrum is well fit by a power law with a photon index Γ = 2.1 ± 0.1 and is dominated by ultraluminous X-ray sources with LX, unabs > 1039 erg s−1. Hard sources (those with the 0.25–2 to 0.25–8 keV flux ratio of <0.6) dominate above ∼2 keV, while soft and supersoft sources (with the flux ratios of 0.6–0.95 and >0.95, respectively) at lower energies. The derived spectrum probably represents the angle-integrated X-ray emission of the near- and supercritically accreting stellar mass black holes and neutron stars in the local Universe. It provides an important constraint on supercritical accretion models and can be used as a reference spectrum for calculations of the X-ray preheating of the Universe by the first generations of X-ray binaries.
Nanoplatforms applied for the loading of anticancer drugs is a cutting-edge approach for drug delivery to tumors and reduction of toxic effects on healthy cells. In this study, we describe the ...synthesis and compare the sorption properties of four types of potential doxorubicin-carriers, in which iron oxide nanoparticles (IONs) are functionalized with cationic (polyethylenimine, PEI), anionic (polystyrenesulfonate, PSS), and nonionic (dextran) polymers, as well as with porous carbon. The IONs are thoroughly characterized by X-ray diffraction, IR spectroscopy, high resolution TEM (HRTEM), SEM, magnetic susceptibility, and the zeta-potential measurements in the pH range of 3-10. The degree of doxorubicin loading at pH 7.4, as well as the degree of desorption at pH 5.0, distinctive to cancerous tumor environment, are measured. Particles modified with PEI were shown to exhibit the highest loading capacity, while the greatest release at pH 5 (up to 30%) occurs from the surface of magnetite decorated with PSS. Such a slow release of the drug would imply a prolonged tumor-inhibiting action on the affected tissue or organ. Assessment of the toxicity (using Neuro2A cell line) for PEI- and PSS-modified IONs showed no negative effect. In conclusion, the preliminary evaluation of the effects of IONs coated with PSS and PEI on the rate of blood clotting was carried out. The results obtained can be taken into account when developing new drug delivery platforms.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A powerful outburst of X-ray radiation from the supermassive black hole Sgr A* at the centre of the Milky Way is believed to be responsible for the illumination of molecular clouds in the central ...~100 pc of the Galaxy (Sunyaev, Markevitch & Pavlinsky; Koyama et al.). The reflected/reprocessed radiation comes to us with a delay corresponding to the light propagation time that depends on the 3D position of molecular clouds with respect to Sgr A*. We suggest a novel way of determining the age of the outburst and positions of the clouds by studying characteristic imprints left by the outburst in the spatial and time variations of the reflected emission. We estimated the age of the outburst that illuminates the Sgr A molecular complex to be ~110 yr. This estimate implies that we see the gas located ~10 pc further away from us than Sgr A*. If the Sgr B2 complex is also illuminated by the same outburst, then it is located ~130 pc closer than our Galactic Center. The outburst was short (less than a few years) and the total amount of emitted energy in X-rays is ... erg, where p3 is the mean hydrogen density of the cloud complex in units of 10 super( 3) cm super( -3). Energetically, such fluence can be provided by a partial tidal disruption event or even by a capture of a planet. Further progress in more accurate positioning and timing of the outburst should be possible with future X-ray polarimetric observations and long-term systematic observations with Chandra and XMM-Newton. A few hundred years long X-ray observations would provide a detailed 3D map of the gas density distribution in the central ~100 pc region. (ProQuest: ... denotes formulae/symbols omitted.)
Abstract
The average operating time before structural and technological failures of the submersible part of a typical ESP is 64.5–81.9% of the average operating time of new ESPs. Given that the set ...of typical ESPs includes a significant share of repaired and mixed (equipped with new and refurbished units) installations, this fact can be interpreted as evidence of poor quality of repair. The data obtained from Tatneft and Bashneft companies agree with this conclusion. The data provided by Nizhnevartovskneftegaz company do not contradict this conclusion. The high values of T
tkt
obtained by Rosneft-Samaraneftegaz are a consequence of poor identification of the causes of ESP lifting during control operations, as a result of which some failures are treated as design and technological ones.
Abstract
The transforming mechanism of rocking machines is an articulated four-link mechanism made following the symmetrical and asymmetrical kinematic schemes. On the straight line passing through ...the extreme positions of the base of the bolt and the balancing lever, there is a center of rotation of the crank in symmetrical mechanisms. In different variants they are asymmetrical mechanisms. The dimensions of the converting mechanism of Russian symmetrical rocking machines are smaller than foreign asymmetrical rocking machines. This method can be used to show the contrast between technical and operational indicators of the rocking machines manufactured using various kinematic schemes. A contrast of the data multiplied by
S
0
K
/
K
1
with the real data of rocking machines revealed their compliance, which confirms the correctness of the method.
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