We report the detection of the 1.3 mm continuum and the molecular emission of the disks of the young triple system SR24 by analyzing ALMA (The Atacama Large Millimeter/Submillimter Array) ...subarcsecond archival observations. We estimate the mass of the disks (0.025 M☉ and 4 × 10−5 M⊕ for SR24S and SR24N, respectively) and the dynamical mass of the protostars (1.5 M☉ and 1.1 M☉). A kinematic model of the SR24S disk to fit its C18O (2-1) emission allows us to develop an observational method to determine the tilt of a rotating and accreting disk. We derive the size, inclination, position angle, and sense of rotation of each disk, finding that they are strongly misaligned ( ) and possibly rotate in opposite directions as seen from Earth, in projection. We compare the ALMA observations with 12CO SMA archival observations, which are more sensitive to extended structures. We find three extended structures and estimate their masses: a molecular bridge joining the disks of the system, a molecular gas reservoir associated with SR24N, and a gas streamer associated with SR24S. Finally, we discuss the possible origin of the misaligned SR24 system, concluding that a closer inspection of the northern gas reservoir is needed to better understand it.
ABSTRACT
We present the kinematic results for the supernova remnant (SNR) CTB 1, obtained with the PUMA equipment of the 2.1-m telescope at San Pedro Mártir National Astronomical Observatory, Baja ...California, Mexico. The observations were made on the H α line using a Fabry–Perot interferometer. The kinematics derived from the Fabry–Perot velocity cubes allowed us to estimate a kinematic distance for this SNR. We estimate that CTB1 is about 3.8 kpc from the sun, corresponding to a linear diameter of 19 pc, with an expansion velocity of $286 \rm ~ km ~s^{-1}$. Additionally, we analyse the diffuse X-ray emission from CTB 1 using data from the XMM–Newton observatory. From the best fits to the spectrum of southwest and northeast regions, we obtained a hot plasma temperature $\sim 0.1-0.3 ~\rm keV$ with an overabundance in O and Ne and a lower abundance in Fe, which could be caused by a SNR with a stellar progenitor between 10 to $70 \, \rm {\rm M}_{\odot }$. The initial energy of the supernova explosion is estimated between (0.6–1.0) × 1050 erg for soft X-ray emission. The X-ray emission also presents a non-thermal component of low surface brightness in the hard X-ray band. Images in radio and X-ray emission allow us to classify CTB 1 as mixed-morphology supernova type. The evolution models show that the cloudy ISM model is the only one that reproduces the mixed morphology type observed in the SNR CTB 1.
ABSTRACT
We present observations of the optical and X-ray emission from the Galactic supernova remnant W51C. From S ii Fabry–Pérot interferometry and H α and S ii images we detect filaments that are ...part of the optical counterpart of the supernova remnant. We obtain the kinematic distance to W51C, showing that it is one of the shortest distances reported in the literature. We also estimate other physical properties such as the velocity of the shock induced in the cloudlets emitted at optical wavelengths and the electron density of those cloudlets. From XMM–Newton observatory archival data, we obtain images of the diffuse X-ray emission of this supernova remnant. The spectrum of the X-ray emission is explored to estimate X-ray parameters such as luminosity and temperature of the hot plasma in the supernova remnant. We fit a thermal model with a plasma temperature of 1.4 keV for an X-ray thermal luminosity of 2.0 × 1036 erg s−1. With the parameters described above we test the model proposed by White & Long to explain the mixed morphology observed in W51C. We obtain an initial energy of the supernova explosion of 8.4 × 1050 erg and an age of 13 000 yr. The derived initial energy is typical of supernova remnants, but in disagreement with respect to older estimations that found higher values and suggested that W51C was the result of the explosion of two supernovae.
ABSTRACT
We present observations in X-ray and optical emission of the supernova remnant (SNR) 0520–69.4 in the Large Magellanic Cloud. Using XMM–Newton observatory data, we produced images of the ...diffuse X-ray emission and spectra to obtain the X-ray parameters, such as luminosity and temperature, of hot plasma in the SNR. Diffuse X-ray emission with filled-centre morphology goes beyond the Hα region, suggesting that the hot gas escapes through the pores of the Hα shell. We fitted a model that has a plasma temperature of 1.1 × 107 K for an X-ray thermal luminosity of 3.3 × 1035 erg s−1. However, from Hα and O iii Fabry–Perot observations obtained with the Marseille Hα Survey of the Magellanic Clouds and the Milky Way at La Silla, European Southern Observatory, we are able to obtain physical parameters such as the velocity of the shock induced in the cloudlets emitting at optical wavelengths and the electron density of this gas. With the parameters described above, we test the model proposed by White & Long (1991, ApJ, 373, 543) for explaining the mixed-morphology observed.
ABSTRACT
Ground-based and satellite observations have revealed dust temperatures as low as ∼5−7 K in the centre of low-mass, pre-stellar cloud cores, where star formation takes place. However, ...external heating may rise the outer core temperatures up to ∼15−20 K. Such low temperatures at the centre of pre-stellar cores are a key factor to constrain the conditions that lead to the formation of gravitationally bound protostellar systems as was recently captured by highly-resolved Atacama large millimeter/submillimeter array observations. Here, we report consistent smoothed particle hydrodynamics collapse calculations of cold cores that demonstrate the formation of close protobinary systems via small-scale fragmentation of a gravitationally unstable protostellar disc. The results indicate that mean binary separations, of tens of astronomical units, are a consequence of disc fragmentation in cold pre-stellar cores. Cloud cores initially with temperatures ≤6 K and a low amplitude (a = 0.1), m = 2 density perturbation formed close protobinaries that were followed deep into the non-isothermal collapse for several orbital periods and appeared to survive as independent stellar entities. At temperatures ≥7 K disc fragmentation is no longer observed and the calculations terminate with the formation of a wide protobinary, which may occasionally be accompanied by small substellar objects emerging by fragmentation of the circumbinary disc. When the perturbation amplitude is raised to a = 0.25, disc fragmentation occurs again only in cores with initial temperatures ≤6 K. Therefore, increasing the perturbation amplitude does not necessarily imply that there will be disc fragmentation at higher core temperatures.
The thermal structure of filtration combustion waves in the metallic Mo - Ti system in nitrogen is studied by dynamic color pyrometry. It's shown that the combustion of the samples is conducted in ...the surface mode. This mode is characterized by the propagation of a reaction wave in a narrow near-surface layer of the sample followed by the penetration of combustion from the surface to the centre. The peculiarities of combustion observed are the presence of local reaction sources in the surface reaction wave and the complex three-dimensional structure of the temperature field in the reaction wave (local reaction source - surface reaction wave - inside reaction wave). The measurements have shown that with increasing nitrogen pressure, the maximum temperature inside the sample rises by 200 K.
We present the classical Bondi accretion theory for the case of non-isothermal accretion processes onto a supermassive black hole (SMBH), including the effects of X-ray heating and the radiation ...force due to electron scattering and spectral lines. The radiation field is calculated by considering an optically thick, geometrically thin, standard accretion disc as the emitter of UV photons and a spherical central object as a source of X-ray emission. In our analysis, the UV emission from the accretion disc is assumed to have an angular dependence, and the X-ray radiation from the central object is assumed to be isotropic. This allows us to build streamlines in any angular direction. The influence of both types of radiation is evaluated for different flux fractions of the X-ray and UV emissions with and without the effects of spectral line driving. We find that the radiation emitted near the SMBH interacts with the infalling matter and modifies the accretion dynamics. In the presence of line driving, a transition takes place from pure type 1 and 2 to type 5 solutions, which takes place regardless of whether the UV emission dominates the X-ray emission. We computed the radiative factors at which this transition occurs, and discard type 5 solution from all our models. We also provide estimated values of the accretion radius and accretion rate in terms of the classical Bondi values. The results are useful for constructing proper initial conditions for time-dependent hydrodynamical simulations of accretion flows onto SMBHs at the centre of galaxies.
Coatings based on aluminium nickelides and Ti2AIC Ti3AlC2 MAX-phases are obtained by the method of self-propagating high-temperature synthesis. The processes occurring in the powder mixture of nickel ...and aluminium, as well as in the titanium-aluminium-carbon mixture are studied. The effect of the thickness of the coating on the maximum temperature and velocity of combustion wave is found. The coating consists of small crystals NiAl, Ni3Al or Ti2AlC, Ti3AlC3, fused together. The coating has high electrical conductivity and can be used as heat-resistant protective coatings or electric heaters.
Using the method of self-propagating high-temperature synthesis, coatings based on aluminum nickelides were obtained. The processes occurring in the layers of a powder mixture of nickel and aluminum ...are studied. The influence of the coating thickness and the degree of dilution of the powder mixture with aluminum oxide on the maximum temperature of the combustion wave and the rate of its propagation is established. The coating consists of small crystals of NiAl, Ni3Al, fused together. The coating has good electrical conductivity and can be used as electric heaters.
Abstract
In this paper, we derive a novel circular velocity relation for a test particle in a 3D gravitational potential applicable to every system of curvilinear coordinates, suitable to be reduced ...to orthogonal form. As an illustration of the potentiality of the determined circular velocity expression, we perform the rotation curves analysis of UGC 8490 and UGC 9753 and we estimate the total and dark matter mass of these two galaxies under the assumption that their respective dark matter haloes have spherical, prolate, and oblate spheroidal mass distributions. We employ stellar population synthesis models and the total H i density map to obtain the stellar and H i+He+metals rotation curves of both galaxies. The subtraction of the stellar plus gas rotation curves from the observed rotation curves of UGC 8490 and UGC 9753 generates the dark matter circular velocity curves of both galaxies. We fit the dark matter rotation curves of UGC 8490 and UGC 9753 through the newly established circular velocity formula specialized to the spherical, prolate, and oblate spheroidal mass distributions, considering the Navarro, Frenk, and White, Burkert, Di Cintio, Einasto, and Stadel dark matter haloes. Our principal findings are the following: globally, cored dark matter profiles Burkert and Einasto prevail over cuspy Navarro, Frenk, and White, and Di Cintio. Also, spherical/oblate dark matter models fit better the dark matter rotation curves of both galaxies than prolate dark matter haloes.
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