A candidate for the parent body of the Taurid complex and its search ephemeris

Untypical asteroid 5025 P-L, with its perihelion close to the orbit of Mercury and its aphelion between the orbits of Jupiter and Saturn, seems to be a good candidate for the parent body of the Taurid complex of small interplanetary objects. Evidence that this asteroid is a major source of meteoroids as well as an analysis of the orbits of asteroidal and cometary members of the Taurid complex, lead to the conclusion that 5025 P-L might be regarded as a remnant of a giant comet which was a progenitor of the overall complex according to the hypothesis of Clube and Napier. Unfortunately, the orbit of 5025 P-L is very poorly determined because the computations were based upon only three positional observations over an arc of only four days in October 1960. Any further research on the problem of origin and evolution of the Taurid complex needs better determined orbit of this key asteroid. Therefore its new positions are necessary. In order to enable the search of eventual trails of 5025 P-L on plates which can be found in archives, its ephemeris for the opposition in 1960, when the asteroid passed about 0.5 AU from the Earth, is presented

NUMERYCZNE ASPEKTY ODWZOROWANIA WTÓRNEGO POLA MAGNETYCZNEGO W MAGNETYCZNEJ TOMOGRAFII INDUKCYJNEJ

Magnetic Induction Tomography (MIT) belongs to the noncontact electromagnetic imaging techniques. This paper focuses on determination of a secondary magnetic field map calculated with the help of the Biot-Savart law around the low-conductivity object. The inclusions of various shapes and different electrical conductivities values and two measurement planes are considered. In each case the objects’ single maximal cell volume with assumed uniform eddy current density has been determined. In order to keep the relative error below 1% the object should be divided in most cases into elements with maximal cell volume equal to 0.244 mm3 for yz − plane, and 0.03 mm3 for xy − plane.Magnetyczna Tomografia Indukcyjna (MIT) należy do bezkontaktowych, elektromagnetycznych technik obrazowania. Artykuł skupia się na wyznaczeniu mapy wtórnego pola magnetycznego obliczonego za pomocą prawa Biota-Savarta wokół obiektu słaboprzewodzącego. Przeanalizowano wtrącenia o różnym kształcie i różnej wartości konduktywności elektrycznej oraz dwie płaszczyzny pomiarowe. W każdym przypadku została wyznaczona maksymalna objętość pojedynczej komórki obiektu z założoną stałą wartością gęstości prądu. W celu uzyskania błędu względnego poniżej 1% obiekt powinien zostać podzielony w większości przypadków na elementy z maksymalną objętością równą 0,244 mm3 dla płaszczyzny yz oraz 0,03 mm3 dla płaszczyzny xy

Double Compact Objects as Low-frequency Gravitational Wave Sources

We study the Galactic field population of double compact objects (NS-NS, BH-NS, BH-BH binaries) to investigate the number (if any) of these systems that can potentially be detected with LISA at low gravitational-wave frequencies. We calculate the Galactic numbers and physical properties of these binaries and show their relative contribution from the disk, bulge and halo. Although the Galaxy hosts 10^5 double compact object binaries emitting low-frequency gravitational waves, only a handful of these objects in the disk will be detectable with LISA, but none from the halo or bulge. This is because the bulk of these binaries are NS-NS systems with high eccentricities and long orbital periods (weeks/months) causing inefficient signal accumulation (small number of signal bursts at periastron passage in 1 yr of LISA observations) rendering them undetectable in the majority of these cases. We adopt two evolutionary models that differ in their treatment of the common envelope phase that is a major (and still mostly unknown) process in the formation of close double compact objects. Depending on the adopted evolutionary model, our calculations indicate the likely detection of about 4 NS-NS binaries and 2 BH-BH systems (model A; likely survival of progenitors through CE) or only a couple of NS-NS binaries (model B; suppression of the double compact object formation due to CE mergers).Comment: 12 pages, ApJ accepted, major change

Missing Black Holes Unveil The Supernova Explosion Mechanism

It is firmly established that the stellar mass distribution is smooth, covering the range 0.1-100 Msun. It is to be expected that the masses of the ensuing compact remnants correlate with the masses of their progenitor stars, and thus it is generally thought that the remnant masses should be smoothly distributed from the lightest white dwarfs to the heaviest black holes. However, this intuitive prediction is not borne out by observed data. In the rapidly growing population of remnants with observationally determined masses, a striking mass gap has emerged at the boundary between neutron stars and black holes. The heaviest neutron stars reach a maximum of two solar masses, while the lightest black holes are at least five solar masses. Over a decade after the discovery, the gap has become a significant challenge to our understanding of compact object formation. We offer new insights into the physical processes that bifurcate the formation of remnants into lower mass neutron stars and heavier black holes. Combining the results of stellar modeling with hydrodynamic simulations of supernovae, we both explain the existence of the gap, and also put stringent constraints on the inner workings of the supernova explosion mechanism. In particular, we show that core-collapse supernovae are launched within 100-200 milliseconds of the initial stellar collapse, implying that the explosions are driven by instabilities with a rapid (10-20 ms) growth time. Alternatively, if future observations fill in the gap, this will be an indication that these instabilities develop over a longer (>200 milliseconds) timescale.Comment: ApJ, accepted: comments added on recent Ugliano et al. and Kreidberg et al. studie

On The Maximum Mass of Stellar Black Holes

We present the spectrum of compact object masses: neutron stars and black holes that originate from single stars in different environments. In particular, we calculate the dependence of maximum black hole mass on metallicity and on some specific wind mass loss rates (e.g., Hurley et al. and Vink et al.). Our calculations show that the highest mass black holes observed in the Galaxy M_bh = 15 Msun in the high metallicity environment (Z=Zsun=0.02) can be explained with stellar models and the wind mass loss rates adopted here. To reach this result we had to set Luminous Blue Variable mass loss rates at the level of about 0.0001 Msun/yr and to employ metallicity dependent Wolf-Rayet winds. With such winds, calibrated on Galactic black hole mass measurements, the maximum black hole mass obtained for moderate metallicity (Z=0.3 Zsun=0.006) is M_bh,max = 30 Msun. This is a rather striking finding as the mass of the most massive known stellar black hole is M_bh = 23-34 Msun and, in fact, it is located in a small star forming galaxy with moderate metallicity. We find that in the very low (globular cluster-like) metallicity environment the maximum black hole mass can be as high as M_bh,max = 80 Msun (Z=0.01 Zsun=0.0002). It is interesting to note that X-ray luminosity from Eddington limited accretion onto an 80 Msun black hole is of the order of about 10^40 erg/s and is comparable to luminosities of some known ULXs. We emphasize that our results were obtained for single stars only and that binary interactions may alter these maximum black hole masses (e.g., accretion from a close companion). This is strictly a proof-of-principle study which demonstrates that stellar models can naturally explain even the most massive known stellar black holes.Comment: 15 pages, ApJ accepte

Development of a spray-ejector condenser for the use in a negative CO2 emission gas power plant

One promising solution for developing low-emission power technologies is using gaseous fuel combustion in pure oxygen when the exhaust gas mixture is composed of H2O and CO2, and where CO2 is separated after steam condensation. The paper presents the results of computational analyses providing to the Spray-Ejector Condenser (SEC) development, which is one of the crucial components of the negative CO2 gas power plant (nCO2PP) cycle development. The proposed design of the ejector-condenser to ensure the high effectivity of vapor condensation and CO2 compression with preparation to separation, ready for application in gas power cycle, is a novelty of this research. Different computational techniques leading to the development and better understating of ejector operation were applied. The main operating conditions in the characteristic connected with the developed nCO2pp cycle points were investigated to evaluate the impact of the operating conditions on SEC performances. The amount of motive water needed for the cooling purpose is susceptible to the inlet water pressure and temperature and strongly affects the generated pressure of the suction stream. The preliminary results confirm that the SEC's basic design and geometrical dimensions can be applied in the negative CO2 power plant cycle. Results from CFD modeling give the possibility to investigate the turbulent flow of water/steam/CO2 mixture together with the condensation process occurring at this same time. It is found that the average droplet diameter and motive water supplying method significantly effects the condensation intensity. The further direction of the presented computational research activities and results is to test various designs of Spray-Ejector Condensers that will enable the evaluation of the direct contact condensation process and develop the final geometrical design. © 2023 The AuthorsDevelopment of a spray-ejector condenser for the use in a negative CO2 emission gas power plantpublishedVersio

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements