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Kurita, Yasuyuki, and Chiyozo Takayama. "Secondary orbital interaction vs. orbital distortion in stereoselectivity." Tetrahedron 46, no. 11 (January 1990): 3789–802. http://dx.doi.org/10.1016/s0040-4020(01)90514-9.
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Rauw, G., A. Pigulski, Y. Nazé, A. David-Uraz, G. Handler, F. Raucq, E. Gosset, et al. "BRITE photometry of the massive post-RLOF system HD149 404." Astronomy & Astrophysics 621 (December 20, 2018): A15. http://dx.doi.org/10.1051/0004-6361/201833594.
Повний текст джерелаАнотація:
Context. HD 149 404 is an evolved non-eclipsing O-star binary that has previously undergone a Roche lobe overflow interaction. Aims. Understanding some key properties of the system requires a determination of the orbital inclination and of the dimensions of the components. Methods. The BRITE-Heweliusz satellite was used to collect photometric data of HD 149 404. Additional photometry was retrieved from the SMEI archive. These data were analysed using a suite of period search tools. The orbital part of the lightcurve was modelled with the nightfall binary star code. The Gaia-DR2 parallax of HD 149 404 was used to provide additional constraints. Results. The periodograms reveal a clear orbital modulation of the lightcurve with a peak-to-peak amplitude near 0.04 mag. The remaining non-orbital part of the variability is consistent with red noise. The lightcurve folded with the orbital period reveals ellipsoidal variations, but no eclipses. The minimum when the secondary star is in inferior conjunction is deeper than the other minimum due to mutual reflection effects between the stars. Combined with the Gaia-DR2 parallaxes, the photometric data indicate an orbital inclination in the range of 23°–31° and a Roche lobe filling factor of the secondary larger than or equal to 0.96. Conclusions. The luminosity of the primary star is consistent with its present-day mass, whereas the more evolved secondary appears overluminous for its mass. We confirm that the primary’s rotation period is about half the orbital period. Both features most probably stem from the past Roche lobe overflow episode.
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Raucq, F., G. Rauw, L. Mahy, and S. Simón-Díaz. "Fundamental parameters of massive stars in multiple systems: The cases of HD 17505A and HD 206267A." Astronomy & Astrophysics 614 (June 2018): A60. http://dx.doi.org/10.1051/0004-6361/201732376.
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Context. Many massive stars are part of binary or higher multiplicity systems. The present work focusses on two higher multiplicity systems: HD 17505A and HD 206267A. Aims. Determining the fundamental parameters of the components of the inner binary of these systems is mandatory to quantify the impact of binary or triple interactions on their evolution. Methods. We analysed high-resolution optical spectra to determine new orbital solutions of the inner binary systems. After subtracting the spectrum of the tertiary component, a spectral disentangling code was applied to reconstruct the individual spectra of the primary and secondary. We then analysed these spectra with the non-LTE model atmosphere code CMFGEN to establish the stellar parameters and the CNO abundances of these stars. Results. The inner binaries of these systems have eccentric orbits with e ~ 0.13 despite their relatively short orbital periods of 8.6 and 3.7 days for HD 17505Aa and HD 206267Aa, respectively. Slight modifications of the CNO abundances are found in both components of each system. The components of HD 17505Aa are both well inside their Roche lobe, whilst the primary of HD 206267Aa nearly fills its Roche lobe around periastron passage. Whilst the rotation of the primary of HD 206267Aa is in pseudo-synchronization with the orbital motion, the secondary displays a rotation rate that is higher. Conclusions. The CNO abundances and properties of HD 17505Aa can be explained by single star evolutionary models accounting for the effects of rotation, suggesting that this system has not yet experienced binary interaction. The properties of HD 206267Aa suggest that some intermittent binary interaction might have taken place during periastron passages, but is apparently not operating anymore.
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Mossoux, E., L. Mahy, and G. Rauw. "The long-period massive binary HD 54662 revisited." Astronomy & Astrophysics 615 (July 2018): A19. http://dx.doi.org/10.1051/0004-6361/201732095.
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Context. HD 54662 is an O-type binary star belonging to the CMa OB1 association. Because of its long-period orbit, this system is an interesting target to test the adiabatic wind shock model. Aims. The goal of this study is to improve our knowledge of the orbital and stellar parameters of HD 54662 and to analyze its X-ray emission to test the theoretical scaling of X-ray emission with orbital separation for adiabatic wind shocks. Methods. We applied a spectral disentangling code to a set of optical spectra to determine the radial velocities and the individual spectra of the primary and secondary stars. The orbital solution of the system was established and the reconstructed individual spectra were analyzed by means of the CMFGEN model atmosphere code. We fitted two X-ray spectra using a Markov chain Monte Carlo algorithm and compared these spectra to the emission expected from adiabatic shocks. Results. We determine an orbital period of 2103.4 days, a surprisingly low orbital eccentricity of 0.11, and a mass ratio m2/m1 of 0.84. Combined with the orbital inclination inferred in a previous astrometric study, we obtain surprisingly low masses of 9.7 and 8.2 M⊙. From the disentangled primary and secondary spectra, we infer O6.5 spectral types for both stars, of which the primary is about two times brighter than the secondary. The softness of the X-ray spectra for the two observations, the very small variation of best-fitting spectral parameters, and the comparison of the X-ray-to-bolometric luminosity ratio with the canonical value for O-type stars allow us to conclude that X-ray emission from the wind interaction region is quite low and that the observed emission is rather dominated by the intrinsic emission from the stars. We cannot confirm the runaway status previously attributed to HD 54662 by computing the peculiar radial and tangential velocities. We find no X-ray emission associated with the bow shock detected in the infrared. Conclusions. The lack of hard X-ray emission from the wind-shock region suggests that the mass-loss rates are lower than expected and/or that the pre-shock wind velocities are much lower than the terminal wind velocities. The bow shock associated with HD 54662 possibly corresponds to a wind-blown arc created by the interaction of the stellar winds with the ionized gas of the CMa OB1 association rather than by a large differential velocity between the binary and the surrounding interstellar medium.
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Gwak, Bogeun. "Coalescence of Kerr Black Holes—Binary Systems from GW150914 to GW170814." Entropy 21, no. 10 (October 20, 2019): 1017. http://dx.doi.org/10.3390/e21101017.
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We investigate the energy of the gravitational wave from a binary black hole merger by the coalescence of two Kerr black holes with an orbital angular momentum. The coalescence is constructed to be consistent with particle absorption in the limit in which the primary black hole is sufficiently large compared with the secondary black hole. In this limit, we analytically obtain an effective gravitational spin–orbit interaction dependent on the alignments of the angular momenta. Then, binary systems with various parameters including equal masses are numerically analyzed. According to the numerical analysis, the energy of the gravitational wave still depends on the effective interactions, as expected from the analytical form. In particular, we ensure that the final black hole obtains a large portion of its spin angular momentum from the orbital angular momentum of the initial binary black hole. To estimate the angular momentum released by the gravitational wave in the actual binary black hole, we apply our results to observations at the Laser Interferometer Gravitational-Wave Observatory: GW150914, GW151226, GW170104, GW170608 and GW170814.
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Politano, M., and R. F. Webbink. "The White Dwarf Mass and Orbital Period Distribution in Zero-Age Cataclysmic Binaries." International Astronomical Union Colloquium 114 (1989): 440–42. http://dx.doi.org/10.1017/s0252921100100028.
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A zero-age cataclysmic binary (ZACB) we define as a binary system at the onset of interaction as a cataclysmic variable. We present here the results of calculations of the distributions of white dwarf masses and of orbital periods in ZACBs, due to binaries present in a stellar population which has undergone continuous, constant star formation for 1010 years.Distributions of ZACBs were calculated for binaries formed t years ago, for log t = 7.4 (the youngest age at which viable ZACBs can form) to log t = 10.0 (the assumed age of the Galactic disk), in intervals of log t = 0.1. These distributions were then integrated over time to obtain the ZACB distribution for a constant rate of star formation. To compute the individual distributions for a given t, we require the density of systems forming (number of pre-cataclysmics forming per unit volume of orbital parameter space), n£(t), and the rates at which the radii of the secondary and of its Roche lobe are changing in time, s (t) and L, s (t), respectively. In calculating nf(t), we assume that the distribution of the orbital parameters in primordial (ZAMS) binaries may be written as the product of the distribution of masses of ZAMS stars (Miller and Scalo 1979), the distribution of mass ratios in ZAMS binaries (cf. Popova, et al., 1982), and the distribution of orbital periods in ZAMS binaries (Abt 1983). In transforming the the orbital parameters from progenitor (ZAMS) to offspring (ZACB) binaries, we assume that all of the orbital energy deposited into the envelope during the common envelope phase leading to ZACB formation goes into unbinding that envelope. R.L, s (t) is determined from orbital angular momentum loss rates due to gravitational radiation (Landau and Lifshitz 1951) and magnetic braking (γ = 2 in Rappaport, Verbunt, and Joss 1983). We turn off magnetic braking if the secondary is completely convective.
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Tokayer, Y. M., H. An, J. P. Halpern, J. Kim, K. Mori, C. J. Hailey, C. B. Adams, et al. "Multiwavelength Observation Campaign of the TeV Gamma-Ray Binary HESS J0632 + 057 with NuSTAR, VERITAS, MDM, and Swift." Astrophysical Journal 923, no. 1 (December 1, 2021): 17. http://dx.doi.org/10.3847/1538-4357/ac2c6a.
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Abstract HESS J0632+057 belongs to a rare subclass of binary systems that emit gamma rays above 100 GeV. It stands out for its distinctive high-energy light curve, which features a sharp “primary” peak and broader “secondary” peak. We present the results of contemporaneous observations by NuSTAR and VERITAS during the secondary peak between 2019 December and 2020 February, when the orbital phase (ϕ) is between 0.55 and 0.75. NuSTAR detected X-ray spectral evolution, while VERITAS detected TeV emission. We fit a leptonic wind-collision model to the multiwavelength spectra data obtained over the four NuSTAR and VERITAS observations, constraining the pulsar spin-down luminosity and the magnetization parameter at the shock. Despite long-term monitoring of the source from 2019 October to 2020 March, the MDM observatory did not detect significant variation in Hα and Hβ line equivalent widths, an expected signature of Be-disk interaction with the pulsar. Furthermore, fitting folded Swift-XRT light-curve data with an intrabinary shock model constrained the orbital parameters, suggesting two orbital phases (at ϕ D = 0.13 and 0.37), where the pulsar crosses the Be-disk, as well as phases for the periastron (ϕ 0 = 0.30) and inferior conjunction (ϕ IFC = 0.75). The broadband X-ray spectra with Swift-XRT and NuSTAR allowed us to measure a higher neutral hydrogen column density at one of the predicted disk-passing phases.
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Sheppard, Rachel Y., Michael T. Thorpe, Abigail A. Fraeman, Valerie K. Fox, and Ralph E. Milliken. "Merging Perspectives on Secondary Minerals on Mars: A Review of Ancient Water-Rock Interactions in Gale Crater Inferred from Orbital and In-Situ Observations." Minerals 11, no. 9 (September 9, 2021): 986. http://dx.doi.org/10.3390/min11090986.
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Phyllosilicates, sulfates, and Fe oxides are the most prevalent secondary minerals detected on Mars from orbit and the surface, including in the Mars Science Laboratory Curiosity rover’s field site at Gale crater. These records of aqueous activity have been investigated in detail in Gale crater, where Curiosity’s X-ray diffractometer allows for direct observation and detailed characterization of mineral structure and abundance. This capability provides critical ground truthing to better understand how to interpret Martian mineralogy inferred from orbital datasets. Curiosity is about to leave behind phyllosilicate-rich strata for more sulfate-rich terrains, while the Mars 2020 Perseverance rover is in its early exploration of ancient sedimentary strata in Jezero crater. It is thus an appropriate time to review Gale crater’s mineral distribution from multiple perspectives, utilizing the range of chemical, mineralogical, and spectral measurements provided by orbital and in situ observations. This review compares orbital predictions of composition in Gale crater with higher fidelity (but more spatially restricted) in situ measurements by Curiosity, and we synthesize how this information contributes to our understanding of water-rock interaction in Gale crater. In the context of combining these disparate spatial scales, we also discuss implications for the larger understanding of martian surface evolution and the need for a wide range of data types and scales to properly reconstruct ancient geologic processes using remote methods.
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Singleton, Daniel A. "A [4 + 3] transition state for a [4 + 2] cycloaddition. A new secondary orbital interaction in Diels-Alder reactions." Journal of the American Chemical Society 114, no. 16 (July 1992): 6563–64. http://dx.doi.org/10.1021/ja00042a049.
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Kashi, Amit, and Amir Michaelis. "Numerical Study of Colliding Winds in Massive Stars." Galaxies 10, no. 1 (December 28, 2021): 4. http://dx.doi.org/10.3390/galaxies10010004.
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We run a numerical experiment ejecting stellar winds in a very massive binary system measuring the properties of the resulting colliding wind structure and accreted mass onto the companion under different conditions. Colliding massive binaries interact and create a colliding wind structure with a shape that depends on the momentum ratio, orbital motion, distance between the stars, and other factors. We run simulations of a static LBV-WR binary and in each simulation abruptly varying the mass loss rate of the LBV from the fiducial value. The modified wind front propagates and interacts with the previous colliding wind structure, and modifies its shape. We calculate the emitted X-ray from the interaction and investigate the proprieties of the new shape. We derive the mass accretion rate onto the secondary, and find that it depends on the momentum ratio of the winds. We then add orbital velocity that reduces the mass accretion rate, a similar behaviour as the analytical estimates based on modified Bondi–Hoyle–Lyttleton. Creating a large set of simulations like those presented here can allow constraining parameters for specific colliding wind binaries and derive their stellar parameters and orbital solution.
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Lanzafame, G., G. Belvedere, and D. Molteni. "Inner Edge Drag by an Asynchronous Primary and Accretion Disc Structure in Close Binaries." International Astronomical Union Colloquium 158 (1996): 117–18. http://dx.doi.org/10.1017/s0252921100038392.
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In this work a 3–D ‘Smoothed Particle Hydrodynamics’ ([1]; [4]; [5]) accretion disc is simulated where particles at its inner edge are dragged by a fast spinning compact central star, as in the case of the intermediate polars. The angular velocity of the central star is twice the orbital angular velocity ωo. This drag can be attributed mainly to viscous interaction in the dense compact star atmosphere, although magnetic coupling may also play a role.Our simulations have been performed for a system with a primary (a white dwarf) mass M1 = 1.3 M⊙, a secondary mass M2 = 2.2 M⊙, a separation between the components (centre to centre) d12 = 6.33 1011 cm and an orbital period = 1.7 d, the integration time being as long as ≃ 75 d. As in [2] and [3], we have considered quasi-polytropic structures with γ = 1.01. We adopt the term quasi-polytropic since we have in fact solved also an energy equation.
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Hasan, Tanveer, P. K. Singh, P. Raj, K. Singhal, and Neeraj Misra. "Vibrational and Quantum Chemical Study of Triphenylantimony(V)-o-salicylate." E-Journal of Chemistry 5, no. 4 (2008): 723–35. http://dx.doi.org/10.1155/2008/351845.
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A complete normal coordinate analysis was performed by two different methods: a classical Wilson G-F matrix method and the semi-empirical molecular orbital PM3 method, for a five coordinate non rigid triphenyl antimony diester SbPh3(O2CR)2,[R=C6H4OH-o], known to be a bioactive molecule. The study of vibrational spectra suggested that the title compound might have secondary bonding interaction between the central antimony atom and the carbonyl oxygen atoms. The atomic charge distribution, geometry optimization and thermochemistry, were also calculated by PM3 method, which help in finding the potential sites of the title compound.
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Taniguchi, Y., and O. Kaburaki. "11.3. The black hole grazer." Symposium - International Astronomical Union 184 (1998): 461–62. http://dx.doi.org/10.1017/s0074180900085570.
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We propose an alternative model for the powering of active galactic nuclei (AGN), based on the assumption that all AGN have experienced mergers. In our model (Kaburaki and Taniguchi 1996; Taniguchi and Kaburaki 1996), a close pair of super-massive black holes (the black hole grazer) orbit one another in a plane roughly perpendicular to the galactic center magnetic field. The orbital motion induces surface charges on the black holes which produce an electric field. This field is strong enough to cause pair creation so that the Roche lobe of the binary system is filled with pair plasmas. Rigid-body rotation of the Roche-lobe magnetosphere drives electrodynamically a powerful synchrotron jet emanating from the center of mass of the binary. Furthermore, a pair of equatorial jets flow from the outer Lagrangian points of the binary system. Although these jets are not so collimated, they interact with the accreting gas ring formed around the orbital plane of the binary, causing broad line regions or H2O maser emission regions (Taniguchi et al. 1996). In addition to the primary jet, two secondary jets are also driven by local accretion disks around the two black holes. The interaction among the primary and the secondary jets may explain detailed jet morphology observed by VLBI facilities.
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Taniguchi, Y., and O. Kaburaki. "The Black Hole Grazer." Symposium - International Astronomical Union 188 (1998): 449–50. http://dx.doi.org/10.1017/s0074180900115979.
Повний текст джерелаАнотація:
We propose an alternative model for the powering of active galactic nuclei (AGN), based on the assumption that all AGN have experienced mergers. In our model (Kaburaki and Taniguchi 1996; Taniguchi and Kaburaki 1996), a close pair of super-massive black holes (the black hole grazer) orbit one another in a plane roughly perpendicular to the galactic center magnetic field. The orbital motion induces surface charges on the black holes which produce an electric field. This field is strong enough to cause pair creation so that the Roche lobe of the binary system is filled with pair plasmas. Rigid-body rotation of the Roche-lobe magnetosphere drives electrodynamically a powerful synchrotron jet emanating from the center of mass of the binary. Furthermore, a pair of equatorial jets flow from the outer Lagrangian points of the binary system. Although these jets are not so collimated, they interact with the accreting gas ring formed around the orbital plane of the binary, causing broad line regions or H2O maser emission regions (Taniguchi et al. 1996). In addition to the primary jet, two secondary jets are also driven by local accretion disks around the two black holes. The interaction among the primary and the secondary jets may explain detailed jet morphology observed by VLBI facilities.
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Rawat, Nikita, J. C. Pandey, Arti Joshi, and Umesh Yadava. "A step towards unveiling the nature of three cataclysmic variables: LS Cam, V902 Mon, and SWIFT J0746.3-1608." Monthly Notices of the Royal Astronomical Society 512, no. 4 (March 26, 2022): 6054–66. http://dx.doi.org/10.1093/mnras/stac844.
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ABSTRACT We have carried out detailed time-resolved timing analyses of three cataclysmic variables (CVs) namely LS Cam, V902 Mon, and SWIFT J0746.3-1608, using the long-baseline, high-cadence optical photometric data from the Transiting Exoplanet Survey Satellite. Our analysis of LS Cam observations hints the presence of a superorbital period of ∼4.025 ± 0.007 d along with negative and positive superhump periods of ∼3.30 and 3.70 h, respectively. These results can be explained as an interaction of nodal and apsidal precession of the accretion disc with orbital motion. For the other two sources, V902 Mon and SWIFT J0746.3-1608, we have found evidence of a beat period of 2387.0 ± 0.6 and 2409.5 ± 0.7 s, respectively, which were not found in earlier studies. Our results presented in this study indicate the change in the accretion mode during the entire observing period for both sources. For V902 Mon, an apparent orbital period derivative of (6.09 ± 0.60) × 10−10 was also found. Moreover, the second harmonic of orbital frequency dominates the power spectrum of SWIFT J0746.3-1608, suggestive of ellipsoidal modulation of the secondary star. Present analyses suggest that LS Cam could be a superhumping CV, whereas V902 Mon and SWIFT J0746.3-1608 are likely to be variable disc-overflow accreting intermediate polars.
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Jiao, Yinchun, and Frank Weinhold. "What Is the Nature of Supramolecular Bonding? Comprehensive NBO/NRT Picture of Halogen and Pnicogen Bonding in RPH2···IF/FI Complexes (R = CH3, OH, CF3, CN, NO2)." Molecules 24, no. 11 (May 31, 2019): 2090. http://dx.doi.org/10.3390/molecules24112090.
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We employ a variety of natural bond orbital (NBO) and natural resonance theory (NRT) tools to comprehensively investigate the nature of halogen and pnicogen bonding interactions in RPH2···IF/FI binary complexes (R = CH3, OH, CF3, CN, and NO2) and the tuning effects of R-substituents. Though such interactions are commonly attributed to “sigma-hole”-type electrostatic effects, we show that they exhibit profound similarities and analogies to the resonance-type 3-center, 4-electron (3c/4e) donor-acceptor interactions of hydrogen bonding, where classical-type “electrostatics” are known to play only a secondary modulating role. The general 3c/4e resonance perspective corresponds to a continuous range of interatomic A···B bond orders (bAB), spanning both the stronger “covalent” interactions of the molecular domain (say, bAB ≥ ½) and the weaker interactions (bAB ˂ ½, often misleadingly termed “noncovalent”) that underlie supramolecular complexation phenomena. We show how a unified NBO/NRT-based description of hydrogen, halogen, pnicogen, and related bonding yields an improved predictive utility and intuitive understanding of empirical trends in binding energies, structural geometry, and other measurable properties that are expected to be manifested in all such supramolecular interaction phenomena.
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Lee, Youngdae, Sang Chul Kim, Dae-Sik Moon, Hong Soo Park, Maria R. Drout, Yuan Qi Ni, and Hyobin Im. "Discovery of a Short-period and Unusually Helium-deficient Dwarf Nova KSP-OT-201701a by the KMTNet Supernova Program." Astrophysical Journal Letters 925, no. 2 (February 1, 2022): L22. http://dx.doi.org/10.3847/2041-8213/ac4c41.
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Abstract We present the first ever discovery of a short-period and unusually helium-deficient dwarf nova KSP-OT-201701a by the Korea Microlensing Telescope Network Supernova Program. The source shows three superoutbursts, each led by a precursor outburst, and several normal outbursts in BVI during the span of ∼2.6 yr with supercycle and normal cycle lengths of about 360 and 76 days, respectively. Spectroscopic observations near the end of a superoutburst reveal the presence of strong double-peaked H i emission lines together with weak He i emission lines. The helium-to-hydrogen intensity ratios measured by He i λ5876 and Hα lines are 0.10 ± 0.01 at a quiescent phase and 0.26 ± 0.04 at an outburst phase, similar to the ratios found in long-period dwarf novae, while significantly lower than those in helium cataclysmic variables (He CVs). Its orbital period of 51.91 ± 2.50 minutes, which is estimated based on time-series spectroscopy, is a bit shorter than the superhump period of 56.52 ± 0.19 minutes, as expected from the gravitational interaction between the eccentric disk and the secondary star. We measure its mass ratio to be 0.37 − 0.21 + 0.32 using the superhump period excess of 0.089 ± 0.053. The short orbital period, which is under the period minimum, the unusual helium deficiency, and the large mass ratio suggest that KSP-OT-201701a is a transition object evolving to an He CV from a long-period dwarf nova with an evolved secondary star.
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Guan, Tianzhu, Ning Li, Ya Gao, Longfei Zhang, Qin Hu, Huaxiang Li, Ming Yang, Lixia Xiao, Lei Yuan, and Zhenquan Yang. "Interaction behavior between bisphenol AP and pepsin: Insights from density functional theory, and spectroscopic and molecular dynamic simulation." Quality Assurance and Safety of Crops & Foods 14, no. 2 (April 11, 2022): 1–12. http://dx.doi.org/10.15586/qas.v14i2.1023.
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Overuse of polymer materials has caused increasing direct human exposure to bisphenol AP (BPAP). Through the contaminated environment and food chains, the adverse effects of BPAP on humans and plants induce growing concerns. In this study, the effects of BPAP on pepsin structure changes were exhaustively investigated by multi-spectral methods. Under mimic physiological conditions, BPAP caused a gradient intrinsic fluorescence quenching by inducing microenvironmental changes surrounding residues with the endogenous fluorescence in pepsin. During the ground-state complex formation, the senior structures of pepsin were altered by BPAP addition. Fourier transform infrared spectroscopy and circular dichroism spectroscopy showed that the secondary and tertiary structures of pepsin were changed after the addition of BPAP. Thermodynamic parameter analysis demonstrated that the pepsin and BPAP binding was a spontaneous process that was mainly driven by hydrophobic interaction and van der Waals force. With BPAP as the subject of density functional theory experiments, the energies of the highest occupied molecular orbital, the lowest unoccupied molecular orbital, and the electrostatic potential were calculated to evaluate the electronic distribution of BPAP. Molecular docking experiments displayed that in the specific interaction pattern, hydrogen-bonding between one of the hydroxyl groups and specific amino acids was vital in stabilizing the BPAP−pepsin complex. The root mean square deviation, total hydrogen bonds statistic, and Ramachandran map obtained by molecular dynamic simulations validated the findings and predicted the rationality of the complex structure. This study provides an experimental and theoretical basis for understanding the binding mechanism of bisphenol pollution and pepsin. It also puts forward strategies to strengthen food safety and achieve precise control of environmental contaminants in the food industry.
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Wong, Ian, Avi Shporer, George Zhou, Daniel Kitzmann, Thaddeus D. Komacek, Xianyu Tan, René Tronsgaard, et al. "TOI-2109: An Ultrahot Gas Giant on a 16 hr Orbit." Astronomical Journal 162, no. 6 (November 23, 2021): 256. http://dx.doi.org/10.3847/1538-3881/ac26bd.
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Abstract We report the discovery of an ultrahot Jupiter with an extremely short orbital period of 0.67247414 ± 0.00000028 days (∼16 hr). The 1.347 ± 0.047 R Jup planet, initially identified by the Transiting Exoplanet Survey Satellite (TESS) mission, orbits TOI-2109 (TIC 392476080)—a T eff ∼ 6500 K F-type star with a mass of 1.447 ± 0.077 M ☉, a radius of 1.698 ± 0.060 R ☉, and a rotational velocity of v sin i * = 81.9 ± 1.7 km s−1. The planetary nature of TOI-2109b was confirmed through radial-velocity measurements, which yielded a planet mass of 5.02 ± 0.75 M Jup. Analysis of the Doppler shadow in spectroscopic transit observations indicates a well-aligned system, with a sky-projected obliquity of λ = 1.°7 ± 1.°7. From the TESS full-orbit light curve, we measured a secondary eclipse depth of 731 ± 46 ppm, as well as phase-curve variations from the planet’s longitudinal brightness modulation and ellipsoidal distortion of the host star. Combining the TESS-band occultation measurement with a K s -band secondary eclipse depth (2012 ± 80 ppm) derived from ground-based observations, we find that the dayside emission of TOI-2109b is consistent with a brightness temperature of 3631 ± 69 K, making it the second hottest exoplanet hitherto discovered. By virtue of its extreme irradiation and strong planet–star gravitational interaction, TOI-2109b is an exceptionally promising target for intensive follow-up studies using current and near-future telescope facilities to probe for orbital decay, detect tidally driven atmospheric escape, and assess the impacts of H2 dissociation and recombination on the global heat transport.
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Bujarrabal, V., J. Alcolea, J. Mikołajewska, A. Castro-Carrizo, and S. Ramstedt. "High-resolution observations of the symbiotic system R Aqr." Astronomy & Astrophysics 616 (August 2018): L3. http://dx.doi.org/10.1051/0004-6361/201833633.
Повний текст джерелаАнотація:
We have observed the symbiotic stellar system R Aqr, aiming to describe the gravitational interaction between the white dwarf (WD) and the wind from the Mira star, the key phenomenon driving the symbiotic activity and the formation of nebulae in such systems. We present high-resolution ALMA maps of the 12CO and 13CO J = 3−2 lines, the 0.9 mm continuum distribution, and some high-excitation molecular lines in R Aqr. The maps, which have resolutions ranging between 40 mas and less than 20 mas probe the circumstellar regions at suborbital scales as the distance between the stars is ~40 mas. Our observations show the gravitational effects of the secondary on the stellar wind. The AGB star was identified in our maps from the continuum and molecular line data, and we estimated the probable position of the secondary from a new estimation of the orbital parameters. The (preliminary) comparison of our maps with theoretical predictions is surprisingly satisfactory and the main expected gravitational effects are directly mapped for the first time. We find a strong focusing in the equatorial plane of the resulting wind, which shows two plumes in opposite directions that have different velocities and very probably correspond to the expected double spiral due to the interaction. Our continuum maps show the very inner regions of the nascent bipolar jets, at scales of some AU. Continuum maps obtained with the highest resolution show the presence of a clump that very probably corresponds to the emission of the ionized surroundings of the WD and of a bridge of material joining both stars, which is likely material flowing from the AGB primary to the accretion disk around the WD secondary.
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Politano, M., and R. F. Webbink. "The White Dwarf Mass and Orbital Period Distributions in Zero-Age Cataclysmic Variables." International Astronomical Union Colloquium 122 (1990): 392–93. http://dx.doi.org/10.1017/s0252921100068901.
Повний текст джерелаАнотація:
A zero-age cataclysmic variable (ZACV) we define as a binary system at the onset of interaction as a cataclysmic variable. We present here the results of calculations of the distributions of white dwarf masses and of orbital periods in ZACVs, due to binaries present in a stellar population which has undergone continuous, constant star formation for 1010 years. These results differ from previous work (Politano and Webbink 1988) in that an improved criterion for stability against rapid mass transfer by the secondary to the white dwarf has been used. A brief outline of the method and key assumptions made in this calculation is given in Politano and Webbink (1988).The white dwarf mass distribution of ZACVs (shown in Figure 1) contains two components: systems with helium white dwarfs and systems with C-0 white dwarfs. Systems with helium white dwarfs comprise slightly greater than 50% of all ZACVs. The helium white dwarfs have masses which range from 0.27 to 0.46 solar mass. The C-0 white dwarfs have masses which range from 0.54 solar mass up to the Chandrasekhar mass. (Note: systems with O-Ne-Mg white dwarfs are not distinguished from systems with C-0 white dwarfs in this calculation. Presumably, these O-Ne-Mg systems comprise the upper end of the white dwarf mass distribution.)
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Shiber, Sagiv. "The Morphology of the Outflow in the Grazing Envelope Evolution." Galaxies 6, no. 3 (September 6, 2018): 96. http://dx.doi.org/10.3390/galaxies6030096.
Повний текст джерелаАнотація:
We study the grazing envelope evolution (GEE), where a secondary star, which orbits the surface of a giant star, accretes mass from the giant envelope and launches jets. We conduct simulations of the GEE with different half-opening angles and velocities, and simulate the onset phase and the spiralling-in phase. We discuss the resulting envelope structure and the outflow geometry. We find in the simulations of the onset phase with narrow jets that a large fraction of the ejected mass outflows along the polar directions. The mass ejected at these directions has the fastest velocity and the highest angular momentum magnitude. In the simulations of the spiralling-in phase, a large fraction of the ejected mass concentrates around the orbital plane. According to our findings, the outflow with the highest velocity is closer to the poles as we launch narrower jets. The outflow has a toroidal shape accompanied by two faster rings, one ring at each side of the equatorial plane. The interaction of the jets with the giant envelope causes these outflow structures, as we do not include in our simulations the secondary star gravity and the envelope self-gravity.
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Sarna, M. J. "From Common Envelope to Pre-Cataclysmic Variables: An Observational Test of Common Envelope Evolution." International Astronomical Union Colloquium 158 (1996): 453–56. http://dx.doi.org/10.1017/s0252921100039397.
Повний текст джерелаАнотація:
The generally accepted evolutionary scenario for cataclysmic variables (CVs) is common envelope (CE) evolution (Iben & Livio 1993) proposed by Paczyñski (1976). The secondary spirals towards the giant’s compact core converting orbital energy into kinetic energy of the giant’s envelope and the envelope is ejected. The dynamics of the red dwarf and red giant envelope interaction have been studied by several groups (Livio & Soker 1988; Taam & Bodenheimer 1991). After the ejection of the red giant envelope the post common envelope detached binaries (PCEBs) are formed. These can be divided into three groups:• Hot subdwarf with a red dwarf star inside a planetary nebula.• Hot subdwarf with a red dwarf star without a planetary nebula.• Hot white dwarf with a red dwarf star without a planetary nebula. Next, due to angular momentum loss by magnetic braking and/or gravitational radiation, the red dwarf component fills its Roche lobe and a cataclysmic variable is formed.
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Gonzalez, Jean-François, Gerrit van der Plas, Christophe Pinte, Nicolás Cuello, Rebecca Nealon, François Ménard, Alexandre Revol, Laetitia Rodet, Maud Langlois, and Anne-Lise Maire. "Spirals, shadows, and precession in HD 100453 – I. The orbit of the binary." Monthly Notices of the Royal Astronomical Society 499, no. 3 (September 26, 2020): 3837–56. http://dx.doi.org/10.1093/mnras/staa2938.
Повний текст джерелаАнотація:
ABSTRACT In recent years, several protoplanetary discs have been observed to exhibit spirals, both in scattered light and (sub)millimetre continuum data. The HD 100453 binary star system hosts such a disc around its primary. Previous work has argued that the spirals were caused by the gravitational interaction of the secondary, which was assumed to be on a circular orbit, coplanar with the disc (meaning here the large outer disc, as opposed to the very small inner disc). However, recent observations of the CO gas emission were found incompatible with this assumption. In this paper, we run SPH simulations of the gas and dust disc for seven orbital configurations taken from astrometric fits and compute synthetic observations from their results. Comparing to high-resolution ALMA 12CO data, we find that the best agreement is obtained for an orbit with eccentricity e = 0.32 and semimajor axis a = 207 au, inclined by 61° relative to the disc plane. The large misalignment between the disc and orbit planes is compatible with the tidal evolution of a circumprimary disc in an eccentric, unequal-mass binary star.
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Guimon, C., G. Pfister-Guillouzo, D. Ilavsky, M. Marchalin, and A. Martvon. "Structure électronique et réactivité des pyridyl-isothiocyanates. Étude quantique et photoélectronique." Canadian Journal of Chemistry 64, no. 8 (August 1, 1986): 1467–73. http://dx.doi.org/10.1139/v86-242.
Повний текст джерелаАнотація:
On the basis of molecular orbital calculations made in association with ultraviolet photoélectron spectroscopy (ups), it is demonstrated that the regioselectivity of the cycloadditions of pyridyl-2-isothiocyanate with 1,3-dipoles is directed by frontier orbitals. The different cycloadditions (4 + 2, 2 + 3, 2 + 2) vary with the overlap of these orbitals and this shows the importance of secondary interactions, namely the localization of the orbitals on the atoms adjacent to the bonds that are formed during the addition.
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Huber, D., R. Kissmann, and O. Reimer. "Relativistic fluid modelling of gamma-ray binaries." Astronomy & Astrophysics 649 (May 2021): A71. http://dx.doi.org/10.1051/0004-6361/202039278.
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Context. In the first paper of this series, we presented a numerical model for the non-thermal emission of gamma-ray binaries in a pulsar-wind-driven scenario. Aims. We apply this model to one of the best-observed gamma-ray binaries, the LS 5039 system. Methods. The model involves a joint simulation of the interaction between the pulsar wind and the stellar wind and the transport of electron pairs from the pulsar wind accelerated at the emerging shock structure. We compute the synchrotron and inverse Compton emission in a post-processing step while consistently accounting for relativistic beaming and γγ-absorption in the stellar radiation field. Results. The wind interaction leads to the formation of an extended, asymmetric wind collision region that develops strong shocks, turbulent mixing, and secondary shocks in the turbulent flow. Both the structure of the collision region and the resulting particle distributions show significant orbital variation. In addition to the acceleration of particles at the bow-like pulsar wind and the Coriolis shock, the model naturally accounts for the re-acceleration of particles at secondary shocks that contribute to the emission at very-high-energy (VHE) gamma-rays. The model successfully reproduces the main spectral features of LS 5039. While the predicted light curves in the high-energy and VHE gamma-ray band are in good agreement with observations, our model still does not reproduce the X-ray to low-energy gamma-ray modulation, which we attribute to the employed magnetic field model. Conclusions. We successfully model the main spectral features of the observed multi-band, non-thermal emission of LS 5039 and thus further substantiate a wind-driven interpretation of gamma ray binaries. Open issues relate to the synchrotron modulation, which might be addressed through a magnetohydrodynamic extension of our model.
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Sulis, S., D. Dragomir, M. Lendl, V. Bourrier, B. O. Demory, L. Fossati, P. E. Cubillos, et al. "Multi-season optical modulation phased with the orbit of the super-Earth 55 Cancri e." Astronomy & Astrophysics 631 (November 2019): A129. http://dx.doi.org/10.1051/0004-6361/201936066.
Повний текст джерелаАнотація:
Context. 55 Cnc e is a transiting super-Earth orbiting a solar-like star with an orbital period of ~17.7 h. In 2011, using the Microvariability and Oscillations in Stars (MOST) space telescope, a quasi-sinusoidal modulation in flux was detected with the same period as the planetary orbit. The amplitude of this modulation was too large to be explained as the change in light reflected or emitted by the planet. Aims. The MOST telescope continued to observe 55 Cnc e for a few weeks per year over five years (from 2011 to 2015), covering 143 individual transits. This paper presents the analysis of the observed phase modulation throughout these observations and a search for the secondary eclipse of the planet. Methods. The most important source of systematic noise in MOST data is due to stray-light reflected from the Earth, which is modulated with both the orbital period of the satellite (101.4 min) and the Earth’s rotation period. We present a new technique to deal with this source of noise, which we combined with standard detrending procedures for MOST data. We then performed Markov chain Monte Carlo analyses of the detrended light curves, modeling the planetary transit and phase modulation. Results. We find phase modulations similar to those seen in 2011 in most of the subsequent years; however, the amplitude and phase of maximum light are seen to vary, from year to year, from 113 to 28 ppm and from 0.1 to 3.8 rad. The secondary eclipse is not detected, but we constrain the geometric albedo of the planet to less than 0.47 (2σ). Conclusions. While we cannot identify a single origin of the observed optical modulation, we propose a few possible scenarios. Those include star-planet interaction, such as coronal rains and spots rotating with the motion of the planet along its orbit, or the presence of a transiting circumstellar torus of dust. However, a detailed interpretation of these observations is limited by their photometric precision. Additional observations at optical wavelengths could measure the variations at higher precision, contribute to uncovering the underlying physical processes, and measure or improve the upper limit on the albedo of the planet.
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Harris, D. M., and C. H. K. Williamson. "Instability of secondary vortices generated by a vortex pair in ground effect." Journal of Fluid Mechanics 700 (April 18, 2012): 148–86. http://dx.doi.org/10.1017/jfm.2012.108.
Повний текст джерелаАнотація:
AbstractIn this work, we investigate the approach of a descending vortex pair to a horizontal ground plane. As in previous studies, the primary vortices exhibit a ‘rebound’, due to the separation of secondary opposite-sign vortices underneath each primary vortex. On each side of the flow, the weaker secondary vortex can become three-dimensionally unstable, as it advects around the stronger primary vortex. It has been suggested in several recent numerical simulations that elliptic instability is the origin of such waviness in the secondary vortices. In the present research, we employ a technique whereby the primary vortices are visualized separately from the secondary vortices; in fact, we are able to mark the secondary vortex separation, often leaving the primary vortices invisible. We find that the vortices are bent as a whole in a Crow-type ‘displacement’ mode, and, by keeping the primary vortices invisible, we are able to see both sides of the flow simultaneously, showing that the instability perturbations on the secondary vortices are antisymmetric. Triggered by previous research on four-vortex aircraft wake flows, we analyse one half of the flow as an unequal-strength counter-rotating pair, noting that it is essential to take into account the angular velocity of the weak vortex around the stronger primary vortex in the analysis. In contrast with previous results for the vortex–ground interaction, we find that the measured secondary vortex wavelength corresponds well with the displacement bending mode, similar to the Crow-type instability. We have analysed the elliptic instability modes, by employing the approximate dispersion relation of Le Dizés & Laporte (J. Fluid Mech., vol. 471, 2002, p. 169) in our problem, finding that the experimental wavelength is distinctly longer than predicted for the higher-order elliptic modes. Finally, we observe that the secondary vortices deform into a distinct waviness along their lengths, and this places two rows of highly stretched vertical segments of the vortices in between the horizontal primary vortices. The two rows of alternating-sign vortices translate towards each other and ultimately merge into a single vortex row. A simple point vortex row model is able to predict trajectories of such vortex rows, and the net result of the model’s ‘orbital’ or ‘passing’ modes is to bring like-sign vortices, from each secondary vortex row, close to each other, such that merging may ensue in the experiments.
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Eupen, F., L. Labadie, R. Grellmann, K. Perraut, W. Brandner, G. Duchêne, R. Köhler, et al. "The GRAVITY young stellar object survey." Astronomy & Astrophysics 648 (April 2021): A37. http://dx.doi.org/10.1051/0004-6361/202039599.
Повний текст джерелаАнотація:
Context. Close young binary stars are unique laboratories for the direct measurement of pre-main-sequence (PMS) stellar masses and their comparison to evolutionary theoretical models. At the same time, a precise knowledge of their orbital parameters when still in the PMS phase offers an excellent opportunity for understanding the influence of dynamical effects on the morphology and lifetime of the circumstellar as well as circumbinary material. Aims. The young T Tauri star WW Cha was recently proposed to be a close binary object with strong infrared and submillimeter excess associated with circum-system emission, which makes it dynamically a very interesting source in the above context. The goal of this work is to determine the astrometric orbit and the stellar properties of WW Cha using multi-epoch interferometric observations. Methods. We derive the relative astrometric positions and flux ratios of the stellar companion in WW Cha from the interferometric model fitting of observations made with the VLTI instruments AMBER, PIONIER, and GRAVITY in the near-infrared from 2011 to 2020. For two epochs, the resulting uv-coverage in spatial frequencies permits us to perform the first image reconstruction of the system in the K band. The positions of nine epochs are used to determine the orbital elements and the total mass of the system. Combining the orbital solution with distance measurements from Gaia DR2 and the analysis of evolutionary tracks, we constrain the mass ratio. Results. We find the secondary star orbiting the primary with a period of T = 206.55 days, a semimajor axis of a = 1.01 au, and a relatively high eccentricity of e = 0.45. The dynamical mass of Mtot = 3.20 M⊙ can be explained by a mass ratio between ∼0.5 and 1, indicating an intermediate-mass T Tauri classification for both components. The orbital angular momentum vector is in close alignment with the angular momentum vector of the outer disk as measured by ALMA and SPHERE, resulting in a small mutual disk inclination. The analysis of the relative photometry suggests the presence of infrared excess surviving in the system and likely originating from truncated circumstellar disks. The flux ratio between the two components appears variable, in particular in the K band, and may hint at periods of triggered higher and lower accretion or changes in the disks’ structures. Conclusions. The knowledge of the orbital parameters, combined with a relatively short period, makes WW Cha an ideal target for studying the interaction of a close young T Tauri binary with its surrounding material, such as time-dependent accretion phenomena. Finding WW Cha to be composed of two (probably similar) stars led us to reevaluate the mass of WW Cha, which had been previously derived under the assumption of a single star. This work illustrates the potential of long baseline interferometry to precisely characterize close young binary stars separated by a few astronomical units. Finally, when combined with radial velocity measurements, individual stellar masses can be derived and used to calibrate theoretical PMS models.
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Lavail, A., O. Kochukhov, G. A. J. Hussain, C. Argiroffi, E. Alecian, and J. Morin. "The large-scale magnetic field of the eccentric pre-main-sequence binary system V1878 Ori." Monthly Notices of the Royal Astronomical Society 497, no. 1 (July 9, 2020): 632–42. http://dx.doi.org/10.1093/mnras/staa1993.
Повний текст джерелаАнотація:
ABSTRACT We report time-resolved, high-resolution optical spectropolarimetric observations of the young double-lined spectroscopic binary V1878 Ori. Our observations were collected with the ESPaDOnS spectropolarimeter at the Canada–France–Hawaii Telescope through the BinaMIcS large programme. V1878 Ori A and B are partially convective intermediate mass weak-line T Tauri stars on an eccentric and asynchronous orbit. We also acquired X-ray observations at periastron and outside periastron. Using the least-squares deconvolution technique (LSD) to combine information from many spectral lines, we clearly detected circular polarization signals in both components throughout the orbit. We refined the orbital solution for the system and obtained disentangled spectra for the primary and secondary components. The disentangled spectra were then employed to determine atmospheric parameters of the two components using spectrum synthesis. Applying our Zeeman Doppler imaging code to composite Stokes IV LSD profiles, we reconstructed brightness maps and the global magnetic field topologies of the two components. We find that V1878 Ori A and B have strikingly different global magnetic field topologies and mean field strengths. The global magnetic field of the primary is predominantly poloidal and non-axisymmetric (with a mean field strength of 180 G). While the secondary has a mostly toroidal and axisymmetric global field (mean strength of 310 G). These findings confirm that stars with very similar parameters can exhibit radically different global magnetic field characteristics. The analysis of the X-ray data shows no sign of enhanced activity at periastron, suggesting the lack of strong magnetospheric interaction at this epoch.
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García, José I., José A. Mayoral, and Luis Salvatella. "Do Secondary Orbital Interactions Really Exist?" Accounts of Chemical Research 33, no. 10 (October 2000): 658–64. http://dx.doi.org/10.1021/ar0000152.
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Wannere, Chaitanya S., Ankan Paul, Rainer Herges, K. N. Houk, Henry F. Schaefer, and Paul Von Ragué Schleyer. "The existence of secondary orbital interactions." Journal of Computational Chemistry 28, no. 1 (2006): 344–61. http://dx.doi.org/10.1002/jcc.20532.
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Zabel, Matthias, Ralph R. Schneider, Thomas Wagner, Adesina T. Adegbie, Uwe de Vries, and Sadat Kolonic. "Late Quaternary Climate Changes in Central Africa as Inferred from Terrigenous Input to the Niger Fan." Quaternary Research 56, no. 2 (September 2001): 207–17. http://dx.doi.org/10.1006/qres.2001.2261.
Повний текст джерелаАнотація:
AbstractTime series of terrigenous source elements (Al, K, Ti, Zr) from core GeoB4901-8 recovered from the deep-sea fan of the Niger River record variations in riverine sediment discharge over the past 245,000 yr. Although the flux rates of all the elements depend on physical erosion, which is mainly controlled by the extent of vegetation coverage in central Africa, element/Al ratios reflect conditions for chemical weathering in the river basin. Maximum sediment input to the ocean occurs during cold and arid periods, when precipitation intensity and associated freshwater runoff are reduced. High carbonate contents during the same periods indicate that the sediment supply has a positive effect on river-induced marine productivity. In general, variations in the terrestrial signals contain a strong precessional component in tune with changes in low-latitude solar radiation. However, the terrestrial signal lags the insolation signal by several thousand years. K/Al, Ti/Al, and Zr/Al records reveal that African monsoonal precipitation depends on high-latitude forcing. We attribute the shift between insolation cycle and river discharge to the frequently reported nonlinear response of African climate to primary orbital configurations, which may be caused by a complex interaction of the secondary control parameters, such as surface albedo and/or thermohaline circulation.
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Mihrin, D., A. Voute, P. W. Jakobsen, K. L. Feilberg, and R. Wugt Larsen. "The effect of alkylation on the micro-solvation of ethers revealed by highly localized water librational motion." Journal of Chemical Physics 156, no. 8 (February 28, 2022): 084305. http://dx.doi.org/10.1063/5.0081161.
Повний текст джерелаАнотація:
The specific far-infrared spectral signatures associated with highly localized large-amplitude out-of-plane librational motion of water molecules have recently been demonstrated to provide sensitive spectroscopic probes for the micro-solvation of organic molecules [Mihrin et al., Phys. Chem. Chem. Phys. 21(4), 1717 (2019)]. The present work employs this direct far-infrared spectroscopic approach to investigate the non-covalent intermolecular forces involved in the micro-solvation of a selection of seven ether molecules with systematically varied alkyl substituents: dimethyl ether, diethyl ether, diisopropyl ether, ethyl methyl ether, t-butyl methyl ether, and t-butyl ethyl ether. The ranking of the observed out-of-plane water librational band signatures for this selected series of ether–water complexes embedded in inert neon matrices at 4 K reveals information about the interplay of directional intermolecular hydrogen bond motifs and non-directional and long-range dispersion interactions for the micro-solvated structures. These far-infrared observables differentiate minor subtle effects introduced by specific alkyl substituents and serve as rigorous experimental benchmarks for modern quantum chemical methodologies of various levels of scalability, which often fail to accurately predict the structural variations and corresponding vibrational signatures of the closely related systems. The accurate interaction energies of the series of ether–water complexes have been predicted by the domain based local pair natural orbital coupled cluster theory with single-, double-, and perturbative triple excitations, followed by a local energy decomposition analysis of the energy components. In some cases, the secondary dispersion forces are in direct competition with the primary intermolecular hydrogen bonds as witnessed by the specific out-of-plane librational signatures.
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Kuszlewicz, James S., Thomas S. H. North, William J. Chaplin, Allyson Bieryla, David W. Latham, Andrea Miglio, Keaton J. Bell, et al. "KOI-3890: a high-mass-ratio asteroseismic red giant+M-dwarf eclipsing binary undergoing heartbeat tidal interactions." Monthly Notices of the Royal Astronomical Society 487, no. 1 (May 2, 2019): 14–23. http://dx.doi.org/10.1093/mnras/stz1185.
Повний текст джерелаАнотація:
Abstract KOI-3890 is a highly eccentric, 153-d period eclipsing, single-lined spectroscopic binary system containing a red giant star showing solar-like oscillations alongside tidal interactions. The combination of transit photometry, radial velocity observations, and asteroseismology has enabled the detailed characterization of both the red giant primary and the M-dwarf companion, along with the tidal interaction and the geometry of the system. The stellar parameters of the red giant primary are determined through the use of asteroseismology and grid-based modelling to give a mass and radius of $M_{\star }=1.04\pm 0.06 \, \textrm{M}_{\odot }$ and $R_{\star }=5.8\pm 0.2 \, \textrm{R}_{\odot }$, respectively. When combined with transit photometry, the M-dwarf companion is found to have a mass and radius of $M_{\mathrm{c}}=0.23\pm 0.01 \, \textrm{M}_{\odot }$ and $R_{\mathrm{c}}=0.256\pm 0.007 \, \textrm{R}_{\odot }$. Moreover, through asteroseismology we constrain the age of the system through the red giant primary to be $9.1^{+2.4}_{-1.7}\,\mathrm{Gyr}$. This provides a constraint on the age of the M-dwarf secondary, which is difficult to do for other M-dwarf binary systems. In addition, the asteroseismic analysis yields an estimate of the inclination angle of the rotation axis of the red giant star of $i=87.6^{+2.4}_{-1.2}$ degrees. The obliquity of the system – the angle between the stellar rotation axis and the angle normal to the orbital plane – is also derived to give $\psi =4.2^{+2.1}_{-4.2}$ degrees, showing that the system is consistent with alignment. We observe no radius inflation in the M-dwarf companion when compared to current low-mass stellar models.
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van der Plas, G., F. Ménard, J. F. Gonzalez, S. Perez, L. Rodet, C. Pinte, L. Cieza, S. Casassus, and M. Benisty. "ALMA study of the HD 100453 AB system and the tidal interaction of the companion with the disk." Astronomy & Astrophysics 624 (April 2019): A33. http://dx.doi.org/10.1051/0004-6361/201834134.
Повний текст джерелаАнотація:
Context. The complex system HD 100453 AB with a ring-like circumprimary disk and two spiral arms, one of which is pointing to the secondary, is a good laboratory in which to test spiral formation theories. Aims. We aim to resolve the dust and gas distribution in the disk around HD 100453 A and to quantify the interaction of HD 100453 B with the circumprimary disk. Methods. Using ALMA band 6 dust continuum and CO isotopologue observations we have studied the HD 100453 AB system with a spatial resolution of 0′′.09 × 0′′.17 at 234 GHz. We used smoothed particle hydrodynamics (SPH) simulations and orbital fitting to investigate the tidal influence of the companion on the disk. Results. We resolve the continuum emission around HD 100453 A into a disk between 0′′.22 and 0′′.40 with an inclination of 29.5° and a position angle of 151.0°, an unresolved inner disk, and excess mm emission cospatial with the northern spiral arm which was previously detected using scattered light observations. We also detect CO emission from 7 au (well within the disk cavity) out to 1′′.10, overlapping with HD 100453 B at least in projection. The outer CO disk position angle (PA) and inclination differ by up to 10° from the values found for the inner CO disk and the dust continuum emission, which we interpret as due to gravitational interaction with HD 100453 B. Both the spatial extent of the CO disk and the detection of mm emission at the same location as the northern spiral arm are in disagreement with the previously proposed near co-planar orbit of HD 100453 B. Conclusions. We conclude that HD 100453 B has an orbit that is significantly misaligned with the circumprimary disk. Because it is unclear whether such an orbit can explain the observed system geometry we highlight an alternative scenario that explains all detected disk features where another, (yet) undetected, low mass close companion within the disk cavity, shepherds a misaligned inner disk whose slowly precessing shadows excite the spiral arms.
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Rosén, L., O. Kochukhov, E. Alecian, C. Neiner, J. Morin та G. A. Wade. "Magnetic field topology of the cool, active, short-period binary system σ2 Coronae Borealis". Astronomy & Astrophysics 613 (травень 2018): A60. http://dx.doi.org/10.1051/0004-6361/201731706.
Повний текст джерелаАнотація:
Aims. The goal of this work is to study the cool, active binary star σ2 CrB, focussing on its magnetic field. The two F9–G0 components of this system are tidally locked and in a close orbit, increasing the chance of interaction between their magnetospheres. Methods. We used Stokes IV data from the twin spectropolarimeters Narval at the TBL and ESPaDOnS at the CFHT. The least-squares deconvolution multi-line technique was used to increase the signal-to-noise ratio of the data. We then applied a new binary Zeeman–Doppler imaging code to reconstruct simultaneously the magnetic topology and brightness distribution of both components of σ2 CrB. This analysis was carried out for two observational epochs in 2014 and 2017. Results. A previously unconfirmed magnetic field of the primary star has been securely detected. At the same time, the polarisation signatures of the secondary appear to have a systematically larger amplitude than that of the primary. This corresponds to a stronger magnetic field, for which the magnetic energy of the secondary exceeds that of the primary by a factor of 3.3–5.7. While the magnetic energy is similar for the secondary star in the two epochs, the magnetic energy is about twice as high in 2017 for the primary. The magnetic field topology of the two stars in the earlier epoch (2014) is very different. The fractions of energy in the dipole and quadrupole components of the secondary are similar and thereafter decrease with increasing harmonic angular degree ℓ. At the same time, for the primary the fraction of energy in the dipole component is low and the maximum energy contribution comes from ℓ = 4. However, in the 2017 epoch both stars have similar field topologies and a systematically decreasing energy with increasing ℓ. In the earlier epoch, the magnetic field at the visible pole appears to be of opposite polarity for the primary and secondary, suggesting linked magnetospheres. The apparent rotational periods of both σ2 CrB components are longer than the orbital period, which we interpret as an evidence of a solar-like differential rotation. Conclusions. Despite their nearly identical fundamental parameters, the components of σ2 CrB system exhibit different magnetic field properties. This indicates that the magnetic dynamo process is a very sensitive function of stellar parameters.
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Lv, Shuang, Feng-Yang Bai, Xiu-Mei Pan, and Liang Zhao. "Theoretical insight into the role of urea in the hydrolysis reaction of NO2 as a source of HONO and aerosols." Environmental Chemistry 15, no. 6 (2018): 372. http://dx.doi.org/10.1071/en18083.
Повний текст джерелаАнотація:
Environmental contextUrea is an important component of dissolved organic nitrogen in rainfall and aerosols, but the sources and the mechanisms of its production are not well understood. This computational study explores the effects of urea and water on the hydrolysis of NO2 and urea nitrate production. The results will aid our interpretation of the role of urea in the formation of atmospheric secondary nitrogen contaminants and aerosols. AbstractThe effects of urea on the hydrolysis reaction 2NO2 + mH2O (m = 1–3) have been investigated by theoretical calculations. The energy barrier (−2.67 kcal mol−1) of the urea-promoted reaction is lower than the naked reaction by 14.37 kcal mol−1. Urea also has a better catalytic effect on the reaction than methylamine and ammonia. Urea acts as a catalyst and proton transfer medium in this process, and the produced HONO may serve as a source of atmospheric nitrous acid. In addition, the subsequent reactions include clusters of nitrite, urea, and nitric acid. Then urea nitrate (UN), which is a typical HNO3 aerosol, can be formed in the subsequent reactions. The production of the acid-base complex (UN-2) is more favourable with an energy barrier of 0.10 kcal mol−1, which is 3.88 kcal mol−1 lower than that of the zwitterions NH2CONH3+NO3− (UN-1). The formation of zwitterions and the hydrolysis reaction are affected by humidity. The multi water-promoted hydrolysis reactions exhibit better thermodynamic stability when the humidity is increased. The extra water molecules act as solvent molecules to reduce the energy barrier. The natural bond orbital (NBO) analysis is employed to describe the donor-acceptor interactions of the complexes. The hydrogen bond interaction between the urea carbonyl and nitric acid of UN-2 is the strongest. The potential distribution maps of the urea nitrate and hydrate are examined, and the result shows that they tend to form zwitterions.
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Meng, Xiangcun, Xuefei Chen, and Zhanwen Han. "The single degenerate channel for the progenitors of Type Ia supernovae." Proceedings of the International Astronomical Union 4, S252 (April 2008): 379–82. http://dx.doi.org/10.1017/s1743921308023259.
Повний текст джерелаАнотація:
AbstractWe have carried out a detailed study of the single-degenerate channel for the progenitors of type Ia supernovae (SNe Ia). In the model, a carbon-oxygen white dwarf (CO WD) accretes hydrogen-rich material from an unevolved or a slightly evolved non-degenerate companion to increase its mass to Chandrasekhar mass limit. Incorporating the prescription of Hachisuet al. (1999a) for the accretion efficiency into Eggleton's stellar evolution code and assuming that the prescription is valid for all metallicities, we performed binary stellar evolution calculations for more than 25,000 close WD binary systems with various metallicities. The initial parameter spaces for SNe Ia are presented in an orbital period-secondary mass (logPi,M2i) plane for eachZ.Adopting the results above, we studied the birth rate of SNe Ia for variousZvia binary population synthesis. From the study, we see that for a highZ, SNe Ia occur systemically earlier and the peak value of the birth rate is larger if a single starburst is assumed. The Galactic birth rate from the channel is lower than (but comparable to) that inferred from observations.We also showed the distributions of the parameters of the binary systems at the moment of supernova explosion and the distributions of the properties of companions after supernova explosion. The former provides physics input to simulate the interaction between supernova ejecta and its companion, and the latter is helpful for searching the companions in supernova remnants.
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Garcia, Jose I., Jose A. Mayoral, and Luis Salvatella. "ChemInform Abstract: Do Secondary Orbital Interactions Really Exist?" ChemInform 31, no. 52 (December 26, 2000): no. http://dx.doi.org/10.1002/chin.200052289.
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Van Reeth, T., J. Southworth, J. Van Beeck, and D. M. Bowman. "V456 Cyg: An eclipsing binary with tidally perturbed g-mode pulsations." Astronomy & Astrophysics 659 (March 2022): A177. http://dx.doi.org/10.1051/0004-6361/202142833.
Повний текст джерелаАнотація:
Context. Many well-known bright stars have been observed by the ongoing transiting exoplanet survey satellite (TESS) space mission. For several of them, these new data reveal previously unobserved variability, such as tidally perturbed pulsations in close binary stars. Aims. Using newly detected gravity-mode (g-mode) pulsations in V456 Cyg, we aim to determine the global stellar properties of this short-period eclipsing binary and evaluate the interaction between these pulsations and the tides. Methods. We model the binary orbit and determine the physical properties of the component stars using the TESS photometry and published spectroscopy. We then measure the pulsation frequencies from the residuals of the light curve fit using iterative prewhitening, and analyse them to determine the global asteroseismic stellar parameters. We evaluate the pulsation parameters as a function of the orbital phase. Results. We find that the pulsations belong to the secondary component of V456 Cyg and that this star likely has a uniform radial rotation profile, synchronous (νrot = 1.113 (14) d−1) with the binary orbit (νorb = 1.122091 (8) d−1). The observed g modes are amplified by almost a factor three in the stellar hemisphere facing the primary. We present evidence that this is caused by tidal perturbation of the pulsations, with the mode coupling being strongly affected. Conclusions. V456 Cyg is only the second object for which tidally perturbed high-order g-mode pulsations are identified, after π5 Ori. This opens up new opportunities for tidal g-mode asteroseismology, as it demonstrates another avenue in which g modes and tides can interact with each other.
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Burdisso, Marina, Anna Gamba, Remo Gandolfi, and Roberta Oberti. "Steric effects vs secondary orbital interactions in nitrone cycloadditions." Tetrahedron 44, no. 12 (January 1988): 3735–48. http://dx.doi.org/10.1016/s0040-4020(01)86003-8.
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Hu, Di, and Derek A. Pratt. "Secondary orbital interactions in the propagation steps of lipid peroxidation." Chemical Communications 46, no. 21 (2010): 3711. http://dx.doi.org/10.1039/c0cc00019a.
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Si, Mrinal Kanti, and Bishwajit Ganguly. "Computational evidence that hyperconjugative orbital interactions are responsible for the stability of intramolecular Te⋯O/Te⋯S non-covalent interactions and comparable to hydrogen bonds in quasi-cyclic systems." New Journal of Chemistry 40, no. 11 (2016): 9132–38. http://dx.doi.org/10.1039/c6nj01707j.
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Matsumoto, Kiyoshi, Hirokazu Iida, Takane Uchida, Yoshimi Yabe, Akikazu Kakehi, and J. William Lown. "1,3-Dipolar cycloaddition reactions of monocyclic aziridines with dimethyl 1-cyclobutene-1,2-dicarboxylate." Canadian Journal of Chemistry 72, no. 10 (October 1, 1994): 2108–17. http://dx.doi.org/10.1139/v94-268.
Повний текст джерелаАнотація:
The thermally induced [2 + 3] cycloadditions of certain monocyclic aziridines to dimethyl 1-cyclobutene-1,2-dicarboxylate are described. The structures of the resulting bicyclic adducts were established unambiguously by X-ray analyses. The stereochemistries of the [2 + 3] adducts were interpreted in terms of dipole–dipole interactions and secondary orbital interactions. In certain cases an initial thermal conrotatory ring opening of the cyclobutene to 2,3-di(methoxycarbonyl)-1,3-butadiene precedes the [2 + 3] cycloaddition, affording the unexpected pyrrolidine adducts 12a and 12b. The structures and stereochemistries of the latter established by X-ray analysis strongly suggest that secondary orbital interactions between the phenyl and ester groups control and stereochemistry of the reactions.
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Toma, Lucio, Paolo Quadrelli, Giancarlo Perrini, Remo Gandolfi, Cristiana Di Valentin, Antonino Corsaro та Pierluigi Caramella. "Cycloadditions of Nitrile Oxides to α,β-Unsaturated Aldehydes. Frontier Orbital Interactions and Secondary Orbital Interactions at Work in Determining Regiochemistry". Tetrahedron 56, № 25 (червень 2000): 4299–309. http://dx.doi.org/10.1016/s0040-4020(00)00356-2.
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Levandowski, Brian J., Dennis Svatunek, Barbara Sohr, Hannes Mikula, and K. N. Houk. "Secondary Orbital Interactions Enhance the Reactivity of Alkynes in Diels–Alder Cycloadditions." Journal of the American Chemical Society 141, no. 6 (January 29, 2019): 2224–27. http://dx.doi.org/10.1021/jacs.8b13088.
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Jasiński, Radomir. "Regio- and stereoselectivity of [2+3]cycloaddition of nitroethene to (Z)-N-aryl-C-phenylnitrones." Collection of Czechoslovak Chemical Communications 74, no. 9 (2009): 1341–49. http://dx.doi.org/10.1135/cccc2009037.
Повний текст джерелаАнотація:
The cycloaddition reactions of nitroethene to (Z)-N-aryl-C-phenylnitrones lead to mixtures of stereoisomeric cis- and trans-2-aryl-4-nitro-3-phenylisoxazolidines. Regioselectivity of these reactions is determined by the character of nucleophile–electrophile interactions, while stereoselectivity is determined by the steric factors and the character of secondary orbital interactions.
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Powers, Timothy S., Weiqin Jiang, Jing Su, William D. Wulff, Beth E. Waltermire, and Arnold L. Rheingold. "Asymmetric Exo-Selective Diels−Alder Reactions by Steric Attenuation of Secondary Orbital Interactions." Journal of the American Chemical Society 119, no. 27 (July 1997): 6438–39. http://dx.doi.org/10.1021/ja963881b.
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Levandowski, Brian J., Dennis Svatunek, Barbara Sohr, Hannes Mikula, and K. N. Houk. "Correction to “Secondary Orbital Interactions Enhance the Reactivity of Alkynes in Diels–Alder Cycloadditions”." Journal of the American Chemical Society 141, no. 46 (November 6, 2019): 18641. http://dx.doi.org/10.1021/jacs.9b11320.
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