A Search for Companions to Brown Dwarfs in the Taurus and Chamaeleon Star Forming Regions

We present the results of a search for companions to young brown dwarfs in the Taurus and Chamaeleon I star forming regions (1/2-3 Myr). We have used WFPC2 on board HST to obtain F791W and F850LP images of 47 members of these regions that have spectral types of M6-L0 (0.01-0.1 Msun). An additional late-type member of Taurus, FU Tau (M7.25+M9.25), was also observed with adaptive optics at Keck Observatory. We have applied PSF subtraction to the primaries and have searched the resulting images for objects that have colors and magnitudes that are indicative of young low-mass objects. Through this process, we have identified promising candidate companions to 2MASS J04414489+2301513 (rho=0.105"/15 AU), 2MASS J04221332+1934392 (rho=0.05"/7 AU), and ISO 217 (rho=0.03"/5 AU). We reported the discovery of the first candidate in a previous study, showing that it has a similar proper motion as the primary through a comparison of astrometry measured with WFPC2 and Gemini adaptive optics. We have collected an additional epoch of data with Gemini that further supports that result. By combining our survey with previous high-resolution imaging in Taurus, Chamaeleon, and Upper Sco (10 Myr), we measure binary fractions of 14/93 = 0.15+0.05/-0.03 for M4-M6 (0.1-0.3 Msun) and 4/108 = 0.04+0.03/-0.01 for >M6 (10 AU. Given the youth and low density of these three regions, the lower binary fraction at later types is probably primordial rather than due to dynamical interactions among association members. The widest low-mass binaries (>100 AU) also appear to be more common in Taurus and Chamaeleon than in the field, which suggests that the widest low-mass binaries are disrupted by dynamical interactions at >10 Myr, or that field brown dwarfs have been born predominantly in denser clusters where wide systems are disrupted or inhibited from forming.Comment: Astrophysical Journal, in pres

BIOCHEMICAL AND MORPHOLOGICAL INVESТIGAТIONS ON IRRADIATED WIТH ULTRAVIOLET RАYS AND INFECTED WIТH GRIPPE VIRUS СНIСК EMBRYOS

The study of biochemical and morphological changes occurring under the combined effect (interaction) of vira and macroorganisms is an important рrоblem in virology. Biochemical investigations have been reported in literature under various aspects. Thus Voluiskaya  investigates the sugar in the pulmonary tissue of infected with grippe virus (GV) mice and finds out 20-50 % increase of sugar as compared to control animals. Tovarnitzki studies the biochemical alterations in experimentally produced grippe infection of white mice and comes to the conclusion that the pathological process in grippe conditions is generalized and involves а number of visceral organs and the central nervous system. Knight investigates the aminoacid content of the allantoic fluid (AF) in chick embryos (СЕ), not contaminated and contaminated with grippe virus. Killborne and Horsfall established аn increased protein content in the AF of the СЕ, infected with GV. Lutikova finds out an increase of the total nitrogen аnd phosphorus in the chorioallantoic membranes of СЕ, infected with GV. Panayotov studies in СЕ substrates, injected with different vira, the following indices: Ph, aminoacid content, рrеsеnсе of RNA аnd DNA, phosphatese activity, aldolasc, pyrophosphatase etc. The effect of ultraviolet rays (UVR) оn the GV has bееn investigated bу numerous authors. Thus Wells and Brown carry out follow-up studies on the effect of UVR upon aerosol of GV.Salk and associates (cited bу Levin - 20) investigates the action of the UVR on the virulence of the GV.Vaskhov, Rosiisky аnd Smorodintzev study the influence of UVR оn the  pulmonary  suspension, containing GV. Ermeev and Chalkina study the effect of UVR on purified GV, type А. Zakastelskaia proves the infectious аnd toxic action of the allantoic fluid containing GV. Manolova studies the effect of UVR оn purified and nоn purified grippe vira В, А and А-1. Rappoport, Dyhno and assoc., Panayotov and assoc., аnd Sfoyanov follow the morphological changes in СЕ treated with microorganisms.In the pertinent literature surveyed nо informations were found concerning the effect of UVR оn the СЕ infected with GV; hеnсе the study of the biochemical indices аnd pathohistological alterations in СЕ irradiated with UVR and infected with GV is of utmost interest.The purpose of the present work is determination of the biochemical characteristics, the presence of hemagglutination activity for the GV аnd the morphological alterations in the AF of the СЕ infected with GV

Dicke Coherent Narrowing in Two-Photon and Raman Spectroscopy of Thin Vapour Cells

The principle of coherent Dicke narrowing in a thin vapour cell, in which sub-Doppler spectral lineshapes are observed under a normal irradiation for a l/2 thickness, is generalized to two-photon spectroscopy. Only the sum of the two wave vectors must be normal to the cell, making the two-photon scheme highly versatile. A comparison is provided between the Dicke narrowing with copropagating fields, and the residual Doppler-broadening occurring with counterpropagating geometries. The experimental feasibility is discussed on the basis of a first observation of a two-photon resonance in a 300 nm-thick Cs cell. Extension to the Raman situation is finally considered

Narrow structure in the coherent population trapping resonances in rubidium and Rayleigh scattering

The measurement of the coherent-population-trapping (CPT) resonances in uncoated Rb vacuum cells has shown that the shape of the resonances is different in different cells. In some cells the resonance has a complex shape - a narrow Lorentzian structure, which is not power broadened, superimposed on the power broadened CPT resonance. The results of the performed investigations on the fluorescence angular distribution are in agreement with the assumption that the narrow structure is a result of atom interaction with Rayleigh scattering light. The results are interesting for indication of the vacuum cleanness of the cells and building of magnetooptical sensors

Fluorescence in quantum dynamics: accurate spectra require post-mean-field approaches

Real time modeling of fluorescence with vibronic resolution entails the representation of the light–matter interaction coupled to a quantum-mechanical description of the phonons and is therefore a challenging problem. In this work, taking advantage of the difference in timescales characterizing internal conversion and radiative relaxation—which allows us to decouple these two phenomena by sequentially modeling one after the other—we simulate the electron dynamics of fluorescence through a master equation derived from the Redfield formalism. Moreover, we explore the use of a recent semiclassical dissipative equation of motion [C. M. Bustamante et al., Phys. Rev. Lett. 126, 087401 (2021)], termed coherent electron electric-field dynamics (CEED), to describe the radiative stage. By comparing the results with those from the full quantum-electrodynamics treatment, we find that the semiclassical model does not reproduce the right amplitudes in the emission spectra when the radiative process involves the de-excitation to a manifold of closely lying states. We argue that this flaw is inherent to any mean-field approach and is the case with CEED. This effect is critical for the study of light–matter interaction, and this work is, to our knowledge, the first one to report this problem. We note that CEED reproduces the correct frequencies in agreement with quantum electrodynamics. This is a major asset of the semiclassical model, since the emission peak positions will be predicted correctly without any prior assumption about the nature of the molecular Hamiltonian. This is not so for the quantum electrodynamics approach, where access to the spectral information relies on knowledge of the Hamiltonian eigenvalues