Photon escape probabilities in expanding atmospheres

A comparison of mean number of scatterings and escape probabilities has been made in isotropic scattering and dipole scattering by using the angle-averaged partial frequency redistribution functionR _I. We have solved the equations of radiative transfer and statistical equilibrium simultaneously in a spherically symmetric expanding atmosphere. Two cases of atmospheric extension (i.e.)B/A=3 and 10 (whereB andA are the outer and inner radii of the atmosphere) have been treated. We find that the partial frequency redistribution gives a larger mean number of scatterings compared to that given by complete redistribution. Velocities tend to reduce the mean number of scatterings and in crease the mean escape probabilities.     

Non-linear scattering probability of longitudinal plasma waves in a magnetoactive plasma system

We use the semi-quantum approach to study the Compton scattering and non-linear scattering processes in a magnetoative plasma under the weak turbulence regime. Analytical expressions for these two types of scattering probabilities are derived from first principles forl-l waves. Transiting to limiting cases, the results obtained in this investigation are shown to be identical to previous derivations by other workers.     

The astrophysical parameters of Majaess-95 and Majaess-225

Most astrophysical parameters of the two stellar clusters Majaess 95 and Majaess 225 have been investigated here for the first time using the third data release of the Gaia space mission (Gaia-DR3). The membership probabilities of stars were assigned using the pyUPMASK algorithm. The parallaxes offset has been corrected using the zero-point correction code of Lindegren et al. (Lindegren et al. 2021, A&A, 649, A4). Using the clusters' members with membership probabilities >0.50, we calculated the distance to the clusters of 3311 and 3020 (±130) pc, respectively, which agree with the results from our isochrone fitting on the color-magnitude diagram. The ages are found to be 282 (±20) and 12.6 (±2) Ma. Also, the reddening, heliocentric distances, luminosity function, mass function, and total mass were estimated. On studying the dynamic state (relaxation time), we found that Majaess-95 is a relaxed cluster, while Majaess-225 is not relaxed yet.     

S-matrix approach to interacting quantum field theory in curved space-time1)

We give an analysis of mutually interacting quantum fields in given unquantized Robertson-Walker universes using an S-matrix approach. Transition probabilities and particle number mean values are discussed in detail with the intention to read off the underlying physics and to apply them to scattering and decay processes.     

A steady-state model of NEA binaries formed by tidal disruption of gravitational aggregates

We present results of a simulation of a steady-state binary near-Earth asteroid (NEA) population. This study combines previous work on tidal disruption of gravitational aggregates [Walsh, K.J., Richardson, D.C., 2006. Icarus 180, 201-216] with a Monte Carlo simulation of NEA planetary encounters. Evolutionary effects include tidal evolution and binary disruption from close planetary encounters. The results show that with the best known progenitor (small Main Belt asteroids) shape and spin distributions, and current estimates of NEA lifetime and encounter probabilities, that tidal disruption should account for approximately 1-2% of NEAs being binaries. Given the best observed estimate of a ∼15% binary NEA fraction, we conclude that there are other formation mechanisms that contribute significantly to this population. We also present the expected distribution of binary orbital and physical properties for the steady-state binary NEAs formed by tidal disruption. We discuss the effects on binary fraction and properties due to changes in the least constrained parameters, and other possible effects on our model that could account for differences between the presented results and the observed binary population. Finally, we model possible effects of a significant population of binaries migrating to the near-Earth population from the Main Belt.     

Discussion on the maximum likelihood method for determination of membership in open clusters

We suggest some objective criteria for pruning the vector point diagram, necessary when calculating the membership probabilities of stars in a cluster field from their proper motions. We present a staggered procedure of data pruning, and the determinations of the orientation of the field points and the distribution parameters of the two-component (cluster members and field stars) population.     

Spin-orbit electric dipole transmissions in beryllium-like ions

We have used configuration interaction wavefunctions to calculate energy levels, wavelengths, oscillator strengths and transition probabilities for spin-orbit electric dipole transitions between the 2s ², 2s2p, and 2p ² states in beryllium-like ions (Z = 6–10). Some significant differences with previous calculations are obtained. A common set of radial functions is used.     

Membership of faint stars in the globular cluster M3

A proper motion study from Tautenburg Schmidt plates is presented for the globular cluster M3 and its vicinity. The plates were scanned with the Automated Photographic Measuring (APM) system in Cambridge (UK). A photographic B,V photometry and star counts on the deepest plates were carried out. With a limiting magnitude of about B = 21.4 proper motions with an accuracy from 2 to 3 mas/yr have been obtained for stars with B 19. The proper motions were determined using a stepwise regression method with 3rd order polynomials in the plate-to-plate solutions with about 2000 reference galaxies. The results which were corrected for systematic errors dependent on position and magnitude of the stars were used for the determination of membership probabilities. We also looked for possible internal motions of M3.     

Search for possible connections between isolated radio pulsars and supernova remnants

We have developed a method of searching for the connections between the isolated radio pulsars and supernova remnants, based on the analysis of their kinematic characteristics. We investigate fairly young (τ _ch ≲ 10⁶ yr) radio pulsars with known proper motions and estimated distances (dispersion measures), and supernova remnants located no more than 1–2 kpc away from them. Using a standard empirical radial velocity distribution, we have constructed 100–200 thousand trajectories for each of these pulsars, tracing back their possible motion in the Galactic gravitational field on a time-scale of a few million years. The probabilities of their close encounters with the SNRs at epochs consistent with the age of the pulsar are analyzed. When these probabilities exceed considerably their reference values, obtained by assuming a purely random encounter between the objects, we conclude that the pulsars may have originated in the SNRs under consideration. Out of eight preselected pairs of pulsar-SNR association candidates, two pairs, J 1829-1751 / G16.2-2.7 and J 1833-0827 / G24.7-0.6 may have a common origin with a high probability.     

Effect of the star limb darkening law on the probabilities of discovering detached close binary stars as eclipsing variables

The probabilities of discovering detached close binary (type DM) stars as eclipsing variables are calculated as a function of the mass of the main component, mass ratio, major semiaxis, and angle of inclination of the orbit. The case of total limb darkening (hypothesis “D”) is examined. This is compared with earlier results for uniformly bright stellar disks (hypothesis “U”). Based on data from Svechnikov and Kuznetsova’s Catalog of Approximate Photometric and Absolute Elements of Eclipsing Variables, the spatial density of stars of this type in the neighborhood of the sun is estimated to be ≈ 460 · 10 ⁻⁶ pc⁻³. __________ Translated from Astrofizika, Vol. 49, No. 1, pp. 151–169 (February 2006).     

Minor Mergers of Galaxies: Theory and Observations

We compare results from numerical simulations with observations of edge-on galaxies interacting/merging with a small companion (Schwarzkopf and Dettmar,2000), hereafter S&D00). Observations show a clear influence of the merging and interacting process on disk scale parameters h (radial scalelength), z ₀ (vertical scalelength) and their ratio (h/z ₀), leading to a heating and thickening of the stellar disk. Our numerical simulations show the same behaviour but differ significantly in the magnitude of the change of the disk scale parameters. This revised version was published online in September 2006 with corrections to the Cover Date.     

Spectrum variability of 25 Sextantis

Vibrational transition probabilities: namely, Franck-Condon factors andr-centroids, have been evaluated using an approximate analytical method for theB-A system of MgO. Morse potential energy curves forB ¹⁺ andA ¹ states of MgO have been constructed by use of the latest spectroscopic data. The value ofr-centroids for the band have been found to decrease linearly with the corresponding wavelength. We show results for six new bands in the umbral spectrum of the Sun.     

疏散星团NGC6530的成员研究和空间运动

利用上海天文台40厘米折射望远镜照相观测资料所得出的恒星自行,按最大似然原理确定了疏散星团NGC6530天区内恒星的成员概率．分析表明星团成员确定是非常有效的,成员概率p≥0．9的恒星计有250颗．最后,确定了星团的空间运动,并作了简单的讨论．     

On possibility of detection of variable sources using the data of “Cold” surveys carried out on RATAN-600

In this study we attempt to assess the possibility of detection of variable sources using the data of the 7.6-cm wavelength surveys carried out on the RATAN-600 radio telescope in the period from 1980 through 1994. Objects selected according to certain criteria from the RCR catalog are used to construct the calibration curves and to estimate the accuracy of the resulting calibration curves and determine the r.m.s. errors for the measured source flux densities. To check the calibration sources for the presence of variable objects, quantitative estimates are performed for a number of parameters that characterize variability, in particular, for the long-term variability index V and the χ ² (chi-square) probability p. The long-term variability index was found to be positive for 14 out of approximately 80 calibration sources, possibly indicating that these sources are variable. The most likely candidate variables are the three sources with the χ ² probability p > 0.95. Five sources have χ ² probabilities in the 0.85 < p < 0.95 interval, and the remaining six in the 0.6 < p < 0.8 interval. Nine out of 14 objects are possibly variable in the optical range. The light curves and spectra are determined for possible variable sources and a number of “non-variable” objects. We plan to use the results of this study in our future searches for variable radio sources using the data of the “Cold” surveys.     

voboz: an almost-parameter-free halo-finding algorithm

We have developed an algorithm, called voboz (VOronoi BOund Zones), to find haloes in an N -body dark matter simulation; it has as little dependence on free parameters as we can manage. By using the Voronoi diagram, we achieve non-parametric, 'natural' measurements of each particle's density and set of neighbours. We then eliminate much of the ambiguity in merging sets of particles together by identifying every possible density peak, and measuring the probability that each does not arise from Poisson noise. The main halo in a cluster tends to have a high probability, while its subhaloes tend to have lower probabilities. The first parameter in voboz controls the subtlety of particle unbinding, and may be eliminated if one is cavalier with processor time; even if one is not, the results saturate to the parameter-free answer when the parameter is sufficiently small. The only parameter that remains, an outer density cut-off, does not influence whether or not haloes are identified, nor does it have any effect on subhaloes; it only affects the masses returned for supercluster haloes.     

Somef-values for transitions in ZrII,ZrIII and SrI

Transition probabilities were calculated for certain transitions in ZrII, ZrIII and SrI. For these allowed transitions Hartree-Fock wavefunctions were calculated for use in determining the absolute line strength. The methods developed by C. Froese-Fischer and Mayers and O'Brien for calculating the wavefunctions were used in determining those for the transitions in ZrII, ZrIII and SrI. Theoretical and experimentalf-values were compared in the case of SrI, and the results were in reasonable agreement for transition probabilities based on dipole velocity calculations.     

Statistical Revision of the Moment Method

The moment method is a well known technique, which uses a time series ofthe first 3 moments of a spectral line, to estimate the (discrete) modeparameters and m. The method, contrary to Doppler imaging,also yields other interesting(real-valued) parameters such as the inclination angle i, or v sin i,during its identification procedure.In this paper, we are not only interested in the estimation of thesereal-valued parameters themselves but also inreliable estimates for their uncertainty.We designed a statistical formalism for the moment method based on theso-called generalized estimating equations (GEE). This formalismaims to estimate the uncertainty of the real-valued parameters taking intoaccount that the different moments of a line profile are correlated and –more importantly – that the uncertainty of the observed moments depends onthe pulsation parameters. The latter property of the moment method makesthe least-squares technique a poor choice to estimate the uncertainty ofthe real-valued parameters. We implemented the GEE method and presentan application to a high-resolution spectroscopic dataset of the slowly pulsating B star HD181558.     

Some vibrational bands of theC-X system of V0 molecules in the umbral spectrum of the Sun

Vibrational transition probabilities namely Franck-Condon factors and r-centroids have been evaluated using an approximate analytical method for theC-X system of V0. Morse potential energy curves forX _{4 –} andC _{4 –} states of V0 have been constructed using the latest spectroscopic data. The value of r-centroids for the band have been found to increase linearly with the corresponding wavelength. We show results for new transition and ten new bands in the umbral spectrum of the Sun.     

The ellipsoidal variables

We perform a Monte Carlo analysis of the eclipse probabilities of short-period binary systems in an attempt to estimate the distribution of ellipsoidal variable system with Main-Sequence components. Our results suggest that possibly as many as one in four of the non-eclipsing, spectroscopic binaries withP(d)10, and Main-Sequence components withM _v 10 could be ellipsoidal variable systems. This result, while an upper limit, would seem to hold irrespective of primary spectral type (B5 to G5).