Rotation Curves Research Articles

The Descartes Code (Spin Orbital Rotation of Photons)–IV. The Harress-Sagnac Color Excess in the Rotation Curves of Galaxies

In 1933, Zwicky formulated the significant bifurcation point in the history of astrophysics. Zwicky postulated an unknown dark matter in order to explain the color excess in the observed Doppler effect in the rotation curves of galaxies. However, until now we have not detected these dark matter particles. In this contribution, we propose to come back to this bifurcation point and to interpret the observed color excess as the Harress-Sagnac effect known in the rotating interferometers. We have described photon properties in those rotating interferometers based on the old color theory of Descartes—rotating light globules (spin-orbital rotation of photons). Therefore, the color excess observed in the rotation curves of galaxies can be interpreted as the additional color excess of photons emitting from distant rotating stars. Formulae for these color excesses are given for different locations of the rotating galaxy inspired by Zwicky’s core-shell model of galaxies. A part of Zwicky’s enigma is an unknown influence of the Solar gravitational field at 1 AU on the distant photon properties. From the forgotten Gerber’s retarded potential formula we have derived an expression for the acceleration of distant photons towards the Sun at 1 AU as ax = 1.171 × 10⁻¹⁰ ms⁻². This is a very surprising coincidence with the Milgrom empirical value a0 = (1.2 ± 0.1) × 10⁻¹⁰ ms⁻². Therefore, we propose to test this new formula at the surface of Mercury and Mars in order to reveal if our gravitational models are universal or “geocentric”, valid for the surroundings of the Earth only.

Retarded Gravity in Disk Galaxies

Disk galaxies have a typical dimension of a few tens of kiloparsecs. It follows from the theory of general relativity that any signal originating from the galactic center will be noticed at the outskirts of the galaxy only tens of thousands of years later. This retardation effect, however, is absent in modelling used to calculate rotation curves throughout entire galaxies and their external gas. The considerable differences between Newtonian predictions and observed velocities are currently removed either by assuming dark matter or by suggesting various modifications to the laws of gravity, MOND being a long standing alternative to Newtonian gravity. In previous papers we have shown that by applying general relativity in a rigorous fashion, without neglecting retardation, one can explain the rotational velocities of galactic matter without modifying gravity or adding dark matter. Moreover, it was shown that dark matter effects, as they appear in gravitational lensing, the Tully-Fisher relation, and mass estimations based on the virial theorem could also be explained as retarded-gravity effects. It must be noted, however, that the proposed theory relies on the existence of a mass flow (of a changing rate) into the galaxy; a requirement that was not directly observed. In the original paper on the subject only one galaxy (M33) was analysed in detail. This was later amended with a published study of eleven galaxies. Here we give a more comprehensive retardation analysis of 143 galaxies of different types from the SPARC Galaxy collection. We show that in most cases we obtain very accurate fits to the data.

Radial and azimuthal gradients of the moving groups in Gaia DR3: The slow and fast bar degeneracy problem

The structure and dynamics of the central bar of the Milky Way (MW) are still under debate whilst being fundamental ingredients for the evolution of our Galaxy. The recent Gaia DR3 offers an unprecedented detailed view of the 6D phase space of the MW, allowing for a better understanding of the complex imprints of the bar on the phase space. We aim to identify and characterise the dynamical moving groups across the MW disc, and use their large-scale distribution to help constrain the properties of the Galactic bar. We used 1D wavelet transforms of the azimuthal velocity ($V_ distribution in bins of radial velocity to robustly detect the kinematic substructure in the Gaia DR3 catalogue. We then connected these structures across the disc to measure the azimuthal (phi ) and radial ($R$) gradients of $V_ of the moving groups. We simulated thousands of perturbed distribution functions using backward integration, sweeping a large portion of parameter space of feasible Galaxy models that include a bar, in order to compare them with the data and to explore and quantify the degeneracies. The radial gradient of the Hercules moving group ($ V_ R$ = 28.1pm 2.8 $) cannot be reproduced by our simple models of the Galaxy that show much larger slopes both for a fast and a slow bar. This suggests the need for more complex dynamics (e.g. a different bar potential, spiral arms, a slowing bar, a complex circular velocity curve, external perturbations, etc.). We measured an azimuthal gradient for Hercules of $ V_ = -0.63pm $deg$^ $ and find that it is compatible with both the slow and fast bar models. Our analysis points out that in using this type of analysis, at least two moving groups are needed to start breaking the degeneracies. We conclude that it is not sufficient for a model to replicate the local velocity distribution; it must also capture its larger-scale variations. The accurate quantification of the gradients, especially in the azimuthal direction, will be key for the understanding of the dynamics governing the disc.

Geometry-driven and dark-matter-sustained Milky Way rotation curves with Gaia DR3

ABSTRACT Thanks to Gaia DR2, we proved for the first time that a general relativistic Milky Way rotation curve is statistically indistinguishable from its state-of-the-art dark matter analogue. Those results supported the ansatz that gravitational dragging can explain the observed flatness of the Milky Way rotation curve with a consistent radial matter density profile. To challenge again such a scenario, we select 719 143 young disc stars within |z| < 1 kpc and up to R ≃ 19 kpc from Gaia DR3 providing a much larger sample of high-quality astrometric and spectrophotometric data of unprecedented homogeneity. This sample comprises 241 918 OBA stars, 475 520 RGB giants, and 1705 Cepheides that we use to fit, as with DR2, both a classical velocity profile model, i.e. with a dark matter halo, and a general relativistic analogue derived from a dust disc-scale metric. Once more, further corroborating our earlier findings, both models are found to explain, with similar statistical quality, the new observed rotational velocities derived from different combinations of the selected sets of stars belonging to the disc of our Galaxy. The geometrical effect is found to drive the velocity profile from 10 kpc outwards, while being responsible for ∼30–37 per cent of this profile already at the Sun distance, similarly to the halo contribution in the classical model. This confirms our previous results on the contribution of Einstein’s geometry and pushes to further investigate the role of General Relativity in tracing the Milky Way rotation curve; notably, the origin of this gravitational dragging remains undetermined, necessitating a dedicated in-depth exploration.

A serendipitous discovery of H i-rich galaxy groups with MeerKAT

ABSTRACT We report on the serendipitous discovery of 49 H i-rich galaxies in a 2.3 h Open Time observation with MeerKAT. We present their properties including their H i masses, intensity and velocity maps, and spectra. We determine that at least three H i-rich galaxy groups have been detected, potentially as part of a supergroup. Some members of these galaxy groups show clear interaction with each other in their H i emission. We cross-match the detections with PanSTARRS, Wide-field Infrared Survey Explorer, and Galaxy Evolution Explorer, and obtain stellar masses and star formation rates. One source is found to be a potential OH megamaser, but further follow-up is required to confidently determine this. For six sources with sufficient spatial resolution in H i, we produce rotation curves with BBarolo, generate mass models, and derive a dark matter halo mass. While the number of galaxies detected in this relatively short pointing appears to be at the high end of expectations compared to other MeerKAT observations and group H i mass function studies, this finding highlights the capability of MeerKAT for other serendipitous discoveries, and the potential for many more H i-rich galaxies to be revealed within both existing and upcoming Open Time data sets.

Dual-stage theoretical model of magnetorheological dampers and experimental verification

The theoretical model for predicting the damping characteristics of magnetorheological dampers (MRDs) not only facilitates the optimization of MRD parameters, but also provides assistance for the theoretical design of MRDs. However, some existing models have limitations in fully characterizing the damping characteristics of MRDs. In this paper, the working stage of MRDs was categorized into yield and pre-yield stages based on whether the internal magnetorheological fluid attains the dynamic shear yield state or not, and the Herschel–Bulkley model with pre-yield viscosity (HBPV) and improved polynomial model (IPOL) were employed to respectively characterize the yield and pre-yield stages of MRDs. Subsequently, the HBPV-IPOL model was proposed to characterize the complete damping characteristics of MRDs in low-frequency vibration conditions, with considering the local loss effect of the fluid in the model. To accurately characterize the magnetic induction intensity in the MRD damping channel, employing the steady-state finite element method for magnetic field analysis; on this basis, dividing the damping channel to investigate the variation trends of the magnetic induction intensity in different regions. Simultaneously, the zero-field region hypothesis was proposed to quantitatively consider the influence of minute magnetic induction intensity in the traditional zero-field regions on the damping characteristics of MRDs. Finally, integrating the impact trends of currents in different regions, and employing the HBPV model to determine the impact magnitude of each region within the damping channel on the damping characteristics of the MRD in the yield stage. In the pre-yield stage, polynomial curves were fitted to experimental damping force–velocity curves, and the obtained polynomials were employed to predict the damping characteristics. Extensive experiments have been conducted on MRD samples to assess the predictive performance of the model on MRD damping characteristics under sinusoidal displacement excitation vibration conditions with different excitation currents, vibration frequencies and vibration amplitudes.

A new kinematic model of the Galaxy: analysis of the stellar velocity field from Gaia Data Release 3

ABSTRACT This work presents the results of a kinematic analysis of the Galaxy that uses a new model as applied to the newest available Gaia data. We carry out the Taylor decomposition of the velocity field up to second order for 18 million high luminosity stars (i.e. OBAF-type stars, giants, and subgiants) from the Gaia DR3 data. We determine the components of mean stellar velocities and their first and second partial derivatives (relative to cylindrical coordinates) for more than 28 thousand points in the plane of our Galaxy. We estimate Oort’s constants A, B, C, and K and other kinematics parameters and map them as a function of Galactocentric coordinates. The values found confirm the results of our previous works and are in excellent agreement with those obtained by other authors in the solar neighbourhood. In addition, the introduction of second order partial derivatives of the stellar velocity field allows us to determine the values of the vertical gradient of the Galaxy azimuthal, radial, and vertical velocities. Also, we determine the mean of the Galaxy rotation curve for Galactocentric distances from 4 to 18 kpc by averaging Galactic azimuths in the range −30° < θ < + 30° about the direction Galactic Centre – Sun – Galactic anticentre. Maps of the velocity components and of their partial derivatives with respect to coordinates within 10 kpc of the Sun reveal complex substructures, which provide clear evidence of non-axisymmetric features of the Galaxy. Finally, we show evidence of differences in the Northern and Southern hemispheres stellar velocity fields.

Dark matter effects explanation with the torsion in the Minkowski space

Investigating rotation curves and the Tully–Fisher ratio within galaxies represents a central theme of extensive research and scientific interest. Despite several theoretical models, a comprehensive explanation of the observed correlation between galaxy types and their rotation curves remains elusive. This study endeavors to bridge this knowledge gap by delving into the discernible connection between the presence of dark matter and galaxy classification. By meticulously examining the gravitational field’s dependency on its source’s point symmetry, we introduce a novel theoretical framework that offers a coherent rationale for these empirical findings. Our proposed model explains the appearance of dark matter as a direct consequence of the reduction of point symmetry in gravitational systems. Neither arbitrary systems with a high mass density nor a perfectly spherically symmetric mass distribution give the observable effects of dark matter. Special attention was paid to the axial symmetry scenario as a reasonable approach for modeling the mass distribution in most galaxies. We thoroughly analyzed, showing strong agreement with experimental observations for dwarf, Sb, and Scd galaxies. Thus, our study provides a compelling theoretical foundation for elucidating the intricate interplay between galaxy types, rotation curves, and the presence of dark matter, shedding new light on the dynamics of the cosmos.

Comments on Non–Dark Matter Theories Explaining the Galaxy Rotation Curves and Globular Cluster Velocity Dispersions

Comments on Non–Dark Matter Theories Explaining the Galaxy Rotation Curves and Globular Cluster Velocity Dispersions

Why Mature Galaxies Seem to Have Filled the Universe Shortly After the Big Bang — A New Cosmological Model, that Predicted the JWST Observations

The Azimulthal Hyper-Projection (AHP) onto spacetime Model of Cosmology is just an extension of the familiar Atlas map of a globe in geography. The Atlas is an azimuthal projection of 3 spacial dimensions projected onto a 2 dimensional plane. The important feature of an Atlas is that the geometry expands asymptotic toward the horizon, and is therefore POSITIONALLY DEPENDENT, such that if North America is centrally positioned, then Siberia and Alaska are viewed as extremely remote. Thus if the Bering Strait were centrally positioned, then longitudinal meridians of North America would likewise be viewed as being remotely separated. AHP extends this concept to a hyper-projection of 5 dimensions onto spacetime. However as viewed in spacetime, geodesics appear to be expanding outward in 3 dimensional space away from the observer. Thus by extension, AHP is also POSITIONALLY DEPENDENT, such that the separations between remote galaxies appear (measures) to be much greater than they would appear from their mutual local group, and vice versa our local group of galaxies would appear to be mutually separated with extreme distances from a remote perspective. A proposed experiment (figure 14) is offered to prove that two separated objects, as measure from a remote distance \((\sim 40 AU)\) are greater than their respective distance, as measured locally. Red-shifting is alternatively proposed as azimuthal angular projections of wavelengths \(\lambda\). Magnitude is alternatively proposed as a function of Lambert's cosine law of illumination, over expanding geodesics. From established \(z\) values, the Universal hypersphere is calculated (figure 9). A function of this projected hypersphere is shown to match the Universal expansion rate, as established from supernova cosmology survey points, and also satisfies the Cosmological Constant \(\Lambda\), without dark energy. Flattened galaxy rotation curves are simply and accurately explained as measured expanding geodesics and apparent increasing density, along the observer's line of sight (figure 11, equation 20). As well, this model provides a reasonable explanation of the James Web Space Telescope findings: of maturely developed galaxies at the time of the early universe. The justification of such a radically novel model is from recent observations from the first dataset, provided by NASA's James Webb Space Telescope (JWST) of six massive galaxies, at a time in the early universe, seem to defy conventional cosmological models, as they appear to be as mature and developed as our own local group. Such unexpected discoveries JUSTIFY A RADICALLY NOVEL MODEL OF COSMOLOGY. TO QUOTE JOEL LEJA, ASSISTANT PROFESSOR OF ASTRONOMY AND ASTROPHYSICS AT PENN STATE “IT TURNS OUT WE FOUND SOMETHING SO UNEXPECTED IT ACTUALLY CREATES PROBLEMS FOR SCIENCE. IT CALLS THE WHOLE PICTURE OF EARLY GALAXY FORMATION INTO QUESTION”.

The Hertzsprung progression of classical Cepheids in the Gaia era

ABSTRACT A new fine grid of non-linear convective pulsation models for the so-called ‘bump Cepheids’ is presented to investigate the Hertzprung progression (HP) phenomenon shown by their light and radial pulsation velocity curves. The period corresponding to the centre of the HP is investigated as a function of various model assumptions, such as the efficiency of superadiabatic convection, the mass–luminosity relation, and the metal and helium abundances. The assumed mass–luminosity relation is found to significantly affect the phenomenon but variations in the chemical composition as well as in the stellar mass (at fixed mass–luminosity relation) also play a key role in determining the value of the HP centre period. Finally, the predictive capability of the presented theoretical scenario is tested against observed light curves of bump Cepheids in the ESA Gaia data base, also considering the variation of the pulsation amplitudes and of the Fourier parameters R21 and Φ21 with the pulsation period. A qualitative agreement between theory and observations is found for what concerns the evolution of the light curve morphology as the period moves across the HP centre, as well for the pattern in period–amplitude, period–R21, and period–Φ21 planes. A larger sample of observed Cepheids with accurate light curves and metallicities is required in order to derive more quantitative conclusions.

EDGE – Dark matter or astrophysics? Breaking dark matter heating degeneracies with H i rotation in faint dwarf galaxies

ABSTRACT Low-mass dwarf galaxies are expected to reside within dark matter haloes that have a pristine, ‘cuspy’ density profile within their stellar half-light radii. This is because they form too few stars to significantly drive dark matter heating through supernova-driven outflows. Here, we study such simulated faint systems ($10^4 \le M_{\star }\le 2 \times 10^6 \, \mbox{M}_\mathrm{\odot }$) drawn from high-resolution (3 pc) cosmological simulations from the ‘Engineering Dwarf Galaxies at the Edge of galaxy formation’ (EDGE) project. We confirm that these objects have steep and rising inner dark matter density profiles at z = 0, little affected by galaxy formation effects. But five dwarf galaxies from the suite also showcase a detectable H i reservoir ($M_{\mathrm{H\, {\small I} }}\approx 10^{5}-10^{6} \, \mbox{M}_\mathrm{\odot }$), analogous to the observed population of faint, H i-bearing dwarf galaxies. These reservoirs exhibit episodes of ordered rotation, opening windows for rotation curve analysis. Within actively star-forming dwarfs, stellar feedback easily disrupts the tenuous H i discs ($v_{\phi , g}\approx 10\, \mathrm{km} \, \mathrm{s}^{-1}$), making rotation short-lived ($\ll 150 \, \mathrm{Myr}$) and more challenging to interpret for dark matter inferences. In contrast, we highlight a long-lived ($\ge 500 \, \mathrm{Myr}$) and easy-to-interpret H i rotation curve extending to $\approx 2\, r_{1/2, \text{3D}}$ in a quiescent dwarf, that has not formed new stars since z = 4. This stable gas disc is supported by an oblate dark matter halo shape that drives high-angular momentum gas flows. Our results strongly motivate further searches for H i in rotation curves in the observed population of H i-bearing low-mass dwarfs, that provide a key regime to disentangle the respective roles of dark matter microphysics and galaxy formation effects in driving dark matter heating.

How many random observations are needed for good phase coverage of a periodic source?

The specific problem considered is the number of radial velocity measurements required to obtain good estimates of physical parameters of binary star. It is assumed that observations are made at random binary phases. The loss of information due to poor phase coverage is explored, and a suggested limit on the largest acceptable gap introduced. The statistical distribution of maximum gap lengths can then be used to specify the minimum number of velocity measurements to obtain good phase coverage with a specified confidence limit. The effects of non-zero orbital eccentricity are discussed, as are the ramifications of having multiple binary targets. The theory is also applicable to the characterisation of the radial velocity curves induced by exoplanets on their host stars, provided that the periods and eccentricities are known (from e.g. transit observations).

Nanoparticles hybridization in bidirectional flowing of Prandtl–Eyring material with temperature-dependent conductivity: A numerical approach

Due to the vast applications of nanofluids in hybrid cooling processes and their role in improving heat transfer in thermal systems, an attempt has been made to investigate the consequence of temperature-dependent thermal conductivity in the bidirectional flowing of Prandtl–Eyring (PE) hybrid nanomaterial. Zirconium dioxide (ZrO2) and copper (Cu) nanoparticles have been dispersed into an engine oil (EO) to create an effective hybrid nanomaterial. Viscous dissipation, magnetization, linear thermal radiation, and Ohmic heating mechanisms also influence the dynamics of the hybrid nanomaterial. The governing equations have been parameterized by using similarity transformations and the thermophysical properties of nanoparticles. Keller–Box simulations for the modeled problem have been conducted using an in-house code developed in MATHEMATICA. Convergence analysis has been presented and robust validation of the results has been performed to certify the accuracy of the numerical inspection. Post-processing of the results has been carried out by plotting temperature and velocity curves. Drag coefficient and Nusselt number have been formulated and analyzed in tabular forms. The rate of heat transfer is developed with the hybridization of ZrO2 and Cu nanoparticles into the base liquid, while drag forces are enhanced when utilizing PE material as the base liquid.

Cosmological and idealized simulations of dark matter haloes with velocity-dependent, rare and frequent self-interactions

ABSTRACT Dark matter self-interactions may have the capability to solve or at least mitigate small-scale problems of the cosmological standard model, Lambda cold dark matter. There are a variety of self-interacting dark matter models that lead to distinguishable astrophysical predictions and hence varying success in explaining observations. Studies of dark matter (DM) density cores on various mass scales suggest a velocity-dependent scattering cross-section. In this work, we investigate how a velocity dependence alters the evolution of the DM distribution for frequent DM scatterings and compare to the velocity-independent case. We demonstrate that these cases are qualitatively different using a test problem. Moreover, we study the evolution of the density profile of idealized DM haloes and find that a velocity dependence can lead to larger core sizes and different time-scales of core formation and core collapse. In cosmological simulations, we investigate the effect of velocity-dependent self-interaction on haloes and satellites in the mass range of ≈1011–$10^{14} \, \mathrm{M_\odot }$. We study the abundance of satellites, density, and shape profiles and try to infer qualitative differences between velocity-dependent and velocity-independent scatterings as well as between frequent and rare self-interactions. We find that a strongly velocity-dependent cross-section can significantly amplify the diversity of rotation curves, independent of the angular dependence of the differential cross-section. We further find that the abundance of satellites in general depends on both the velocity dependence and the scattering angle, although the latter is less important for strongly velocity-dependent cross-sections.

Misalignment of jet, orbital plane, and accretion disk observed in black hole binaries

Black holes are interesting objects and prove to be the leading edge of testing and verifying of our understandings in gravity. Among some of the most sought after quantities is the spin of the black hole: it is closely related to how the black hole system behaves. Various attempts have been made to derive the spin of black holes, in which the orientation in space could be deduced using the spectrum produced by the accretion disk, observation of the jets produced by black holes, and calculation of the orbit of black hole binaries using light and velocity curves. These observations, however, can sometimes lead to disagreeing results. In this paper, conflicts of the orientations of the spins of black holes measured using these different methods are presented. Sources including XTE J1550-564, V404 Cyg, and V4641 Sgr display misaligned accretion disk with orbital plane and/or jets. Explanations of how such misalignments could arise are also given, including warped accretion disks and precessing jets.

Data-driven modeling for residual velocity of projectile penetrating reinforced concrete slabs

The penetration of projectiles into reinforced concrete (RC) structures is crucial for defense technology. However, accurately estimating the resistance of RC structures to projectile penetration is challenging due to complex parameter nonlinearities. This paper proposes a data-driven modeling methodology that combines validated finite element (FE) simulations with machine learning (ML) algorithms to investigate the penetration resistance of RC slabs against projectiles. The methodology employs an extreme learning machine (ELM) network to identify extreme conditions characterizing penetration resistance, reducing data requirements, and improving prediction efficiency. Predicted results from the ELM network are then used as input for a recurrent neural network (RNN) to predict residual velocity curves over time, a crucial metric for evaluating penetration resistance. To cover various loading scenarios, 64 sets of FE models with different incident velocities, caliber-radius-head (CRH), and projectile masses are developed based on available experimental studies. The Johnson-Holmquist II model and Johnson-Cook model are employed for concrete and steel, respectively, to describe material behavior at high strain rates. The FE prediction results form a training sample database, and ML models are established using CRH, incident velocity, and projectile mass as input layers and projectile residual velocity as the output layer. The results demonstrate high Pearson correlation coefficients of 0.984 and 0.991 for the ELM and RNN prediction results, respectively, with numerical simulation results. The proposed networks provide accurate and efficient alternatives to time-consuming FE simulations for predicting projectile penetration performance. This strategy offers a new ML-based method for rapid evaluation, particularly for in-situ applications.

Building stellar bulges and halo cores from massive clumps observed in the DYNAMO-HST sample

ABSTRACT We present N-body simulations of the process of bulge formation in disc galaxies due to inward migration of massive stellar clumps. The process is accompanied by dark halo heating, with a quasi-isothermal core replacing the initial central density cusp, transforming an initially dark matter dominated central region into a baryon dominated one. The characteristics of the clumps are chosen to be compatible with low redshift observations of stellar clumps in DYNAMO-HST galaxies, which may be relatively long lived in terms of being robust against internal starburst-instigated disruption. We thus test for disruption due to tidal stripping using different clump internal radial profiles; Plummer, Hernquist, and Jaffe, in ascending order of see per central density profile. Our calculations predict that in order for clump migration to be effective in building galactic bulges and dark halo cores, steeply increasing central clump profiles, or a less massive or less concentrated haloes, are preferred. The dependence on such factors may contribute to the diversity in observed total mass distributions and resulting rotation curves in galaxies. When the process is most efficient, a ‘bulge-halo conspiracy’, with a singular isothermal total density akin to that observed bright galaxies, results.

Numerical analyses of M31 dark matter profiles

In this paper, we reproduce the rotation curve of the Andromeda galaxy (M31) by taking into account its bulge, disk and halo components, considering the last one to contain the major part of dark matter mass. Hence, our prescription is to split the galactic bulge into two components, namely, the inner and main bulges, respectively. Both bulges are thus modeled by exponential density profiles since we underline that the widely accepted de Vaucouleurs law fails to reproduce the whole galactic bulge rotation curve. In addition, we adopt various well-known phenomenological dark matter profiles to estimate the dark matter mass in the halo region. Moreover, we apply the least-squares fitting method to determine from the rotation curve the model free parameters, namely, the characteristic (central) density, scale radius and consequently the total mass. To do so, we perform Markov chain Monte Carlo statistical analyses based on the Metropolis algorithm, maximizing our likelihoods adopting velocity and radii data points of the rotation curves. We do not fit separately the components for bulges, disk and halo, but we perform an overall fit including all the components and employing all the data points. Thus, we critically analyze our corresponding findings and, in particular, we employ the Bayesian information criterion to assess the most accredited model to describe M31 dark matter dynamics.

Spectroscopic searches for evolutionary orbital period changes in WR+OB binaries: The case of WR 127 (Hen 3-1772)

Aims. We aim to determine the secular evolution of the orbital period of the short-period binary system WR 127 (WN3b+O9.5V, P ≈ 9.555d). Methods. We performed new low-resolution spectroscopic observations of WR 127 with the 2.5 m CMO SAI telescope to construct the radial velocity curves of the components. Our results suggest component masses of MWRsin3(i) = 11.8 ± 1.4 M⊙ and MOsin3(i) = 17.2 ± 1.4 M⊙. By comparing these values with archival radial velocity curves we were able to create an (O − C) plot with an accuracy sufficient to search for the orbital period change in WR 127. Results. We report the reliable detection of a secular increase in the orbital period of WR 127 at a rate of Ṗ = 0.83 ± 0.14 s yr−1, which corresponds to a dynamical mass-loss rate from the Wolf-Rayet (WR) star of ĖWR = (2.6 ± 0.5) × 10−5 M⊙ yr−1. Conclusions. The mass-loss rate from WR stars in three Wolf-Rayet+OB binaries (WR 127, CX Cep, and V444 Cyg) as inferred from spectroscopic and photometric measurements suggests a preliminary empirical correlation between a WR star’s mass and its dynamical mass-loss rate of ṀWR ∼ MWR1.8. This relation is important for the understanding of the evolution of massive close binaries that include WR stars as such an evolution is a precursor of gravitational-wave binary merging events with neutron stars and black holes.