RAS_WEB (Page 33)

Dynamical dark energy in light of cosmic distance measurements II: a study using current observations Xiaoma Wang, Gan Gu, Xiaoyong Mu, Shuo Yuan, Gong-Bo Zhao arXiv:2404.06310v1 Announce Type: new Abstract: We extract key information of dark energy from current observations of BAO, OHD and $H_0$, and find hints of dynamical behaviour of dark energy. In particular, a dynamical dark energy model whose equation of state crosses $-1$ is favoured by observations. We also find that the Universe has started accelerating at a lower redshift than expected.arXiv:2404.06310v1 Announce Type: new Abstract: We extract key information of dark energy from current observations of BAO, OHD and $H_0$,Read More →

The AstraLux-TESS high-spatial resolution imaging survey. Search for stellar companions of 215 planet candidates from TESS J. Lillo-Box, M. Morales-Calder’on, D. Barrado, O. Balsalobre-Ruza, A. Castro-Gonz’alez, I. Mendigut’ia, N. Hu’elamo, B. Montesinos, M. Vioque arXiv:2404.06316v1 Announce Type: new Abstract: Chance-aligned sources or blended companions can cause false positives in planetary transit detections or simply bias the determination of the candidate properties. In the era of high-precision space-based photometers, the need for high-spatial resolution images has demonstrated to be critical for validating and confirming transit signals. This already applied to the Kepler mission, it is now applicable to the TESS survey and will be critical forRead More →

Calibration of luminosity correlations of gamma-ray bursts using quasars Sarveshkumar Purohit, Shantanu Desai arXiv:2404.06334v1 Announce Type: new Abstract: In order to test the efficacy of Gamma-ray Bursts (GRBs) as cosmological probes, we the characterize the scatter in the correlations between six pairs of GRB related observables, which have previously also been studied in arXiv:2011.14040. However, some of these observables depend on the luminosity distance, for which one needs to assume an underlying cosmological model. In order to circumvent this circularity problem, we use X-ray and UV fluxes of quasars as distance anchors to calculate the luminosity distance in a model-independent manner, which in turn getsRead More →

Does the Earth’s rotation speed really tend to accelerate for a long time? Zinovy Malkin arXiv:2404.06343v1 Announce Type: new Abstract: Recently published studies suggested that the difference between Universal and Coordinated Time UT1-UTC could reach a large positive value in a few years, making it necessary to introduce a negative leap second into the UTC scale for the first time in its history. Based on the latest UT1 series provided by the International Earth Rotation and Reference Systems Service (IERS) and its prediction, it was shown that the tendency to acceleration of the Earth’s rotation observed over past four years most likely will return toRead More →

Dynamics of Star Cluster Formation: Mergers in Gas Rich Environments Jeremy Karam, Alison Sills arXiv:2404.06348v1 Announce Type: new Abstract: We perform high resolution simulations of forming star clusters as they merge inside giant molecular clouds (GMCs) using hydrodynamics coupled to N-body dynamics to simultaneously model both the gas and stars. We zoom in to previously run GMC simulations and resolve clusters into their stellar and gas components while including the surrounding GMC environment. We find that GMC gas is important in facilitating the growth of clusters in their embedded phase by promoting cluster mergers. Mergers induce asymmetric expansion of the stellar component of the clustersRead More →

Analyzing the Atmospheric Dispersion Correction of the Gemini Planet Imager: residual dispersion above design requirements Malachi Noel, Jason J. Wang, Bruce Macintosh, Katie Crotts, Christian Marois, Eric L. Nielsen, Robert J. De Rosa, Katie Scalzo, Kent Wallace arXiv:2404.06378v1 Announce Type: new Abstract: The Atmospheric Dispersion Corrector (ADC) of the Gemini Planet Imager (GPI) corrects the chromatic dispersion caused by differential atmospheric refraction (DAR), making it an important optic for exoplanet observation. Despite requiring less than 5 mas of residual DAR to avoid potentially affecting the coronagraph, the GPI ADC averages $sim7$ and $sim11$ mas of residual DAR in $H$ and $J$ band respectively. We analyzedRead More →

Reconciling $S_8$: Insights from Interacting Dark Sectors Rahul Shah, Purba Mukherjee, Supratik Pal arXiv:2404.06396v1 Announce Type: new Abstract: We do a careful investigation of the prospects of dark energy (DE) interacting with cold dark matter (CDM) in alleviating the $S_8$ clustering tension. To this end, we consider various well-known parametrizations of the DE equation of state (EoS), and consider perturbations in both the dark sectors, along with an interaction term. Moreover, we perform a separate study for the phantom and non-phantom regimes. Using CMB, BAO and SNIa datasets, the constraints on the model parameters for each case have been obtained and a generic reduction inRead More →

Helium Reionization from Empirical Quasar Luminosity Functions before and after JWST Arghyadeep Basu, Enrico Garaldi, Benedetta Ciardi arXiv:2404.06409v1 Announce Type: new Abstract: Recently, models of the quasar luminosity function (QLF) rooted on large observational compilations have been produced that, unlike their predecessors, feature a smooth evolution with time. This bypasses the need to assume an ionizing emissivity evolution when simulating helium reionization with observations-based QLF, thus yielding more robust constraints. We combine one such QLF with a cosmological hydrodynamical simulation and 3D multi-frequency radiative transfer. The simulated reionization history is consistently delayed in comparison to most other models in the literature. The predicted intergalactic mediumRead More →

Gravitational wave seismology of charged strange stars in the Cowling approximation: the fluid pulsation modes Jos’e D. V. Arba~nil, C’esar H. Lenzi, Juan M. Z. Pretel, C’esar O. V. Flores arXiv:2404.06412v1 Announce Type: new Abstract: In this work we study, within the framework of Cowling approximation, the effect of the electric charge on the gravitational wave frequency of fluid oscillation modes of strange quark stars. For this purpose, the dense matter of the stellar fluid is described by the MIT bag model equation of state (EoS), while for the electric charge profile, we consider that the electric charge density is proportional to the energy density.Read More →

Detection of Contact Binary Candidates Observed By TESS Using Autoencoder Neural Network Xu Ding, ZhiMing Song, ChuanJun Wang, KaiFan Ji arXiv:2404.06424v1 Announce Type: new Abstract: Contact binary may be the progenitor of a red nova that eventually produces a merger event and have a cut-off period around 0.2 days. Therefore, a large number of contact binaries is needed to search for the progenitor of red novae and to study the characteristics of short-period contact binaries. In this paper, we employ the Phoebe program to generate a large number of light curves based on the fundamental parameters of contact binaries. Using these light curves as samples,Read More →

Alfven Wave Mode Conversion in Neutron Star Magnetospheres: A Semi-analytic Approach Alexander Y. Chen, Yajie Yuan, Dominic Bernardi arXiv:2404.06431v1 Announce Type: new Abstract: We write down the force-free electrodynamics (FFE) equations in dipole coordinates, and solve for normal modes corresponding to Alfv’enic perturbations in the magnetosphere of a neutron star. We show that a single Alfv’en wave propagating on dipole field lines spontaneously sources a fast magnetosonic (fms) wave at the next order in the perturbation expansion, without needing 3-wave interaction. The frequency of the sourced fms wave is twice the original Alfv’en wave frequency, and the wave propagates spherically outwards. The properties of theRead More →

ClassiPyGRB: Machine Learning-Based Classification and Visualization of Gamma Ray Bursts using t-SNE Keneth Garcia-Cifuentes, Rosa L. Becerra, Fabio De Colle arXiv:2404.06439v1 Announce Type: new Abstract: Gamma-ray burst (GRBs) are the brightest events in the universe. For decades, astrophysicists have known about their cosmological nature. Every year, space missions such as Fermi and SWIFT detect hundreds of them. In spite of this large sample, GRBs show a complex taxonomy in the first seconds after their appearance, which makes it very difficult to find similarities between them using conventional techniques. It is known that GRBs originate from the death of a massive star or from the mergerRead More →

Constraining electron number density in the Sun via Earth-based neutrino flavor data Caroline Laber-Smith, Eve Armstrong, A. Baha Balantekin, Elizabeth K. Jones, Lily Newkirk, Amol V. Patwardhan, Sarah Ranginwala, M. Margarette Sanchez, Hansen Torres arXiv:2404.06468v1 Announce Type: new Abstract: Neutrino flavor transformation offers a window into the physics of various astrophysical environments, including our Sun and the more exotic environs of core-collapse supernovae and binary neutron-star mergers. Here, we apply an inference framework – specifically: statistical data assimilation (SDA) – to neutrino flavor evolution in the Sun. We take a model for solar neutrino flavor evolution, together with Earth-based neutrino measurements, to infer solar properties.Read More →

Uncovering Tidal Treasures: Automated Classification of Faint Tidal Features in DECaLS Data Alexander J. Gordon, Annette M. N. Ferguson, Robert G. Mann arXiv:2404.06487v1 Announce Type: new Abstract: Tidal features are a key observable prediction of the hierarchical model of galaxy formation and contain a wealth of information about the properties and history of a galaxy. Modern wide-field surveys such as LSST and Euclid will revolutionise the study of tidal features. However, the volume of data will far surpass the capacity to inspect each galaxy to identify the feature visually, thereby motivating an urgent need to develop automated detection methods. This paper presents a visual classificationRead More →

The jet of BP Tau A. V. Dodin, S. A. Potanin, M. A. Burlak, D. V. Cheryasov, N. P. Ikonnikova, S. A. Lamzin, B. S. Safonov, N. I. Shatskii, A. M. Tatarnikov arXiv:2404.06491v1 Announce Type: new Abstract: A strong global magnetic field of young low-mass stars and a high accretion rate are the necessary conditions for the formation of collimated outflows (jets) from these objects. But it is still unclear whether these conditions are also sufficient. We aim to check whether BP Tau, an actively accreting young star with a strong magnetic field, has a jet. We carried out narrowband SII 672 nm imaging andRead More →

Detection of Rydberg lines from the atmosphere of Betelgeuse W. R. F. Dent, G. Harper, A. M. S. Richards, P. Kervella, L. D. Matthews arXiv:2404.06501v1 Announce Type: new Abstract: Emission lines from Rydberg transitions are detected for the first time from a region close to the surface of Betelgeuse. The H30${alpha}$ line is observed at 231.905 GHz, with a FWHM ~42 km/s and extended wings. A second line at 232.025 GHz (FWHM ~21 km/s), is modeled as a combination of Rydberg transitions of abundant low First Ionization Potential metals. Both H30${alpha}$ and the Rydberg combined line X30${alpha}$ are fitted by Voigt profiles, and collisional broadeningRead More →

Evidence for Primordial Alignment: Insights from Stellar Obliquity Measurements for Compact Sub-Saturn Systems Brandon T. Radzom, Jiayin Dong, Malena Rice, Xian-Yu Wang, Samuel W. Yee, Tyler R. Fairnington, Cristobal Petrovich, Songhu Wang arXiv:2404.06504v1 Announce Type: new Abstract: Despite decades of effort, the mechanisms by which the spin axis of a star and the orbital axes of its planets become misaligned remain elusive. Particularly, it is of great interest whether the large spin-orbit misalignments observed are driven primarily by high-eccentricity migration — expected to have occurred for short-period, isolated planets — or reflect a more universal process that operates across systems with a variety of present-dayRead More →

Primordial black holes and curvature perturbations from false-vacuum islands Rong-Gen Cai, Yu-Shi Hao, Shao-Jiang Wang arXiv:2404.06506v1 Announce Type: new Abstract: Recently, much attention has been focused on the false-vacuum islands that are flooded by an expanding ocean of true-vacuum bubbles slightly later than most of the other parts of the world. These delayed decay regions will accumulate locally larger vacuum energy density by staying in the false vacuum longer than those already transited into the true vacuum. A false-vacuum island with thus acquired density contrast of a super-horizon size will evolve locally from radiation dominance to vacuum dominance, creating a local baby Universe that canRead More →

Black holes, multiple propagation speeds and energy extraction Vitor Cardoso, Shinji Mukohyama, Naritaka Oshita, Kazufumi Takahashi arXiv:2404.05790v1 Announce Type: cross Abstract: The Standard Model of particle physics predicts the speed of light to be a universal speed of propagation of massless carriers. However, other possibilities exist — including Lorentz-violating theories — where different fundamental fields travel at different speeds. Black holes are interesting probes of such physics, as distinct fields would probe different horizons. Here, we build an exact spacetime for two interacting scalar fields which have different propagation speeds. One of these fields is able to probe the black hole interior of the other,Read More →

Numerical validation of scaling laws for stratified turbulence Pascale Garaud, Greg P. Chini, Laura Cope, Kasturi Shah, Colm-cille P. Caulfield arXiv:2404.05896v1 Announce Type: cross Abstract: Recent theoretical progress using multiscale asymptotic analysis has revealed various possible regimes of stratified turbulence. Notably, buoyancy transport can either be dominated by advection or diffusion, depending on the effective P’eclet number of the flow. Two types of asymptotic models have been proposed, which yield measurably different predictions for the characteristic vertical velocity and length scale of the turbulent eddies in both diffusive and non-diffusive regimes. The first, termed a `single-scale model’, is designed to describe flow structures having largeRead More →