Interferometric measurements are essential to constrain models of stellar systems, by spatially resolving angular distances and diameters well below the classical diffraction limit. In this work, we describe the interferometric module of Phoebe, which could be used just for this purpose. Since binaries in Phoebe are represented by a triangular mesh, our complex model is based on the integration over triangles. Consequently, Roche distortion, rotation, non-synchronicity, misalignment, eclipses of components, darkening, reflection, or irradiation are all accurately accounted for. For comparison purposes, we provide a simplified model, where components are represented by circular disks. The key point of our approach is a possibility of combination with other datasets (light curves, radial velocities), which allows to construct robust models of stellar systems. This draft refers to a development version of Phoebe, available at https://github.com/miroslavbroz/phoebe2/tree/interferometry . It is not yet included in the official Phoebe repository!

Multiple stellar systems are common especially among O and B stars. In order to accurately describe their dynamics, interactions among components must be accounted for. In this work, we describe the new dynamical model in Phoebe, which could be used just for this purpose. The n-body model is based on the Reboundx numerical integrator and accounts for mutual perturbations, oblateness, relativistic effects, or light-time effects. The initial conditions can be set up as hierarchical or two-pairs geometry. For comparison purposes, we also provide a simplified keplerian model. Photometric computations work similarly as before, with Roche distortions for pairs of components (or for centres of mass, if hierarchical), and all mutual eclipses. If the time span of observations is long enough, so that perturbations (precession, resonances) are manifested in eclipse timings or durations, this allows to construct order-of-magnitude more precise models of stellar systems. This draft refers to a development version of Phoebe, available at https://github.com/miroslavbroz/phoebe2/tree/interferometry . It is not yet included in the official Phoebe repository!

Spectroscopic observations constrain the fundamental properties of stellar atmospheres, in particular, the effective temperature, the gravitational acceleration, or the metallicity. In this work, we describe the spectroscopic module for Phoebe, which allows for modelling of spectra, either normalized, or in absolute units (${\rm W}\,{\rm m}^{-2}\,{\rm m}^{-1}$). The module is based on extensive grids of synthetic spectra, taken from literature, which are interpolated and integrated over the surface. As an approximation, we assume that limb darkening is given by an analytical law, while other effects (e.g., eclipses) are treated self-consistently. Our approach is suitable for single stars, binaries, or multiples, and can be further extended to systems with pulsating components. This draft refers to a development version of Phoebe, available at https://github.com/miroslavbroz/phoebe2/tree/spectroscopy2 . It is not yet included in the official Phoebe repository!

specreduce is an AstroPy-coordinated python package whose goal is to be a toolbox of functions and utilities that are relevant to the reduction of spectroscopic data. It is largely focused on optical/IR spectroscopy where the raw data consists of an image projected from a spectrograph onto a 2D imaging detector. The way the spectral and spatial information is encoded into these 2D images can be quite complex and varied (e.g. multi-object vs multi-fiber vs integral field spectroscopy). Methods and algorithms for handling this variety of data have been implemented across many previous and existing data pipelines. Specreduce aims to collect these best practices into a common, shared space that facilitates more collaboration and easier development of future spectroscopic pipelines.

Context. KIC 4150611 is a high-order multiple composed of a triple system. It comprises: (1) a F1V primary (Aa) that is eclipsed on a 94.2d period by a tight 1.52d binary composed of two dim K/M dwarfs (Ab1 and Ab2), which also eclipse each other; (2) an 8.65d eccentric, eclipsing binary composed of two G stars (Ba and Bb); and (3) another faint eclipsing binary composed of two stars of unknown spectral type (Ca and Cb). In addition to its many eclipses, the system is an SB3 spectroscopic multiple (Aa, Ba, and Bb), and the primary (Aa) is a hybrid pulsator that exhibits high amplitude pressure and gravity modes. In aggregate, this richness in physics offers an excellent opportunity to obtain a precise physical characterisation of some of the stars in this system. Aims. In this work we aim to characterise the F1V primary by modelling its complex eclipse geometry and disentangled stellar spectra in preparation for follow-up work that will focus on its pulsations. Methods. We employed a novel photometric analysis of the complicated eclipse geometry of Aa to obtain the orbital and stellar properties of the triple. We acquired 51 TRES spectra at the Fred L. Whipple Observatory, calculating radial velocities and orbital elements of Aa (SB1) and the B binary (SB2). These spectra and radial velocities were used to perform spectral disentangling for Aa, Ba, and Bb. Spectral modelling was applied to the disentangled spectrum of Aa to obtain atmospheric properties. Results. From our eclipse modelling we obtain precise stellar properties of the triple, including the mass ratios (M-Aa/(M-Ab1 + M-Ab2) = 3.61 +/- 0.01, M-Ab1/M-Ab2 = 1.113 +/- 0.001), the separation ratio (a(Aab)/a(Ab1Ab2) = 21.81 +/- 0.01), orbital periods (P-Aab = 94.29486 +/- 0.00008d, P-Ab1Ab2 = 1.522248 +/- 0.000001d), and stellar radii (R-Aa = 1.64 +/- 0.06 R-circle dot, R-Ab1 = 0.42 +/- 0.01 R-circle dot, R-Ab2 = 0.38 +/- 0.01 R-circle dot). Via radial velocity fitting and spectral disentangling, we find orbital elements for Aa, Ba, and Bb that are in excellent agreement with each other and with previous results in the literature. Spectral modelling on the disentangled spectrum of Aa provides constraints on the effective temperature (T-eff = 7280 +/- 70 K), surface gravity (log(g) = 4.14 +/- 0.18 dex), micro-turbulent velocity (v(micro) = 3.61 +/- 0.19 km s(-1)), rotation velocity (v sin i = 127 +/- 4 km s(-1)), and metallicity ([M/H] = - 0.23 +/- 0.06) that are also in good agreement with previous spectral modelling. Particular attention is paid to the light fraction of Aa, which our spectroscopic analysis determines to be between 0.92 and 0.94, while our eclipse modelling prefers a lower light fraction of 0.84 +/- 0.03, similar to the previous literature value of 0.85. However, the eclipse models are still able to obtain an excellent fit to the solution when constrained to light fractions between 0.92 and 0.96, while our spectroscopic analysis proves to be far more sensitive to the light fraction, leading us to conclude that the higher light fraction from spectroscopy is likely the correct solution.

The Astropy Project supports and fosters the development of open-source and openly developed Python packages that provide commonly needed functionality to the astronomical community. A key element of the Astropy Project is the core package astropy, which serves as the foundation for more specialized projects and packages. In this article, we summarize key features in the core package as of the recent major release, version 5.0, and provide major updates on the Project. We then discuss supporting a broader ecosystem of interoperable packages, including connections with several astronomical observatories and missions. We also revisit the future outlook of the Astropy Project and the current status of Learn Astropy. We conclude by raising and discussing the current and future challenges facing the Project.

In this paper we present a catalog of 4584 eclipsing binaries observed during the first two years (26 sectors) of the TESS survey. We discuss selection criteria for eclipsing binary candidates, detection of hitherto unknown eclipsing systems, determination of the ephemerides, the validation and triage process, and the derivation of heuristic estimates for the ephemerides. Instead of keeping to the widely used discrete classes, we propose a binary star morphology classification based on a dimensionality reduction algorithm. Finally, we present statistical properties of the sample, we qualitatively estimate completeness, and we discuss the results. The work presented here is organized and performed within the TESS Eclipsing Binary Working Group, an open group of professional and citizen scientists; we conclude by describing ongoing work and future goals for the group. The catalog is available from http://tessEBs.villanova.edu and from MAST.

Eclipsing Binaries (EBs) are known to be the source of most accurate stellar parameters, which are important for testing theories of stellar evolution.With improved quality and quantity of observations using space telescopes like TESS, there is an urgent need for accuracy in modeling to obtain precise parameters.We use the soon to be released PHOEBE 2.3 EB modeling package to test the robustness and accuracy of parameters and their dependency on choice of parameters for optimization.

Traditionally, the effects of interstellar extinction on binary star light curves have been treated as a uniform reduction in the observed brightness of the system that is independent of the orbital phase. However, unless the orbital plane of the system coincides with the plane of the sky, or if the two stars are completely identical and present with minimal mutual irradiation and tidal/rotational distortions, then this is unlikely to be an accurate representation of the effect of interstellar extinction. Here, we present an updated treatment of interstellar extinction as incorporated in the PHOEBE 2.2 release (publicly available from ) and assess the importance of using such an approach in the modeling of different types of binary systems. We also present the incorporation of PHOENIX model atmospheres into the PHOEBE 2.2 release, providing increased fidelity on computed observables down to lower temperatures than previously available. The importance of these new code developments is then highlighted via an extincted toy model of the eclipsing white-dwarf-subdwarf binary SDSS J235524.29+044855.7, demonstrating that, in the age of the Rubin Observatory Legacy Survey of Space and Time as well as complementary space-based photometric missions, a proper accounting for extinction and as well as the use of realistic model atmospheres will be essential in deriving accurate binary parameters.

The parameter space of binary star light curve models is highly complex and degenerate, thus basic fitting approaches often fail to yield a good (and correct) estimate of the parameter values and their uncertainties. On the other hand, we have an increasingly large number of fitting and sampling algorithms available that can be relatively easily interfaced with open-source eclipsing binary packages, like PHOEBE2. We showcase several fitting methods, including local and global minimizers, nested sampling and machine learning methods, and evaluate their performance on fitting a light curve model with PHOEBE2.

PHOEBE 2 is a Python package for modeling the observables of eclipsing star systems, but until now it has focused entirely on the forward model-that is, generating a synthetic model given fixed values of a large number of parameters describing the system and the observations. The inverse problem, obtaining orbital and stellar parameters given observational data, is more complicated and computationally expensive as it requires generating a large set of forward models to determine which set of parameters and uncertainties best represents the available observational data. The process of determining the best solution and also of obtaining reliable and robust uncertainties on those parameters often requires the use of multiple algorithms, including both optimizers and samplers. Furthermore, the forward model of PHOEBE has been designed to be as physically robust as possible, but it is computationally expensive compared to other codes. It is useful, therefore, to use whichever code is most efficient given the reasonable assumptions for a specific system, but learning the intricacies of multiple codes presents a barrier to doing this in practice. Here we present release 2.3 of PHOEBE (publicly available from), which introduces a general framework for defining and handling distributions on parameters and utilizing multiple different estimation, optimization, and sampling algorithms. The presented framework supports multiple forward models, including the robust model built into PHOEBE itself.

Context. Massive stars play an important role in the mechanical and chemical evolution of galaxies. Understanding the internal processes of these stars is vital to our understanding of their evolution and eventual end products. Deformations from spherical geometry are common for massive stars; however, the tools that are currently available for the study of these systems are almost exclusively one-dimensional. Aims. We present a new spectroscopic analysis tool tailored for massive stars that deviate from spherical symmetry. This code (entitled SPAMMS ) is a spectroscopic patch model that takes the three-dimensional surface geometry of the system into account to produce spectral profiles at given phases and orientations. Methods. In using the Wilson–Devinney-like code PHOEBE in combination with the nonlocal thermodynamic equilibrium radiative transfer code FASTWIND , we created a three-dimensional mesh that represents the surface geometry of our system and we assigned FASTWIND emergent intensity line profiles to each mesh triangle, which take the local parameters such as temperature, surface gravity, and radius into account. These line profiles were then integrated across the visible surface, where their flux contribution and radial velocity are taken into account, thus returning a final line profile for the visible surface of the system at a given phase. Results. We demonstrate that SPAMMS can accurately reproduce the morphology of observed spectral line profiles for overcontact systems. Additionally, we show how line profiles of rapidly-rotating single stars differ when taking rotational distortion into account, and the effects that these can have on the determined parameters. Finally, we demonstrate the code’s ability to reproduce the Rossiter–Mclaughlin and Struve–Sahade effects.

Eclipsing binary stars allow for the direct measurement of stellar parameters and distances and are therefore an important tool in the calibration of stellar relationships. In benchmark cases, we can achieve a precision of 2-3% in fundamental stellar parameters. Due to tighter constraints caused by mutual eclipse events, systems with additional companions allow achieving precision as low as 0.5%. Triple systems have also been proposed as a mechanism for explaining an overabundance of short-period tight binaries. Despite all of this, we do not yet have a complete model for these multiple star systems that include tight binaries. In order to precisely and accurately model these complex systems, we must take into account several considerations, including: light time effects, perturbations to orbital elements, and the distortion of the stellar surfaces. Including all of these into a comprehensive treatment of triple and higher order systems within PHOEBE is currently under development and planned for an upcoming release.

A general framework for dealing with irradiation effects in the bolometric sense-specifically, reflection with heat absorption and the consequent redistribution of the absorbed heat-for systems of astrophysical bodies where the boundaries are used as support for the description of the processes, is presented. Discussed are its mathematical and physical properties, as well as its implementation approximations, with a focus on three plausible redistribution processes (uniform, latitudinal, and local redistribution). These are tested by extending PHOEBE 2.1 (http://phoebe-project. org/), the open-source package for modeling eclipsing binaries, and applied to a toy model of the known two-body eclipsing systems.