uvcombine combines single-dish and interferometric data. It can combine high-resolution images that are missing large angular scales (Fourier-domain short-spacings) with low-resolution images containing the short/zero spacing. uvcombine includes the "feathering" technique for interferometry data, implementing a similar approach to CASA’s (ascl:1107.013) feather task but with additional options. Also included are consistency tests for the flux calibration and single-dish scale by comparing the data in the uv-overlap range.

The Universal Transit Modeller (UTM) is a light-curve simulator for all kinds of transiting or eclipsing configurations between arbitrary numbers of several types of objects, which may be stars, planets, planetary moons, and planetary rings. A separate fitting program, UFIT (Universal Fitter) is part of the UTM distribution and may be used to derive best fits to light-curves for any set of continuously variable parameters. UTM/UFIT is written in IDL code and its source is released in the public domain under the GNU General Public License.

The util_2comp software utilities generate predictions of far-infrared Galactic dust emission and reddening based on a two-component dust emission model fit to Planck HFI, DIRBE and IRAS data from 100 GHz to 3000 GHz. These predictions and the associated dust temperature map have angular resolution of 6.1 arcminutes and are available over the entire sky. Implementations in IDL and Python are included.

The time dependent Monte-Carlo code URILIGHT, written in Fortran 90, assumes homologous expansion. Energy deposition resulting from the decay of radioactive isotopes is calculated by a Monte-Carlo solution of the γ-ray transport, for which interaction with matter is included through Compton scattering and photoelectric absorption. The temperature is iteratively solved for in each cell by requiring that the total emissivity equals the total absorbed energy.

URecon reconstructs the initial conditions of N-body simulations from late time (<i>e.g.</i>, z=0) density fields. This simple UNET architecture is implemented in TensorFlow and requires Pylians3 (ascl:2403.012) for measuring power spectrum of density fields. The package includes weights trained on Quijote fiducial cosmology simulations.

URCHIN is a Smoothed Particle Hydrodynamics (SPH) reverse ray tracer (i.e. from particles to sources). It calculates the amount of shielding from a uniform background that each particle experiences. Preservation of the adaptive density field resolution present in many gas dynamics codes and uniform sampling of gas resolution elements with rays are two of the benefits of URCHIN; it also offers preservation of Galilean invariance, high spectral resolution, and preservation of the standard uniform UV background in optically thin gas.

UPSILoN (AUtomated Classification of Periodic Variable Stars using MachIne LearNing) classifies periodic variable stars such as Delta Scuti stars, RR Lyraes, Cepheids, Type II Cepheids, eclipsing binaries, and long-period variables (i.e. superclasses), and their subclasses (e.g. RR Lyrae ab, c, d, and e types) using well-sampled light curves from any astronomical time-series surveys in optical bands regardless of their survey-specific characteristics such as color, magnitude, and sampling rate. UPSILoN consists of two parts, one which extracts variability features from a light curve, and another which classifies a light curve, and returns extracted features, a predicted class, and a class probability. In principle, UPSILoN can classify any light curves having arbitrary number of data points, but using light curves with more than ~80 data points provides the best classification quality.

UPMASK, written in R, performs membership assignment in stellar clusters. It uses photometry and spatial positions, but can take into account other types of data. UPMASK takes into account arbitrary error models; the code is unsupervised, data-driven, physical-model-free and relies on as few assumptions as possible. The approach followed for membership assessment is based on an iterative process, principal component analysis, a clustering algorithm and a kernel density estimation.

unWISE-verse is an integrated Python pipeline for downloading sets of unWISE time-resolved coadd cutouts from the WiseView image service and uploading subjects to Zooniverse.org for use in astronomical citizen science research. This software was initially designed for the Backyard Worlds: Cool Neighbors research project and is optimized for target sets containing low luminosity brown dwarf candidates. However, unWISE-verse can be applied to other future astronomical research projects that seek to make use of unWISE infrared sky maps, such as studies of infrared variable/transient sources.

The unwise_psf Python module renders point spread function (PSF) models appropriate for use in modeling of unWISE coadd images. unwise_psf translates highly detailed single-exposure WISE PSF models in detector coordinates to the corresponding pixelized PSF models in coadd space, accounting for subtleties including the WISE scan direction and its considerable variation near the ecliptic poles. Applications of the unwise_psf module include performing forced photometry on unWISE coadds, constructing WISE-selected source catalogs based on unWISE coadds and masking unWISE coadd regions contaminated by bright stars.

unTimely Catalog Explorer searches for and visualizes detections in the unTimely Catalog, a full-sky, time-domain catalog of detections based on WISE and NEOWISE image data acquired between 2010 and 2020. The tool searches the catalog by coordinates to create finder charts for each epoch with overplotted catalog positions and light curves using the unTimely photometry, to overplot these light curves with AllWISE multi-epoch and NEOWISE-R single exposure (L1b) photometry, and to create image blinks with overlaid catalog positions in GIF format.

unpopular is an implementation of the Causal Pixel Model (CPM) de-trending method to obtain TESS Full-Frame Image (FFI) light curves. The code, written in Python, models the systematics in the light curves of individual pixels as a linear combination of light curves from many other distant pixels and removes shared flux variations. unpopular is able to preserve sector-length astrophysical signals, allowing for the extraction of multi-sector light curves from the FFI data.

Univiewer is a visualisation program for <a href="http://ascl.net/1107.018">HEALPix</a> (ascl:1107.018) maps. It is written in C++ and uses OpenGL and the wxWidgets library for cross-platform portability. Using it you can: - Rotate and zoom maps on the sphere in 3D - Create high-resolution views of square patches of the map - Change maximum and minimum values of the colourmap interactively - Calculate the power spectrum of the full-sky map or a patch - Display any column of a HEALPix map FITS file on the sphere Since Univiewer uses OpenGL for 3D graphics, its performance is dependent your video card. It has been tested successfully on computers with as little as 8Mb video memory, but it is recommended to have at least 32Mb to get good performance. In the 3D view, a HEALPix map is projected onto a ECP pixelation to create a texture which is wrapped around the sphere. In calculating the power spectrum, the spherical harmonic transforms are computed using the same ECP pixelation. This inevitably leads to some discrepancies at small scales due to repixelation effects, but they are reasonably small.

The UniverseMachine applies simple empirical models of galaxy formation to dark matter halo merger trees. For each model, it generates an entire mock universe, which it then observes in the same way as the real Universe to calculate a likelihood function. It includes an advanced MCMC algorithm to explore the allowed parameter space of empirical models that are consistent with observations.

UniPOPS, a suite of programs and utilities developed at the National Radio Astronomy Observatory (NRAO), reduced data from the observatory's single-dish telescopes: the Tucson 12-m, the Green Bank 140-ft, and archived data from the Green Bank 300-ft. The primary reduction programs, 'line' (for spectral-line reduction) and 'condar' (for continuum reduction), used the People-Oriented Parsing Service (POPS) as the command line interpreter. UniPOPS unified previous analysis packages and provided new capabilities; development of UniPOPS continued within the NRAO until 2004 when the 12-m was turned over to the Arizona Radio Observatory (ARO). The submitted code is version 3.5 from 2004, the last supported by the NRAO.

The data analysis UniMAP (Unicorn Multi-window Anomaly Detection Pipeline) leverages the Temporal Outlier Factor (TOF) method to find anomalies in LVC data. The pipeline requires a target detector and a start and stop GPS time describing a time interval to analyze, and has three outputs: 1.) an array of GPS times corresponding to TOF detections; 2.) a long q-transform of the entire data interval with visualizations of the TOF detections in the time series; and 3.) q-transforms of the data windows that triggered TOF detections.

UniDAM obtains a homogenized set of stellar parameters from spectrophotometric data of different surveys. Parallax and extinction data can be incorporated into the isochrone fitting method used in UniDAM to reduce distance and age estimate uncertainties for TGAS stars for distances up to 1 kpc and decrease distance Gaia end-of-mission parallax uncertainties by about a factor of 20 and age uncertainties by a factor of two for stars up to 10 kpc away from the Sun.

The Unicorn pipeline produces data products from the 3D-HST grism survey of four CANDELS fields. It extracts interlaced 2D and 1D spectra for all objects in the Skelton et al. (2014) photometric catalogs. It then fits the 2D spectra and multi-band photometry to determine redshifts and emission line strengths. Unicorn is built on threedhst (ascl:2411.018) and has been superseded by grizli (ascl:1905.001).

Astrochemistry database of chemical species.

Umbrella detects, validates, and identifies asteroids. The core of this software suite, Umbrella2, includes algorithms and interfaces for all steps of the processing pipeline, including a novel detection algorithm for faint trails. A detection pipeline accessible as a desktop program (ViaNearby) builds on the library to provide near real-time data reduction of asteroid surveys on the Wide Field Camera of the Isaac Newton Telescope. Umbrella can read and write MPC optical reports, supports SkyBoT and VizieR querying, and can be extended by user image processing functions to take advantage of the algorithms framework as a multi-threaded CPU scheduler for easy algorithm parallelization.

ULySS (University of Lyon Spectroscopic Analysis Software) is an open-source software package written in the GDL/IDL language to analyze astronomical data. ULySS fits a spectrum with a linear combination of non-linear components convolved with a line-of-sight velocity distribution (LOSVD) and multiplied by a polynomial continuum. ULySS is used to study stellar populations of galaxies and star clusters and atmospheric parameters of stars.

Ulula is an ultra-lightweight 2D hydro code for teaching purposes. The code is written in pure python and is designed to be as short and easy to understand as possible, while not compromising on performance. The latter is achieved with a simple Godunov solver and by using numpy for all array operations.

This three-component package provides a Pythonic implementation of the Nested Sampling integration algorithm for Bayesian model comparison and parameter estimation. It offers multiple implementations for constrained drawing functions and a test suite to evaluate the correctness, accuracy and efficiency of various implementations. The three components are: - a modular framework for nested sampling algorithms (nested_sampling) and their development; - a test framework to evaluate the performance and accuracy of algorithms (testsuite); and - UltraNest, a fast C implementation of a mixed RadFriends/MCMC nested sampling algorithm.

UltraDark.jl simulates cosmological scalar fields. Written in Julia, it is inspired by PyUltraLight (ascl:1810.009) and designed to be simple to use and extend. It solves a non-interacting scalar field Gross-Pitaevskii equation coupled to Poisson's equation for gravitational potential. The scalar field describes scalar dark matter in models including ultralight dark matter, fuzzy dark matter, axion-like particles and the like. It also describes an inflaton field in the reheating epoch of the early universe.

Ujti calculates geodesics, gravitational lenses and gravitational redshift in principle, for any metric. Special attention has been given to compact objects, so the current implementation considers only metrics in spherical coordinates.

UFalcon rapidly post-processes N-body code output into signal maps for many different cosmological probes. The package is able to produce maps of weak-lensing convergence, linear-bias galaxy over-density, cosmic microwave background (CMB) lensing convergence and the integrated Sachs-Wolfe temperature perturbation given a set of N-body lightcones. It offers high flexibility for lightcone construction, such as user-specific survey-redshift ranges, redshift distributions and single-source redshifts. UFalcon also computes the galaxy intrinsic alignment signal, which can be treated as an additive component to the cosmological signal.

UDAT is a pattern recognition tool for mass analysis of various types of data, including image and audio. Based on its WND-CHARM (ascl:1312.002) prototype, UDAT computed a large set of numerical content descriptors from each file it analyzes, and selects the most informative features using statistical analysis. The tool can perform automatic classification of galaxy images by training with annotated galaxy images. It also has unsupervised learning capabilities, such as query-by-example of galaxies based on morphology. That is, given an input galaxy image of interest, the tool can search through a large database of images to retrieve the galaxies that are the most similar to the query image. The downside of the tool is its computational complexity, which in most cases will require a small or medium cluster.

UCLCHEM is a time and depth dependent gas-grain chemical model that can be used to estimate the fractional abundances (with respect to hydrogen) of gas and surface species in every environment where molecules are present. The model includes both gas and surface reactions. The code starts from the most diffuse state where all the gas is in atomic form and evolve sthe gas to its final density. Depending on the temperature, atoms and molecules from the gas freeze on to the grains and they hydrogenate where possible. The advantage of this approach is that the ice composition is not assumed but it is derived by a time-dependent computation of the chemical evolution of the gas-dust interaction process. The code is very modular, has been used to model a variety of regions and can be coupled with the UCL_PDR and SMMOL codes.

UCL_PDR is a time dependent photon-dissociation regions model that calculates self consistently the thermal balance. It can be used with gas phase only species as well as with surface species. It is very modular, has the possibility of accounting for density and pressure gradients and can be coupled with UCL_CHEM as well as with SMMOL. It has been used to model small scale (e.g. knots in proto-planetary nebulae) to large scale regions (high redshift galaxies).

Uncertain_blackholemass predicts virial black hole masses using a neural network model and quantifies their uncertainties. The scripts retrieve data and run feature extraction and uncertainty quantification for regression. They can be used separately or deployed to existing machine learning methods to generate prediction intervals for the black hole mass predictions.

UBER (Universal Boltzmann Equation Solver) solves the general form of Fokker-Planck equation and Boltzmann equation, diffusive or non-diffusive, that appear in modeling planetary radiation belts. Users can freely specify the coordinate system, boundary geometry and boundary conditions, and the equation terms and coefficients. The solver works for problems in one to three spatial dimensions. The solver is based upon the mathematical theory of stochastic differential equations. By its nature, the solver scheme is intrinsically Monte Carlo, and the solutions thus contain stochastic uncertainty, though the user may dictate an arbitrarily small relative tolerance of the stochastic uncertainty at the cost of longer Monte Carlo iterations.

USNO/AE98 contains ephemerides for fifteen of the largest asteroids that The Astronomical Almanac has used since its 2000 edition. These ephemerides are based on the Jet Propulsion Laboratory (JPL) planetary ephemeris DE405 and, thus, aligned to the International Celestial Reference System (ICRS). The data cover the period from 1799 November 16 (JD 2378450.5) through 2100 February 1 (JD 2488100.5). The internal uncertainty in the mean longitude at epoch, 1997 December 18, ranges from 0.05 arcseconds for 7 Iris through 0.22 arcseconds for 65 Cybele, and the uncertainty in the mean motion varies from 0.02 arcseconds per century for 4 Vesta to 0.14 arcseconds per century for 511 Davida. The Astronomical Almanac has published ephemerides for 1 Ceres, 2 Pallas, 3 Juno, and 4 Vesta since its 1953 edition. Historically, these four asteroids have been observed more than any of the others. Ceres, Pallas, and Vesta deserve such attention because as they are the three most massive asteroids, the source of significant perturbations of the planets, the largest in linear size, and among the brightest main belt asteroids. Studying asteroids may provide clues to the origin and primordial composition of the solar system, data for modeling the chaotic dynamics of small solar system bodies, and assessments of potential collisions. Therefore, USNO/AE98 includes more than the traditional four asteroids. The following criteria were used to select main belt asteroids for USNO/AE98: Diameter greater than 300 km, presumably among the most massive asteroids Excellent observing history and discovered before 1850 Largest in their taxonomic class The massive asteroids included may be studied for their perturbing effects on the planets while those with detailed observing histories may be used to evaluate the accuracy limits of asteroid ephemerides. The fifteen asteroids that met at least one of these criteria are 1 Ceres (new mass determination) 2 Pallas (new mass determination) 3 Juno 4 Vesta (new mass determination) 6 Hebe 7 Iris 8 Flora 9 Metis 10 Hygiea 15 Eunomia 16 Psyche 52 Europa 65 Cybele 511 Davida 704 Interamnia The refereed paper by Hilton (1999, Astron. J. 117, 1077) describes the USNO/AE98 asteroid ephemerides in detail. The associated USNO/AA Tech Note 1998-12 includes residual plots for all fifteen asteroids and a comparison between these ephemerides and those used in The Astronomical Almanac through 1999. Software to compact, read, and interpolate the USNO/AE98 asteroid ephemerides is also available. It is written in C and designed to work with the C edition of the Naval Observatory Vector Astrometry Software (NOVAS). The programs could be used with tabular ephemerides of other asteroids as well. The associated README file provides the details of this system.

TYCHO is a general, one dimensional (spherically symmetric) stellar evolution code written in structured Fortran 77; it is designed for hydrostatic and hydrodynamic stages including mass loss, accretion, pulsations and explosions. Mixing and convection algorithms are based on 3D time-dependent simulations. It offers extensive on-line graphics using Tim Pearson's PGPLOT (ascl:1103.002) with X-windows and runs effectively on Linux and Mac OS X laptop and desktop computers. NOTE: This code is no longer being supported.

TwoDSSM solves the equations of self-gravitating hydrodynamics in the shearing sheet, with cooling. TwoDSSM is configured to use a simple, exponential cooling model, although it contains code for a more complicated (and perhaps more realistic) cooling model based on a one-zone vertical model. The complicated cooling model can be switched on using a flag.

TWODSPEC offers programs for the reduction and analysis of long-slit and optical fiber array spectra, implemented as extensions to the FIGARO package (<a href="http://ascl.net/1203.013">ascl:1203.013</a>). The software are currently distributed as part of the Starlink software collection (<a href="http://ascl.net/1110.012">ascl:1110.012</a>). These programs are designed to do as much as possible for the user, to assist quick reduction and analysis of data; for example, LONGSLIT can fit multiple Gaussians to line profiles in batch and decides how many components to fit.

TWO-POP-PY runs a two-population dust evolution model that follows the upper end of the dust size distribution and the evolution of the dust surface density profile and treats dust surface density, maximum particle size, small and large grain velocity, and fragmentation. It derives profiles that describe the dust-to-gas ratios and the dust surface density profiles well in protoplanetary disks, in addition to the radial flux by solid material rain out.

The Twinkle suite, offered in both GPU and CPU versions, models binary lenses. It overcomes computational challenges in microlensing planet detection; the code incorporates optimizations on multiple fronts, from the numerical evaluation of lens equation coefficients to the solution of the algebraic equations. Twinkle also provides an improved method for identifying ghost images.

Twinkle calculates and plots the stellar spectral energy distribution (SED) using empirical photometric data and stellar model grids. The code was originally created to help calculate the excess infrared (IR) flux from a star; the presence of an IR excess indicates dust orbiting the star. This dust likely results from the grinding and collisions of asteroids, influenced by a larger planetary object—pointing to the potential for finding planets. Twinkle quickly calculates the temperature and location of the dust to first order by fitting the assumed blackbody or modified blackbody function to the broadband excess emission.

tvguide determines whether stars and galaxies are observable by TESS. It uses an object's right ascension and declination and estimates the pointing of TESS's cameras using predicted spacecraft ephemerides to determine whether and for how long the object is observable with TESS. tvguide returns a file with two columns, the first the minimum number of sectors the target is observable for and the second the maximum.

TVD solves the magnetohydrodynamic (MHD) equations by updating the fluid variables along each direction using the flux-conservative, second-order, total variation diminishing (TVD), upwind scheme of Jin & Xin. The magnetic field is updated separately in two-dimensional advection-constraint steps. The electromotive force (EMF) is computed in the advection step using the TVD scheme, and this same EMF is used immediately in the constraint step in order to preserve ∇˙B=0 without the need to store intermediate fluxes. The code is extended to three dimensions using operator splitting, and Runge-Kutta is used to get second-order accuracy in time. TVD offers high-resolution per grid cell, second-order accuracy in space and time, and enforcement of the ∇˙B=0 constraint to machine precision. Written in Fortran, It has no memory overhead and is fast. It is also available in a fully scalable message-passing parallel MPI implementation.

TurbuStat implements a variety of turbulence-based statistics described in the astronomical literature and defines distance metrics for each statistic to quantitatively compare spectral-line data cubes, as well as column density, integrated intensity, or other moment maps. The software can simulate observations of fractional Brownian Motion fields, including 2-D images and optically thin H I data cubes. TurbuStat also offers multicore fast-Fourier-transform support and provides a segmented linear model for fitting lines with a break point.

Turbospectrum is a 1D LTE spectrum synthesis code which covers 600 molecules, is fast with many lines, and uses the treatment of line broadening described by Barklem & O’Mara (1998). An updated NLTE version of Turbospectrum, Turbospectrum_NLTE (ascl:2504.012), is available.

Turbospectrum_NLTE updates the spectral synthesis code Turbospectrum (ascl:1205.004) with NLTE capabilities. The code takes a 1D model atmosphere, one or several line lists, and computes the emergent spectrum (flux and/or intensities at various angles), with a prescribed chemical composition. Various parameters can be adjusted, such as microturbulence (vmicro), individual abundances, and isotopic ratios. Turbospectrum_NLTE can also handle the computation for a single chunk of spectrum with a constant wavelength step, or for a number of smaller windows, <i>e.g.</i>, around lines of interest. Calculations can also be done for plane-parallel or spherically symmetric models.

TurboSETI analyzes filterbank data (frequency vs. time) for narrow band drifting signals; its main purpose is to search for signals of extraterrestrial origin. TurboSETI can search the data for hundreds of drift rates (in Hz/sec) and handles either .fil or .h5 file formats. It has several dependencies, including Blimpy (ascl:1906.002) and Astropy (ascl:1304.002).

turboGL is a fast Mathematica code based on a stochastic approach to cumulative weak lensing. It can easily compute the lensing PDF relative to arbitrary halo mass distributions, selection biases, number of observations, halo profiles and evolutions, making it a useful tool to study how lensing depends on cosmological parameters and impact on observations.

TULIPS (Tool for Understanding the Lives, Interiors, and Physics of Stars) creates diagrams of the structure and evolution of stars. It creates plots and movies based on output from the MESA stellar evolution code (ascl:1010.083). TULIPS represents stars as circles of varying size and color. The code can also visualize the size and perceived color of stars, their interior mixing and nuclear burning processes, their chemical composition, and can compare different MESA models.

TTVFaster implements analytic formulae for transit time variations (TTVs) that are accurate to first order in the planet–star mass ratios and in the orbital eccentricities; the implementations are available in several languages, including IDL, Julia, Python and C. These formulae compare well with more computationally expensive N-body integrations in the low-eccentricity, low mass-ratio regime when applied to simulated and to actual multi-transiting Kepler planet systems.

TTVFast efficiently calculates transit times for n-planet systems and the corresponding radial velocities. The code uses a symplectic integrator with a Keplerian interpolator for the calculation of transit times (Nesvorny et al. 2013); it is available in both C and Fortran.

The time series reconstruction method of massive astronomical catalogs reconstructs all celestial objects' time series data for astronomical catalogs with great accuracy. In addition, the program, which requires a Spark cluster, solves the boundary source leakage problem on the premise of ensuring accuracy, and the user can set different parameters for different data sets to filter the error records in the catalogs.

TSP is an astronomical data reduction package that handles time series data and polarimetric data from a variety of different instruments, and is distributed as part of the Starlink software collection (ascl:1110.012).

tshirt (Time Series Helper and Integration Reduction Tool) processes raw data on exoplanet systems for time series science. It reduces raw data to produce flat fields, subtracts bias, and corrects gain. tshirt also performs photometric and optimal spectral extraction of light curves.

TRUVOT decontaminates Swift UVOT grism spectra for transient objects. The technique makes use of template images in a process similar to image subtraction.

TROVE (Theoretical ROVibrational Energies) performs variational calculations of rovibrational energies for general polyatomic molecules of arbitrary structure in isolated electronic states. The software numerically constructs the kinetic energy operator, which is represented as an expansion in terms of internal coordinates. The code is self-contained, requiring no analytical pre-derivation of the kinetic energy operator. TROVE is also general and can be used with any internal coordinates.

tropygal estimates entropy in the context of galactic dynamics, but can be used to estimate the entropy in any context. It focuses on nearest-neighbor estimators, and it also provides a function for density estimates. Additionally, tropygal provides functions for analytical distribution functions and density of states for dynamical models that have analytical expressions.

TROPF (Tidal Response Of Planetary Fluids) enables efficient terrestrial fluid tidal studies across a wide range of parameter space. The software includes several different solutions to the governing equations in classical tidal theory, and can calculate millions of such solutions on several-minute-long timescales. Written in MATLAB/Octave, TROPF can be ported to Python and other languages, as the instructions for building the operator matrices are described in detail and the coding of core TROPF routines adheres to generic sparse matrix operations and avoids functions specific to MATLAB.

TRISTAN (TRIdimensional STANford) is a fully electromagnetic code with full relativistic particle dynamics. The code simulates large-scale space plasma phenomena such as the formation of systems of galaxies. TRISTAN particles which hit the boundaries are arrested there and redistributed more uniformly by having the boundaries slightly conducting, thus allowing electrons to recombine with ions and provides a realistic way of eliminating escaping particles from the code. Fresh particle fluxes can then be introduced independently across the boundaries. Written in 1993, this code has largely been superceded by TRISTAN-MP (ascl:1908.008).

TRISTAN-MP is a fully relativistic Particle-In-Cell (PIC) code for plasma physics computations and self-consistently solves the full set of Maxwell’s equations, along with the relativistic equations of motion for the charged particles. Fields are discretized on a finite 3D or 2D mesh, the computational grid; the code then uses time-centered and space-centered finite difference schemes to advance the equations in time via the Lorentz force equation, and to calculate spatial derivatives, so that the algorithm is second order accurate in space and time. The charges and currents derived from the particles' velocities and positions are then used as source terms to re-calculate the electromagnetic fields. TRISTAN-MP is based on the original TRISTAN code (ascl:2008.025) by O. Buneman (1993).

TRIPPy (TRailed Image Photometry in Python) uses a pill-shaped aperture, a rectangle described by three parameters (trail length, angle, and radius) to improve photometry of moving sources over that done with circular apertures. It can generate accurate model and trailed point-spread functions from stationary background sources in sidereally tracked images. Appropriate aperture correction provides accurate, unbiased flux measurement. TRIPPy requires numpy, scipy, matplotlib, Astropy (ascl:1304.002), and stsci.numdisplay; emcee (ascl:1303.002) and SExtractor (ascl:1010.064) are optional.

TRIPP (TRansient Image Processing Pipeline) detects transients and variable sources using difference imaging analysis and light-curve analysis techniques. It performs image registration, subtraction, and source extraction, producing photometric measurements and light curves for candidate events. Designed for use with networks of small telescopes and large synoptic surveys, the pipeline enables (near) real-time identification of transient phenomena. Though written specifically with LGTS in mind, the pipeline and its optimizations could be broadly beneficial for time-domain astrophysics; TRIPP could feasibly detect OSETI signals in LGTS data.

Written in IDL, TRIPP performs CCD time series reduction and analysis. It provides an on-line check of the incoming frames, performs relative aperture photometry and provides a set of time series tools, such as calculation of periodograms including false alarm probability determination, epoc folding, sinus fitting, and light curve simulations.

TripleLens calculates microlensing light curves for three-body lens systems (3L1S) using a contour integration method with continuous image-track linking. Written in C++ with Python bindings, it extends the algorithms developed for VBBinaryLensing (ascl:1809.004) to handle triple-lens configurations. The software solves complex roots and manages image topology changes to produce accurate magnification curves. TripleLens is useful for modeling microlensing events involving a stellar binary and a planet, where two-lens models are insufficient. The code's modular design allows users to specify lens parameters, source trajectories, and output options for flexible analysis.

triple-stability uses a simple form of an artificial neural network, a multi-layer perceptron, to check whether a given configuration of a triple-star system is dynamically stable. The code is written in Python and the MLP classifier can be imported to other custom Python3 scripts.

TRIP is an interactive computer algebra system that is devoted to perturbation series computations, and specially adapted to celestial mechanics. Its development started in 1988, as an upgrade of the special purpose FORTRAN routines elaborated by J. Laskar for the demonstration of the chaotic behavior of the Solar System. TRIP is a mature and efficient tool for handling multivariate generalized power series, and embeds two kernels, a symbolic and a numerical kernel. This numerical kernel communicates with <a href="http://www.gnuplot.info/">Gnuplot</a> or <a href="http://plasma-gate.weizmann.ac.il/Grace/.">Grace</a> to plot the graphics and allows one to plot the numerical evaluation of symbolic objects.

TRINITY statistically connects dark matter halos, galaxies and supermassive black holes (SMBHs) from z=0-10. Constrained by multiple galaxy (0 < z < 10) and SMBH datasets (0 < z < 6.5), the empirical model finds the posterior probability distributions of the halo-galaxy-SMBH connection and SMBH properties, all of which are allowed to evolve with redshift. TRINITY can predict many observational data, such as galaxy stellar mass functions and quasar luminosity functions, and underlying galaxy and SMBH properties, including SMBH Eddington average Eddington ratios. These predictions are made by different code files. There are basically two types of prediction codes: the first type generates observable data given input redshift or redshift invertals; the second type generates galaxy or SMBH properties as a function of host halo mass and redshift.

Trilogy automatically scales and combines FITS images to produce color or grayscale images using Python scripts. The user assigns images to each color channel (RGB) or a single image to grayscale luminosity. Trilogy determines the intensity scaling automatically and independently in each channel to display faint features without saturating bright features. Each channel's scaling is determined based on a sample of the image (or summed images) and two input parameters. One parameter sets the output luminosity of "the noise," currently determined as 1-sigma above the sigma-clipped mean. The other parameter sets what fraction of the data (if any) in the sample region should be allowed to saturate. Default values for these parameters (0.15% and 0.001%, respectively) work well, but the user is able to adjust them. The scaling is accomplished using the logarithmic function y = a log(kx + 1) clipped between 0 and 1, where a and k are constants determined based on the data and desired scaling parameters as described above.

Trident creates synthetic absorption-line spectra from astrophysical hydrodynamics simulations. It uses the yt package (ascl:1011.022) to read in simulation datasets and extends it to provide realistic synthetic observations appropriate for studies of the interstellar, circumgalactic, and intergalactic media.

triceratops (Tool for Rating Interesting Candidate Exoplanets and Reliability Analysis of Transits Originating from Proximate Stars) validates planet candidates from the Transiting Exoplanet Survey Satellite (TESS). The code calculates the probabilities of a wide range of transit-producing scenarios using the primary transit of the planet candidate and preexisting knowledge of its host and nearby stars. It then uses the known properties of these stars to calculate star-specific priors for each scenario with estimates of stellar multiplicity and planet occurrence rates.

TriArc (reTRIeval ARCturus) uses Bayesian statistics to determine the minimum abundance of an atmospheric species in a given model atmosphere (excluding the species of interest) and spectral noise profile. The code is configured for transmission spectroscopy and is built using the forward modeling capabilities of petitRADTRANS (ascl:2207.014); it also uses PandExo (ascl:1906.016). TriArc has been used to calculate prebiosignature detection thresholds for various potential JWST targets.

TRES simulates hierarchical triple systems with stellar and planetary components, including stellar evolution, stellar winds, tides, general relativistic effects, mass transfer, and three-body dynamics. It combines stellar evolution and interactions with three-body dynamics in a self-consistent way. The code includes the effects of common-envelope evolution, circularized stable mass transfer, tides, gravitational wave emission and up-to-date stellar evolution through SeBa (ascl:1201.003). Other stellar evolution codes, such as SSE (ascl:1303.015), can also be used. TRES is written in the AMUSE (ascl:1107.007) software framework.

TreeFrog reads in particle IDs information between various structure catalogs and cross matches catalogs, assuming that particle IDs are unique and constant across snapshots. Though it is built as a cross correlator (in that it can match particles across several different catalogs), its principle use is as halo merger tree builder. TreeFrog produces links between objects found at different snapshots (or catalogs) and uses several possible functions to evaluate the merit of a link between one object at a given snapshot (or in a given catalog) to another object in a previous snapshot (or different catalog). It can also produce a full graph. The code utilizes MPI and OpenMP. It is optimzed for reading VELOCIraptor (ascl:1911.020) output but can also read output from other structure finders such as AHF (ascl:1102.009).

TreeCorr efficiently computes two-point correlation functions. It can compute correlations of regular number counts, weak lensing shears, or scalar quantities such as convergence or CMB temperature fluctuations. Two-point correlations may be auto-correlations or cross-correlations, including any combination of shear, kappa, and counts. Two-point functions can be done with correct curved-sky calculation using RA, Dec coordinates, on a Euclidean tangent plane, or in 3D using RA, Dec and a distance. The front end is written in Python, which can be used as a Python module or as a standalone executable using configuration files; the actual computation of the correlation functions is done in C++ using ball trees (similar to kd trees), making the calculation extremely efficient, and when available, OpenMP is used to run in parallel on multi-core machines.

The TraP is a pipeline for detecting and responding to transient and variable sources in a stream of astronomical images. Images are initially processed using a pure-Python source-extraction package, PySE (ascl:1805.026), which is bundled with the TraP. Source positions and fluxes are then loaded into a SQL database for association and variability detection. The database structure allows for estimation of past upper limits on newly detected sources, and for forced fitting of previously detected sources which have since dropped below the blind-extraction threshold. Developed with LOFAR data in mind, the TraP has been used with data from other radio observatories.

TRANSPHERE is a simple dust continuum radiative transfer code for spherically symmetric circumstellar envelopes. It handles absorption and re-emission and computes the dust temperature self-consistently; it does not, however, deal with scattering. TRANSPHERE uses a variable eddington factor method for the radiative transfer. The RADMD code (ascl:1108.016) is more versatile, but for a spherically symmetric problem for which scattering is of much concern, it may be easier to use a simple code such as TRANSPHERE. Please note that this code has not been updated since 2006.

A self-organizing map (SOM) can be used to identify planetary candidates from Kepler and K2 datasets with accuracies near 90% in distinguishing known Kepler planets from false positives. TransitSOM classifies a Kepler or K2 lightcurve using a self-organizing map (SOM) created and pre-trained using PyMVPA (ascl:1703.009). It includes functions for users to create their own SOMs.

TransitFit fits exoplanetary transit light-curves for transmission spectroscopy studies. The code uses nested sampling for efficient and robust multi-epoch, multi-wavelength fitting of transit data obtained from one or more telescopes. TransitFit allows per-telescope detrending to be performed simultaneously with parameter fitting, including the use of user-supplied detrending alogorithms. Host limb darkening can be fitted either independently ("uncoupled") for each filter or combined ("coupled") using prior conditioning from the PHOENIX stellar atmosphere models. For this, TransitFit uses the Limb Darkening Toolkit (ascl:1510.003) together with filter profiles, including user-supplied filter profiles.

Transit calculates the transmission or emission spectrum of a planetary atmosphere with application to extrasolar-planet transit and eclipse observations, respectively. It computes the spectra by solving the one-dimensional line-by-line radiative-transfer equation for an atmospheric model.

Transit Clairvoyance uses Artificial Neural Networks (ANNs) to predict the most likely short period transiters to have additional transiters, which may double the discovery yield of the TESS (Transiting Exoplanet Survey Satellite). Clairvoyance is a simple 2-D interpolant that takes in the number of planets in a system with period less than 13.7 days, as well as the maximum radius amongst them (in Earth radii) and orbital period of the planet with maximum radius (in Earth days) in order to predict the probability of additional transiters in this system with period greater than 13.7 days.

We present an IDL graphical user interface-driven software package designed for the analysis of extrasolar planet transit light curves. The Transit Analysis Package (TAP) software uses Markov Chain Monte Carlo (MCMC) techniques to fit light curves using the analytic model of Mandel and Agol (2002). The package incorporates a wavelet based likelihood function developed by Carter and Winn (2009) which allows the MCMC to assess parameter uncertainties more robustly than classic chi-squared methods by parameterizing uncorrelated "white" and correlated "red" noise. The software is able to simultaneously analyze multiple transits observed in different conditions (instrument, filter, weather, etc). The graphical interface allows for the simple execution and interpretation of Bayesian MCMC analysis tailored to a user's specific data set and has been thoroughly tested on ground-based and Kepler photometry. AutoKep provides a similar GUI for the preparation of Kepler MAST archive data for analysis by TAP or any other analysis software. This paper describes the software release and provides instructions for its use.

The Sloan Digital Sky Survey (SDSS) produces large amounts of data daily. transfer, written in Python, provides the effective automation needed for daily data transfer operations and management and operates essentially free of human intervention. This package has been tested and used successfully for several years.

Tranquillity creates an observing screen looking toward a black hole - accretion disk system, seeks the object, then searches and locates its contour. Subsequently, it attempts to locate the first Einstein "echo" ring and its location. Finally, it collates the retrieved information and draws conclusions; these include the accretion disk level inclination compared to the line of sight and the main disk and the first echo median. The displacement, and thus the divergence of the latter two, is the required information in order to construct the divergence plots. Other programs can later on automatically read these plots and provide estimations of the central black hole spin.

TRAN_K2 searches for periodic transits in the photometric time series of the Kepler K2 mission. The search is made by considering stellar variability and instrumental systematics. TRAN_K2 is written in Fortran 77 and has a single input parameter file that can be edited by the user depending on the type of run and parameter ranges to be used.

TRADES (TRAnsits and Dynamics of Exoplanetary Systems) simultaneously fits observed radial velocities and transit times data to determine the orbital parameters of exoplanetary systems from observational data. It uses a dynamical simulator for N-body systems that also fits the available data during the orbital integration and determines the best combination of the orbital parameters using grid search, χ2 minimization, genetic algorithms, particle swarm optimization, and bootstrap analysis.

TPZ, a parallel code written in python, produces robust and accurate photometric redshift PDFs by using prediction tree and random forests. The code also produces ancillary information about the sample used, such as prior unbiased errors estimations (giving an estimation of performance) and a ranking of importance of variables as well as a map of performance indicating where extra training data is needed to improve overall performance. It is designed to be easy to use and a tutorial is available.

TPM carries out collisionless (dark matter) cosmological N-body simulations, evolving a system of N particles as they move under their mutual gravitational interaction. It combines aspects of both Tree and Particle-Mesh algorithms. After the global PM forces are calculated, spatially distinct regions above a given density contrast are located; the tree code calculates the gravitational interactions inside these denser objects at higher spatial and temporal resolution. The code is parallel and uses MPI for message passing.

Visibilities from radio interferometers have not traditionally been used to study the fast transient sky. Millisecond transients (e.g., fast radio bursts) and periodic sources (e.g., pulsars) have been studied with single-dish radio telescopes and a software stack developed over the past few decades. tpipe is an initial attempt to develop the fast transient algorithms for visibility data. Functions exist for analysis of visibilties, such as reading data, flagging data, applying interferometric gain calibration, and imaging. These functions are given equal footing as time-domain techniques like filters and dedispersion. tpipe has been largely superseded by rtpipe (ascl:1706.002).

TPI computes the gravitational dynamics of particles orbiting a supermassive black hole (SBH). A distinction is made to two types of particles: test particles and field particles. Field particles are assumed to move in quasi-static Keplerian orbits around the SBH that precess due to the enclosed mass (Newtonian 'mass precession') and relativistic effects. Otherwise, field-particle-field-particle interactions are neglected. Test particles are integrated in the time-dependent potential of the field particles and the SBH. Relativistic effects are included in the equations of motion (including the effects of SBH spin), and test-particle-test-particle interactions are neglected.

tpfplotter creates a TESS Target Pixel File of a source, overplotting the aperture mask used by the SPOC pipeline and the Gaia catalog to check for possible contaminations within the aperture. The software can create 1-column paper-ready figures, overplotting the Gaia DR2 catalog to the TESS Target Pixel Files, and can create plots for any target observed by TESS. tpfplotter can search by coordinates if the TIC number of the source is not known.

The PLUTO CLOUDY Interface (TPCI) combines the <a href="https://ascl.net/1010.045">PLUTO</a> (ascl:1010.045) and <a href="https://ascl.net/9910.001">CLOUDY</a> (ascl.net:9910.001) simulation codes to simulate hydrodynamic evolution under irradiation from a source. The code solves the photoionization and chemical network of the 30 lightest elements. By combining an equilibrium photoionization solver with a general MHD code, TPCI provides an advanced simulation tool applicable to a variety of astrophysical problems.

TP2VIS creates visibilities from a single dish cube; the TP visibilities can be combined with the interferometric visibilities in a joint deconvolution using, for example, CASA's tclean() method. TP2VIS requires CASA 5.4 (ascl:1107.013) or above.

Toyz is a python web framework that allows scientists to interact with large images and data sets stored on a remote server. A web application is run on the server containing the data and clients are run from web browsers on the user's computer. Toyz displays large FITS images and also renders any image format supported by Pillow (a fork of the Python Imaging Library), contains a GUI to interact with linked plots, and offers a customizable framework that allows students and researchers to create their own work spaces inside a Toyz environment. Astro-Toyz extends the features of the Toyz image viewer, allowing users to view world coordinates and align images based on their WCS.

TORUS is a flexible radiation transfer and radiation-hydrodynamics code. The code has a basic infrastructure that includes the AMR mesh scheme that is used by several physics modules including atomic line transfer in a moving medium, molecular line transfer, photoionization, radiation hydrodynamics and radiative equilibrium. TORUS is useful for a variety of problems, including magnetospheric accretion onto T Tauri stars, spiral nebulae around Wolf-Rayet stars, discs around Herbig AeBe stars, structured winds of O supergiants and Raman-scattered line formation in symbiotic binaries, and dust emission and molecular line formation in star forming clusters. The code is written in Fortran 2003 and is compiled using a standard Gnu makefile. The code is parallelized using both MPI and OMP, and can use these parallel sections either separately or in a hybrid mode.

torchmfbd carries out multi-object multi-frame blind deconvolution (MOMFBD) of point-like or extended objects, and is especially tailored to solar images. The code is built on PyTorch and provides a high-level interface for adding observations, defining phase diversity channels, and adding regularization. It can deal with spatially variant PSFs either by mosaicking the images or by defining a spatially variant PSF. torchmfbd supports smooth solutions and solutions based on the ℓ 1 penalization of the isotropic undecimated wavelet transform of the object, and regularizations are easily extendable. The code also includes an API and a configuration file.

Torch simulates coupled gas and N-body dynamics in astrophysical systems such as newly forming star clusters. It combines the FLASH (ascl:1010.082) code for gas dynamics and the ph4 code for direct N-body evolution via the AMUSE framework.

topoaccel calculates topological acceleration for several of the S^3 quotient spaces considered 'regular', in that they have a Platonic solid as one of their fundamental domain shapes, and are globally homogeneous. The topoaccel scripts can be run using the free-licensed software package Maxima (https://maxima.sourceforge.io/documentation.html).

TOPCAT is an interactive graphical viewer and editor for tabular data. Its aim is to provide most of the facilities that astronomers need for analysis and manipulation of source catalogues and other tables, though it can be used for non-astronomical data as well. It understands a number of different astronomically important formats (including FITS and VOTable) and more formats can be added. It offers a variety of ways to view and analyse tables, including a browser for the cell data themselves, viewers for information about table and column metadata, and facilities for 1-, 2-, 3- and higher-dimensional visualisation, calculating statistics and joining tables using flexible matching algorithms. Using a powerful and extensible Java-based expression language new columns can be defined and row subsets selected for separate analysis. Table data and metadata can be edited and the resulting modified table can be written out in a wide range of output formats. It is a stand-alone application which works quite happily with no network connection. However, because it uses Virtual Observatory (VO) standards, it can cooperate smoothly with other tools in the VO world and beyond, such as VODesktop, Aladin and ds9. Between 2006 and 2009 TOPCAT was developed within the AstroGrid project, and is offered as part of a standard suite of applications on the AstroGrid web site, where you can find information on several other VO tools. The program is written in pure Java and available under the GNU General Public Licence. It has been developed in the UK within the <a href="http://ascl.net/1110.012">Starlink</a> and AstroGrid projects, and under PPARC and STFC grants. Its underlying table processing facilities are provided by STIL.

This collection of Mathematica scripts and one MATLAB code provides a toolkit for visualizing the dynamical structures of the Circular Restricted Three-Body Problem (CR3BP). The Mathematica codes generate zero-velocity curves, effective potential energy surfaces and trajectories for the test particle in different perturbation settings. The included MATLAB script specifically calculates and visualizes the Hill region, defining the boundaries of allowable motion for a given Jacobi constant. These codes are aimed as an introduction to the study of the CR3BP and celestial mechanics as a whole.

tomso loads and saves input and output files for and from stellar evolution and oscillation codes. The functions are bundled together in modules that correspond with a specific stellar evolution code, stellar oscillation code, or file format. tomso supports the FGONG format and various input/output files for ADIPLS (ascl:1109.002), GYRE (ascl:1308.010), MESA (ascl:1010.083), and STARS (ascl:1107.008). tomso's main purpose is to provide a compact interface for manipulating input and output data in these formats and simplify research that uses them.

TomograPy is an open-source software freely available on the Python Package Index that can perform fast tomographic inversions that scale linearly with the number of measurements, linearly with the length of the reconstruction cube (and not the number of voxels) and linearly with the number of cores and can use data from different sources and with a variety of physical models. For performance, TomograPy uses a parallelized-projection algorithm. It relies on the World Coordinate System standard to manage various data sources. A variety of inversion algorithms are provided to perform the tomographic-map estimation. A test suite is provided along with the code to ensure software quality. Since it makes use of the Siddon algorithm it is restricted to rectangular parallelepiped voxels but the spherical geometry of the corona can be handled through proper use of priors.

The TOM Toolkit combines a flexible, searchable database of all information related to a scientific research project, with an observation and data analysis control system, and communication and data visualization tools. This Toolkit includes a fully operational TOM (Target and Observation Manager) system in addition to a range of optional tools for specific tasks, including interfaces to widely-used observing facilities and data archives and data visualization tools. With TOM Toolkit, project teams can develop and customize a system for their own science goals, without needing specialist expertise in databasing.

The toise framework estimates the sensitivity of natural-medium neutrino detectors such as IceCube-Gen2 to sources of high-energy astrophysical neutrinos. It uses parameterizations of a detector's fiducial area or volume, selection efficiency, energy resolution, angular resolution, and event classification efficiency to convert (surface) neutrino fluxes into mean event rates in bins of observable space. These are then used to estimate statistical quantities of interest, <i>e.g.</i>, the median sensitivity to some flux (<i>i.e.</i>, 90% upper limit assuming the true flux is zero) or the median discovery potential (<i>i.e.</i>, the flux level at which the null hypothesis would be rejected at 5 sigma in 50% of realizations).