arXiv subjects

Milagros Colazo

Publications and source records attributed to Milagros Colazo.

5 recordsLinked to original sources

arXiv2025

Asteroid phase curve modeling with empirical correction for shape and viewing geometry

We present a novel empirical method for correcting asteroid phase curves for rotational and geometrical effects using precomputed spin-and-shape models. Our approach normalizes sparse photometric data to a pole-on geometry, enabling consistent phase-curve fitting across apparitions. We fit both the H,G1,G2 and H,G12 phase functions to the normalized data. We also numerically derive new constraints on parameter ranges that ensure physically meaningful solutions. These constraints are based on the requirement that the reduced magnitude must monotonically decrease with phase angle and remain within plausible slope bounds. Compared to earlier bounds, our new constraints are more permissive. We also compare derivative-based and derivative-free optimization methods, highlighting convergence issues with the HG12 function and offering mitigation strategies. We applied our method to over 25,000 asteroids observed by the ATLAS survey, demonstrating its usability. The new method enables the selection of the preferred spin-and-shape solution based on either statistical phase-curve model selection criteria and/or physically motivated constraints on the phase-curve shape.

astro-ph.EP↗

arXiv2025

Historical Surveys to Rubin First Look: Absolute Colors of trans-Neptunian objects

We present a comprehensive photometric study of trans-Neptunian objects (TNOs) by combining data from SDSS, Col-OSSOS, DES, and the recent Rubin First Look (RFL) data. Our database comprises 43 677 measurements in the u, g, r, i, and z filters, from which we derived 2 193 phase curves for 781 unique objects. From these data, we computed 2 542 absolute color measurements for 633 objects, allowing a statistical characterization of phase coloring effects. Our results show correlations between colors at opposition and their variation with phase angle, indicating that redder (bluer) objects tend to become redder (bluer) as the phase angle increases. With a larger sample and the application of phase corrections, the colors show no strong bimodality nor correlation with orbital parameters. Notably, our dataset includes the first photometric measurements from Rubin Observatory during RFL, covering eight objects: five newly discovered TNOs and three previously known. These early LSST observations occupy sparsely sampled regions of parameter space, particularly at faint magnitudes, highlighting the discovery and characterization potential of the full survey.

astro-ph.EP↗

arXiv2025

A catalog of near-IR absolute magnitudes of Solar System small bodies

Context. Phase curves of small bodies are useful tools to obtain their absolute magnitudes and phase coefficients. The former relates to the object's apparent brightness, while the latter relates to how the light interacts with the surface. Data from multi-wavelength photometric surveys, which usually serendipitously observe small bodies, are becoming the cornerstone of large statistical studies of the Solar System. Nevertheless, to our knowledge, all studies have been carried out in visible wavelengths. Aims. We aim to provide the first catalog of absolute magnitudes in near-infrared filters (Y, J, H, and K). We will study the applicability of a non-linear model to these data and compare it with a simple linear model. Methods. We compute the absolute magnitudes using two photometric models: the HG* 12 and the linear model. We employ a combination of Bayesian inference and Monte Carlo sampling to calculate the probability distributions of the absolute magnitudes and their corresponding phase coefficients. We use the combination of four near-infrared photometric catalogs to create our input database. Results. We produced the first catalog of near-infrared magnitudes. We obtained absolute magnitudes for over 10 000 objects (with at least one absolute magnitude measured), with about 180 objects having four absolute magnitudes. We confirmed that a linear model that fits the phase curves produces accurate results. Since a linear behavior well describes the curves, fitting to a restricted phase angle range (in particular, larger than 9.5 deg) does not substantially affect the results. Finally, we also detect a phase-coloring effect in the near-infrared, as observed in visible wavelengths for asteroids and trans-Neptunian objects.

astro-ph.EP↗

arXiv2021

Easy asteroid phase curve fitting for the Python ecosystem: Pyedra

A trending astronomical phenomenon to study is the variation in brightness of asteroids, caused by its rotation on its own axis, non-spherical shapes, changes of albedo along its surface and its position relative to the sun. The latter behaviour can be visualized on a "Phase Curve" (phase angle vs. reduced magnitude). To enable the comparison between several models proposed for this curve we present a Python package called Pyedra. Pyedra implements three phase-curve-models, and also providing capabilities for visualization as well as integration with external datasets. The package is fully documented and tested following a strict quality-assurance workflow, with a user-friendly programmatic interface. In future versions, we will include more models, and additional estimation of quantities derived from parameters like diameter, and types of albedo; as well as enabling correlation of information of physical and orbital parameters.

astro-ph.EP↗

arXiv2021

The determination of asteroid H and G phase function parameters using GAIA DR2

The Gaia mission will provide the scientific community with high-quality observations of asteroids of all categories. The second release of Gaia data (DR2) was published in 2018 and consisted of 22 months of observations of 14,099 known Solar System objects, mainly asteroids. The purpose of this work is to obtain a catalogue of phase function parameters (H and G) for all the asteroids that are observed by the Gaia mission, and which were published in DR2. For this purpose, we introduced an algorithm capable of building this catalogue from the magnitude and UTC epoch data present in the DR2 database. Since Gaia will never observe asteroids with a phase angle of 0° (corresponding with the opposition), but with phase angles higher than 10°, we added data from ground observations (corresponding to small phase angles) and thus improved the determination of the $H$ and $G$ parameters of the phase function. In this case, we also build a catalogue of the parameters of the H, G1, G2 phase function. We compared our results of the H, G function with those of the Astorb database and observed that the level of agreement is satisfactory.

astro-ph.EP↗