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En la actualidad, estamos viviendo la revolución de los grandes relevamientos astronómicos. Gracias a estos telescopios, instalados en tierra u en órbita, contamos con millones de observaciones de cientos de miles de asteroides en un amplia variedad de filtros fotométricos. Es necesario que la comunidad científica esté preparada para analizar y sacar el máximo provecho de esta importante cantidad de datos. Más aún, es interesante la posibilidad de combinar observaciones específicas, llevadas a cabo por el/la astrónomo/a con los datos (usualmente esporádicos) de los grandes relevamientos. Es ampliamente conocido el brillo de los asteroides varía debido a diferentes factores. Dos características importantes que podemos estudiar de los asteroides son sus curvas de luz y curvas de fase. A partir de las curvas de luz, podemos estimar diferentes parámetros relacionados a las propiedades rotacionales del objeto, como por ejemplo su período de rotación, su forma y el la orientación del eje de rotación. Por otro lado, estudiando las curvas de fase, es posible obtener la magnitud absoluta del objeto a partir de la cual se puede estimar su diámetro. Debido a que los grandes telescopios se encuentran en funcionamiento durante una cantidad considerable de años, es posible obtener millones de observaciones de un mismo asteroide para diferentes épocas. A partir de estos datos fotométricos podemos construir curvas de fase para miles de objetos. El objetivo principal de este trabajo es desarrollar herramientas para la lectura, el procesamiento y el análisis de grandes volúmenes de datos. Además, se busca identificar el potencial de estas herramientas para “alertar” sobre objetos que merecen un estudio detallado con observaciones planificadas.

Context. We are in an era of large catalogs and, thus, statistical analysis tools for large data sets, such as machine learning, play a fundamental role. One example of such a survey is the Sloan Moving Object Catalog (MOC), which lists the astrometric and photometric information of all moving objects captured by the Sloan field of view. One great advantage of this telescope is represented by its set of five filters, allowing for taxonomic analysis of asteroids by studying their colors. However, until now, the color variation produced by the change of phase angle of the object has not been taken into account. Aims. In this paper, we address this issue by using absolute magnitudes for classification. We aim to produce a new taxonomic classification of asteroids based on their magnitudes that is unaffected by variations caused by the change in phase angle. Methods. We selected 9481 asteroids with absolute magnitudes of Hg, Hi and Hz, computed from the Sloan Moving Objects Catalog using the HG*12 system. We calculated the absolute colors with them. To perform the taxonomic classification, we applied a unsupervised machine learning algorithm known as fuzzy C-means. This is a useful soft clustering tool for working with data sets where the different groups are not completely separated and there are regions of overlap between them. We have chosen to work with the four main taxonomic complexes, C, S, X, and V, as they comprise most of the known spectral characteristics. Results. We classified a total of 6329 asteroids with more than 60% probability of belonging to the assigned taxonomic class, with 162 of these objects having been characterized by an ambiguous classification in the past. By analyzing the sample obtained in the plane Semimajor axis versus inclination, we identified 15 new V-type asteroid candidates outside the Vesta family region. © M. Colazo et al. 2022.

Context. We use the phase curves of small bodies to measure absolute magnitudes and, together with complementary theoretical and laboratory results, to understand the micro- and macroscopic properties of their surfaces. Although we can observe asteroids up to phase angles of about 30 deg, the range of phase angles covered by outer Solar System objects usually does not go further than 7−10 deg for centaurs and 2 deg for trans-Neptunian objects, and a linear relation between magnitude and phase angle may be assumed. Aims. We aim to directly compare data taken for objects in the inner Solar System (inside the orbit of Jupiter) with data for centaurs and trans-Neptunian objects. Methods. We use the SLOAN Moving Objects Catalog (MOC) data to construct phase curves restricted to phase angles of less than or equal to 7.5 deg, which is compatible with the angles observed for the trans-Neptunian and Centaur population. We assume a linear model for the photometric behavior to obtain absolute magnitudes and phase coefficients in the ugirz, V, and R filters. Results. We obtain absolute magnitudes in seven filters for over 4000 objects. Our comparison with outer Solar System objects suggests the surfaces have a common property: intrinsically redder objects become blue with increasing phase angle, while the opposite happens for intrinsically bluer objects. © A. Alvarez-Candal et al. 2022.

The view of the gamma-ray universe is being continuously expanded by space high-energy (HE) and ground-based very-high-energy (VHE) observatories. Yet, the angular resolution limitation still precludes a straightforward identification of these gamma-ray emitting sources. Radio observations are an effective tool for searching their possible counterparts at lower energies because the same population of relativistic electrons responsible for radio emission can also produce HE/VHE emission via inverse-Compton scattering. The Cygnus region is crowded by many gamma-ray sources, most of them remaining unidentified. In order to find possible counterparts to unidentified gamma-ray sources, we carried out a deep survey of the Cygnus region using the Giant Metrewave Radio Telescope at 610 and 325 MHz. We did a detailed search for counterparts in the error circle of HE/VHE sources. We report 36 radio sources found in the error ellipse of 15 HE sources, and 11 in those of VHE sources. Eight sources have a very steep radio spectral index a < -1.5, these are most likely to be pulsars and will be followed up for a periodicity search. Such a significant number of pulsar candidates within the error circle of HE/ VHE sources prompts a fresh look at the energetics and efficacy of pulsars and pulsar wind nebulae in this context.

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 consists 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 were observed during the Gaia mission and that were published in DR2. For this purpose, we introduce an algorithm capable of building this catalogue from the magnitude and UTC epoch data present in the DR2 data base. Because Gaia will never observe asteroids with a phase angle of 0° (corresponding to 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. We also built a catalogue of the parameters of the H, G1 andG2 phase function. We compared our results of the H, G functions with those of the Astorb data base and observed that the level of agreement is satisfactory. © 2021 The Author(s).