Context. Recent results for asteroid rotation periods from the TESS mission showed how strongly previous studies have underestimated the number of slow rotators, revealing the importance of studying those targets. For most slowly rotating asteroids (those with P > 12 h), no spin and shape model is available because of observation selection effects. This hampers determination of their thermal parameters and accurate sizes. Also, it is still unclear whether signatures of different surface material properties can be seen in thermal inertia determined from mid-infrared thermal flux fitting. Aims. We continue our campaign in minimising selection effects among main belt asteroids. Our targets are slow rotators with low light-curve amplitudes. Our goal is to provide their scaled spin and shape models together with thermal inertia, albedo, and surface roughness to complete the statistics. Methods. Rich multi-apparition datasets of dense light curves are supplemented with data from Kepler and TESS spacecrafts. In addition to data in the visible range, we also use thermal data from infrared space observatories (mainly IRAS, Akari and WISE) in a combined optimisation process using the Convex Inversion Thermophysical Model. This novel method has so far been applied to only a few targets, and therefore in this work we further validate the method itself. Results. We present the models of 16 slow rotators, including two updated models. All provide good fits to both thermal and visible data.The obtained sizes are on average accurate at the 5% precision level, with diameters found to be in the range from 25 to 145 km. The rotation periods of our targets range from 11 to 59 h, and the thermal inertia covers a wide range of values, from 2 to <400 J m−2 s−1∕2 K−1, not showing any correlation with the period. Conclusions. With this work we increase the sample of slow rotators with reliable spin and shape models and known thermal inertia by 40%. The thermal inertia values of our sample do not display a previously suggested increasing trend with rotation period, which mightbe due to their small skin depth.
Photometric observations of the nearly equal-mass binary near-Earth asteroid 2017 YE5 were carried out at the Observatório Astronômico do Sertão de Itaparica (OASI, Brazil) and at the Blue Mountains Observatory (BMO, Australia) between July and August 2018, shortly after it made a close approach to Earth in June 2018. These observations allowed to determine an orbital period of the system in good agreement with the result of the radar observations. Our results also indicate that the 2017 YE5 system is not fully locked in a synchronous spin-orbit resonance, as there is a possible asynchronous component or tumbling rotator in the system. Additional data obtained at the Observatorio Astronómico Nacional de San Pedro Mártir (OAN-SPM, Mexico) in August 2018 allowed to derive the colour indices and the low resolution spectrum, which indicate that the object has a very reddish surface similar to the outer Solar system objetcs. This is consistent with a dark albedo of about 3 per cent, derived from an effective diameter of the combined components and an absolute magnitude of 19.2. Infrared data obtained at the NASA’s IRTF exhibit a thermal emission in the 2.5 μm range for which a low albedo of 2-4 per cent was adjusted by applying a thermal model. Regarding to the taxonomic classification, we found that the 2017 YE5 is a D-type in the Bus-DeMeo taxonomy. Therefore, according to our results and considering that the 2017 YE5 system has a typical comet orbit (TJ = 2.87), we suggest that it is a dormant Jupiter-family binary comet.
The observation of NEOs allows us to study the physical properties of the smallest size bodies of our Solar System and help impose constraints on their origin and evolution. The solar phase curve is a very important tool to derive diverse physical properties of a small body so that we set up an observational campaign to derive the phase curve parameters (H, G1, G2) for a large number of NEOs. We present here the obtained phase curves for 12 NEOs, along with the rotation period for 2 of them and the V-R color for 4. The data was acquired mainly at the Astronomical Observatory of Sertão de Itaparica (Brazil), with some NEOs also observed at the Osservatorio di Campo Imperatore (Italy). Considering all the objects observed throughout our campaign we analyzed a homogeneous dataset of 30 NEOs along with data acquired by ATLAS (Asteroid Terrestrial-impact Last Alert System telescopes survey) for MB asteroids. The behavior in the phase space G1-G2 of 21,865 MBA and 103 NEOs was analyzed, separating the objects in intervals of albedos and sizes. From the large MB data set we found evidence that the distribution in the G1-G2 phase space has strong dependence not only on the albedo but also on the object’s size. This is particularly true for the smaller objects. The main result being that, on the contrary to what occurs with the MB larger objects, we are unable to estimate the albedo of a NEO from its phase curve parameters.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.