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- Devogèle, Maxime, et al.
(författare)
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New Evidence for a Physical Link between Asteroids (155140) 2005 UD and (3200) Phaethon
- 2020
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Ingår i: The Planetary Science Journal. - : Institute of Physics (IOP). - 2632-3338. ; 1:1
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Tidskriftsartikel (refereegranskat)abstract
- In 2018, the near-Earth object (155140) 2005 UD (hereafter UD) experienced a close fly by of the Earth. We present results from an observational campaign involving photometric, spectroscopic, and polarimetric observations carried out across a wide range of phase angles (07–88°). We also analyze archival NEOWISE observations. We report an absolute magnitude of H V = 17.51 ± 0.02 mag and an albedo of p V = 0.10 ± 0.02. UD has been dynamically linked to Phaethon due their similar orbital configurations. Assuming similar surface properties, we derived new estimates for the diameters of Phaethon and UD of D = 5.4 ± 0.5 km and D = 1.3 ± 0.1 km, respectively. Thermophysical modeling of NEOWISE data suggests a surface thermal inertia of and regolith grain size in the range of 0.9–10 mm for UD and grain sizes of 3–30 mm for Phaethon. The light curve of UD displays a symmetric shape with a reduced amplitude of Am(0) = 0.29 mag and increasing at a linear rate of 0.017 mag/° between phase angles of 0° and ~25°. Little variation in light-curve morphology was observed throughout the apparition. Using light-curve inversion techniques, we obtained a sidereal rotation period P = 5.235 ± 0.005 hr. A search for rotational variation in spectroscopic and polarimetric properties yielded negative results within observational uncertainties of ~10% μm−1 and ~16%, respectively. In this work, we present new evidence that Phaethon and UD are similar in composition and surface properties, strengthening the arguments for a genetic relationship between these two objects.
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| 2. |
- Fedorets, Grigori, et al.
(författare)
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Optimizing asteroid orbit computation for Gaia with normal points
- 2018
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 620
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Tidskriftsartikel (refereegranskat)abstract
- Context. In addition to the systematic observations of known solar-system objects (SSOs), a continuous processing of new discoveries requiring fast responses is implemented as the short-term processing of Gaia SSO observations, providing alerts for ground-based follow-up observers. The common independent observation approach for the purposes of orbit computation has led to unrealistically large ephemeris prediction uncertainties when processing real Gaia data. Aims. We aim to provide ground-based observers with a cloud of sky positions that is shrunk to a fraction of the previously expected search area by making use of the characteristic features of Gaia astrometry. This enhances the efficiency of Gaia SSO follow-up network and leads to an increased rate of asteroid discoveries with reasonably constrained orbits with the help of ground-based follow-up observations of Gaia asteroids. Methods. We took advantage of the separation of positional errors of Gaia S SO observations into a random and systematic component. We treated the Gaia observations in an alternative way by collapsing up to ten observations that correspond to a single transit into a single so-called normal point. We implemented this input procedure in the Gaia S SO short-term processing pipeline and the OpenOrb software. Results. We validate our approach by performing extensive comparisons between the independent observation and normal point input methods and compare them to the observed positions of previously known asteroids. The new approach reduces the ephemeris uncertainty by a factor of between three and ten compared to the situation where each point is treated as a separate observation. Conclusions. Our new data treatment improves the sky prediction for the Gaia SSO observations by removing low-weight orbital solutions. These solutions originate from excessive curvature of observations, introduced by short-term variations of Gaia attitude on the one hand, and, as a main effect, shrinking of systematic error bars in the independent observation case on the other hand. We anticipate that a similar approach may also be utilized in a situation where observations from a single observatory dominate.
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| 3. |
- Hobbs, David, et al.
(författare)
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All-sky visible and near infrared space astrometry
- 2021
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Ingår i: Experimental Astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 51:3, s. 783-843
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Tidskriftsartikel (refereegranskat)abstract
- The era of all-sky space astrometry began with the Hipparcos mission in 1989 and provided the first very accurate catalogue of apparent magnitudes, positions, parallaxes and proper motions of 120 000 bright stars at the milliarcsec (or milliarcsec per year) accuracy level. Hipparcos has now been superseded by the results of the Gaia mission. The second Gaia data release contained astrometric data for almost 1.7 billion sources with tens of microarcsec (or microarcsec per year) accuracy in a vast volume of the Milky Way and future data releases will further improve on this. Gaia has just completed its nominal 5-year mission (July 2019), but is expected to continue in operations for an extended period of an additional 5 years through to mid 2024. Its final catalogue to be released ∼ 2027, will provide astrometry for ∼ 2 billion sources, with astrometric precisions reaching 10 microarcsec. Why is accurate astrometry so important? The answer is that it provides fundamental data which underpin much of modern observational astronomy as will be detailed in this White Paper. All-sky visible and Near-InfraRed (NIR) astrometry with a wavelength cutoff in the K-band is not just focused on a single or small number of key science cases. Instead, it is extremely broad, answering key science questions in nearly every branch of astronomy while also providing a dense and accurate visible-NIR reference frame needed for future astronomy facilities.
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