* Astronomy

Title: Visible and near-infrared observations of asteroid 2012 DA14 during its closest approach of February 15th, 2013
Authors: J. de Leon, J. L. Ortiz, N. Pinilla-Alonso, A. Cabrera-Lavers, A. Alvarez-Candal, N. Morales, R. Duffard, P. Santos-Sanz, J. Licandro, A. Perez-Romero, V. Lorenzi

Near-Earth asteroid 2012 DA14 made its closest approach on February 15th, 2013, when it passed at a distance of 27,700 km from the Earth's surface (inside the geosynchronous satellite ring). It was the first time an asteroid of moderate size was predicted to get that close to the Earth, becoming bright enough to permit a detailed study from ground based telescopes. Asteroid 2012 DA14 was poorly characterised before its closest approach. The main objective of this work was to obtain new and valuable data to better understand its physical properties, and to evaluate the effects of such a close approach on the object. We acquired data using several telescopes on four Spanish observatories: the 10.4m Gran Telescopio Canarias and the 3.6m Telescopio Nazionale Galileo, both in "El Roque de los Muchachos" Observatory (ORM, La Palma); the 2.2m CAHA telescope, in "Calar Alto2 Observatory (Almeria); the f/3 0.77m telescope in "La Hita" Observatory (Toledo); and the f/8 1.5m telescope in "Sierra Nevada" Observatory (Granada). We obtained visible and near-infrared colour photometry, visible spectra and time-series photometry. Visible spectra together with visible and near-infrared colour photometry of 2012 DA14 show that the object can be classified as an L-type asteroid, a not very common spectral type among the asteroid population. The time-series photometry indicates a rotational period around 9 hours, and the large amplitude of the variation suggests that the object is very elongated and irregular, with an equivalent diameter around 22m. We obtain an absolute magnitude of H_R = 24.1 ± 0.2, corresponding to 24.6 ± 0.2 in V. From the absolute photometry, together with some constraints on size and shape, we compute a geometric albedo of p_V = 0.34 ± 0.20.

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