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|Title:||The Earth transiting the Sun as seen from Jupiter's moons: detection of an inverse Rossiter-McLaughlin effect produced by the opposition surge of the icy Europa||Authors:||MOLARO, Paolo
|Issue Date:||2015||Journal:||MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY||Number:||453||Issue:||2||First Page:||1684||Abstract:||We report on a multiwavelength observational campaign which followed the Earth's transit on the Sun as seen from Jupiter on 2014 January 2014. Simultaneous observations of Jupiter's moons Europa and Ganymede obtained with high accuracy radial velocity planetary searcher (HARPS) from La Silla, Chile and HARPS-N from La Palma, Canary Islands were performed to measure the Rossiter-McLaughlin effect due to the Earth's passage using the same technique successfully adopted for the 2012 Venus Transit. The expected modulation in radial velocities was of ≈20 cm s<SUP>-1</SUP> but an anomalous drift as large as ≈38 m s<SUP>-1</SUP>, i.e. more than two orders of magnitude higher and opposite in sign, was detected instead. The consistent behaviour of the two spectrographs rules out instrumental origin of the radial velocity drift and Birmingham Solar Oscillations Network observations rule out the possible dependence on the Sun's magnetic activity. We suggest that this anomaly is produced by the opposition surge on Europa's icy surface, which amplifies the intensity of the solar radiation from a portion of the solar surface centred around the crossing Earth which can then be observed as a sort of inverse Rossiter-McLaughlin effect. in fact, a simplified model of this effect can explain in detail most features of the observed radial velocity anomalies, namely the extensions before and after the transit, the small differences between the two observatories and the presence of a secondary peak closer to Earth passage. This phenomenon, observed here for the first time, should be observed every time similar Earth alignments occur with rocky bodies without atmospheres. We predict that it should be observed again during the next conjunction of Earth and Jupiter in 2026.||Acknowledgments:||Based on observations collected at the European Southern Observatory, Chile. Program ESO N. 092.C-0832(E) and at the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. Program A28 TAC-22. We warmly thank Steven Hale for providing the BiSON data of the days of our observations. Very useful discussions with Emilio Molinari, Gaspare Lo Curto, Claudio Lopresti and Gerardo Avila in different stages of this work are also acknowledged. We thank also Harutyunyan Avet for his competent assistance with the HARPS-N observations.||URI:||http://hdl.handle.net/20.500.12386/25072||URL:||https://academic.oup.com/mnras/article/453/2/1684/1144327||ISSN:||0035-8711||DOI:||10.1093/mnras/stv1721||Bibcode ADS:||2015MNRAS.453.1684M||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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checked on Sep 25, 2020
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