Authors: Gomes-Júnior A. R., Assafin M., Braga-Ribas F., Benedetti-Rossi G., Morgado B. E., Camargo J. I. B., Vieira-Martins R., Desmars J., Sicardy B., Barry T., Campbell-White J., Fernández-Lajús E., Giles D., Hanna W., Hayamizu T., Hirose T., De Horta A., Horvat R., Hosoi K., Jehin E., Kerr S., Machado D. I., Mammana L. A., Maybour D., Owada M., Rahvar S., and Snodgrass C.
%F: AA(UNESP - São Paulo State University, Grupo de Dinâmica Orbital e Planetologia, Guaratinguetá - SP 12516-410, Brazil; Observatório do Valongo/UFRJ, Ladeira Pedro Antônio 43, Rio de Janeiro - RJ 20080-090, Brazil; Laboratório Interinstitucional de e-Astronomia - LIneA, Rua Gal. José Cristino 77, Rio de Janeiro - RJ 20921-400, Brazil 0000-0002-3362-2127), AB(Observatório do Valongo/UFRJ, Ladeira Pedro Antônio 43, Rio de Janeiro - RJ 20080-090, Brazil; Laboratório Interinstitucional de e-Astronomia - LIneA, Rua Gal. José Cristino 77, Rio de Janeiro - RJ 20921-400, Brazil), AC(Laboratório Interinstitucional de e-Astronomia - LIneA, Rua Gal. José Cristino 77, Rio de Janeiro - RJ 20921-400, Brazil; Federal University of Technology - Paraná (UTFPR / DAFIS), Rua Sete de Setembro, 3165, Curitiba, PR 80230-901, Brazil; Observatório Nacional/MCTI, R. General José Cristino 77, Rio de Janeiro - RJ 20921-400, Brazil; LESIA, Observatoire de Paris - Section Meudon, 5 Place Jules Janssen - 92195 Meudon Cedex, France), AD(Laboratório Interinstitucional de e-Astronomia - LIneA, Rua Gal. José Cristino 77, Rio de Janeiro - RJ 20921-400, Brazil; Observatório Nacional/MCTI, R. General José Cristino 77, Rio de Janeiro - RJ 20921-400, Brazil; LESIA, Observatoire de Paris - Section Meudon, 5 Place Jules Janssen - 92195 Meudon Cedex, France 0000-0002-4106-476X), AE(Laboratório Interinstitucional de e-Astronomia - LIneA, Rua Gal. José Cristino 77, Rio de Janeiro - RJ 20921-400, Brazil; Observatório Nacional/MCTI, R. General José Cristino 77, Rio de Janeiro - RJ 20921-400, Brazil 0000-0003-0088-1808), AF(Laboratório Interinstitucional de e-Astronomia - LIneA, Rua Gal. José Cristino 77, Rio de Janeiro - RJ 20921-400, Brazil; Observatório Nacional/MCTI, R. General José Cristino 77, Rio de Janeiro - RJ 20921-400, Brazil), AG(Observatório do Valongo/UFRJ, Ladeira Pedro Antônio 43, Rio de Janeiro - RJ 20080-090, Brazil; Laboratório Interinstitucional de e-Astronomia - LIneA, Rua Gal. José Cristino 77, Rio de Janeiro - RJ 20921-400, Brazil; Observatório Nacional/MCTI, R. General José Cristino 77, Rio de Janeiro - RJ 20921-400, Brazil), AH(Institut Poytechnique des Sciences Avancées IPSA, 63 boulevard de Brandebourg, Ivry-sur-Seine F-94200, France; Institut de Mécanique Céleste et de Calcul des Éphémérides, IMCCE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ Paris 06, Univ. Lille, 77 Av. Denfert-Rochereau, Paris F-75014, France), AI(LESIA, Observatoire de Paris - Section Meudon, 5 Place Jules Janssen - 92195 Meudon Cedex, France), AJ(Penrith Observatory, Western Sydney University, School of Computing, Engineering and Mathematics, Kingswood, NSW 2747, Australia), AK(SUPA, School of Science and Engineering, University of Dundee, Nethergate, Dundee DD1 4HN, UK 0000-0002-3913-3746), AL(Facultad de Ciencias Astronómicas y Geofísicas - Universidad Nacional de La Plata, Paseo del Bosque S/N - 1900, La Plata, Argentina; Instituto de Astrofísica de La Plata (CCT La Plata - CONICET/UNLP), Paseo del Bosque S/N - 1900, La Plata, Argentina), AM(Penrith Observatory, Western Sydney University, School of Computing, Engineering and Mathematics, Kingswood, NSW 2747, Australia), AN(Royal Astronomical Society of New Zealand, Occultation Section; International Occultation Timing Association (IOTA), Columbia Falls, MT 59912, USA), AO(Japan Occultation Information Network (JOIN), Japan), AP(Japan Occultation Information Network (JOIN), Japan), AQ(Penrith Observatory, Western Sydney University, School of Computing, Engineering and Mathematics, Kingswood, NSW 2747, Australia), AR(Penrith Observatory, Western Sydney University, School of Computing, Engineering and Mathematics, Kingswood, NSW 2747, Australia), AS(Japan Occultation Information Network (JOIN), Japan), AT(Space sciences, Technologies & Astrophysics Research (STAR) Institute, Université de Liège, Liège B-4000, Belgium), AU(Astronomical Association of Queensland, 5 Curtis Street, Pimpama QLD 4209, Australia; Occultation Section of the Royal Astronomical Society of New Zealand (RASNZ), Wellington PO Box 3181, New Zealand), AV(Polo Astronômico Casimiro Montenegro Filho/FPTI-BR, Avenida Tancredo Neves 6731, Foz do Iguaçu, PR 85867-900, Brazil; Universidade Estadual do Oeste do Paraná, Avenida Tarquínio Joslin dos Santos 1300, Foz do Iguaçu, PR 85870-650, Brazil), AW(Facultad de Ciencias Astronómicas y Geofísicas - Universidad Nacional de La Plata, Paseo del Bosque S/N - 1900, La Plata, Argentina; Complejo Astronómico El Leoncito (CASLEO), Av. España 1512 Sur, J5402DSP - San Juan - Argentina), AX(Penrith Observatory, Western Sydney University, School of Computing, Engineering and Mathematics, Kingswood, NSW 2747, Australia), AY(Japan Occultation Information Network (JOIN), Japan), AZ(Department of Physics, Sharif University of Technology, P.O. Box 11155-9161 Tehran, Iran 0000-0002-7084-5725), BA(Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ, UK)
Title: The first observed stellar occultations by the irregular satellite Phoebe (Saturn IX) and improved rotational period
Abstract: We report six stellar occultations by Phoebe (Saturn IX), an irregular satellite of Saturn, obtained between mid-2017 and mid-2019. The 2017 July 6 event was the first stellar occultation by an irregular satellite ever observed. The occultation chords were compared to a 3D shape model of the satellite obtained from Cassini observations. The rotation period available in the literature led to a sub-observer point at the moment of the observed occultations where the chords could not fit the 3D model. A procedure was developed to identify the correct sub-observer longitude. It allowed us to obtain the rotation period with improved precision compared to the currently known value from literature. We show that the difference between the observed and the predicted sub-observer longitude suggests two possible solutions for the rotation period. By comparing these values with recently observed rotational light curves and single-chord stellar occultations, we can identify the best solution for Phoebe's rotational period as 9.27365 ± 0.00002 h. From the stellar occultations, we also obtained six geocentric astrometric positions in the ICRS as realized by the Gaia DR2 with uncertainties at the 1-mas level.
Keywords: faint, observation, occultation, Phoebe, position, rotation, Saturn, star
Journal: Monthly Notices of the Royal Astronomical Society
Volume: 492
Pages: 770-781
Year: 2020
Bibliogaphic Code: 2020MNRAS.492..770G
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