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Trio of Stellar Occultations by Pluto One Year Prior to New Horizons' Arrival

Pasachoff, Jay M. and Person, Michael J. and Bosh, Amanda S. and Sickafoose, Amanda A. and Zuluaga, Carlos and Kosiarek, Molly R. and Levine, Stephen E. and Osip, David J. and Schiff, Avery and Seeger, Christina H. and Babcock, Bryce A. and Rojo, Patricio and Servajean, Elise (2016) Trio of Stellar Occultations by Pluto One Year Prior to New Horizons' Arrival. Astronomical Journal, 151 (4). Art. No. 97. ISSN 0004-6256.

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We observed occultations by Pluto during a predicted series of events in 2014 July with the 1 m telescope of the Mt. John Observatory in New Zealand. The predictions were based on updated astrometry obtained in the previous months at the USNO, CTIO, and Lowell Observatories. We successfully detected occultations by Pluto of an R = 18 mag star on July 23 (14:23:32 ± 00:00:04 UTC to 14:25:30 ± 00:00:04 UTC), with a drop of 75% of the unocculted stellar signal, and of an R = 17 star on July 24 (11:41:30 ± 00:00:08 UTC to 11:43:28 ± 00:00:08 UTC), with a drop of 80% of the unocculted stellar signal, both with 20 s exposures with our frame-transfer Portable Occultation, Eclipse, and Transit System. Since Pluto had a geocentric velocity of 22.51 km s^(−1) on July 23 and 22.35 km s^(−1) on July 24, these intervals yield limits on the chord lengths (surface and lower atmosphere) of 2700 ± 130 km and 2640 ± 250 km, respectively, indicating that the events were near central, and therefore provide astrometric constraints on the prediction method. Our coordinated observations with the 4 m AAT in Australia on July 23 and the 6.5 m Magellan/Clay on Las Campanas, the 4.1 m Southern Astrophysical Research Telescope on Cerro Pachön, the 2.5 m DuPont on Las Campanas (LCO), the 0.6 m SARA-South on Cerro Tololo of the Southeastern Association for Research in Astronomy (SARA), the MPI/ESO 2.2 m on La Silla, and the 0.45 m Cerro Calán telescope and 0.36 telescope in Constitución in Chile on July 27 and 31, which would have provided higher-cadence observations for studies of Pluto's atmosphere, were largely foiled by clouds, but led to detection with the LCO Magellan/Clay and DuPont Telescopes on July 31 of the grazing occultation of a previously unknown 15th-magnitude star, completing the trio of occultations successfully observed and reported in this paper.

Item Type:Article
Related URLs:
URLURL TypeDescription
Pasachoff, Jay M.0000-0002-4372-4928
Kosiarek, Molly R.0000-0002-6115-4359
Additional Information:© 2016 The American Astronomical Society. Received 2015 May 18; accepted 2016 February 1; published 2016 March 24. This work was supported in part by NASA Planetary Astronomy grants to Williams College (NNX12AJ29G) and to MIT (NNX10AB27G), as well as grants from USRA (#8500-98-003) and NASA’s Ames Research Center (#NAS2-97-01) to Lowell Observatory. A.R.S. was supported by NSF grant AST-1005024 for the Keck Northeast Astronomy Consortium REU, with partial support from U.S. DoD’s ASSURE program. P.R. acknowledges support from FONDECYT through grant 1120299. A.A.S. acknowledges support from South Africa’s National Research Foundation. We thank Wesley Fraser for his prediction of the Quaoar occultations and to David Herald for forwarding the prediction of the Nix occultation. We thank Alan Gilmore for his expert assistance on site. We are grateful for the collaboration at Mt. John of Robert Lucas. We thank James Jenkins for operating the telescope at Cerro Calán. J.M.P. thanks Andrew Ingersoll and Caltech Planetary Sciences for hospitality and Visitor status.
Funding AgencyGrant Number
Universities Space Research Association (USRA)8500-98-003
Department of DefenseUNSPECIFIED
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1120299
National Research Foundation (South Africa)UNSPECIFIED
Subject Keywords:Kuiper belt objects: individual (Pluto, Quaoar) – planets and satellites: atmospheres – planets and satellites: individual (Nix) – occultations
Issue or Number:4
Record Number:CaltechAUTHORS:20160603-144600085
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Official Citation:Jay M. Pasachoff et al 2016 The Astronomical Journal 151 97
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:67655
Deposited By: Tony Diaz
Deposited On:04 Jun 2016 17:52
Last Modified:09 Mar 2020 13:18

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