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The 2003 November 14 occultation by Titan of TYC 1343-1865-1: II. Analysis of light curves |
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| Authors: | A Zalucha A Fitzsimmons JL Elliot J Thomas-Osip HB Hammel VS Dhillon TR Marsh FW Taylor PGJ Irwin |
| Institution: | a Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Ave., Room 54-1721, Cambridge, MA 02139, USA b Department of Physics and Astronomy, Queen's University, Belfast BT7 1NN, Northern Ireland, UK c Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Ave., Room 54-422, Cambridge, MA 02139, USA d Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001, USA e Las Campanas Observatory, Observatories of the Carnegie Institute of Washington, Casilla 601, La Serena, Chile f Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA g Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK h Department of Physics, University of Warwick, Coventry CV4 7AL, UK i Atmospheric, Oceanic, and Planetary Physics, University of Oxford, Clarendon Laboratory, Parks Rd, Oxford, OX1 3PU, UK |
| Abstract: | We observed a stellar occultation by Titan on 2003 November 14 from La Palma Observatory using ULTRACAM with three Sloan filters: u′, g′, and i′ (358, 487, and 758 nm, respectively). The occultation probed latitudes 2° S and 1° N during immersion and emersion, respectively. A prominent central flash was present in only the i′ filter, indicating wavelength-dependent atmospheric extinction. We inverted the light curves to obtain six lower-limit temperature profiles between 335 and 485 km (0.04 and 0.003 mb) altitude. The i′ profiles agreed with the temperature measured by the Huygens Atmospheric Structure Instrument Fulchignoni, M., and 43 colleagues, 2005. Nature 438, 785–791] above 415 km (0.01 mb). The profiles obtained from different wavelength filters systematically diverge as altitude decreases, which implies significant extinction in the light curves. Applying an extinction model Elliot, J.L., Young, L.A., 1992. Astron. J. 103, 991–1015] gave the altitudes of line of sight optical depth equal to unity: 396±7 and 401±20 km (u′ immersion and emersion); 354±7 and 387±7 km (g′ immersion and emersion); and 336±5 and 318±4 km (i′ immersion and emersion). Further analysis showed that the optical depth follows a power law in wavelength with index 1.3±0.2. We present a new method for determining temperature from scintillation spikes in the occulting body's atmosphere. Temperatures derived with this method are equal to or warmer than those measured by the Huygens Atmospheric Structure Instrument. Using the highly structured, three-peaked central flash, we confirmed the shape of Titan's middle atmosphere using a model originally derived for a previous Titan occultation Hubbard, W.B., and 45 colleagues, 1993. Astron. Astrophys. 269, 541–563]. |
| Keywords: | Titan Occultations Atmospheres structure |
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