PLUTO's ATMOSPHERE FROM STELLAR OCCULTATIONS IN 2012 AND 2013

• Published in: The Astrophysical journal Vol. 811; no. 1; pp. 1 - 20
• Main Authors: Dias-Oliveira, A, Sicardy, B, Lellouch, E, Vieira-Martins, R, Assafin, M, Camargo, J I B, Braga-Ribas, F, Gomes-Junior, A R, Benedetti-Rossi, G, Colas, F
• Format: Journal Article Web Resource
• Language: English
• Published: IOP Publishing 20.09.2015
• Subjects: Astrophysics - Earth and Planetary Astrophysics; Atmospherics; Aérospatiale, astronomie & astrophysique; Barometric pressure; Haze; Noise levels; Occultation; Physical, chemical, mathematical & earth Sciences; Physique, chimie, mathématiques & sciences de la terre; Pluto atmosphere; Space science, astronomy & astrophysics; Stellar occultation; Temperature profiles
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.1088/0004-637X/811/1/53

We analyze two multi-chord stellar occultations by Pluto that were observed on 2012 July 18th and 2013 May 4th, and respectively monitored from five and six sites. They provide a total of fifteen light curves, 12 of which were used for a simultaneous fit that uses a unique temperature profile, assuming a clear (no haze) and pure N2 atmosphere, but allowing for a possible pressure variation between the two dates. We find a solution that satisfactorily fits (i.e., within the noise level) all of the 12 light curves, providing atmospheric constraints between ~1190 km (pressure ~11 mu bar) and ~1450 km (pressure -0.1 mu bar) from Pluto's center. Alternative explanations like zonal winds or vertical compositional variations of the atmosphere are unable to explain the observed mesospheric negative thermal gradient.