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Title: LIMITS ON QUAOAR'S ATMOSPHERE

Here we present high cadence photometry taken by the Acquisition Camera on Gemini South, of a close passage by the {approx}540 km radius Kuiper belt object, (50000) Quaoar, of a r' = 20.2 background star. Observations before and after the event show that the apparent impact parameter of the event was 0.''019 {+-} 0.''004, corresponding to a close approach of 580 {+-} 120 km to the center of Quaoar. No signatures of occultation by either Quaoar's limb or its potential atmosphere are detectable in the relative photometry of Quaoar and the target star, which were unresolved during closest approach. From this photometry we are able to put constraints on any potential atmosphere Quaoar might have. Using a Markov chain Monte Carlo and likelihood approach, we place pressure upper limits on sublimation supported, isothermal atmospheres of pure N{sub 2}, CO, and CH{sub 4}. For N{sub 2} and CO, the upper limit surface pressures are 1 and 0.7 {mu}bar, respectively. The surface temperature required for such low sublimation pressures is {approx}33 K, much lower than Quaoar's mean temperature of {approx}44 K measured by others. We conclude that Quaoar cannot have an isothermal N{sub 2} or CO atmosphere. We cannot eliminate the possibilitymore » of a CH{sub 4} atmosphere, but place upper surface pressure and mean temperature limits of {approx}138 nbar and {approx}44 K, respectively.« less
Authors:
; ;  [1] ; ;  [2] ;  [3] ;  [4]
  1. Herzberg Institute of Astrophysics, 5071 W. Saanich Rd. Victoria, BCV9E 2E7 (Canada)
  2. Gemini Observatory, Northern Operations Center, 670 N A'ohoku Place, Hilo, HI 96720 (United States)
  3. Gemini Observatory, Southern Operations Center, c/o AURA, Casilla 603, La Serena (Chile)
  4. California Institute of Technology, Division of Geological and Planetary Sciences, 1200 E. California Blvd., Pasadena, CA 91101 (United States)
Publication Date:
OSTI Identifier:
22136525
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 774; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CAMERAS; CARBON MONOXIDE; ECLIPSE; IMPACT PARAMETER; LIMITING VALUES; MARKOV PROCESS; METHANE; MONTE CARLO METHOD; PHOTOMETRY; STARS; STELLAR ATMOSPHERES; SUBLIMATION