Bibcode
Christou, A. A.; Beisker, W.; Casas, R.; Schnabel, C.; Massallé, A.; Díaz-Martin, M. C. Instituto de Astrofísica de Canarias, C/ Vía Láctea s/n, E-38205 La Laguna, Tenerife, Spain) [Predoc Other]; Assafin, M.; Braga-Ribas, F.; Eppich, P.; Bath, K.-L.; Tsamis, V.; Tigani, K.; Farmakopoulos, A.; Douvris, A.; Liakos, A.; Eberle, A.; Farago, O.
Bibliographical reference
Astronomy and Astrophysics, Volume 556, id.A118, 8 pp.
Advertised on:
8
2013
Journal
Citations
3
Refereed citations
3
Description
Aims: Occultations of bright stars by planets provide information
on the state of their atmospheres. An occultation of the bright star 45
Capricornii (HIP 107302) by Jupiter occurred on the night of 3/4 August
2009. Methods: The event was observed at multiple sites in
Europe, Africa and South America and with instruments ranging in
aperture from 0.4 m to 2.2 m. All observations, except one, were carried
out in methane absorption bands centred at 0.89 μm and 2.2 μm to
minimise the planetary contribution to the measured stellar flux.
Following the application of special post-processing techniques,
differential photometry was performed. Nearby bright satellites were
used as reference sources. Results: Fifteen lightcurves were
obtained. The photometric time series for fourteen of these were fitted
to a model atmosphere of constant scale height (H). Estimates of H for
most lightcurves lie within the range 20-30 km with an inverse-variance
weighted mean of 23.6 ± 0.4 km, in good agreement with previous
works. A comparison between half-light times at ingress and at egress
implies an astrometric offset of 10-15 mas in Jupiter's position
relative to the star. Five lightcurves - two for ingress and three for
egress - were numerically inverted into profiles of pressure versus
temperature. Isothermal, mutually consistent behaviour is observed
within the pressure range 3-10 μbar. The inferred temperature of 165
± 5 K is consistent with, but slightly higher than, that measured
by the Galileo Probe at 5° S latitude in 1995 at the same pressure
level. Subtraction of isothermal models for nine cases show the presence
of at least one, and possibly two, non-isothermal layers a few tens of
km below the half-light datum. Their altitudes are similar to those of
features previously reported during the occultation of HIP 9369 in 1999.
Our temperature estimates are consistent with the expected small
magnitude of the perturbation of the atmosphere following the impact
event on Jupiter in July 2009.
Data for the lightcurves are only available at the CDS via anonymous ftp
to http://cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/556/A118