Paper: astro-ph/0510009
Date: Fri, 30 Sep 2005 21:09:40 GMT (62kb)

Title: Young Jupiters are Faint: New Models of the Early Evolution of Giant
Planets

Authors: J. J. Fortney, M. S. Marley, O. Hubickyj, P. Bodenheimer, J. J.
Lissauer

Categories: astro-ph

Comments: 5 pages, submitted to the proceedings of the workshop
"Ultralow-mass star formation and evolution" held in La Palma, Spain, during
June/July 2005 (Astronomical Notes special issue)
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Here we show preliminary calculations of the cooling and contraction of a 2
MJ planet. These calculations, which are being extended to 1-10 MJ, differ from
other published "cooling tracks" in that they include a core accretion-gas
capture formation scenario, the leading theory for the formation of gas giant
planets. We find that the initial post-accretionary intrinsic luminosity of the
planet is ~3 times less than previously published models which use arbitrary
initial conditions. These differences last a few tens of millions of years.
Young giant planets are intrinsically fainter than has been previously
appreciated. We also discuss how uncertainties in atmospheric chemistry and the
duration of the formation time of giant planets lead to challenges in deriving
planetary physical properties from comparison with tabulated model values.

\\ ( http://arXiv.org/abs/astro-ph/0510009 , 62kb)

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Paper: astro-ph/0510010
Date: Fri, 30 Sep 2005 21:44:39 GMT (901kb)

Title: The Circumstellar Environments of NML Cyg and the Cool Hypergiants

Authors: Michael T. Schuster, Roberta M. Humphreys and Massimo Marengo

Categories: astro-ph

Comments: 28 pages, 8 figures, accepted for publication in The Astronomical
Journal
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We present high-resolution HST WFPC2 images of compact nebulosity surrounding
the cool M-type hypergiants NML Cyg, VX Sgr and S Per. The powerful OH/IR
source NML Cyg exhibits a peculiar bean-shaped asymmetric nebula that is
coincident with the distribution of its H2O vapor masers. We show that NML
Cyg's circumstellar envelope is likely shaped by photo-dissociation from the
powerful, nearby association Cyg OB2 inside the Cygnus X superbubble. The OH/IR
sources VX Sgr and S Per have marginally resolved envelopes. S Per's
circumstellar nebula appears elongated in a NE/SW orientation similar to that
for its OH and H2O masers, while VX Sgr is embedded in a spheroidal envelope.
We find no evidence for circumstellar nebulosity around the intermediate-type
hypergiants rho Cas, HR 8752, HR 5171a, nor the normal M-type supergiant mu
Cep. We conclude that there is no evidence for high mass loss events prior to
500-1000 yrs ago for these four stars.

\\ ( http://arXiv.org/abs/astro-ph/0510010 , 901kb)