From: LARRY KLAES (ljk4_at_msn.com)
Date: Tue Oct 04 2005 - 19:45:26 UTC
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)
\\
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
\\
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)
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