Paper: astro-ph/0506738
Date: Wed, 29 Jun 2005 20:00:31 GMT (134kb)

Title: Survey for Transiting Extrasolar Planets in Stellar Systems. II.
Spectrophotometry and Metallicities of Open Clusters

Authors: J. L. Marshall, Christopher J. Burke, D. L. DePoy, Andrew Gould, and
Juna A. Kollmeier (The Ohio State University)
Comments: 38 pages, including 12 figures. Accepted for publication in AJ
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We present metallicity estimates for seven open clusters based on
spectrophotometric indices from moderate-resolution spectroscopy. Observations
of field giants of known metallicity provide a correlation between the
spectroscopic indices and the metallicity of open cluster giants. We use \chi^2
analysis to fit the relation of spectrophotometric indices to metallicity in
field giants. The resulting function allows an estimate of the target-cluster
giants' metallicities with an error in the method of \pm0.08 dex. We derive the
following metallicities for the seven open clusters: NGC 1245,
[m/H]=-0.14\pm0.04; NGC 2099, [m/H]=+0.05\pm0.05; NGC 2324, [m/H]=-0.06\pm0.04;
NGC 2539, [m/H]=-0.04\pm0.03; NGC 2682 (M67), [m/H]=-0.05\pm0.02; NGC 6705,
[m/H]=+0.14\pm0.08; NGC 6819, [m/H]=-0.07\pm0.12. These metallicity estimates
will be useful in planning future extra-solar planet transit searches since
planets may form more readily in metal-rich environments.

\\ ( http://arXiv.org/abs/astro-ph/0506738 , 134kb)

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Paper: astro-ph/0506743
Date: Wed, 29 Jun 2005 21:31:43 GMT (67kb)

Title: Spitzer Observations of G Dwarfs in the Pleiades: Circumstellar Debris
Disks at 100 Myr Age

Authors: J.R. Stauffer, L. Rebull (Spitzer Science Center), J. Carpenter, L.
Hillenbrand (Caltech), D. Backman (NASA-Ames), M.R. Meyer, J.S. Kim, M.D.
Silverstone and E. Young (Steward Observatory, UofA), D.C. Hines (SSI), D.R.
Soderblom (STScI), E.E. Mamajek (Harvard-Smithsonian CfA), P. Morris (SSC),
J. Bouwman (MPIA-Heidelberg), S.E. Strom (NOAO)
Comments: 32 postscript pages including 8 figues and 3 tables. To appear in the
Astronomical Journal
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Fluxes and upper limits in the wavelength range from 3.6 to 70 microns from
the Spitzer Space Telescope are provided for twenty solar-mass Pleiades
members. One of these stars shows a probable mid-IR excess and two others have
possible excesses, presumably due to circumstellar debris disks. For the star
with the largest, most secure excess flux at MIPS wavelengths, HII1101, we
derive Log(L[dust]/L[Sun]) ~ -3.8 and an estimated debris disk mass of 4.2 x
10^-5 M(Earth) for an assumed uniform dust grain size of 10 microns If the
stars with detected excesses are interpreted as stars with relatively recent,
large collision events producing a transient excess of small dust particles,
the frequency of such disk transients is about ~ 10 % for our ~ 100 Myr,
Pleiades G dwarf sample. For the stars without detected 24-70 micron excesses,
the upper limits to their fluxes correspond to approximate 3 sigma upper limits
to their disk masses of 6 x 10^-6 M(Earth) using the MIPS 24 micron upper
limit, or 2 x 10^-4 M(Earth) using the MIPS 70 micron limit. These upper limit
disk masses (for "warm" and "cold" dust, respectively) are roughly consistent,
but somewhat lower than, predictions of a heuristic model for the evolution of
an "average" solar-mass star's debris disk based on extrapolation backwards in
time from current properties of the Sun's Kuiper belt.

\\ ( http://arXiv.org/abs/astro-ph/0506743 , 67kb)