SETI public: 3 Papers

• Previous message: LARRY KLAES: "SETI public: Cosmological Evolution of Hessence Dark Energy and Avoidance of the Big Rip"

Paper: astro-ph/0512352
Date: Wed, 14 Dec 2005 00:40:33 GMT (90kb)

Title: Upper limits on the hot Jupiter fraction in the field of NGC 7789

Authors: D.M.Bramich, Keith Horne

Comments: Submitted to MNRAS (04/11/2005)
\\
We describe a method of estimating the abundance of short-period extrasolar
planets based on the results of a photometric survey for planetary transits. We
apply the method to a 21-night survey with the 2.5m Isaac Newton Telescope of
\~32000 stars in a ~0.5 deg by 0.5 deg square field including the open cluster
NGC 7789. From the colour-magnitude diagram we estimate the mass and radius of
each star by comparison with the cluster main sequence. We search for injected
synthetic transits throughout the lightcurve of each star in order to determine
their recovery rate, and thus calculate the expected number of transit
detections and false alarms in the survey. We take proper account of the
photometric accuracy, time sampling of the observations and criteria
(signal-to-noise and number of transits) adopted for transit detection.
Assuming that none of the transit candidates found in the survey will be
confirmed as real planets, we place conservative upper limits on the abundance
of planets as a function of planet radius, orbital period and spectral type.

\\ ( http://arXiv.org/abs/astro-ph/0512352 , 90kb)

Paper: astro-ph/0512371
Date: Wed, 14 Dec 2005 18:29:41 GMT (49kb)

Title: Polycyclic Aromatic Hydrocarbons Orbiting HD 233517, an Evolved
Oxygen-Rich Red Giant

Authors: M. Jura (UCLA), J. Bohac, B. Sargent, W. J. Forrest, J. Green, D. M.
Watson (Rochester), G. C. Sloan (Cornell), F. Markwick-Kemper (Virginia), C.
H. Chen, J. Najita (NOAO)

Comments: 11 pages, 2 figures, ApJ Letters, in press
\\
We report spectra obtained with the Spitzer Space Telescope in the 5 to 35
micron range of HD 233517, an evolved K2 III giant with circumstellar dust. At
wavelengths longer than 13 microns, the flux is a smooth continuum that varies
approximately as frequency to the -5/3 power. For wavelengths shorter than 13
microns, although the star is oxygen-rich, PAH features produced by carbon-rich
species at 6.3 microns, 8.2 microns, 11.3 microns and 12.7 microns are detected
along with likely broad silicate emission near 20 microns. These results can be
explained if there is a passive, flared disk orbiting HD 233517. Our data
support the hypothesis that organic molecules in orbiting disks may be
synthesized in situ as well as being incorporated from the interstellar medium.

\\ ( http://arXiv.org/abs/astro-ph/0512371 , 49kb)

Astrophysics, abstract
astro-ph/0504649

From: Paul Estrada [view email]

Date (v1): Thu, 28 Apr 2005 20:20:34 GMT (67kb)
Date (revised v2): Tue, 10 May 2005 23:19:41 GMT (68kb)
Date (revised v3): Tue, 13 Dec 2005 21:42:03 GMT (107kb)

A Gas-poor Planetesimal Capture Model for the Formation of Giant Planet Satellite Systems

Authors: P. R. Estrada, I. Mosqueira

Comments: 45 pages, 11 figures, 3 appendices, uses rgfmacro.tex, accepted for publication to Icarus

Assuming that an unknown mechanism (e.g., gas turbulence) removes most of the subnebula gas disk in a timescale shorter than that for satellite formation, we develop a model for the formation of regular (and possibly at least some of the irregular) satellites around giant planets in a gas-poor environment. In this model, which follows along the lines of the work of Safronov et al. (1986), heliocentric planetesimals collide within the planet's Hill sphere and generate a circumplanetary disk of prograde and retrograde satellitesimals extending as far out as $\sim R_H/2$. At first, the net angular momentum of this proto-satellite swarm is small, and collisions among satellitesimals leads to loss of mass from the outer disk, and delivers mass to the inner disk (where regular satellites form) in a timescale $\lesssim 10^5$ years. This mass loss may be offset by continued collisional capture of sufficiently small $< 1$ km interlopers resulting from the disruption of planetesimals in the feeding zone of the giant planet. As the planet's feeding zone is cleared in a timescale $\lesssim 10^5$ years, enough angular momentum may be delivered to the proto-satellite swarm to account for the angular momentum of the regular satellites of Jupiter and Saturn.(abridged)

http://arxiv.org/abs/astro-ph/0504649

• Previous message: LARRY KLAES: "SETI public: Cosmological Evolution of Hessence Dark Energy and Avoidance of the Big Rip"

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