Building a Holistic ATM Model for Future KPI Trade-Offs

We present the model developed within the Vista project, studying the future evolution of trade-offs between Key Performance Indicators. The model has a very broad scope and aims to simulate the changes that business and regulatory forces have at a strategic, pre-tactical and tactical level. The relevant factors that will affect the air transportation system are presented, as well as the scenarios to be simulated. The overall architecture of the model is described and a more detailed presentation of the economic component of the model is given. Some preliminary results of this part of the model illustrate its main mechanisms and capabilities

Vista D2.1 Supporting Data for Business and Regulatory Scenarios Report

Vista examines the effects of conflicting market forces on European performance in ATM, through the evaluation of impact metrics on four key stakeholders, and the environment. The review of regulatory and business factors is presented. Vista will model the current and future (2035, 2050) framework based on the impact of regulatory and business factors. These factors are obtained from a literature review of regulations, projects and technological and operational changes. The current value of those factors and their possible evolution are captured in this deliverable

Debris Disks in NGC 2547

We have surveyed the 30 Myr-old cluster NGC 2547 for planetary debris disks using Spitzer. At 4.5-8 um we are sensitive to the photospheric level down to mid-M stars (0.2 Msol) and at 24 um to early-G stars (1.2 Msol). We find only two to four stars with excesses at 8 um out of ~400-500 cluster members, resulting in an excess fraction <~1 percent at this wavelength. By contrast, the excess fraction at 24 um is ~40 percent (for B-F types). Out of four late-type stars with excesses at 8 um two marginal ones are consistent with asteroid-like debris disks. Among stars with strong 8 um excesses one is possibly from a transitional disk, while another one can be a result of a catastrophic collision. Our survey demonstrates that the inner 0.1-1 AU parts of disks around solar-type stars clear out very thoroughly by 30 Myrs of age. Comparing with the much slower decay of excesses at 24 and 70 um, disks clear from the inside out, of order 10 Myr for the inner zones probed at 8 um compared with a hundred or more Myr for those probed with the two longer wavelengths.Comment: Accepted to ApJ, 29 pages, 13 figs. A Note in Proof concerning cluster's age was added in the original submission of 2007 July 19. Full Tables 1 and 2 in the electronic form together with the article with full resolution figures are available at http://www.astro.ufl.edu/~ngorlova/disksNGC2547

Other Kuiper Belts

When a main sequence star evolves into a red giant and its Kuiper Belt Object's (KBO's) reach a temperature of about 170 K, the dust released during the rapid ice-sublimation of these cometary bodies may lead to a detectable infrared excess at 25 microns, depending upon the mass of the KBO's. Analysis of IRAS data for 66 first ascent red giants with 200 L(Sun) < L < 300 L(Sun) within 150 pc of the Sun provides an upper limit to the mass in KBO's at 45 AU orbital radius that is usually less than about 0.1 M(Earth). With improved infrared data, we may detect systems of KBO's around first ascent red giants that are analogs to our Solar System's KBO's.Comment: 18 pages, 4 figures, accepted by Ap

Spitzer 24 micron Survey of Debris Disks in the Pleiades

We performed a 24 micron 2 Deg X 1 Deg survey of the Pleiades cluster, using the MIPS instrument on Spitzer. Fifty four members ranging in spectral type from B8 to K6 show 24 micron fluxes consistent with bare photospheres. All Be stars show excesses attributed to free-free emission in their gaseous envelopes. Five early-type stars and four solar-type stars show excesses indicative of debris disks. We find a debris disk fraction of 25 % for B-A members and 10 % for F-K3 ones. These fractions appear intermediate between those for younger clusters and for the older field stars. They indicate a decay with age of the frequency of the dust-production events inside the planetary zone, with similar time scales for solar-mass stars as have been found previously for A-stars.Comment: accepted to Ap

Frequency of Debris Disks around Solar-Type Stars: First Results from a Spitzer/MIPS Survey

We have searched for infrared excesses around a well defined sample of 69 FGK main-sequence field stars. These stars were selected without regard to their age, metallicity, or any previous detection of IR excess; they have a median age of ~4 Gyr. We have detected 70 um excesses around 7 stars at the 3-sigma confidence level. This extra emission is produced by cool material (< 100 K) located beyond 10 AU, well outside the ``habitable zones'' of these systems and consistent with the presence of Kuiper Belt analogs with ~100 times more emitting surface area than in our own planetary system. Only one star, HD 69830, shows excess emission at 24 um, corresponding to dust with temperatures > 300 K located inside of 1 AU. While debris disks with Ld/L* > 10^-3 are rare around old FGK stars, we find that the disk frequency increases from 2+-2% for Ld/L* > 10^-4 to 12+-5% for Ld/L* > 10^-5. This trend in the disk luminosity distribution is consistent with the estimated dust in our solar system being within an order of magnitude, greater or less, than the typical level around similar nearby stars.Comment: 11 figure

Envelope Ejection: an Alternative Process for some Early Case B Binaries

We discuss the evolution of binaries with moderately high masses (about 10 - 30 solar masses), and with periods of about 3 - 300d, corresponding mostly to early Case B. These are usually thought to evolve either by reasonably conservative Roche-lobe overflow, if the initial mass ratio is fairly mild, or else by highly non-conservative common-envelope evolution, with spiral-in to short periods (hours, typically), if the initial mass ratio is rather extreme. We discuss here a handful of binaries from part of this period range (about 50 - 250d), which appear to have followed a different path: we argue that they must have lost a large proportion of initial mass (about 70 - 80%), but without shortening their periods at all. We suggest that their behaviour may be due to the fact that stars of such masses, when evolved also to rather large radii, are not far from the Humphreys-Davidson limit where single stars lose their envelopes spontaneously in P Cygni winds, and so have envelopes which are only lightly bound to the core. These envelopes therefore may be relatively easily dissipated by the perturbing effect of a companion. In addition, some or all of the stars considered here may have been close to the Cepheid instability strip when they filled their Roche lobes. One or other, or both, of high luminosity and Cepheid instability, in combination with an appropriately close binary companion, may be implicated

A Flared, Orbiting, Dusty Disk Around HD 233517

We find that the infrared excess around HD 233517, a first ascent red giant, can be naturally explained if the star possesses an orbiting, flared dusty disk. We estimate that the outer radius of this disk is 45 AU and that the total mass within the disk is about 0.01 the mass of the Sun. We speculate that this disk is the result of the engulfment of a low mass companion star that occurred when HD 233517 became a red giant.Comment: ApJ, in pres

A Sub-Millimeter Search of Nearby Young Stars for Cold Dust: Discovery of Debris Disks around Two Low-Mass Stars

(Abridged) We present results from a JCMT/SCUBA 850 um search for cold dust around nearby young stars belonging to the beta Pic (t~12 Myr) and the Local Association (t~50 Myr) moving groups. Unlike most past sub-mm studies, our sample was chosen on the basis of stellar age. Our observations achieve about an order of magnitude greater sensitivity in dust mass compared to previous work in this age range. We detected two of the three M dwarfs in our sample at 850 um, GJ 182 and GJ 803. GJ 182 may also possess a 25 um excess, indicative of warm dust in the inner few AU of its disk. For GJ 803 (AU Mic), sub-mm mapping finds that the 850 um emission is unresolved. A non-detection of the CO 3-2 line indicates the system is gas-poor, and the SED suggests the presence of a large inner disk hole (~17 AU = 1.7 arcsec in radius). These are possible indications that planets at large separations can form around M dwarfs within \~10 Myr. In a companion paper (Kalas, Liu & Matthews 2004), we confirm the existence of a dust disk around GJ 803 using optical coronagraphic imaging. Given its youthfulness, proximity, and detectability, the GJ 803 disk will be a valuable system for studying disk, and perhaps planet, formation in great detail. Overall, sub-mm measurements of debris disks point to a drop in dust mass by a factor of about 10^3 within the first ~10 Myr, with the subsequent decline in the masses of sub-mm detected disks consistent with t^{-0.5} to t^{-1}.Comment: 9 pages, ApJ, in press. Minor changes made to reflect final published manuscrip