THE LOW LEVEL OF DEBRIS DISK ACTIVITY AT THE TIME OF THE LATE HEAVY BOMBARDMENT: ASPITZERSTUDY OF PRAESEPE

Abstract

We present 24 µm photometry of the intermediate-age open cluster Praesepe. We assemble a catalog of 193 probable cluster members that are detected in optical databases, the Two Micron All Sky Survey (2MASS), and at 24 µm, within an area of ∼ 2.47 square degrees. Mid-IR excesses indicating debris disks are found for one early-type and for three solar-type stars. Corrections for sampling statistics yield a 24 µm excess fraction (debris disk fraction) of 6.5 ± 4.1% for luminous and 1.9 ± 1.2% for solar-type stars. The incidence of excesses is in agreement with the decay trend of debris disks as a function of age observed for other cluster and field stars. The values also agree with those for older stars, indicating that debris generation in the zones that emit at 24 µm falls to the older 1-10 Gyr field star sample value by roughly 750 Myr.We discuss our results in the context of previous observations of excess fractions for early-and solar-type stars. We show that solar-type stars lose their debris disk 24 µm excesses on a shorter timescale than early-type stars. Simplistic Monte Carlo models suggest that, during the first Gyr of their evolution, up to 15-30% of solar-type stars might undergo an orbital realignment of giant planets such as the one thought to have led to the Late Heavy Bombardment, if the length of the bombardment episode is similar to the one thought to have happened in our Solar System.In the Appendix, we determine the cluster's parameters via boostrap Monte Carlo isochrone fitting, yielding an age of 757 Myr (± 36 Myr at 1σ confidence) and a distance of 179 pc (± 2 pc at 1σ confidence), not allowing for systematic errors.

Debris disks as signposts of terrestrial planet formation

“…In these stable systems, our dust flux calculations yield typical values for the dust-tostellar-flux ratio F/F star of 0.1−0.5 at 25 μm and 10−35 at 70 μm after 1 Gyr of simulated dynamical and calculated collisional evolution. These values are broadly consistent with the fluxes detected around solar-type stars with observed excesses at 24 and 70 μm (Habing et al 2001;Beichman et al 2006;Moór et al 2006;Trilling et al 2008;Hillenbrand et al 2008;Carpenter et al 2009;Gáspár et al 2009), although our stable simulations yield very few systems with F/F star (70 μm) ≈ 1−10, probably because of the relatively large masses in our outer planetesimal disks (note that our unstable systems can yield those flux levels). Compared with the more sophisticated models of dust production during planetary accretion of Kenyon & Bromley (2008, our calculated fluxes are larger by a factor of a few, notably at 70 μm.…”

“…Observations (mainly with NASA's Spitzer Space Telescope) have shown that roughly 15% of solar-type stars younger than 300 million years have measurable dust fluxes at 24 μm (Gáspár et al 2009) but that this fraction decreases in time and flattens off at ∼3% ). At 70 μm, 16% of stars observable dust and there is no measured decrease in this fraction with age (Trilling et al 2008;Carpenter et al 2009).…”

“…Spitzer observations show that about 15% of solartype stars younger than 300 Myr have significant dust excesses at 24 μm but that this fraction decreases to about 3% for stars older than 1 Gyr (Meyer et al 2008;Carpenter et al 2009). At 70 μm the fraction of stars showing significant excesses is roughly constant in time (at ∼16%) but the upper envelope of the distribution decreases with the stellar age (Trilling et al 2008;Gáspár et al 2009;Carpenter et al 2009). A stars have a significantly higher fraction of dust excesses at both 24 and 70 μm and the excesses themselves are brighter than for FGK stars but the dust lifetime is shorter (Su et al 2006).…”

Chemical abundance analysis of the open clusters Berkeley 32, NGC 752, Hyades, and Praesepe

“…(g) Averages of measurements obtained from the Hipparcos parallaxes by van den Heuvel (1969);Maeder (1971); Mathieu & Mazeh (1988); Mazzei & Pigatto (1988); Boesgaard (1989);Tsvetkov (1993); Piatti et al (1995); Claria et al (1996); Hernandez et al (1998); Loktin & Beshenov (2001); Salaris et al (2004); Kraus & Hillenbrand (2007); and Gáspár et al (2009). assumed that log g = 4.437, T eff, = 5770 K and M bol, = 4.75, in conformity with the IAU recommendations (Andersen 1999). As above, we averaged all our estimates to obtain log g (phot) , listed in Col. 5 of Table 4.…”

TYC 8241 2652 1 and the case of the disappearing disk: No smoking gun yet

“…The IR luminosity of debris disks thus follows the evolution of the larger bodies, which ultimately supply the mass; the typical life time of debris disks is 100 s of Mys to Gyr (e.g., Gáspár et al 2009Gáspár et al , 2013Carpenter et al 2009). …”