Incidence and survival of remnant disks around main-sequence stars

Abstract

Abstract. We present photometric ISO 60 and 170 um measurements, complemented by some IRAS data at 60 µm, of a sample of 84 nearby main-sequence stars of spectral class A, F, G and K in order to determine the incidence of dust disks around such main-sequence stars. Fifty stars were detected at 60 µm; 36 of these emit a flux expected from their photosphere while 14 emit significantly more. The excess emission we attribute to a circumstellar disk like the ones around Vega and β Pictoris. Thirty four stars were not detected at all; the expected photospheric flux, however, is so close to the detection limit that the stars cannot have an excess stronger than the photospheric flux density at 60 µm. Of the stars younger than 400 Myr one in two has a disk; for the older stars this is true for only one in ten. We conclude that most stars arrive on the main sequence surrounded by a disk; this disk then decays in about 400 Myr. Because (i) the dust particles disappear and must be replenished on a much shorter time scale and (ii) the collision of planetesimals is a good source of new dust, we suggest that the rapid decay of the disks is caused by the destruction and escape of planetesimals. We suggest that the dissipation of the disk is related to the heavy bombardment phase in our Solar System. Whether all stars arrive on the main sequence surrounded by a disk cannot be established: some very young stars do not have a disk. And not all stars destroy their disk in a similar way: some stars as old as the Sun still have significant disks.

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.…”

ROSATX‐Ray Spectral Properties of Nearby Young Associations: TW Hydrae, Tucana‐Horologium, and the β Pictoris Moving Group

“…The last sample consists of the K and M dwarfs studied by Fleming et al (1995;D < 7 pc, agese1 Gyr) and all single F and G stars within 14 pc for which data are available in the BSC. 5 Aside from 1 UMa, which likely is a member of the Ursa Major moving group (age 300 Myr; e.g., Messina & Guinan 2002), the stars in the nearby F-G sample likely have ages of at least 2 Gyr (e.g., Habing et al 2001). In Table 1 and Figure 3 we display the mean HRs for the Taurus TTS, local association, Hyades, and field star samples; in calculating these means and their formal errors, we use as weights the inverse squared uncertainties in HR1 and HR2.…”

A Possible Massive Asteroid Belt around ζ Leporis

“…We model the spectral energy distribution (SED) of z Lep with a 1993 Kurucz stellar atmosphere, assuming solar metallicity ( ). We assume no interstellar extinction because [Z/H] p 0.0 (Moshir et al 1989) with green error bars, and from the Infrared Space Observatory (Habing et al 2001) with red error bars. Our 11.7 and 17.9 mm photometry, as reported here, is shown with magenta error bars.…”