Kinematics of Vega-like stars lifetimes and temporal evolution of circumstellar dust disks.pdf

a r X i v : a s t r o - p h / 0 4 0 9 3 1 7 v 1 1 4 S e p 2 0 0 4 Astronomy Astrophysics manuscript no. 1265 February 2, 2008 (DOI: will be inserted by hand later) Kinematics of Vega-like stars: lifetimes and temporal evolution of circumstellar dust disks Manoj P. and H. C. Bhatt Indian Institute of Astrophysics, II Block, Koramangala, Bangalore - 560034 e-mail: manoj@iiap.res.in the date of receipt and acceptance should be inserted later Abstract. We have used the velocity dispersion as an age indicator to constrain the ages of a large sample of main sequence Vega-like stars in order to study the lifetimes and temporal evolution of the dust disks around them. We use Hipparcos mea- surements to compute stellar velocities in the sky plane. The velocity dispersion of Vega-like stars is found to be systematically smaller than that of the normal main sequence field stars for all spectral types, suggesting that the main sequence dusty systems, on average, are younger than normal field stars. The debris disks seem to survive longer around late type stars as compared to early type stars. Further, we find a strong correlation between fractional dust luminosity ( fd ≡ Ldust/L?) and velocity dispersion of stars with dust disks. Fractional dust luminosity is found to drop off steadily with increasing stellar age from early pre-main sequence phase to late main sequence phase. Key words. circumstellar matter – planetary system – stars: kinematics – stars: pre-main sequence – stars: evolution 1. Introduction It has been well established that the majority of pre-main se- quence stars are surrounded by circumstellar disks which are analogous in their properties to the protosolar nebula before the onset of planet formation (e.g., Beckwith 1999; Mundy et al. 2000; Wilner Lay 2000; Beckwith Sargent 1996). Young circumstellar disks lose most of this material due to planet formation and other disk dispersal processes by the time the central stars harbouring these disks reach the