Evolution of a Luminous Hoyle-Lyttleton Accretor

Abstract

We examine the evolution of a Hoyle-Lyttleton accretor, on which mass accretion takes place via the Hoyle-Lyttleton processes, while taking into account the luminosity of the accretor. We consider two cases: (i) a spherical accretor, where the accretor is a spherical radiating source, and (ii) a disk accretor, where the accretor is a disk radiating source. In the well-known case of the classical non-luminous accretor, the growth time depends on the mass, the gas density, and the relative velocity, although the evolution processes are enhanced due to dynamical friction; the evolution time is shortened roughly by a factor of the Coulomb logarithm. In the case of a luminous accretor, we found, the evolutionary picture is drastically changed. The mass of the spherical accretor grows exponentially, but the luminosity approaches the Eddington luminosity, where the evolution timescale is the Eddington timescale, £E (= 4.53 x 10 8 ?7 yr, r\ being the efficiency). The mass and the effective luminosity of the disk accretor, on the other hand, diverge to infinity within a finite time, which is shorter than the Eddington timescale by a factor of the Coulomb logarithm. We discuss applications to several astrophysical situations, including a slow mover in giant molecular clouds and a fast runner in Thorne-Zytkow objects.

Radiative Flow in a Luminous Disk II

“…So far, radiatively driven outflow from a luminous disk has been extensively studied by many researchers (Bisnovatyi-Kogan, Blinnikov 1977;Katz 1980;Icke 1980;Melia, Königl 1989;Misra, Melia 1993;Tajima, Fukue 1996, 1998Watarai, Fukue 1999;Fukue et al 2001;Orihara, Fukue 2003), as on-axis jets (Icke 1989;Sikora et al 1996;Renaud, Henri 1998;Luo, Protheroe 1999;Fukue 2005a), as outflows confined by a gaseous torus (Lynden-Bell 1978;Davidson, McCray 1980;Sikora, Wilson 1981;Fukue 1982), or as jets confined by the outer flow or corona (Sol et al 1989;Marcowith et al 1995;Fukue 1999), and by numerical simulations (Eggum et al 1985(Eggum et al , 1988. Line-driven outflows were also extensively examined (Drew, Verbunt 1985;Vitello, Shlosman 1988;Proga et al 1998;Murray, Chiang 1995;Proga et al 2000;Proga, Kallman 2004).…”

Radiative Flow in a Luminous Disk

“…Such a radiatively driven outflow from a luminous accretion disk has been extensively studied in the context of models for astrophysical jets by many researchers (Bisnovatyi-Kogan, Blinnikov 1977;Katz 1980;Icke 1980;Melia, Königl 1989;Misra, Melia 1993;Tajima, Fukue 1996Watarai, Fukue 1999;Fukue et al 2001;Orihara, Fukue 2003), as on-axis jets (Icke 1989;Sikora et al 1996;Renaud, Henri 1998;Luo, Protheroe 1999;Fukue 2005a), as outflows confined by a gaseous torus (Lynden-Bell 1978;Davidson, McCray 1980;Sikora, Wilson 1981;Fukue 1982), or as jets confined by the outer flow or corona (Sol et al 1989;Marcowith et al 1995;Fukue 1999), and as numerical simulations (Eggum et al 1985(Eggum et al , 1988. In almost all of these studies, however, the disk radiation field was treated as an external field, and the radiation transfer was not solved.…”

Resolved young stellar populations in star-forming regions of the Magellanic Clouds

“…Their low metal abundances suggest that the environments of the Magellanic Clouds (MCs) are closer to that of the early universe during the epoch of its peak star formation at z ∼ 1.5 [98,125], and therefore, they should be considered as the best local templates of primitive star formation. Both the MCs are rich in Hi shells [88,107], Hii regions [36,68] and molecular clouds [50,153]. All these structures are linked to recent star formation, demonstrated by young stellar associations [9,96].…”