
arXiv: astro-ph/0501617
Bright, ultracompact X-ray binaries observed in dense star clusters, such as Galactic globular clusters, must have formed relatively recently, since their lifetimes as persistent bright sources are short (e.g., ~10^8 yr above 10^36 erg/s for a 1.4 Msun neutron star accreting from a degenerate helium companion with an initial mass of ~0.2 Msun). Therefore, we can use the present conditions in a cluster core to study possible dynamical formation processes for these sources. Here we show that direct physical collisions between neutron stars and red giants can provide a sufficient formation rate to explain the observed numbers of bright sources. These collisions produce tight, eccentric neutron star -- white dwarf binaries that decay to contact by gravitational radiation on timescales ~10^6-10^10 yr, usually shorter and often much shorter than the cluster age.
4 pages, 1 figure, in emulateapj style. ApJ Letters, in press, includes corrections in proofs
Astrophysics (astro-ph), FOS: Physical sciences, Astrophysics
Astrophysics (astro-ph), FOS: Physical sciences, Astrophysics
| selected citations These citations are derived from selected sources. This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically). | 55 | |
| popularity This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network. | Top 10% | |
| influence This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically). | Top 10% | |
| impulse This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network. | Top 10% |
