The short period end of the contact binary period distribution based on the All Sky Automated Survey (ASAS)

TL;DR

This study analyzes the period distribution of contact binary stars from the ASAS survey, revealing a peak at shorter periods than previously thought and highlighting the unexplained nature of the shortest period cutoff.

Contribution

It provides the first corrected period distribution of W UMa contact binaries based on a large survey, challenging previous estimates of the period cutoff and distribution.

Findings

Maximum number of contact binaries at P ~ 0.27 days

No evidence for angular momentum evolution in the distribution

Short-period cutoff remains unexplained

Abstract

The search-volume corrected period distribution of contact binaries of the W UMa type appears to reflect primarily the constant number ratio of ~1/500 to the number of stars along the Main Sequence; there exist no evidence for angular momentum evolution. The maximum in contact binary numbers is located at shorter periods than estimated before, P ~ 0.27 d. The drop in numbers towards the cut-off at P ~ 0.215 - 0.22 d still suffers from the small number statistics while the cut-off itself remains unexplained. Only one out of seven short-period ASAS variables with P<0.22 d have been retained in the sample considered here within 8 < V < 13; this short-period field-sky record holder at P=0.2178 d should be studied.