Hot subdwarf binaries from the MUCHFUSS project - Analysis of 12 new systems and a study of the short-period binary population

Abstract

The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims at finding hot subdwarf stars with massive compact companions like massive white dwarfs (M>1.0 M${}_{\odot }$), neutron stars, or stellar-mass black holes. We present orbital and atmospheric parameters and put constraints on the nature of the companions of 12 close hot subdwarf B star (sdB) binaries found in the course of the MUCHFUSS project. The systems show periods between 0.14 and 7.4 days. Three systems most likely have white dwarf companions. SDSS J083006.17+475150.3 is likely to be a rare example of a low-mass helium-core white dwarf. SDSS J095101.28+034757.0 shows an excess in the infrared that probably originates from a third companion in a wide orbit. SDSS J113241.58-063652.8 is the first helium deficient sdO star with a confirmed close companion. This study brings to 142 the number of sdB binaries with orbital periods of less than 30 days and with measured mass functions. We present an analysis of the minimum companion mass distribution and show that it is bimodal. One peak around 0.1 M${}_{\odot }$ corresponds to the low-mass main sequence and substellar companions. The other peak around 0.4 M${}_{\odot }$ corresponds to the white dwarf companions. The derived masses for the white dwarf companions are significantly lower than the average mass for single carbon-oxygen white dwarfs. In a T${}_{\mathrm{eff}}$-log(g) diagram of sdB+dM companions, we find signs that the sdB components are more massive than the rest of the sample. The full sample was compared to the known population of extremely low-mass white dwarf binaries as well as short-period white dwarfs with main sequence companions. Both samples show a significantly different companion mass distribution. We calculate merger timescales and timescales when the companion will fill its Roche Lobe and the system evolves into a cataclysmic variable.

Accepted for publication in A&A, 24 pages, 17 figures, 9 table

References in corpus (13)

• The Stellar Populations of Praesepe and Coma Berenices
• The ELM Survey. I. A Complete Sample of Extremely Low Mass White Dwarfs
• A selection of hot subluminous stars in the GALEX survey II. Subdwarf atmospheric parameters
• Hot subdwarfs from the ESO Supernova Ia Progenitor Survey: II. Atmospheric parameters of subdwarf O stars
• The hot subdwarf B + white dwarf binary KPD 1930+2752 - a Supernova Type Ia progenitor candidate
• An ultra-massive fast-spinning white dwarf in a peculiar binary system
• Abundance studies of sdB stars using UV echelle HST/STIS spectroscopy
• Precise Atmospheric Parameters for the Shortest Period Binary White Dwarfs: Gravitational Waves, Metals, and Pulsations
• The orbits of subdwarf B + main-sequence binaries. I: The sdB+G0 system PG 1104+243
• Asteroseismology revealing trapped modes in KIC 10553698A
• KIC7668647: a 14 day beaming sdB+WD binary with a pulsating subdwarf
• First Attempt at Spectroscopic Detection of Gravity Modes in a Long-Period Pulsating Subdwarf B Star -- PG 1627+017
• Constraints on the winds of hot subdwarf stars from X-ray observations of two sdB binaries with compact companions: CD -30 11223 and PG 1232-136

Cited by in corpus (8)

• The orbits of subdwarf-B + main-sequence binaries: III. The period - eccentricity distribution
• New binaries among UV-selected, hot subdwarf stars and population properties
• The catalogue of radial velocity variable hot subluminous stars from the MUCHFUSS project
• PTF1 J082340.04+081936.5: A hot subdwarf B star with a low mass white dwarf companion in an 87 minute orbit
• An eclipsing post common-envelope system consisting of a pulsating hot subdwarf B star and a brown dwarf companion
• Stellar wind models of subluminous hot stars
• The OmegaWhite survey for short-period variable stars - V. Discovery of an ultracompact hot subdwarf binary with a compact companion in a 44 minute orbit
• HS 2231+2441: an HW Vir system composed by a low-mass white dwarf and a brown dwarf