The MUCHFUSS project - Searching for the most massive companions to hot subdwarf stars in close binaries and finding the least massive ones

TL;DR

The MUCHFUSS project searches for hot subdwarf stars with massive compact companions, discovering several close binaries and candidates, providing insights into binary evolution and the nature of these systems.

Contribution

This study classifies and analyzes a large sample of hot subdwarfs from SDSS, identifying new binary systems and candidates with massive or substellar companions.

Findings

Discovered 201 radial velocity variable subdwarfs.

Identified seven close binary sdBs with short periods.

Found two eclipsing binaries with likely substellar companions.

Abstract

The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims at finding hot subdwarf stars with massive compact companions (massive white dwarfs M>1.0 Msun, neutron stars or stellar mass black holes). The existence of such systems is predicted by binary evolution theory and some candidate systems have been found. We classified about 1400 hot subdwarf stars from the Sloan Digital Sky Survey (SDSS) by colour selection and visual inspection of their spectra. Stars with high velocities have been reobserved and individual SDSS spectra have been analysed. In total 201 radial velocity variable subdwarfs have been discovered and about 140 of them have been selected as good candidates for follow-up time resolved spectroscopy to derive their orbital parameters and photometric follow-up to search for features like eclipses in the light curves. Up to now we found seven close binary sdBs with short orbital periods ranging from 0.21 d to 1.5 d and two eclipsing binaries with companions that are most likely of substellar nature. A new pulsating sdB in a close binary system has been discovered as well.