Kupfer, T and Geier, S and Heber, U and Østensen, RH and Barlow, BN and Maxted, PFL and Heuser, C and Schaffenroth, V and Gänsicke, BT (2015) Hot subdwarf binaries from the MUCHFUSS project - Analysis of 12 new systems and a study of the short-period binary population. Astronomy & Astrophysics, 576. A44 -?. ISSN 0004-6361

[img]
Preview
Text
1501.03692v1.pdf - Published Version
Available under License Creative Commons Attribution.

Download (936kB) | Preview

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$_{\rm eff}$-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.

Item Type: Article
Additional Information: ©EDP Sciences
Uncontrolled Keywords: subdwarfs, binaries: close
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Faculty of Natural Sciences > School of Physical and Geographical Sciences
Related URLs:
Depositing User: Symplectic
Date Deposited: 08 Jul 2015 08:51
Last Modified: 25 May 2016 13:56
URI: http://eprints.keele.ac.uk/id/eprint/657

Actions (login required)

View Item View Item