Article

# Binaries discovered by the SPY project - I. HE 1047-0436: A subdwarf B + white dwarf system

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University of Hamburg, Hamburg, Hamburg, Germany
(Impact Factor: 4.38). 09/2001; 378(1). DOI: 10.1051/0004-6361:20011223
Source: arXiv

ABSTRACT

In the course of our search for double degenerate binaries as potential progenitors of type Ia supernovae with the UVES spectrograph at the ESO VLT (ESO SN Ia Progenitor surveY - SPY) we discovered that the sdB star HE 1047-0436 is radial velocity variable. The orbital period of 1.213253d, a semi-amplitude of 94km/s, and a minimum mass of the invisible companion of 0.44Msol are derived from the analysis of the radial velocity curve. We use an upper limit on the projected rotational velocity of the sdB star to constrain the system inclination and the companion mass to M>0.71Msol, bringing the total mass of the system closer to the Chandrasekhar limit. However, the system will merge due to loss of angular momentum via gravitational wave radiation only after several Hubble times. Atmospheric parameters and metal abundances are also derived. The resulting values are typical for sdB stars. Comment: A&A Letters, accepted, 4 pages, 5 figures

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Available from: Horst Drechsel, Jun 27, 2013
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• "The orbital parameters of TONS 183 and PG 1232−136 were taken from Edelmann et al. (2005) [5]. An orbital solution for HE 1047−0436 was published by Napiwotzki et al. (2001) [12]. The orbital periods (P) and the radial velocity semi-amplitudes (K) are given in Tab. 1. "
##### Article: Spectroscopic Analysis of subluminous B Stars in Binaries with compact Companions
[Hide abstract]
ABSTRACT: The masses of compact objects like white dwarfs, neutron stars and black holes are fundamental to astrophysics, but very difficult to measure. We present the results of an analysis of subluminous B (sdB) stars in close binary systems with unseen compact companions to derive their masses and clarify their nature. Radial velocity curves were obtained from time resolved spectroscopy. The atmospheric parameters were determined in a quantitative spectral analysis. Based on high resolution spectra we were able to measure the projected rotational velocity of the stars with high accuracy. The assumption of orbital synchronization makes it possible to constrain inclination angle and companion mass of the binaries. Five invisible companions have masses that are compatible with that of normal white dwarfs or late type main sequence stars. But four sdBs have very massive companions like heavy white dwarfs > 1 Mo, neutron stars or even black holes. Such a high fraction of massive compact companions is not expected from current models of binary evolution.
01/2007;
• Source
• "The orbital parameters of TONS 183 and PG 1232−136 were taken from Edelmann et al. (2005) [5]. An orbital solution for HE 1047−0436 was published by Napiwotzki et al. (2001) [12]. The orbital periods (P) and the radial velocity semi-amplitudes (K) are given in Tab. 1. "
##### Article: Spectroscopic Analysis of Subluminous B Stars in Binaries - Four Candidate Systems with Neutron Star/Black Hole Companions Discovered
[Hide abstract]
ABSTRACT: The masses of compact objects like white dwarfs, neutron stars and black holes are fundamental to astrophysics, but very difficult to measure. We present the results of an analysis of subluminous B (sdB) stars in close binary systems with unseen compact companions to derive their masses and clarify their nature. Radial velocity curves were obtained from time resolved spectroscopy. The atmospheric parameters were determined in a quantitative spectral analysis. With high resolution spectra we were able to measure the projected rotational velocity of the stars with high accuracy. The assumption of orbital synchronization made it possible to constrain inclination angle and companion mass of the binaries. Five invisible companions have masses that are compatible with white dwarfs or late type main sequence stars. But four sdBs have very massive companions like heavy white dwarfs, neutron stars or even black holes. Such a high fraction of massive compact companions can not be explained with current models of binary evolution.
• Source
• "The orbital parameters of TONS 183 and PG 1232−136 were taken from Edelmann et al. (2005) [5]. An orbital solution for HE 1047−0436 was published by Napiwotzki et al. (2001) [12]. The orbital periods (P) and the radial velocity semi-amplitudes (K) are given in Tab. 1. "
##### Article: Spectroscopic Analyses of subluminous B stars in binaries
[Hide abstract]
ABSTRACT: The masses of compact objects like white dwarfs, neutron stars and black holes are fundamental to astrophysics, but very difficult to measure. We present the results of an analysis of subluminous B (sdB) stars in close binary systems with unseen compact companions to derive their masses and clarify their nature. Radial velocity curves were obtained from time resolved spectroscopy. The atmospheric parameters were determined in a quantitative spectral analysis. With high resolution spectra we were able to measure the projected rotational velocity of the stars with high accuracy. The assumption of orbital synchronization made it possible to constrain inclination angle and companion mass of the binaries. Five invisible companions have masses that are compatible with white dwarfs or late type main sequence stars. But four sdBs have very massive companions like heavy white dwarfs, neutron stars or even black holes. Such a high fraction of massive compact companions can not be explained with current models of binary evolution.