Binaries discovered by the MUCHFUSS project

Østensen, R. H.; Geier, S.; Schaffenroth, V.; Telting, J. H.; Bloemen, S.; Németh, P.; Beck, P. G.; Lombaert, R.; Pápics, P. I.; Tillich, A.; Ziegerer, E.; Machado, L. Fox; Littlefair, S. P.; Dhillon, V. S.; Aerts, C.; Heber, U.; Maxted, P. F. L.; Gänsicke, B. T.; Marsh, T. R.

doi:10.1051/0004-6361/201322022

Cited by 20 publications

(4 citation statements)

References 52 publications

(42 reference statements)

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“…However, multi-color photometry provides another important tool to study the properties of pulsating stars. The three-channel imager ULTRACAM (Dhillon et al 2007) has provided excellent light curves in three filters (e.g., Jeffery et al 2004Jeffery et al , 2005Aerts et al 2006;Østensen et al 2013). An illustrative example is the light curve of the HW Vir binary NYVir (Vučković et al 2007), which shows the pulsations in addition to the reflection effect and the eclipses (see Figure 28).…”

Section: Multi-color Light Curves and Time-series Spectroscopymentioning

confidence: 99%

Hot Subluminous Stars

Heber¹

2016

PASP

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Hot subluminous stars of spectral type B and O are core helium-burning stars at the blue end of the horizontal branch or have evolved even beyond that stage. Most hot subdwarf stars are chemically highly peculiar and provide a laboratory to study diffusion processes that cause these anomalies. The most obvious anomaly lies with helium, which may be a trace element in the atmosphere of some stars (sdB, sdO) while it may be the dominant species in others (He-sdB, He-sdO). Strikingly, the distribution in the Hertzsprung-Russell diagram of He-rich versus He-poor hot subdwarf stars of the globular clusters ω Cen and NGC2808 differ from that of their field counterparts. The metal-abundance patterns of hot subdwarfs are typically characterized by strong deficiencies of some lighter elements as well as large enrichments of heavy elements. A large fraction of sdB stars are found in close binaries with white dwarf or very low-mass main sequence companions, which must have gone through a common-envelope (CE) phase of evolution. Because the binaries are detached they provide a clean-cut laboratory to study this important but yet poorly understood phase of stellar evolution. Hot subdwarf binaries with sufficiently massive white dwarf companions are viable candidate progenitors of type Ia supernovae both in the double degenerate as well as in the single degenerate scenario as helium donors for double detonation supernovae. The hyper-velocity He-sdO star US708 may be the surviving donor of such a double detonation supernova. Substellar companions to sdB stars have also been found. For HWVir systems the companion mass distribution extends from the stellar into the brown dwarf regime. A giant planet to the acoustic-mode pulsator V391 Peg was the first discovery of a planet that survived the red giant evolution of its host star. Evidence for Earth-size planets to two pulsating sdB stars have been reported and circumbinary giant planets or brown dwarfs have been found around HWVir systems from eclipse timings. The high incidence of circumbinary substellar objects suggests that most of the planets are formed from the remaining CE material (second generation planets). Several types of pulsating star have been discovered among hot subdwarf stars, the most common are the gravity-mode sdB pulsators (V1093 Her) and their hotter siblings, the p-mode pulsating V361 Hya stars. Another class of multi-periodic pulsating hot subdwarfs has been found in the globular cluster ω Cen that is unmatched by any field star. Asteroseismology has advanced enormously thanks to the high-precision Kepler photometry and allowed stellar rotation rates to be determined, the interior structure of gravity-mode pulsators to be probed and stellar ages to be estimated. Rotation rates turned out to be unexpectedly slow calling for very efficient angular momentum loss on the red giant branch or during the helium core flash. The convective cores were found to be larger than predicted by standard stellar evolution models requiring very efficient angular momentum tr...

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Section: Multi-color Light Curves and Time-series Spectroscopymentioning

confidence: 99%

Hot Subluminous Stars

Heber¹

2016

PASP

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341

318

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“…For the noneclipsing reflection-effect systems, it is not possible to constrain the inclination, as there is a degeneracy with the radius of the companion (e.g., Hilditch et al 1996). However, it is possible to distinguish between higher and lower inclinations using the shape of the reflection effect (e.g., Østensen et al 2013;Schaffenroth et al 2014), and the change in amplitude from filter to filter contains information about the temperature of the primary. Hence we searched for consistent solutions that fit the light curves in all different bands, assuming an inclination.…”

Section: Reflection-effect Binariesmentioning

confidence: 99%

Multifilter Time-series Observations of Eleven Blue Short-period ATLAS Variable Stars

Koen

Schaffenroth

Knyazev

2023

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Eleven periodic variable stars were observed photometrically through two to four filters from the set UBVR C I C . Phase-folded data for each star cover full cycles of variation. Spectral energy distributions, based on absolute photometry extracted from the literature, are used to inform models of the stars. The stars include four eclipsing systems with hot subdwarfs of spectral type O or B (sdO/B). Periods are in the range 1.8–2.2 hr. Four reflection-effect binaries, with amplitudes as large as 0.5 mag in the R C filter were observed; periods range from 1.6 to 2.4 hr. In two of these latter systems, the primary stars are also sdB stars, while two have white-dwarf components. In all eight of these binaries the companion stars are probably M dwarfs. The remaining three stars are pulsators: one large-amplitude δ Scuti star previously misclassified as an eclipsing system; one field SX Phe star near the Galactic plane; and one multiperiodic high-luminosity star of unknown type. The amplitude is usually a strong function of the wavelength in pulsating stars, but this is not the case for the high-luminosity variable. One possible explanation is that the luminous star has a pulsating companion. The SX Phe and high-luminosity star are both heavily reddened (A V > 5 mag).

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“…We used the SDSS spectroscopic database as the starting point for our survey and obtained follow-up observations of the stars that showed the most significant RV shifts. Conducting more than 200 nights of spectroscopic and photometric follow-up, we constrained the orbits and companion types of 30 newly discovered sdB binaries up to now (Geier et al 2011c(Geier et al , 2011d(Geier et al , 2013b(Geier et al , 2014Østensen et al 2013;Schaffenroth et al 2014b;.…”

Section: Close Hot Subdwarf Binariesmentioning

confidence: 99%

Hot subdwarfs: Small stars marking important events in stellar evolution: Ludwig Biermann Award Lecture 2014

Geier¹

2015

Astron Nachr

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Hot subdwarfs are considered to be the compact helium cores of red giants which lost almost their entire hydrogen envelope. What causes this enormous mass loss is still unclear. Binary interactions are invoked, and a significant fraction of the hot subdwarf population is indeed found in close binaries. In a large project we search for close binary sdBs with the most and the least massive companions. Significantly enhancing the known sample of close binary sdBs we performed the first comprehensive study of this population. Triggered by the discovery of two sdB binaries with close brown dwarf companions in the course of this project, we were able to show that the interaction of stars with substellar companions is an important channel to form sdB stars. Finally, we discovered a unique and very compact binary system consisting of an sdB and a massive white dwarf which qualifies as a progenitor candidate for a supernova of type Ia. In addition to that, we could connect those explosions to the class of hypervelocity hot subdwarf stars which we consider as the surviving companions of such events. Being the stripped cores of red giants, hot subdwarfs turned out to be important markers of peculiar events in stellar evolution ranging all the way from star-planet interactions to the progenitors of stellar explosions used to measure the expansion of our Universe.

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Binaries discovered by the MUCHFUSS project

Cited by 20 publications

References 52 publications

Hot Subluminous Stars

Hot Subluminous Stars

Multifilter Time-series Observations of Eleven Blue Short-period ATLAS Variable Stars

Hot subdwarfs: Small stars marking important events in stellar evolution: Ludwig Biermann Award Lecture 2014

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