Close binary EHB stars from SPY

Napiwotzki, R.; Karl, C.; Lisker, Thorsten; Heber, U.; Christlieb, N.; Reimers, D.; Nelemans, G.; Homeier, D.

doi:10.1023/b:astr.0000044362.07416.6c

Cited by 192 publications

(239 citation statements)

References 14 publications

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“…The radial velocities of all identified hot subdwarf stars (both single-and double-lined) were measured by fitting a set of mathematical functions (Gaussians, Lorentzians and polynomials) to the hydrogen Balmer lines as well as helium lines, if present, using the FITSB2 routine (Napiwotzki et al 2004a) and the Spectrum Plotting and Analysis Suite (SPAS) developed by Hirsch. Figure 4 shows the RVs of 1002 hot subdwarf stars.…”

Section: High Radial Velocity Sample (Hrv)mentioning

confidence: 99%

“…Samples of hot subdwarfs checked for radial velocity (RV) Tables 2-4 and Appendix A are available in electronic form at http://www.aanda.org variations imply the binary fraction ranges from 39% to 78% (e.g. Maxted et al 2001;Napiwotzki et al 2004a). The orbital periods of subdwarf binaries for which orbital parameters could be determined range from 0.07 to >10 d with a peak at 0.5−1.0 d (e.g.…”

Section: Introductionmentioning

confidence: 99%

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The MUCHFUSS project – searching for hot subdwarf binaries with massive unseen companions

Geier

Hirsch

Tillich

et al. 2011

A&A

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102

109

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The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims at finding sdBs with compact companions like supermassive white dwarfs (M > 1.0 M ), neutron stars or black holes. The existence of such systems is predicted by binary evolution theory and recent discoveries indicate that they are likely to exist in our Galaxy. A determination of the orbital parameters is sufficient to put a lower limit on the companion mass by calculating the binary mass function. If this lower limit exceeds the Chandrasekhar mass and no sign of a companion is visible in the spectra, the existence of a massive compact companion is proven without the need for any additional assumptions. We identified about 1100 hot subdwarf stars from the 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 127 radial velocity variable subdwarfs have been discovered. Binaries with high RV shifts and binaries with moderate shifts within short timespans have the highest probability of hosting massive compact companions. Atmospheric parameters of 69 hot subdwarfs in these binary systems have been determined by means of a quantitative spectral analysis. The atmospheric parameter distribution of the selected sample does not differ from previously studied samples of hot subdwarfs. The systems are considered the best candidates to search for massive compact companions by follow-up time resolved spectroscopy.

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Section: High Radial Velocity Sample (Hrv)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The MUCHFUSS project – searching for hot subdwarf binaries with massive unseen companions

Geier

Hirsch

Tillich

et al. 2011

A&A

Self Cite

102

109

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show abstract

“…Given the finite age of the universe, the only way to form ELM white dwarfs is through binary evolution, and we do in fact find almost 100% of ELM white dwarfs in short period systems. This is significantly higher than the binary fraction of 10% for the overall population of white dwarfs that were observed as part of the Supernova-Ia Progenitor surveY (SPY, Napiwotzki et al 2004;Maoz & Hallakoun 2017). Brown et al (2016b) estimate an ELM white dwarf merger rate of 3 × 10 −3 yr −1 over the entire disk of the Milky Way.…”

Section: Introductionmentioning

confidence: 83%

A Gemini snapshot survey for double degenerates

Kilic

Brown

Gianninas

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present the results from a Gemini snapshot radial-velocity survey of 44 lowmass white dwarf candidates selected from the Sloan Digital Sky Survey spectroscopy. To find sub-hour orbital period binary systems, our time-series spectroscopy had cadences of 2 to 8 min over a period of 20-30 min. Through follow-up observations at Gemini and the MMT, we identify four double degenerate binary systems with periods ranging from 53 min to 7 h. The shortest period system, SDSS J123549.88+154319.3, was recently identified as a subhour period detached binary by Breedt and collaborators. Here we refine the orbital and physical parameters of this system. High-speed and time domain survey photometry observations do not reveal eclipses or other photometric effects in any of our targets. We compare the period distribution of these four systems with the orbital period distribution of known double white dwarfs; the median period decreases from 0.64 to 0.24 d for M = 0.3 − 0.5M ⊙ to M < 0.3M ⊙ white dwarfs. However, we do not find a statistically significant correlation between the orbital period and white dwarf mass.

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“…In this sense, [62] estimate a most likely (close) binary fraction f = 4% among EHB stars in NGC 6752, to be compared with an estimated f = 42 − 69% among field sdB stars ( [55,67,65]; see also [38,37] for additional references to field star work).…”

Section: Different Channels For Ehb Stars In the Field Vs Clusters?mentioning

confidence: 99%

Horizontal Branch Stars and the Ultraviolet Universe

Catelan

2009

Astrophysics and Space Science Proceedings

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Summary. Extremely hot horizontal branch (HB) stars and their progeny are widely considered to be responsible for the "ultraviolet upturn" (or UVX) phenomenon observed in elliptical galaxies and the bulges of spirals. Yet, the precise evolutionary channels that lead to the production of these stars remain the source of much debate. In this review, we discuss two key physical ingredients that are required in order for reliable quantitative models of the UV output of stellar populations to be computed, namely, the mass loss rates of red giant branch stars and the helium enrichment "law" at high metallicities. In particular, the recent evidence pointing towards a strong enhancement in the abundances of the α-elements in the Galactic bulge (compared to the disk), and also the available indications of a similar overabundance in (massive) elliptical galaxies, strongly suggest that the helium abundance Y may be higher in ellipticals and bulges than it is in spiral disks by an amount that may reach up to 0.15 at [Fe/H] ∼ +0.5. If so, this would strongly favor the production of hot HB stars at high metallicity in galactic spheroids. We also discuss the existence of mass loss recipes beyond the commonly adopted Reimers "law" that are not only more consistent with the available empirical data, but also much more favorable to the production of extended HB stars at high metallicity. Finally, we discuss new empirical evidence that suggests that different evolutionary channels may be responsible for the production of EHB stars in the field and in clusters.

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Close binary EHB stars from SPY

Cited by 192 publications

References 14 publications

The MUCHFUSS project – searching for hot subdwarf binaries with massive unseen companions

The MUCHFUSS project – searching for hot subdwarf binaries with massive unseen companions

A Gemini snapshot survey for double degenerates

Horizontal Branch Stars and the Ultraviolet Universe

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