Hot subdwarfs from the ESO supernova Ia progenitor survey

Stroeer, A.; Heber, U.; Lisker, Thorsten; Napiwotzki, R.; Christlieb, N.; Reimers, D.

doi:10.1051/0004-6361:20065564

Cited by 157 publications

(276 citation statements)

References 46 publications

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“…In an ongoing project Green et al (2008) analyse all hot subdwarfs from the PG survey down to 14.0 mag. The sample of hot subdwarf stars analysed in the course of the SPY survey reaches down to 16.5 mag Ströer et al 2007), quite similar to the sample of sdBs from the Hamburg Quasar Survey analysed by Edelmann et al (2003).…”

Section: Final Target Samplesupporting

confidence: 52%

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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

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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: Final Target Samplesupporting

confidence: 52%

“…† The binary system has been analysed in Geier et al (2011). ‡ Atmospheric parameters (T eff = 39 400 K, log g = 5.64, log y = −0.55) have been determined by Ströer et al (2007). 2.25931 −3.1 ± 0.9 6 2 .8 ± 1.…”

mentioning

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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“…Heliumpoor stars with temperatures ranging from 30 000 K to 40 000 K were analysed using LTE models with enhanced metal line blanketing (O'Toole & Heber 2006). Metal-free NLTE models (Ströer et al 2007) were used for hydrogen-rich stars with temperatures below 40 000 K showing moderate He-enrichment (log y = −1.0−0.0) and for hydrogen-rich sdOs. Finally, the He-sdOs were analysed with NLTE models taking into account the line-blanketing caused by nitrogen and carbon (Hirsch & Heber 2009).…”

Section: Atmospheric Parameters and Spectroscopic Distancesmentioning

confidence: 99%

“…Most (but not all) He-sdOs are concentrated in a very small region in the T eff -log g plane, slightly blueward of the EHB at T eff = 40 000−80 000 K and log g = 5.60−6.10 (Ströer et al 2007;Nemeth et al 2012). The He-sdBs are scattered above the EHB.…”

Section: Introductionmentioning

confidence: 99%

The catalogue of radial velocity variable hot subluminous stars from the MUCHFUSS project

Geier

Kupfer

Heber

et al. 2015

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The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims to find sdBs with compact companions such as massive white dwarfs, neutron stars, or black holes. Here we provide classifications, atmospheric parameters, and a complete radial velocity (RV) catalogue containing 1914 single measurements for a sample of 177 hot subluminous stars discovered based on SDSS DR7; 110 stars show significant RV variability, while 67 qualify as candidates. We constrain the fraction of close massive compact companions of hydrogen-rich hot subdwarfs in our sample to be smaller than ∼1.3%, which is already close to the theoretical predictions. However, the sample might still contain such binaries with longer periods exceeding ∼8 d. We detect a mismatch between the ΔRV max -distribution of the sdB and the more evolved sdOB and sdO stars, which challenges our understanding of their evolutionary connection. Furthermore, irregular RV variations of unknown origin with amplitudes of up to ∼180 km s −1 on timescales of years, days, and even hours have been detected in some He-sdO stars. They might be connected to irregular photometric variations in some cases.

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“…some of the sdOs. However, the identification of different subgroups in the sdO domain requires a more complicated picture, with additional formation channels needed to account for the complete population (Stroeer et al 2007;Green et al 2008). …”

Section: Introductionmentioning

confidence: 99%

2M0415+0154: a new bright, short-period subdwarf B pulsator

Oreiro

Østensen

Green³

et al. 2009

A&A

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Context. The discovery of stellar oscillations in some subdwarf B stars presents the opportunity of studying the interior structure of these objects, thereby clarifying their possible formation channels. Aims. Our ongoing survey attempts to increase the number of pulsating hot subdwarfs to better understand the complexities of the various subgroups within the population of pulsators and to identify targets suitable for seismological analysis. Methods. Light curves for a list of potential pulsators were obtained at the Nordic Optical Telescope. The candidates were mainly selected based on similar T eff and log g as known pulsators. A frequency analysis of the light curves was performed to investigate the multiperiodic photometric variability.Results. From the sample we surveyed in 2007, 2M0415+0154 was the only star clearly showing photometric modulations. Followup photometry revealed three clear pulsation modes with periods between 143 and 150 s. Additional spectroscopic data was taken on 2M0415+0154 to refine its physical parameters. We find T eff = 34 000 ± 500 K, log g = 5.80 ± 0.05 dex, log (N He /N H ) = −1.60 ± 0.05, which are typical of sdB pulsators in this period range. No evidence of a companion was found. Conclusions. A new short-period sdB star has been discovered, 2M0415+0154. Its physical parameters and oscillation frequencies agree with those of other V361 Hya stars. The relative brightness and simple frequency spectrum of this star make it a suitable target for empirical mode identification, essential for a seismological analysis of simple pulsators.

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Hot subdwarfs from the ESO supernova Ia progenitor survey

Cited by 157 publications

References 46 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

The catalogue of radial velocity variable hot subluminous stars from the MUCHFUSS project

2M0415+0154: a new bright, short-period subdwarf B pulsator

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