Effective temperatures and luminosities of very hot O type subdwarfs

Schönberner, D.; Drilling, J. S.

doi:10.1086/161839

Cited by 42 publications

(38 citation statements)

References 10 publications

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“…KV Vel, the central star of PN DS 1, was discovered to be a variable by Drilling et al (1984), with a period of 8.5 h. Drilling (1985) showed this star to be a double-lined spectroscopic binary and determined the primary stellar temperature to be 77,000 ± 8000 K from the ratio of the integrated near to far-UV flux from an IUE spectrum (Schönberner & Drilling 1984). Kilkenny et al (1988) presented a light curve in the U, B, V , and I bands, which confirmed the amplitude of 0.6 mag.…”

Section: A23 Dsmentioning

confidence: 99%

“…Walton et al (1993) reported no B − V color change with the orbital phase, which would indicate that the irradiated side of the companion is very hot. Indeed, the analysis of Pollacco & Bell (1993) determined a temperature on the bright side of the secondary of ∼25,000 K. They also deduced that the primary effective temperature is T eff ∼125,000 K from the ratio of integrated far-and near-UV light (Schönberner & Drilling 1984) and that the polar temperature is 115,500 K. This estimate is higher than was previously published (35,000-45,000 K; Bond et al 1978;Walton et al 1993), but it appears to be the best value to adopt in the absence of a full spectral fitting.…”

Section: A12 a 46mentioning

confidence: 99%

“…From their Figure 6, we measured the amplitude of their light curve, excluding the eclipses, to be 0.6 mag. The parameters they derived from the light and radial velocity curve analyses are reliant on the primary's effective temperature, which could only be estimated from a variety of indirect methods such as the He ii Zanstra temperature or the ratio of far-and near-UV integrated light (Schönberner & Drilling 1984). They also estimated the secondary star's mass to be 0.15 M (or a spectral type of M6V).…”

Section: A12 a 46mentioning

confidence: 99%

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Binary Central Stars of Planetary Nebulae Discovered Through Photometric Variability. I. What We Know and What We Would Like to Find Out

Marco

Hillwig

Smith

2008

The Astronomical Journal

106

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Shaping axisymmetric planetary nebulae is easier if a companion interacts with a primary at the top of the asymptotic giant branch. To determine the impact of binarity on planetary nebula formation and shaping, we need to determine the central star of planetary nebula binary fraction and period distribution. The short-period binary fraction has been known to be 10-15% from a survey of ∼100 central stars for photometric variability indicative of irradiation effects, ellipsoidal variability, or eclipses. This survey technique is known to be biased against binaries with long periods and this fact is used to explain why the periods of all the binaries discovered by this survey are smaller than 3 days. In this paper we assess the status of knowledge of binary central stars discovered because of irradiation effects. We determine that, for average parameters, this technique should be biased against periods longer than 1-2 weeks, so it is surprising that no binaries were found with periods longer than 3 days. Even more puzzling is the fact that 9 out of 12 of the irradiated binaries have periods smaller than 1 day, a fact that is starkly at odds with post-common envelope predictions. We suggest that either all common envelope models tend to overestimate post-common envelope periods or this binary survey might have suffered from additional, unquantified biases. If the latter hypothesis is true, the currently known short-period binary fraction is put in serious doubt. We also introduce a new survey for binary-related variability, which will enable us to better quantify biases and determine an independent value for the short-period binary fraction.

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Section: A23 Dsmentioning

confidence: 99%

Section: A12 a 46mentioning

confidence: 99%

Section: A12 a 46mentioning

confidence: 99%

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Binary Central Stars of Planetary Nebulae Discovered Through Photometric Variability. I. What We Know and What We Would Like to Find Out

Marco

Hillwig

Smith

2008

The Astronomical Journal

106

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“…This further indicates that the spectral type of HD 145718 is A5Ve. Schönberner & Drilling (1984) suggested that HD 320156 (=LSS 4300) is a close binary system consisting of a helium supergiant of ∼1 M and a less luminous secondary. Our FEROS spectrum is compatible with this hypothesis.…”

Section: Hd 145718mentioning

confidence: 99%

New Herbig Ae/Be stars confirmed via high-resolution optical spectroscopy

Ancker

Audard²,

Henning

et al. 2010

A&A

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We present FEROS high-resolution (R ∼ 45 000) optical spectroscopy of 34 Herbig Ae/Be star candidates with previously unknown or poorly constrained spectral types. Within the sample, 16 sources are positionally coincident with nearby (d < 250 pc) star-forming regions (SFRs). All the candidates have reported infrared excess. We determine the spectral type and luminosity class of the sources, derive their radial and projected rotational velocities, and constrain their distances employing spectroscopic parallaxes and photometry from the literature. We confirm 13 sources as Herbig Ae/Be stars and find one classical T Tauri star. Three sources are emission line early-type giants (B, A, and F stars with luminosity class III) and may be Herbig Ae/Be stars. One source is a main-sequence Atype star. Fourteen sources are post-main-sequence giant and supergiant stars (7 with Hα emission and 7 without). Two sources are extreme emission-line stars and no accurate spectral classification was possible because of strong veiling. Most of the sources appear to be background stars at distances over 700 pc. We show that high-resolution optical spectroscopy is a crucial tool for distinguishing young stars (in particular Herbig Be stars) from post-main sequence stars in samples taken from emission-line star catalogs based on low-resolution spectroscopy. Within the sample, three young stars (CD-38 4380, Hen 3-1145, and HD 145718) and one early-type luminosity class III giant with emission lines (Hen 3-416) are at distances closer than 300 pc and are positionally coincident with a nearby SFR. These 4 sources are likely to be nearby young stars and are interesting for follow-up observations at high-angular resolution. Furthermore, seven confirmed Herbig Ae/Be stars at d > 700 pc (Hen 2-80, Hen 3-1121 N&S, HD 313571, MWC 953, WRAY 15-1435, and Th 17-35) are inside or close (<5 ) to regions with extended 8 μm continuum emission and in their 20 vicinity have astronomical sources characteristic of SFRs (e.g., HII regions, molecular clouds, dark nebulae, masers, young stellar-objects). These 7 sources are likely to be members of SFRs.

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“…To determine the temperature of the subdwarf companion, Kaler (1983) computed the Zanstra temperatures using the H and He ii nebular lines and constrained the primary component's temperature in between 32 000 and 60 000 K. In a most recent study, PB94 presented a new Zanstra analysis based on the Hβ and He ii nebular lines and estimated the temperatures as 48 000 and 82 000 K, respectively. They also employed the R‐technique of Schönberner & Drilling (1984) and derived a temperature of 63 000 ± 12 000 K for the primary star and considering the temperature range found from several methods they decided to adopt a temperature of 60 000 ± 10 000 K in the light‐curve analysis. However, the simultaneous two‐colour photometry gives us an opportunity to derive more accurate and approximate values for the temperatures of the binary components, which we have found as 49 500 K (fixed) for the primary and 3874 ± 120 K for the secondary star.…”

Section: Simultaneous Light‐curve Solutionsmentioning

confidence: 99%

Two-colour photometry of the binary planetary nebula nuclei UU Sagitte and V477 Lyrae: oversized secondaries in post-common-envelope binaries

Afşar¹,

İbanoǧlu²

2008

Monthly Notices of the Royal Astronomical Society

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We present new V‐ and R‐passband CCD photometry of UU Sge and V477 Lyr, the eclipsing binary nuclei of the planetary nebulae Abell 63 and Abell 46, respectively. We have performed a simultaneous analysis of VR light curves and estimated the effective temperatures for the primary and secondary stars to be 78 000 ± 3000 and 6136 ± 240 K for UU Sge, 49 500 ± 4500 and 3874 ± 350 K for V477 Lyr. We have also reanalysed the previously measured radial velocities and combined the results with those obtained from the analysis of the light curves to derive absolute parameters of the components. The secondary stars have larger radii than expected from their main‐sequence counterparts at the same masses. We have determined the post‐common‐envelope ages and the thermal time‐scales of the systems and examined the possible reasons of expanded radius of the secondary components, together with some selected post‐common envelope binaries. We conclude that the secondary components of the nuclei of the planetary nebulae are still out of thermal equilibrium along with two post‐common envelope systems: HS 1136+6646 and RE 1016−053. For other systems, magnetic activity has been suggested as the more plausible reason for their expanded radii. We have also estimated the common‐envelope efficiency parameters of UU Sge and V477 Lyr.

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Effective temperatures and luminosities of very hot O type subdwarfs

Cited by 42 publications

References 10 publications

Binary Central Stars of Planetary Nebulae Discovered Through Photometric Variability. I. What We Know and What We Would Like to Find Out

Binary Central Stars of Planetary Nebulae Discovered Through Photometric Variability. I. What We Know and What We Would Like to Find Out

New Herbig Ae/Be stars confirmed via high-resolution optical spectroscopy

Two-colour photometry of the binary planetary nebula nuclei UU Sagitte and V477 Lyrae: oversized secondaries in post-common-envelope binaries

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