On the nature of the Be star HR 7409 (7 Vul)

Vennes, S.; Kawka, A.; Jonić, Slavica; Pirkovic, I.; Iliev, L.; Kubát, Jiřı́; Šlechta, M.; Németh, P.; Kraus, M.

doi:10.1111/j.1365-2966.2011.18350.x

Cited by 6 publications

(16 citation statements)

References 48 publications

(56 reference statements)

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“…Consequently, for critical rotation at the equator, we obtain ≈ 440 km s −1 , which implies that the inclination must be higher then about 58 • . It is notable that this last estimate agrees well with that of Vennes et al (2011), although we used different values of basic physical properties of the system. Finally, we note that the probable rotational period of the primary should be between about 0 d .45 and 0 d .53 for the range of inclinations from 58 • to 90 • .…”

Section: Probable Physical Properties Of the Binary Systemsupporting

confidence: 68%

“…003473 ± 0 . 000048, the range of V 0 and both possible values of T eff , we obtain the primary radius R = 3.75 -4.02 R N , which is notably smaller than that estimated by Vennes et al (2011). The corresponding range of the absolute magnitude M bol is from −2 m .35 to −2 m .52.…”

Section: Luminosity Mass and Radius Of The Primarymentioning

confidence: 53%

“…The B5 star 7 Vul (HR 7409, HD 183537, HIP 95818, Boss 4981; V=6 m .3-6 m .4 var.) was recently discovered to be a Be star and a spectroscopic binary with a 69 d orbital period and a low-mass companion, not readily seen in the spectra (Vennes et al 2011). A modest history of the previous investigations of this object was summarised in that study and here we only add a few brief comments.…”

Section: Introductionmentioning

confidence: 93%

“…4.2. The nature of the line-profile changes of the He i 6678 Å line Vennes et al (2011), using phase-averaged spectra, argued that the asymmetry of the He i 6678 Å line profiles varies with the orbital phase and tentatively suggested that it might be due to the presence of a weak line of the secondary component. On the other hand -since the pioneering work by Walker et al (1979) -it is well known that the hot emission-line stars are often exhibiting rapid line-profile changes, sometimes in the form of subfeatures travelling across the line profiles.…”

Section: An Improved Ephemerismentioning

confidence: 99%

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A new study of the spectroscopic binary 7 Vul with a Be star primary

Harmanec,

Lipták,

Koubský

et al. 2020

Preprint

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We confirmed the binary nature of the Be star 7 Vul, derived a more accurate spectroscopic orbit with an orbital period of 69 d .4212 ± 0 d .0034, and improved the knowledge of the basic physical elements of the system. Analyzing available photometry and the strength of the Hα emission, we also document the long-term spectral variations of the Be primary. In addition, we confirmed rapid light changes with a period of 0 d .5592, which is comparable to the expected rotational period of the Be primary, but note that its amplitude and possibly its period vary with time. We were able to disentangle only the He i 6678 Å line of the secondary, which could support our tentative conclusion that the secondary appears to be a hot subdwarf. A search for this object in high-dispersion far-UV spectra could provide confirmation. Probable masses of the binary components are (6 ± 1) M N and (0.6 ± 0.1) M N . If the presence of a hot subdwarf is firmly confirmed, 7 Vul might be identified as a rare object with a B4-B5 primary; all Be + hot subdwarf systems found so far contain B0-B3 primaries.

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Section: Probable Physical Properties Of the Binary Systemsupporting

confidence: 68%

Section: Luminosity Mass and Radius Of The Primarymentioning

confidence: 53%

Section: Introductionmentioning

confidence: 93%

Section: An Improved Ephemerismentioning

confidence: 99%

See 2 more Smart Citations

A new study of the spectroscopic binary 7 Vul with a Be star primary

Harmanec,

Lipták,

Koubský

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…m 4 var.) was recently discovered to be a Be star and a spectroscopic binary with a 69 d orbital period and a lowmass companion, not readily seen in the spectra (Vennes et al 2011). A modest history of the previous investigations of this object was summarised in that study and here we only add a few brief comments.…”

Section: Introductionmentioning

confidence: 93%

A new study of the spectroscopic binary 7 Vul with a Be star primary

Harmanec

Lipták

Koubský

et al. 2020

A&A

Self Cite

View full text Add to dashboard Cite

We confirmed the binary nature of the Be star 7 Vul, derived a more accurate spectroscopic orbit with an orbital period of 69.d4212±0.d0034, and improved the knowledge of the basic physical elements of the system. Analyzing available photometry and the strength of the Hα emission, we also document the long-term spectral variations of the Be primary. In addition, we confirmed rapid light changes with a period of 0.d5592, which is comparable to the expected rotational period of the Be primary, but note that its amplitude and possibly its period vary with time. We were able to disentangle only the He I 6678 Å line of the secondary, which could support our tentative conclusion that the secondary appears to be a hot subdwarf. A search for this object in high-dispersion far-UV spectra could provide confirmation. Probable masses of the binary components are (6 ± 1) 𝓜⊙N and (0.6 ± 0.1) 𝓜⊙N. If the presence of a hot subdwarf is firmly confirmed, 7 Vul might be identified as a rare object with a B4-B5 primary; all Be + hot subdwarf systems found so far contain B0-B3 primaries.

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Hot Subluminous Stars

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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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On the nature of the Be star HR 7409 (7 Vul)

Cited by 6 publications

References 48 publications

A new study of the spectroscopic binary 7 Vul with a Be star primary

A new study of the spectroscopic binary 7 Vul with a Be star primary

A new study of the spectroscopic binary 7 Vul with a Be star primary

Hot Subluminous Stars

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