A New Helium-Rich Star, BD +13°3224

Berger, Jacques; Greenstein, Jesse L.

doi:10.1086/127962

Cited by 15 publications

(5 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…V652 Her (= BD+13° 3224) was discovered by Berger & Greenstein (1963) to be hydrogen‐deficient, and shown by Landolt (1975) to be variable with a very short period near 0.108 d. An atmospheric analysis by Hill et al (1981) derived log L /L ⊙ = 3.1 ± 0.2, log R /R ⊙ = 1.6 ± 0.2, T eff = 26 500 ± 2000 K and a hydrogen abundance of ∼1–2 per cent by number. Lynas‐Gray et al (1984) determined a mass of 0.7 M ⊙ , and radial velocity studies combined with photometric data showed that the star is a radial pulsator (Hill et al 1981).…”

Section: V652 Hermentioning

confidence: 99%

Period changes in the pulsating extreme helium stars V652 Her and BX Cir

Kilkenny¹,

Crause²,

Wyk³

2005

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Thirty‐four new timings of maxima of the radially pulsating extreme helium (EHe) star V652 Her (= BD+13° 3224) obtained during 1996–2004 are reported. The quartic ephemeris (for the pulsation period decrease) is extended and the higher‐order terms are defined more accurately. We also report 45 new timings of maxima for the closely similar star BX Cir (= LSS 3184) over the same baseline and present the first evidence that this star also shows a decreasing period. The data obtained thus far can be represented by a quadratic ephemeris – a linearly decreasing period in BX Cir – though the decrease rate (dP/dn∼ 3.7 × 10−10 d) is much smaller than in V652 Her.

show abstract

Section: V652 Hermentioning

confidence: 99%

Period changes in the pulsating extreme helium stars V652 Her and BX Cir

Kilkenny¹,

Crause²,

Wyk³

2005

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…Just over fifty years ago, Berger & Greenstein (1963) used the Palomar 5-m (200-inch) telescope to show that the early B star BD+13…”

Section: Introductionmentioning

confidence: 99%

“…Just over fifty years ago, Berger & Greenstein (1963) used the Palomar 5-m (200-inch) telescope to show that the early B star BD+13 • 3224 is hydrogen deficient and a probable subdwarf. Whilst all permitted neutral helium lines were visible, the hydrogen Balmer lines were unexpectedly weak, although still detectable.…”

Section: Introductionmentioning

confidence: 99%

Subaru and Swift observations of V652 Herculis: resolving the photospheric pulsation★

Jeffery

Kurtz

Shibahashi

et al. 2015

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

High resolution spectroscopy with the Subaru High Dispersion Spectrograph, and Swift ultraviolet photometry are presented for the pulsating extreme helium star V652 Her. Swift provides the best relative ultraviolet photometry obtained to date, but shows no direct evidence for a shock at ultraviolet or X-ray wavelengths. Subaru has provided high spectral and high temporal resolution spectroscopy over 6 pulsation cycles (and eight radius minima). These data have enabled a line-by-line analysis of the entire pulsation cycle and provided a description of the pulsating photosphere as a function of optical depth. They show that the photosphere is compressed radially by a factor of at least two at minimum radius, that the phase of radius minimum is a function of optical depth and the pulse speed through the photosphere is between 141 and 239 km s −1 (depending how measured) and at least ten times the local sound speed. The strong acceleration at minimum radius is demonstrated in individual line profiles; those formed deepest in the photosphere show a jump discontinuity of over 70 km s −1 on a timescale of 150 s. The pulse speed and line profile jumps imply a shock is present at minimum radius. These empirical results provide input for hydrodynamical modelling of the pulsation and hydrodynamical plus radiative transfer modelling of the dynamical spectra.

show abstract

“…BD+13 • 3224 = V652 Her is an extreme helium star and a B-type giant discovered by Berger & Greenstein (1963). With a nitrogen-rich, carbon-poor surface, it pulsates with a period of 0.108 d which is decreasing at a substantial rate (cf.…”

Section: The Shocking Case Of V652 Herculismentioning

confidence: 99%

The origin and pulsations of extreme helium stars

Jeffery

2013

Proc. IAU

View full text Add to dashboard Cite

Abstract. Stars consume hydrogen in their interiors but, generally speaking, their surfaces continue to contain some 70% hydrogen (by mass) throughout their lives. Nevertheless, many types of star can be found with hydrogen-deficient surfaces, in some cases with as little as one hydrogen atom in 10 000. Amongst these, the luminous B-and A-type extreme helium stars are genuinely rare; only ∼ 15 are known within a very substantial volume of the Galaxy.Evidence from surface composition suggests a connection to the cooler R CrB variables and some of the hotter helium-rich subdwarf O stars. Arguments currently favour an origin in the merger of two white dwarfs; thus there are also connections with AM CVn variables and Type Ia supernovae. Pulsations in many extreme helium stars provide an opportune window into their interiors. These pulsations have unusual properties, some being "strange" modes, and others being driven by Z-bump opacities. They have the potential to deliver distance-independent masses and to provide a unique view of pulsation physics.We review the evolutionary origin and pulsations of these stars, and introduce recent progress and continuing challenges.

show abstract

A New Helium-Rich Star, BD +13°3224

Cited by 15 publications

References 6 publications

Period changes in the pulsating extreme helium stars V652 Her and BX Cir

Period changes in the pulsating extreme helium stars V652 Her and BX Cir

Subaru and Swift observations of V652 Herculis: resolving the photospheric pulsation★

The origin and pulsations of extreme helium stars

Contact Info

Product

Resources

About