Dr Walker reply

Walker, P R

doi:10.1136/hrt.55.1.112-b

Cited by 4 publications

(3 citation statements)

References 11 publications

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“…The carbon stars with strong Merrill±Sanford bands are extremely red, with U 2 BY B 2 V and V 2 I each typically about 5 mag (Walker 1976(Walker , 1979. Thus the 4000-A Ê region is about 100 000 times fainter than the region at the red sensitivity limit of the detector.…”

Section: O B S E Rvat I O N Smentioning

confidence: 99%

SiC2 in carbon stars: Merrill-Sanford absorption bands between 4100 and 5500 Å

Sarre

Hurst

Evans

2002

Monthly Notices of the Royal Astronomical Society

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Observations and identifications of the Merrill–Sanford bands of the silicon dicarbide molecule are reported for a range of N and J stars. The data were recorded at 0.8−1.6 Å resolution between 4100 and 5500 Å. A full description of the assignments and spectral features in the stars is given. The spectra are characterized by absorption from the ground vibrational level (0, 0, 0) and from higher‐lying vibrational levels involving one quantum of excitation in ν1, and up to two quanta in ν2 and ν3, giving rise to numerous hot‐bands. The first results of rotational contour calculations are presented, and are consistent with SiC2 lying in the upper atmosphere of the star with a rotational temperature substantially lower than that of the photosphere.

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Section: O B S E Rvat I O N Smentioning

confidence: 99%

SiC2 in carbon stars: Merrill-Sanford absorption bands between 4100 and 5500 Å

Sarre

Hurst

Evans

2002

Monthly Notices of the Royal Astronomical Society

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“…This non‐detection is certainly due to variability rather than error because the star is not visible on an UKST V ‐plate taken 1 month later. Also included are measurements in R and I from Walker (1979) for KDM 6546 and in I from Udalski et al (1998) for RAW 21.…”

Section: Variabilitymentioning

confidence: 99%

Suspected cool R Coronae Borealis stars in the Magellanic Clouds

Morgan¹,

Hatzidimitriou²,

Cannon³

et al. 2003

Monthly Notices of the Royal Astronomical Society

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Six stars out of a sample of ∼2300 carbon stars in the Magellanic Clouds have been identified as having strong C2 bands but CN bands that are very weak or absent. It is argued that five of these are likely to be R Coronae Borealis (RCB) stars on the basis of their spectral characteristics and peculiar colours. Most are variables and the Large Magellanic Cloud (LMC) members have extreme radial velocities that are more like the planetary nebula population than the carbon stars. This sample consists of four LMC members (only one of them previously recognized as an RCB star), one Small Magellanic Cloud (SMC) member (the first RCB star reported in the SMC) and one foreground Galactic star.

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“…(Pojmanski 2002). There are a few other scattered observations in the literature (Eggen 1972;Walker 1979). All of these various observations were transformed to the V-band.…”

Section: Observationsmentioning

confidence: 99%

A Unique Dust Formation Episode in the SC‐Type Star UY Centauri

Steinfadt¹,

Clayton²,

Evans³

et al. 2005

PUBL ASTRON SOC PAC

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We report the first detection of new dust formation in an SC star. The prototype of the SC stars, UY Cen, underwent a decline of 2 magnitudes in the V-band. The SC stars show pulsational variations and have 60 µm excesses indicating past dust formation. It has been suggested that as a star evolves from oxygen rich to carbon rich, there is a short period of time when C/O∼1 that the star appears spectroscopically as an SC star and ceases to produce dust. The SC star, BH Cru, has shown large spectroscopic and pulsation period variations in only 30 years, indicating rapid evolution but it has shown no sign of new dust formation. UY Cen has not shown any pulsation or spectroscopic variations accompanying the onset of its dust formation. In addition, UY Cen did not show emission in the resonance lines of Na I, K I or Rb I when it was at its faintest, although these lines were a feature of the carbon stars R Lep and V Hya during similar faint phases.

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Dr Walker reply

Cited by 4 publications

References 11 publications

SiC2 in carbon stars: Merrill-Sanford absorption bands between 4100 and 5500 Å

SiC2 in carbon stars: Merrill-Sanford absorption bands between 4100 and 5500 Å

Suspected cool R Coronae Borealis stars in the Magellanic Clouds

A Unique Dust Formation Episode in the SC‐Type Star UY Centauri

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