Time-Series Observations of O Stars. II. Optical Observations of zeta Ophiuchi

Reid, Andy; Bolton, C. T.; Crowe, R.; Fieldus, M. S.; Fullerton, A. W.; Gies, Douglas R.; Howarth, I. D.; McDavid, D.; Prinja, R. K.; Smith, K. C.

doi:10.1086/173315

Cited by 45 publications

(39 citation statements)

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“…This shows that the line formation position in the atmosphere is not the only parameter controlling line variability. For instance, Reid et al (1993) suggested that for the fast rotator ζ Oph, equator-to-pole temperature gradients lead to formation of He ii (He i) lines primarily at the pole (equator).…”

Section: Spatially Resolved Variabilitymentioning

confidence: 99%

Radial dependence of line profile variability in seven O9–B0.5 stars

Martins

Marcolino

Hillier

et al. 2015

A&A

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Context. Massive stars show a variety of spectral variabilities: discrete absorption components in UV P-Cygni profiles, optical line profile variability, X-ray variability, and radial velocity modulations. Aims. Our goal is to study the spectral variability of single OB stars to better understand the relation between photospheric and wind variability. For that, we rely on high spectral resolution and on high signal-to-noise ratio optical spectra collected with the spectrograph NARVAL on the Télescope Bernard Lyot at Pic du Midi. Methods. We investigated the variability of twelve spectral lines by means of the temporal variance spectrum. The selected lines probe the radial structure of the atmosphere from the photosphere to the outer wind. We also performed a spectroscopic analysis with atmosphere models to derive the stellar and wind properties and to constrain the formation region of the selected lines. Results. We show that variability is observed in the wind lines of all bright giants and supergiants on a daily timescale. Lines formed in the photosphere are sometimes variable, sometimes not. The dwarf stars do not show any sign of variability. If variability is observed on a daily timescale, it can also (but not always) be observed on hourly timescales, albeit with lower amplitude. There is a very clear correlation between amplitude of the variability and fraction of the line formed in the wind. Strong anti-correlations between the different parts of the temporal variance spectrum are observed. Conclusions. Our results indicate that variability is stronger in lines formed in the wind. A link between photospheric and wind variability is not obvious from our study, since wind variability is observed regardless of the level of photospheric variability. Different photospheric lines also show different degrees of variability.

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Section: Spatially Resolved Variabilitymentioning

confidence: 99%

Radial dependence of line profile variability in seven O9–B0.5 stars

Martins

Marcolino

Hillier

et al. 2015

A&A

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“…It has been known for a long time to present different kinds of spectral variability, such as discrete absorption components in the UV (DACs), emission line episodes, and line profile variations (LPVs) (see e.g., Howarth et al 1984;Reid et al 1993;Howarth et al 1993;Jankov et al 2000;Walker et al 2005). This object also shows a very high rotational velocity: v sin i values around 400 or even 500 km s −1 have been reported in the literature (Walker et al 1979;Repolust et al 2004).…”

Section: ζ Ophmentioning

confidence: 99%

Analysis of Galactic late-type O dwarfs: more constraints on the weak wind problem

Marcolino

Bouret

Martins

et al. 2009

A&A

117

169

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Aims. We investigate the stellar and wind properties of a sample of late-type O dwarfs. Previous analyses of such stars have found very low mass-loss rates; rates much lower than predicted by theory (the weak wind problem). Methods. Far-UV to optical spectra of five Galactic O stars were analyzed: HD 216898 (O9IV/O8.5V), HD 326329 (O9V), HD 66788 (O8V/O9V), ζ Oph (O9.5Vnn), and HD 216532 (O8.5V((n))). We used a grid of TLUSTY models to obtain effective temperatures, gravities, rotational velocities, and to identify wind lines. Wind parameters for each object were obtained using expanding atmosphere models calculated with the CMFGEN code.Results. The spectra of our sample have primarily a photospheric origin. A weak wind signature is seen in C iv λλ1548, 1551, from which mass-loss rates consistent with previous CMFGEN results for O8-O9V stars were derived (∼10 −10 −10 −9 M yr −1 ). A discrepancy of roughly two orders of magnitude is found between these mass-loss rates and the values predicted by theory (Ṁ Vink ), confirming a breakdown or a steepening of the modified wind momentum-luminosity relation at log L /L < ∼ 5.2. We have estimated the carbon abundance for the stars of our sample and concluded that its value cannot be reduced to sufficiently small values to solve the weak wind problem. Upper limits onṀ were established for all objects using lines of different ions: P v λλ1118, 1128, C iii λ1176, N v λλ1239, 1243, Si iv λλ1394, 1403, and N iv λ1718. All the values obtained are in disagreement with theoretical predictions, bringing support to the reality of weak winds. Together with C iv λλ1548, 1551, the use of N v λλ1239, 1243 results in the lowest mass-loss rates: the upper limits indicate thatṀ must be less than about −1.0 dexṀ Vink . Upper mass-loss rate limits obtained for other transitions are also low: they indicate thatṀ must be less than about (−0.5 ± 0.2) dexṀ Vink . We studied the behavior of the Hα line with different mass-loss rates. For two stars, only models with very lowṀ's provide the best fit to the UV and optical spectra. We also explored ways to fit the observed spectra with the theoretical mass-loss rates. By using large amounts of X-rays, we could reduce the predicted wind emission to the observed levels. However, unrealistic X-ray luminosities had to be used (log L X /L Bol > ∼ −3.5). The validity of the models used in our analyses is discussed.

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“…If we alternatively suppose the periodic variations of NSV 26083 to be due to rotation modulation of stellar spot(s), the rotational period can be estimated as follows (Reid et al 1993):…”

Section: Search For Periodicities In the Light Curvesmentioning

confidence: 99%

“…Following the discussion by Reid et al (1993), we use R e ¼ 1:5R Ã , where R Ã is the radius of NSV 26083. If Zhang & Kwok's (1993) results of T eA ¼ 31;800 K, log g ¼ 3:1, and M ¼ 0:8 M are adopted, the rotational period P crit would be as large as 48 hr.…”

Section: Search For Periodicities In the Light Curvesmentioning

confidence: 99%

Evidence for a Binary Origin of the Young Planetary Nebula Hubble 12

Hsia

2006

Astron J

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Young planetary nebulae play an important role in stellar evolution when intermediate-to low-mass stars (0.8-8 M ) evolve from the proto-planetary nebula phase to the planetary nebula phase. Many young planetary nebulae display distinct bipolar structures as they evolve away from the proto-planetary nebula phase. One possible cause of their bipolarity could be a binary origin for their energy source. Here we report on our detailed investigation of the young planetary nebula Hubble 12, which is well known for its extended hourglass-like envelope. We present evidence with time-series photometric observations for the existence of an eclipsing binary at the center of Hubble 12. In addition, low-resolution spectra of the central source show absorption features such as CN, G band, and Mg b, which can be suggestive of a low-mass nature for the secondary component.

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Time-Series Observations of O Stars. II. Optical Observations of zeta Ophiuchi

Cited by 45 publications

References 0 publications

Radial dependence of line profile variability in seven O9–B0.5 stars

Radial dependence of line profile variability in seven O9–B0.5 stars

Analysis of Galactic late-type O dwarfs: more constraints on the weak wind problem

Evidence for a Binary Origin of the Young Planetary Nebula Hubble 12

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