New aspects of line-profile variability in P Cygni's optical spectrum

Маркова, Н.

doi:10.1051/aas:2000217

Cited by 16 publications

(20 citation statements)

References 22 publications

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“…Additionally we have found some new features of the objects. In particular, our spectra suggest that HD 168625 (B6 Ia + ) and HD 183143 (B7 Ia) could be considered as candidate objects showing "blueward migrating DACs" (e.g., Markova 2000). We also suggest a new explanation for the complicated shape of the absorption line profiles in the spectrum of AS 314.…”

Section: Discussionmentioning

confidence: 56%

An atlas of spectra of B6–A2 hypergiants and supergiants from 4800 to 6700 Å

Ченцов

Ermakov

Клочкова

et al. 2003

A&A

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Abstract. We present an atlas of spectra of 5 emission-line stars: the low-luminosity luminous blue variables (LBVs) HD 168625 and HD 160529, the white hypergiants (and LBV candidates) HD 168607 and AS 314, and the supergiant HD 183143. The spectra were obtained with 2 echelle spectrometers at the 6-m telescope of the Russian Academy of Sciences in the spectral range 4800 to 6700 Å, with a resolution of 0.4 Å. We have identified 380 spectral lines and diffuse interstellar bands within the spectra. Specific spectral features of the objects are described.

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Section: Discussionmentioning

confidence: 56%

An atlas of spectra of B6–A2 hypergiants and supergiants from 4800 to 6700 Å

Ченцов

Ermakov

Клочкова

et al. 2003

A&A

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“…This supports our study. Thus, we conclude that, during the last two decades, although in quiescence, P Cygni experienced at least two low-amplitude SD cycles with several short-term microvariations (de Groot et al 2001a,b;Markova 2000; superimposed.…”

Section: Discussionmentioning

confidence: 58%

“…The time scale of the SD oscillations is obviously too long to be explained in terms of pulsation instability like strange-mode oscillations (Kiriakidis et al 1993;Glatzel et al 1999), gravitymode oscillations or relaxation oscillations (Stothers & Chin 1995. On the other hand, the only mechanism that could produce phases of enhanced mass-loss rate in LBVs which repeat on time scale of years to decades are quasi-secular oscillations of the stellar envelope between dynamical stable and unstable states, according to the theoretical evolutionary tracks of Stothers & Chin (1995, 2000. Van Genderen (2001) suggested that the long SD-phases could perhaps be identified with the "secular cycles" in Stothers & Chin's models.…”

Section: Discussionmentioning

confidence: 99%

“…The evolutionary status of these objects is still a subject of ongoing debates. In some stellar models, the LBV phase occurs during (or shortly after) the mainsequence phase, produces an enormous mass loss, and prevents evolution to the red (Schaller et al 1992;Meynet et al 1994;Langer et al 1994); in others, the LBVs are post-red-supergiant objects in a late blue phase of dynamical instability (Stothers & Chin 1996, 2000. Some believe that two types of LBVs appear to exist: "classical" LBVs with M bol brighter than −9.5 mag and "low luminous" LBVs with M bol weaker than −9.5 mag, both of which share the main characteristics of the class, but may be in different evolutionary state (e.g.…”

Section: Introductionmentioning

confidence: 99%

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P Cygni in a short S Doradus phase. Spectroscopic and photometric evidences

Маркова

Morrison

Markov

2001

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Abstract.We studied the long-term spectral and photometric behaviour of P Cygni over the 13.8 year interval from March 1985 to January 1999. The UBV photometry reveals a slow (∼7.4-year), low-amplitude (∼0.1 mag) variation in V in which the star becomes redder when it brightens and vice versa. It underwent a possible maximum in the winter of 1985 (between JD 2 446 000 and JD 2 446 200), a minimum in the winter of 1989 (between JD 2 447 500 and JD 2 447 700), a maximum in the fall of 1992 (between JD 2 448 800 and JD 2 449 000), and a minimum in the spring of 1996 (between JD 2 450 100 and JD 2 450 300) The properties of this variation are typical for weak-active S Dor variables in "short S Dor phase" (van Genderen 2001). Simultaneous spectroscopic observations show changes in the Hα equivalent width (corrected for the effect of the changing continuum) in positive correlation with the 7.4-year photometric oscillation in the V -band brightness. This result is interpreted as an indication that in P Cygni an increase in the stellar brightness, during the 7.4-year SD phase, is likely accompanied by an increase in the mass-loss rate. In this behaviour P Cygni is similar to S Dor and R71. From simple considerations, it is concluded that the 7.4-year SD cycle is probably a combination of an increasing radius/decreasing effective temperature and an expanding pseudo-photosphere.

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“…Note that a variation in the continuum will act in a direction opposite to the measured emission and absorption equivalent width. Motivated by this possibility, Markova (2000a) has recently performed an extensive study of line-profile variability in P Cygni's optical spectrum including more than 60 lines formed in different layers of the stellar wind. The results obtained show that line-strength variations (both in absorption and emission), similar to and in phase with the ST variability traced by Hα, do in fact occur in almost all lines in the optical, including the strongest lines of SiIV, which presumably form near or at the base of the supersonic wind.…”

Section: Discussionmentioning

confidence: 99%

Simultaneous H$\mathsf{\alpha}$ and photometric observations of P Cygni

Маркова

Scuderi

Groot

et al. 2001

A&A

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Abstract. For the first time an extensive set of (quasi-) simultaneous photometric (UBV ) and spectroscopic (Hα line profiles) observations of P Cygni, covering a period from May, 1990 to June, 1994 was analyzed in terms of time variability. It is found that the Hα equivalent width (EW ) exhibits two different patterns of variability: a slower one, called Long-Term (LT) variability, with an amplitude of about 30Å and a characteristic duration of about 600 days and a faster one, called Short-Term (ST) variability, with an amplitude up to 10Å and duration of 40 to 60 days. Suggestive evidence for EW variation on a longer time scale (about few years) also exists. The variations in the Hα luminosity are not solely due to changes in the underlying continuum but also reflect variations in the physical properties of the wind. We find, in terms of a simplified spherically-symmetric wind model, that the LT variation of the line can be successfully explained in terms of a 26% alteration of the mass-loss rate, possibly accompanied by variations in the velocity field. From the analysis of the photometric behaviour of the star we find evidence for a very slow variation in the stellar brightness with an amplitude of about 0.13 mag and a duration of about 2600 days, i.e. about 7 years. During this variation, i.e. when the star brightens, the effective temperature decreases (by about 10%) and the radius increases (by about 7%). The properties of this Very Long Term (VLT) variation suggest that P Cygni has probably experienced a normal S Dor-type variation with a minimum phase around 1988 and a maximum phase in 1992. Some hints for a positive correlation between mass loss variations and changes in the stellar radius, due to the normal SD variability, do exist implying that the behaviour of P Cygni is more likely similar to that of R71 and S Dor but different from e.g. AG Car, R127 and HD 160529. Superimposed on the VLT component in the photometric variability of P Cygni, we observe ST brightness variations with an amplitude between 0.1 and 0.2 mag which appears to recur on a time scale of three to four months. The colour behaviour of these microvariations, at least of those which appear near the maximum phase of the VLT variation, is redder in B − V and bluer in U − B when the star brightens in V . The properties of this ST photometric variability are similar to the properties of the so-called "100 d-type micro-variations", recognized in other LBVs by van Genderen et al. (1997a,b). Based on time-scale evidences we suggest that the microvariabilities observed are rather due to "relaxation oscillations" (Stothers & Chin 1995) than to strange-mode oscillations in the stellar interior. Evidence for a close relationship between ST variations in Hα and changes in the stellar brightness and temperature is found. From other results about P Cygni's spectral variations (Markova 2000a), we conclude that the ST variability of the wind is most likely connected with processes in the stellar photosphere.

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New aspects of line-profile variability in P Cygni's optical spectrum

Cited by 16 publications

References 22 publications

An atlas of spectra of B6–A2 hypergiants and supergiants from 4800 to 6700 Å

An atlas of spectra of B6–A2 hypergiants and supergiants from 4800 to 6700 Å

P Cygni in a short S Doradus phase. Spectroscopic and photometric evidences

Simultaneous H$\mathsf{\alpha}$ and photometric observations of P Cygni

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