Interplay between pulsations and mass loss in the blue supergiant 55 Cygnus = HD 198 478

Kraus, M.; Haucke, M.; Cidale, L. S.; Venero, R. O. J.; Nickeler, D. H.; Németh, P.; Niemczura, E.; Tomić, S.; Aret, A.; Kubát, Jiřı́; Kubátová, B.; Oksala, M. E.; Curé, M.; Kamiński, K.; Dimitrov, W.; Fagas, M.; Polińska, M.

doi:10.1051/0004-6361/201425383

Cited by 41 publications

(53 citation statements)

References 87 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Consequently, the width of a line provides no reliable indicator for the contribution of stellar rotation, and we suspect that sin i of LHA 120-S 73 is (much) smaller than 50 km s −1 . If present, pulsations might also (quasi-)periodically enhance the mass loss of the star (see, e.g., Aerts et al 2010b;Kraus et al 2015a), so that during specific times density peaks might form in the radial outflow. Depending on the pulsation modes, this "pulsed" mass loss might be confined within the equatorial plane, leading to ring structures in the outflow.…”

Section: Origin Of the Circumstellar Ringsmentioning

confidence: 99%

Inhomogeneous molecular ring around the B[e] supergiant LHA 120-S 73

Kraus

Cidale

Arias

et al. 2016

A&A

Self Cite

View full text Add to dashboard Cite

Context. B[e] supergiants are evolved massive stars, enshrouded in a dense wind and surrounded by a molecular and dusty disk. The mechanisms that drive phases of enhanced mass loss and mass ejections, responsible for the shaping of the circumstellar material of these objects, are still unclear. Aims. We aim to improve our knowledge on the structure and dynamics of the circumstellar disk of the Large Magellanic Cloud B[e] supergiant LHA 120-S 73. Methods. High-resolution optical and near-infrared spectroscopic data were obtained over a period of 16 and 7 yr, respectively. The spectra cover the diagnostic emission lines from [Ca ii] and [O i], as well as the CO bands. These features trace the disk at different distances from the star. We analyzed the kinematics of the individual emission regions by modeling their emission profiles. A lowresolution mid-infrared spectrum was obtained as well, which provides information on the composition of the dusty disk. Results. All diagnostic emission features display double-peaked line profiles, which we interpret as due to Keplerian rotation. We find that the profile of each forbidden line contains contributions from two spatially clearly distinct rings. In total, we find that LHA 120-S 73 is surrounded by at least four individual rings of material with alternating densities (or by a disk with strongly nonmonotonic radial density distribution). Moreover, we find that the molecular ring must have gaps or at least strong density inhomogeneities, or in other words, a clumpy structure. The optical spectra additionally display a broad emission feature at 6160-6180 Å, which we interpret as molecular emission from TiO. The mid-infrared spectrum displays features of oxygen-and carbon-rich grain species, which indicates a long-lived, stable dusty disk.We cannot confirm the previously reported high value for the stellar rotation velocity. He i λ 5876 is the only clearly detectable pure atmospheric absorption line in our data. Its line profile is strongly variable in both width and shape and resembles of those seen in non-radially pulsating stars. A proper determination of the real underlying stellar rotation velocity is hence not possible. Conclusions. The existence of multiple stable and clumpy rings of alternating density recalls ring structures around planets. Although there is currently insufficient observational evidence, it is tempting to propose a scenario with one (or more) minor bodies or planets revolving around LHA 120-S 73 and stabilizing the ring system, in analogy to the shepherd moons in planetary systems.

show abstract

Section: Origin Of the Circumstellar Ringsmentioning

confidence: 99%

Inhomogeneous molecular ring around the B[e] supergiant LHA 120-S 73

Kraus

Cidale

Arias

et al. 2016

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…Long-term ground-based photometry of mmag-level precision (e.g., van Genderen 1989;Lamers et al 1998, and references therein) and spectroscopy of km s −1 precision (e.g., Markova et al 2005;Simón-Díaz et al 2010;Martins et al 2015;Kraus et al 2015) devoted to blue supergiants typically had sparse sampling and led to aliasing and high noise levels in the Fourier spectra. As a result, the interpretation of blue supergiant variability from groundbased data remained limited.…”

Section: Introductionmentioning

confidence: 99%

K2 photometry and HERMES spectroscopy of the blue supergiant ρ Leo: rotational wind modulation and low-frequency waves

Aerts

Bowman

Simón‐Díaz

et al. 2018

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We present an 80-d long uninterrupted high-cadence K2 light curve of the B1Iab supergiant ρ Leo (HD 91316), deduced with the method of halo photometry. This light curve reveals a dominant frequency of f rot = 0.0373 d −1 and its harmonics. This dominant frequency corresponds with a rotation period of 26.8 d and is subject to amplitude and phase modulation. The K2 photometry additionally reveals multiperiodic low-frequency variability (< 1.5 d −1 ) and is in full agreement with low-cadence high-resolution spectroscopy assembled during 1800 days. The spectroscopy reveals rotational modulation by a dynamic aspherical wind with an amplitude of about 20 km s −1 in the Hα line, as well as photospheric velocity variations of a few km s −1 at frequencies in the range 0.2 to 0.6 d −1 in the Si III 4567Å line. Given the large macroturbulence needed to explain the spectral line broadening of the star, we interpret the detected photospheric velocity as due to travelling super-inertial low-degree large-scale gravity waves with dominant tangential amplitudes and discuss why ρ Leo is an excellent target to study how the observed photospheric variability propagates into the wind.

show abstract

“…S. S.-D. et al: Low-frequency photospheric and wind variability in HD 2905 Meanwhile, important advances can be also achieved using ground-based time-resolved spectroscopy (e.g., Kraus et al, 2015;Aerts et al, 2017). Indeed, these complementary observations will become decisive for disentangling the intricate -and most likely interconnected -photospheric and wind variability present in the whole massive star domain (see Ebbets, 1982;Prinja et al, 1996;Fullerton et al, 1996;Kaufer et al, 1996Kaufer et al, , 1997Rivinius et al, 1997;Morel et al, 2004;Markova et al, 2005Markova et al, , 2008Martins et al, 2015, for some illustrative examples).…”

Section: Introductionmentioning

confidence: 99%

Low-frequency photospheric and wind variability in the early-B supergiant HD 2905

Diaz

Aerts

Urbaneja

et al. 2018

A&A

View full text Add to dashboard Cite

Context. Despite the important advances in space asteroseismology during the last decade, the early phases of evolution of stars with masses above ∼15 M (including the O stars and their evolved descendants, the B supergiants) have been only vaguely explored up to now. This is due to the lack of adequate observations for a proper characterization of the complex spectroscopic and photometric variability occurring in these stars. Aims. Our goal is to detect, analyze and interpret variability in the early-B type supergiant HD 2905 (κ Cas, B1 Ia) using long-term, ground based, high resolution spectroscopy. Methods. We gather a total of 1141 high-resolution spectra covering some 2900 days with three different high-performance spectrographs attached to 1 -2.6m telescopes at the Canary Islands observatories. We complement these observations with the Hipparcos light curve, which includes 160 data points obtained during a time span of ∼1200 days. We investigate spectroscopic variability of up to 12 diagnostic lines by using the zero and first moments of the line profiles. We perform a frequency analysis of both the spectroscopic and photometric dataset using Scargle periodograms. We obtain single snapshot and time-dependent information about the stellar parameters and abundances by means of the fastwind stellar atmosphere code. Results. HD 2905 is a spectroscopic variable with peak-to-peak amplitudes in the zero and first moments of the photospheric lines of up to 15% and 30 km s −1 , respectively. The amplitude of the line-profile variability is correlated with the line formation depth in the photosphere and wind. All investigated lines present complex temporal behavior indicative of multi-periodic variability with timescales of a few days to several weeks. No short-period (hourly) variations are detected. The Scargle periodograms of the Hipparcos light curve and the first moment of purely photospheric lines reveal a low-frequency amplitude excess and a clear dominant frequency at ∼0.37 d −1 . In the spectroscopy, several additional frequencies are present in the range 0.1 -0.4 d −1 . These may be associated with heat-driven gravity modes, convectively-driven gravity waves, or sub-surface convective motions. Additional frequencies are detected below 0.1 d −1 . In the particular case of Hα, these are produced by rotational modulation of a non-spherically symmetric stellar wind. Conclusions. Combined long-term uninterrupted space photometry with high-precision spectroscopy is the best strategy to unravel the complex low-frequency photospheric and wind variability of B supergiants. 3D simulations of waves and of convective motions in the sub-surface layers can shed light on a unique interpretation of the variability.

show abstract

Interplay between pulsations and mass loss in the blue supergiant 55 Cygnus = HD 198 478

Cited by 41 publications

References 87 publications

Inhomogeneous molecular ring around the B[e] supergiant LHA 120-S 73

Inhomogeneous molecular ring around the B[e] supergiant LHA 120-S 73

K2 photometry and HERMES spectroscopy of the blue supergiant ρ Leo: rotational wind modulation and low-frequency waves

Low-frequency photospheric and wind variability in the early-B supergiant HD 2905

Contact Info

Product

Resources

About