Wind variability of B supergiants

Prinja, R. K.; Massa, Derck; Fullerton, A. W.

doi:10.1051/0004-6361:20020503

Cited by 61 publications

(102 citation statements)

References 44 publications

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“…Deviations from spherical symmetry in hot massive star winds are also suggested by optical observations (e.g. Prinja 1990;Prinja et al 2002) and the presence of equatorial disc components, denser and slower with respect to the polar wind, also results from simulations (ud-Doula et al 2006). …”

Section: Discussionsupporting

confidence: 60%

An alternative hypothesis for the outburst mechanism in supergiant fast X-ray transients: the case of IGR J11215–5952

Sidoli¹,

Romano

Mereghetti³

et al. 2007

A&A

145

222

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Context. The physical mechanism responsible for the short outbursts in a recently recognised class of high mass X-ray binaries, the supergiant fast X-ray transients (SFXTs), is still unknown. Two main hypotheses have been proposed to date: the sudden accretion by the compact object of small ejections originating in a clumpy wind from the supergiant donor, or outbursts produced at (or near) the periastron passage in wide and eccentric orbits, to explain the low (∼10 32 erg s −1 ) quiescent emission. Neither proposed mechanisms explain the whole phenomenology of these sources. IGR J11215-5952, discovered in April 2005 by the INTEGRAL satellite, is a SFXT which undergoes an outburst every 329 days, a periodicity likely associated with the orbital period of the binary system. Aims. We propose a new explanation for the outburst mechanism, based on the X-ray observations of the unique SFXT known to display periodic outbursts, IGR J11215-5952. Methods. We performed three Target of Opportunity (ToO) Results. XMM-Newton observed the source on 2007 February 9, for 23 ks, at the peak of the outburst, while INT EGRAL started the observation two days later, failing to detect the source, which had already undergone the decaying phase of the fast outburst. XMM-Newton data show large variability, with a bright flare at the beginning of the observation (lasting about 1 h), followed by a lower intensity phase (about one order of magnitude fainter) with a large variability as well as low level flaring activity. The spin periodicity discovered by RXTE is confirmed, and a spin-phase spectral variability is observed and studied in detail. The Swift campaign performed in July 2007 reveals a second outburst on 2007 July 24, as bright as that observed about 165 days before. Conclusions. The new X-ray observations allow us to propose an alternative hypothesis for the outburst mechanism in SFXTs, linked to the possible presence of a second wind component, in the form of an equatorial disc from the supergiant donor. We discuss the applicability of the model to the short outburst durations of all other SFXTs, where a clear periodicity in the outbursts has not been found yet. The new outburst from IGR J11215-5952 observed in July suggests that the true orbital period is ∼165 days, instead of 329 days, as previously thought.

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Section: Discussionsupporting

confidence: 60%

An alternative hypothesis for the outburst mechanism in supergiant fast X-ray transients: the case of IGR J11215–5952

Sidoli¹,

Romano

Mereghetti³

et al. 2007

A&A

145

222

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“…Detailed analyses of the 1993 and 1995 IUE MEGA campaign data of this star have been presented in the literature. The 1993 data are thoroughly discussed in Massa et al (1995a), while Prinja et al (1995) and Howarth et al (1998) present time-series analyses of both data sets. These studies, however, provide periods for the rotationally modulated wind variations rather than for the slower evolving DAC structures we model in this paper.…”

Section: Observationsmentioning

confidence: 99%

“…The horizontal bow shape of these features clearly differs from the more triangular shape of the DACs. These modulations exhibit a possible period in HD 64760 of $1.2 days ( Fullerton et al 1997;Prinja et al 2002), although careful inspection of the flux difference image reveals that these shallow modulations alternate over time with comparable absorption features that extend even more horizontally (i.e., they are almost completely horizontal without the rounded bowlike shape). Clear examples of both types of horizontal features are observed around 4.8 and 6 days, and around 7.3 and 8.5 days.…”

mentioning

confidence: 99%

Modeling Ultraviolet Wind Line Variability in Massive Hot Stars

Lobel¹,

Blomme²

2008

ApJ

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We model the detailed time-evolution of discrete absorption components (DACs) observed in P Cygni profiles of the Si iv k1400 resonance doublet lines of the fast-rotating supergiant HD 64760 (B0.5 Ib). We adopt the common assumption that the DACs are caused by corotating interaction regions (CIRs) in the stellar wind. We perform 3D radiative transfer calculations with hydrodynamic models of the stellar wind that incorporate these large-scale density-and velocity-structures. We develop the 3D transfer code Wind3D to investigate the physical properties of CIRs with detailed fits to the DAC shape and morphology. We constrain the properties of large-scale wind structures with detailed fits to DACs observed in HD 64760. A model with two spots of unequal brightness and size on opposite sides of the equator-20% AE 5% and 8% AE 5% brighter than the stellar surface and with opening angles of 20 AE 5 and 30 AE 5 diameter, respectively-provides the best fit to the observed DACs. The recurrence time of the DACs compared to the estimated rotational period corresponds to spot velocities that are 5 times slower than the rotational velocity. The massloss rate of the structured-wind model for HD 64760 does not exceed the rate of the spherically symmetric smoothwind model by more than 1%. The fact that DACs are observed in a large number of hot stars constrains the clumping that can be present in their winds, as substantial amounts of clumping would tend to destroy the CIRs.

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“…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). Such data are in any case needed to perform a reliable seismic characterization of these extreme stellar objects.…”

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

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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.

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Wind variability of B supergiants

Cited by 61 publications

References 44 publications

An alternative hypothesis for the outburst mechanism in supergiant fast X-ray transients: the case of IGR J11215–5952

An alternative hypothesis for the outburst mechanism in supergiant fast X-ray transients: the case of IGR J11215–5952

Modeling Ultraviolet Wind Line Variability in Massive Hot Stars

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

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