Search

The structured winds of single massive stars can be classified into two broad groups: stochastic structure and organized structure. While the former is typically identified with clumping, the latter is typically associated with rotational modulations, particularly the paradigm of Co-rotating Interaction Regions (CIRs). While CIRs have been explored extensively in the UV band, and moderately in the X-ray and optical, here we evaluate radio variability from CIR structures assuming free-free opacity in a dense wind. Our goal is to conduct a broad parameter study to assess the observational feasibility, and to this end, we adopt a phenomenological model for a CIR that threads an otherwise spherical wind. We find that under reasonable assumptions, it is possible to obtain radio variability at the 10% level. The detailed structure of the folded light curve depends not only on the curvature of the CIR, the density contrast of the CIR relative to the wind, and viewing inclination, but also on wavelength. Comparing light curves at different wavelengths, we find that the amplitude can change, that there can be phase shifts in the waveform, and the the entire waveform itself can change. These characterstics could be exploited to detect the presence of CIRs in dense, hot winds., to appear inn MNRAS

We present e-MERLIN 21 cm (L-band) observations of single luminous OB stars in the Cygnus OB2 association, from the Cyg OB2 Radio Survey Legacy programme. The radio observations potentially offer the most straightforward, least model-dependent, determinations of mass-loss rates, and can be used to help resolve current discrepancies in mass-loss rates via clumped and structured hot star winds. We report here that the 21 cm flux densities of O3 to O6 supergiant and giant stars are less than ∼70 μJy. These fluxes may be translated to ‘smooth’ wind mass-loss upper limits of ∼4.4–4.8 × 10−6 M⊙ yr −1 for O3 supergiants and ≲2.9 × 10−6 M⊙ yr −1 for B0 to B1 supergiants. The first ever resolved 21 cm detections of the hypergiant (and luminous blue variable candidate) Cyg OB2 #12 are discussed; for multiple observations separated by 14 d, we detect an ∼69 per cent increase in its flux density. Our constraints on the upper limits for the mass-loss rates of evolved OB stars in Cyg OB2 support the model that the inner wind region close to the stellar surface (where Hα forms) is more clumped than the very extended geometric region sampled by our radio observations.

The MiMeS project is a large-scale, high resolution, sensitive spectropolarimetric investigation of the magnetic properties of O and early B type stars. Initiated in 2008 and completed in 2013, the project was supported by 3 Large Program allocations, as well as various programs initiated by independent PIs and archival resources. Ultimately, over 4800 circularly polarized spectra of 560 O and B stars were collected with the instruments ESPaDOnS at the Canada-France-Hawaii Telescope, Narval at the T\'elescope Bernard Lyot, and HARPSpol at the European Southern Observatory La Silla 3.6m telescope, making MiMeS by far the largest systematic investigation of massive star magnetism ever undertaken. In this paper, the first in a series reporting the general results of the survey, we introduce the scientific motivation and goals, describe the sample of targets, review the instrumentation and observational techniques used, explain the exposure time calculation designed to provide sensitivity to surface dipole fields above approximately 100 G, discuss the polarimetric performance, stability and uncertainty of the instrumentation, and summarize the previous and forthcoming publications., Comment: Accepted by MNRAS

The professor of astrophysics has received a prize from the AIP for his children's book Planetarium.

We analyze a 162 ks HETG Chandra observation of the O7.5 III(n)((f)) star xi Per, together with contemporaneous H alpha observations. The X-ray spectrum of this star is similar to other single O stars, and not pathological in any way. Its UV wind lines are known to display cyclical time variability, with a period of 2.086 days, which is thought to be associated with co-rotating interaction regions (CIRs). We examine the Chandra and H alpha data for variability on this time scale. We find that the X-rays vary by about 15% over the course of the observations and that this variability is out of phase with variable absorption on the blue wing of the H alpha profiles (assumed to be a surrogate for the UV absorption associated with CIRs). While not conclusive, both sets of data are consistent with models where the CIRs are either a source of X-rays or modulate them., Accepted by MNRAS. 9 pages, 9 figures

We report on high-resolution optical time-series spectroscopy of the central star of the `Eskimo' planetary nebula NGC~2392. Datasets were secured with the ESO 2.3m in 2006 March and CFHT 3.6m in 2010 March to diagnose the fast wind and photospheric properties of the central star. The HeI and HeII recombination lines reveal evidence for clumping and temporal structures in the fast wind that are erratically variable on timescales down to ~ 30 min. (i.e. comparable to the characteristic wind flow time). We highlight changes in the overall morphology of the wind lines that cannot plausibly be explained by line-synthesis model predictions with a spherically homogeneous wind. Additionally we present evidence that the UV line profile morphologies support the notion of a high-speed, high-ionization polar wind in NGC~2392. Analyses of deep-seated, near-photospheric absorption lines reveals evidence for low-amplitude radial velocity shifts. Fourier analysis points tentatively to a ~ 0.12-d modulation in the radial velocities, independently evident in the ESO and CFHT data. We conclude that the overall spectroscopic properties support the notion of a (high inclination) binary nucleus in NGC~2392 and an asymmetric fast wind.

We present new, contemporaneous HST STIS and XMM observations of the O7 III(n)((f)) star xi Per. We supplement the new data with archival IUE spectra, to analyze the variability of the wind lines and X-ray flux of xi Pper. The variable wind of this star is known to have a 2.086 day periodicity. We use a simple, heuristic spot model which fits the low velocity (near surface) IUE wind line variability very well, to demonstrate that the low velocity absorption in the new STIS spectra of N IV 1718 and Si IV 1402 vary with the same 2.086 day period. It is remarkable that the period and amplitude of the STIS data agree with those of the IUE spectra obtained 22 years earlier. We also show that the time variability of the new XMM fluxes are also consistent with the 2.086 day period. Thus, our new, multi-wavelength coordinated observations demonstrate that the mechanism which causes the UV wind line variability is also responsible for a significant fraction of the X-rays in single O stars. The sequence of events for the multi-wavelength light curve minima is: Si IV 1402, N IV 1718, and X-ray flux, each separated by a phase of about 0.06 relative to the 2.086 day period. Analysis of the X-ray fluxes shows that they become softer as they weaken. This is contrary to expectations if the variability is caused by periodic excess absorption. Further, the high resolution X-ray spectra suggest that the individual emission lines at maximum are more strongly blue shifted. If we interpret the low velocity wind line light curves in terms of our model, it implies that there are two bright regions, i.e., regions with less absorption, separated by 180 deg, on the surface of the star. We note that the presence and persistent of two spots separated by 180 deg suggests that a weak dipole magnetic field is responsible for the variability of the UV wind line absorption and X-ray flux in xi Per., 23 pages, 14 figures

To diagnose the time-variable structure in the fast winds of central stars of planetary nebulae (CSPN), we present an analysis of P Cygni line profiles in FUSE satellite far-UV spectroscopic data. Archival spectra are retrieved to form time-series datasets for the H-rich CSPN NGC 6826, IC 418, IC 2149, IC 4593 and NGC 6543. Despite limitations due to the fragmented sampling of the time-series, we demonstrate that in all 5 CSPN the UV resonance lines are variable primarily due to the occurrence of blueward migrating discrete absorption components (DACs). Empirical (SEI) line-synthesis modelling is used to determine the range of fluctuations in radial optical depth, which are assigned to the temporal changes in large-scale wind structures. We argue that DACs are common in CSPN winds, and their empirical properties are akin to those of similar structures seen in the absorption troughs of massive OB stars. Constraints on PN central star rotation velocities are derived from Fast-Fourier Transform analysis of photospheric lines for our target stars. Favouring the causal role of co-rotating interaction regions, we explore connections between normalised DAC accelerations and rotation rates of PN central stars and O stars. The comparative properties suggest that the same physical mechanism is acting to generate large-scale structure in the line-driven winds in the two different settings.

Highly time-resolved time-tagged FUSE satellite spectroscopic data are analysed to establish the far-ultraviolet (FUV) absorption line characteristics of the nova-like cataclysmic variable binary, V3885 Sgr. We determine the temporal behaviour of low (Lyβ, C iii, N iii) and high (S iv, P v, O vi) ion species, and highlight corresponding orbital phase modulated changes in these lines. On average, the absorption troughs are blueshifted due to a low-velocity disc wind outflow. Very rapid (∼5 min) fluctuations in the absorption lines are isolated, which are indicative of stochastic density changes. Doppler tomograms of the FUV lines are calculated which provide evidence for structures where a gas stream interacts with the accretion disc. We conclude that the line depth and velocity changes as a function of orbital phase are consistent with an asymmetry that has its origin in a line-emitting, localized disc–stream interaction region.

We present optical ESO time-series and UV archival (FUSE, HST, IUE) spectroscopy of the H-rich central star of He 2-138. Our study targets the central star wind in a very young planetary nebula, and explores physical conditions that may provide clues to the nature of the preceding post-AGB super-wind phases of the star. We provide evidence for a dense, slowly accelerating outflow that is variable on time-scales of hours. Line-synthesis modelling (SEI and CMFGEN) of low and high ionization UV and optical lines is interpreted in terms of an asymmetric, two-component outflow, where high-speed high-ionization gas forms mostly in the polar region. Slower, low ionization material is then confined primarily to a cooler equatorial component of the outflow. A dichotomy is also evident at photospheric levels. We also document temporal changes in the weak photospheric lines of He 2-138, with tentative evidence for a 0.36-day modulation in blue-to-red migrating features in the absorption lines. These structures may betray 'wave-leakage' of prograde non-radial pulsations of the central star. These multi-waveband results on the aspherical outflow of He 2-138 are discussed in the context of current interest in understanding the origin of axi- and point-symmetric planetary nebulae.

Luminous, massive stars provide one of the greatest feedback mechanisms of energy and material back into the interstellar medium (ISM), providing ’food’ for the ever on-going star formation from galaxy to galaxy. An important parameter in desperate need of pinning down is the rate at which OB stars lose mass, such that we obtain an accurate picture of massive star stellar winds. Strong evidence suggests that previous mass-loss rates have been over-estimated and descrepancies between different mass-loss diagnostics excite the need for structured stellar wind models on both small (clumping) and large (co-rotating interaction regions) scales. COBRaS, the eMERLIN Legacy Cyg OB II Radio Survey shall deliver high resolution, deep field maps at both Land C-band to deliver accurate mass-loss estimates of a large sample of O and B stars. In manufacturing the most substanstial radio dataset of the Cyg OB II region, COBRaS is expected to clarify our understanding of massive star winds and constrain clumping (small-scale structure) by probing the outer region of OB stellar winds.

We report on the analysis of the Chandra-ACIS data of O, B and WR stars in the young association Cyg OB2. X-ray spectra of 49 O-stars, 54 B-stars and 3 WR-stars are analyzed and for the brighter sources, the epoch dependence of the X-ray fluxes is investigated. The O-stars in Cyg\,OB2 follow a well-defined scaling relation between their X-ray and bolometric luminosities: log(Lx/Lbol) = -7.2 +/- 0.2. This relation is in excellent agreement with the one previously derived for the Carina OB1 association. Except for the brightest O-star binaries, there is no general X-ray overluminosity due to colliding winds in O-star binaries. Roughly half of the known B-stars in the surveyed field are detected, but they fail to display a clear relationship between Lx and Lbol. Out of the three WR stars in Cyg OB2, probably only WR144 is itself responsible for the observed level of X-ray emission, at a very low log(Lx/Lbol) = -8.8 +/- 0.2. The X-ray emission of the other two WR-stars (WR145 and 146) is most probably due to their O-type companion along with a moderate contribution from a wind-wind interaction zone., Accepted for an ApJS Special Issue devoted to the Chandra Cygnus OB2 Legacy Survey

(Abridged) We provide empirical constraints on the different physical components that can act to yield temporal variability in predominantly or partially wind-formed optical lines of luminous OB stars, and thus potentially affect the reliable determination of fundamental parameters, including mass-loss rates via clumped winds. Using time-series spectroscopy from epochs spread over $\sim$ 4 years, a case study of the O9.5 supergiant $\alpha$ Cam is presented. We demonstrate that the He I 5876 (2$^3$P$^0$--3$^3$D) line is an important diagnostic for photospheric and wind variability in this star. The optical line profiles of $\alpha$ Cam are affected by (i) deep-seated fluctuations close to, or at, the photosphere, (ii) atmospheric velocity gradients, and (iii) large-scale stellar wind structure. This study provides new empirical perspectives on accurate line-synthesis modelling of stellar wind signatures in massive luminous stars. Using a pure Halpha line-synthesis code we interpret maximum changes in the red-ward and peak emission of $\alpha$ Cam in terms of mass-loss rate differences in the range $\sim$ 5.1 $\times$ 10$^{-6}$ to 6.5 $\times$ 10$^{-6}$ M$_\odot$ yr$^{-1}$. However, the models generally fail to reproduce the morphology of blueward (possibly absorptive) regions of the profiles.

We reconsider the use of the equivalent width of CIV 1549, EW(CIV), as an indicator of the oxygen abundance in star-forming galaxies, as proposed by Heckman et al. for nearby starbursts. We refine the local calibration of EW(CIV) vs. log (O/H) by using a restricted wavelength window which minimises blending with interstellar absorption lines. When applied to the stellar component only of the complex CIV 1549 features in two high redshift galaxies with good quality spectra, MS1512-cB58 (z = 2.7268) and Q1307-BM1163 (z = 1.4105), the local calibration gives values of the oxygen abundance which are in good agreement with other metallicity determinations based on nebular emission and interstellar absorption lines. Our main conclusion is that for this method to give reliable results at high redshifts, it should only be used on data of sufficiently high spectral resolution (R > 1000) for stellar and interstellar CIV components to be clearly separated. Oxygen abundances will be systematically overestimated if the local calibration is applied to spectra of high-z galaxies obtained with the low resolving powers (R ~ 200-300) of many current wide field surveys. It will also be necessary to understand better the causes of the scatter in the local relation, before we can be confident of inferences from it at high z., 7 pages, 4 figures, accepted for MNRAS (revision fixes up wrong fig.2)

By exploiting Far Ultraviolet Spectroscopic Explorer (FUSE) satellite time-series data, we have probed the relation between accretion disc geometry and bipolar outflow in the low-inclination, nova-like cataclysmic variable (CV) V592 Cas. Our results show that the outflow is strictly modulated on the orbital period and not on the (negative or positive) superhump periods of this system. This implies that the precession of either the disc eccentricity or its tilt is not directly affecting the structure and global dynamics of the outflow. The principal variability in the ultraviolet resonance lines is characterized by Doppler shifts of the entire blueward absorption troughs, in concert for a range of low- and high-ionization cases. The repetitive behaviour is asymmetric and highly non-sinusoidal over the orbital cycle of the system. The disc wind characteristics derived here allow V592 Cas to be added to a growing number of non-magnetic CVs which exhibit orbitally modulated wind variability. The origin of the departure in axisymmetry, which has to be fixed in the binary star frame, remains to be established.

We provide direct observational evidence for a link between photospheric activity and perturbations in the dense inner-most stellar wind regions of the B supergiant starOri. The results, which are relevant to our understanding of the origin of wind structure, are based on a multi-spectral line analysis of optical time-series data secured in 1998 using the HEROS spectrograph on the ESO Dutch 0.9-m telescope in La Silla. A period of ∼1.9 days is consistently identified in Balmer, He  absorption, and weak metal lines such as Si  and C . The primary characteristic is a large-amplitude swaying of the central absorption trough of the line, with differential velocities in lines formed at varying depths in the atmosphere. The variance resulting from the "S-wave" velocity behaviour of the lines is constrained within ± the projected rotation velocity (∼80 km s −1 ) in the weakest absorption lines, but extends blue-ward to over −200 km s −1 in Hα. A second (superimposed) 1.9 day signal is present at more extended blue-ward velocities (to ∼−300 km s −1 ) in lines containing stronger circumstellar components. Inspection of archival optical data from 1996 provides evidence that this modulation signal has persisted for at least 2.5 years. Non-radial pulsational modelling is carried out in an attempt to reproduce the key observational characteristics of the line profile variability. Only limited success is obtained with prograde (m = −1) modes. The principal S-wave pattern cannot be matched by these models and remains enigmatic.

We present results from time-series optical spectroscopy of the low-inclination, nova-like cataclysmic variable, V592 Cas. The data span the wavelength range from similar to4000 to 5000 Angstrom. and include Balmer lines (Hbeta to Hepsilon) as well as He I and He II. The Balmer lines are generally characterized by shallow absorption troughs with superimposed narrower central emission components. The absorption troughs are variable on time-scales of at least similar to20 min, but the fluctuations are asymmetric such that they are more dominant on the blueward side of the profile out to similar to-2000 km s(-1). Fourier analysis reveals modulation periods for emission radial velocities and absorption changes of similar to0.114 and 0.103 d; we support earlier suggestions that the latter is likely to be 1-day alias of the former, which is essentially the system orbital period. However, there is a phase lag of similar to0.3 between absorption and emission changes. The Balmer absorption changes are compared to the predicted behaviour caused by the (stream overflowing) SW Sex phenomenon. There are several discrepancies in this scenario, including the highly asymmetric nature of blueward changes, the velocity amplitudes, and the phase relation to the emission changes. The role of a disc wind in V592 Cas is also discussed; in particular, with this data set, we cannot rule in or rule out the possibility that axisymmetry of the outflow is broken because it is seated on a warped/tilted inner disc, which is implied by previous evidence for negative superhumps in this system.

We present radio and submillimetre observations of the O4I(n)f star ζ Pup, and discuss structure in the outer region of its wind (~ 10-100 R*). The properties of bremsstrahlung, the dominant emission process at these wavelengths, make it sensitive to structure and allow us to study how the amount of structure changes in the wind by comparing the fluxes at different wavelengths. To look for variability, we acquired 3.6 and 6 cm observations with the Australia Telescope Compact Array (ATCA). We supplemented these with archive observations from the NRAO Very Large Array (VLA). We did not find variability at more than the ± 20 % level. The long integration time does allow an accurate determination of the fluxes at 3.6 and 6 cm. Converting these fluxes into a mass loss rate, we find M = 3.5 x 10-6 M⊙/yr. This value confirms the significant discrepancy with the mass loss rate derived from the Hα profile, making ζ Pup an exception to the usually good agreement between Hα and radio mass loss rates. We also observed ζ Pup at 850 μm with the James Clerk Maxwell Telescope (JCMT) and at 20 cm with the VLA. A smooth wind model shows that the millimetre fluxes are too high compared to the radio fluxes. While recombination of helium in the outer wind cannot be discounted as an explanation, the wealth of evidence for structure strongly suggests this as the explanation for the discrepancy. Model calculations show that the structure needs to be present in the inner ~ 70 R* of the wind, but that it decays significantly, or maybe even disappears, beyond that radius.

We present Far Ultraviolet Spectroscopic Explorer (FUSE) satellite time-series data of the low-inclination, nova-like cataclysmic variable RW Sex. The data span the wavelength range between ∼905 and 1188 A, which contains the resonance lines of C iii, N iii, S iv, P v, S vi and O vi. All these spectral lines are present in the form of blueshifted absorption components, with no evidence for the lines redward of rest velocity; the FUSE data probe the fast disc-wind of RW Sex. The time-variable nature of these features is established. Substantial line profile variability is observed, confined between ∼−1000 and 0 km s−1 , and modulated on the orbital period of the system (∼0.245 d) . The fundamental characteristics of the temporal behaviour are very similar between the low and high ionization lines. The wind-dominated lines exhibit a cyclic increase in absorption optical depth which is accompanied by a shift in the maximum absorption velocity from ∼−1000 km s−1 to near zero velocity. We argue that the empirical evidence from the FUSE analysis supports an interpretation of blueshifted absorptive changes as opposed to the action of a variable (in velocity) blueshifted (perhaps disc-formed) emission component. This conclusion is further bolstered by an analysis of archival Hubble Space Telescope (HST) Goddard High Resolution Spectrograph (GHRS) data of RW Sex. We discuss a phenomenological picture of the ultraviolet (UV) line profile variability where the symmetry of a confined bipolar wind in RW Sex is broken by assuming that the outflow is oblique, perhaps because it is seated on a warped or tilted disc. The temporal UV absorption properties of non-eclipsing nova-like systems are compared.

We present the most suitable data sets available in the International Ultraviolet Explorer (IUE) archive for the study of time-dependent stellar winds in early B supergiants. The UV line prole variability in 11 B0 to B3 stars is analysed, compared and discussed, based on 16 separate data sets comprising over 600 homogeneously reduced high-resolution spectrograms. The targets include \normal" stars with moderate rotation rates and examples of rapid rotators. A gallery of grey-scale images (dynamic spectra) is presented, which demonstrates the richness and range of wind variability and highlights dierent structures in the winds of these stars. This work emphasises the suitability of B supergiants for wind studies, under-pinned by the fact that they exhibit unsaturated wind lines for a wide range of ionization. The wind activity of B supergiants is substantial and has highly varied characteristics. The variability evident in individual stars is classied and described in terms of discrete absorption components, spontaneous absorption, bowed structures, recurrence, and ionization variability and stratication. Similar structures can occur in stars of dierent fundamental parameters, but also dierent structures may occur in the same star at a given epoch. We discuss the physical phenomena that may be associated with the spectral signatures. The diversity of wind patterns evident likely reflects the role of stellar rotation and viewing angle in determining the observational characteristics of azimuthally extended structure rooted at the stellar surface. In addition, SEI line-synthesis modelling of the UV wind lines is used to provide further information about the state of the winds in our program stars. Typically the range, implied by the line prole variability, in the product of mass-loss rate and ion fraction ( _ Mq i) is a factor of 1.5, when integrated between 0.2 and 0.9 v1 ;i t can however be several times larger over localised velocity regions. At a given eective temperature the mean relative ion ratios can dier by a factor of 5. The general excess in predicted (forward-scattered) emission in the low velocity regime is discussed in terms of structured outflows. Mean ion fractions are estimated over the B0 to B1 spectral classes, and trends in the ionic ratios as a function of wind velocity are described. The low values obtained for the ion fractions of UV resonance lines may reflect the role of clumping in the wind.

We report on the results of an extended optical spectroscopic monitoring campaign on the early-type B supergiant HD 64760 (B0.5 Ib). The study is based on high-resolution echelle spectra obtained with the Landessternwarte Heidelberg's Heros instrument at ESO La Silla. Ninety-nine spectra were collected over 103 nights between January 19 and May 1, 1996. The Halpha line shows a characteristic profile with a central photo-spheric absorption superimposed by symmetrically blue- and red-shifted wind-emission humps. The time-averaged line profile is well described by a differentially rotating and expanding radiation-driven wind: the redistribution of the wind emission flux into a double peak profile is interpreted in terms of the resonance zone effect in rotating winds as first described by Petrenz & Puls (1996). Detailed time-series analyses of the line profile variations across the Halpha profile reveal for the first time in an optical data set of HD 64760 a periodic 2.4-day modulation of the inner and outer flanks of the Halpha emission humps. The stronger modulations of the inner flanks of the emission humps at photospheric velocities are due to complex width variations of the underlying photospheric Halpha profile. The weaker variations of the outer flanks are in phase and reflect variations at the base of the stellar wind. The detected 2.4-day modulation period together with a second period of 1.2 days (in the red emission hump only) is in excellent agreement with the outer-wind modulation periods as reported by Fullerton et al. (1997) from intensive IUE UV time-series observations in 1993 and 1995. The 2.4-day period is further detected in the photospheric He I lambda4026 line as prograde traveling (pseudo-)absorption and emission features. The observed variability pattern is indicative for low-order non-radial pulsations in the photosphere of HD 64760. The non-radial pulsations are identified as the source of persistent, regularly spaced stellar surface structure which is maintained throughout the photosphere - wind transition zone (this work) out into the UV regime of the terminal velocity outflow.

In common with other early-type stars, epsilon Ori (B0 Ia) shows evidence for structure in its stellar wind. Variations in optical and ultraviolet line profiles reveal the presence of large-scale structure in the inner wind. The detection of X-rays and the existence of black troughs in saturated ultraviolet lines are indicative of small-scale structure. The geometric extent of both types of structure is poorly known. In principle, large-scale structure can be detected directly from very high spatial resolution observations that resolve the stellar wind. A simpler technique is to look for the presence of additional flux compared to that expected from a smooth wind. The run of this excess flux as a function of wavelength indicates how fast structure decays in the wind. If there is variability in the excess flux, it shows us that the structure must be large-scale. Such variability is suggested by two previous 6 cm radio observations of epsilon Ori: Abbott et al. (1980) found 1.6 +/- 0.5 mJy, while Scuderi et al. (1998) measured only 0.60 +/- 0.06 mJy. This could indicate that the large-scale structure persists beyond similar to50 R-*. To further investigate this variability, we used the Very Large Array (VLA) to monitor epsilon Ori over a 5-day period in February 1999. We supplemented our data with observations from the VLA archive. In an attempt to resolve the stellar wind, we also obtained a series of high spatial resolution observations with the Multi-Element Radio Linked Interferometer Network (MERLIN) during January-March 1999. From this combined material we find no evidence for variability and we conclude that the Abbott et al. (1980) flux determination is in error. The data do show substantial excess flux at millimetre wavelengths, compared to a smooth wind. This excess is confirmed by a submillimetre observation which we obtained with the James Clerk Maxwell Telescope (JCMT). The behaviour of epsilon Ori is therefore similar to what had been found previously for alpha Cam, delta Ori A, kappa Ori and zeta Pup. While the present data do not allow very strong constraints, they show that considerable structure must persist up to at least similar to10 R-* in the wind of epsilon Ori. The combined radio fluxes are used to derive a mass-loss rate of log (M) over dot (M./yr) = 5.73 +/- 0.04. This value is in good agreement with the Halpha mass-loss rate. The good agreement between Halpha and radio mass-loss rates for hot stars in general remains puzzling, as it implies that the same amount of structure is present in very different formation regions.

We present a spatially resolved, high-spectral resolution (R=12000) K-band temporal monitoring of Rigel using AMBER at the VLTI. Rigel was observed in the Bracket Gamma line and its nearby continuum in 2006-2007, and 2009-2010. These unprecedented observations were complemented by contemporaneous optical high-resolution spectroscopy. We analyse the near-IR spectra and visibilities with the 1D non-LTE radiative-transfer code CMFGEN. The differential and closure phase signal exhibit asymmetries that are interpreted as perturbations of the wind. A systematic visibility decrease is observed across the Bracket Gamma. During the 2006-2007 period the Bracket Gamma and likely the continuum forming regions were larger than in the 2009-2010 epoch. Using CMFGEN, we infer a mass-loss rate change of about 20% between the two epochs. We further find time variations in the differential visibilities and phases. The 2006-2007 period is characterized by noticeable variations of the differential visibilities in Doppler position and width and by weak variations in differential and closure phase. The 2009-2010 period is much more quiet with virtually no detectable variations in the dispersed visibilities but a strong S-shape signal is observed in differential phase coinciding with a strong ejection event discernible in the optical spectra. The differential phase signal that is sometimes detected is reminiscent of the signal computed from hydrodynamical models of corotating interaction regions. For some epochs the temporal evolution of the signal suggests the rotation of the circumstellar structures., Comment: Paper accepted in the A&A journal

We report on the time-dependent behaviour of ultraviolet spectral lines in Hubble Space Telescope Goddard High-Resolution Spectrograph data of the classical nova V603 Aql. In particular, episodic blueshifted absorption (extending to similar to -2500 km s(-1)) is present, with a variability time-scale down to similar to1 min. The data provide a rare opportunity to study the rapid evolution of absorption structures that may be associated with accretion-disc winds in cataclysmic variables. At least three absorption events are recorded (at blueward velocities only) over similar to5 h, each lasting similar to 10-15 min. The derived velocity, acceleration and optical depth properties provide an empirical picture of stochastically variable structures in the outflow, with no evidence for short-term (less than similar to 1h) cyclic or modulated behaviour in the overall absorption properties. In contrast, the emission components of the ultraviolet resonance lines are very stable in velocity and strength in this low-inclination system. On at least two occasions there is an intriguing short-term 'flare' in the ultraviolet continuum flux (of up to similar to 40 per cent). Though there is no clear one-to-one relation in these data between the continuum fluctuations and the occurrence of the absorption events, the time-scales for the two variable phenomena are essentially the same. The irregular absorption episodes in the ultraviolet data of V603 Aql presently defy a clear physical interpretation. Their overall characteristics are discussed in the context of instabilities in radiation-pressure-driven disc winds.

We present results from time-resolved Hubble Space Telescope(HST) GHRS ultraviolet spectroscopy of the nova-like cataclysmic variable BZ Cam. Extensive changes are recorded in the extended absorption troughs of the UV resonance line profiles, which betray a highly unsteady and continuously variable supersonic outflow. The large-scale line-profile changes are almost exclusively confined to blueshifted velocities, although the Si iv and C iv emission components reveal orbital phase-linked velocity shifts. The character of the accretion-disc wind of BZ Cam can alter radically on time-scales down to 100 s or less. Correlated behaviour is noted in lines of low and high ionization stages, which may reflect localized density changes. Aside from the incidence of enormous line-profile changes on remarkably short time-scales, BZ Cam provides an important benchmark for the simultaneous presence of very strong absorption and well-developed emission components in Si iv, C iii and C iv, for an estimated low-inclination (i

We discuss why B supergiant winds are particularly well suited for wind studies, and present or refer to dynamic spectra which suggest the presence of disks, bifurcated winds, shock formation, rotationally modulated winds and the spontaneous generation of wind enhancements. They underscore the strength and richness of wind variability in B supergiants and the challenges these phenomena present to theoretical studies of stellar winds.

We present the results from a 28-day IUE time-series campaign monitoring the stellar wind of the O5-type giant HD 93843. The principal aim was to study variability in the wind of a star with a normal projected rotation velocity. Systematic changes are identified, amidst continuous line-profile variability, in the absorption troughs of the Si IV and N V resonance lines. The patterns observed have characteristic time-scales of several days and are mimicked by fluctuations (of several 100 km s(-1)) in the blue wings of the saturated C IV P Cygni profile.Fourier analysis provides support for the repeatability of wind structures in HD 93843 on a 7.1-d 'period'. Power at this frequency is evident only at intermediate and high velocities (i.e., above similar to 0.3 of the terminal velocity). The long modulation time-scale suggests that changes in the star itself probably provide the physical source for triggering the onset of wind structure. Unfortunately the rotational, photometric, pulsational and magnetic properties of HD 93843 are too poorly constrained or known to permit a more detailed interpretation of the 7.1-d wind modulation in terms of potential inhomogeneities at the stellar surface. Nevertheless, our study demonstrates that the incidence of cyclic, possibly regular, stellar-wind variability is not restricted to rapid rotators. Comparisons with other OB stars which have exhibited repetitive wind changes on 'periods' of several days suggest that the time-dependent UV properties of HD 93843 are more akin to those of the O4-type supergiant zeta Puppis.

Archival HST FOS and GHRS data sets have been used to collect ultraviolet evidence for large- and small-scale stellar wind structure in extragalactic Local Group OB stars (i.e. SMC, LMC including R136, M31, M33 and NGC 6822). By comparison with previous studies of Galactic OB stars, wind activity is principally diagnosed in individual spectrograms via the presence of 'narrow absorption components' and saturated 'black' absorption troughs in the resonance line doublets. Their characteristics broadly suggest that these stars share the same physical mechanisms for perturbing the winds as those that act in Galactic stars. Both of these spectral indicators are also used to provide reliable measures of wind terminal velocities. These velocities are directly compared with previously published Galactic values, without reliance on model profile fitting. Relative to Galactic OB stars, the most discrepant terminal velocities (and wind line profiles) result from main-sequence early O-type stars in the SMC.

‘The definitive version is available at www.blackwell-synergy.com.’ Copyright Blackwell Publishing. DOI: 10.1046/j.1365-8711.1998.01844.x [Full text of this article is not available in the UHRA]

Cross-correlation provides an effective line-averaging function for spectra containing many line features, a result which can be exploited in order to perform time-series and spatial-domain analyses of absorption-line variability in data of (relatively) poor quality. We apply this method to high-resolution IUE spectra. For the known non-radial pulsator HD 93521 (09.5 V), time-series analysis of the cross-correlation function recovers two periods that are confirmed in independent optical data (P-1 = 1.77 h, P-2 = 2.90 h); there is no statistically significant excess power at these frequencies in lines formed in the stellar wind. By comparing phase information from the time-series analysis with results from pulsation models we estimate l=10+/-1 and 6+/-1 as the harmonic degrees for P-1 and P-2, respectively, with l+m less than or similar to 2 for each mode (where pn is the azimuthal order of the mode).We also present evidence for absorption-line variability in HD 64760 (HR 3090; B0.5 Ib), finding marginally significant signals with P-1 = 8.9 h (or, possibly, 14.2h) and P-2 = 29 h. The longer period is present, with a strong signal, in wind-formed lines. We consider possible circumstellar and (quasi-)photospheric origins for P-2, and conclude that this signal probably does not arise through rotational modulation (with the corollary that the stellar-wind signal also does not arise in corotating structures, contrary to previous suggestions). The phase behaviour of the signals is consistent with non-radial pulsation models characterized by l=5+/-1 (P-1) and 2+/-1 (P-2), with l+m less than or equal to 1, supporting a previous suggestion by Baade that both low- and higher-order modes are present; the wind modulation at P-2 may then result from leakage of pulsation energy into the supersonic outflow. The lack of significant photometric variability is a serious difficulty for this model (any sinusoidal photometric variability at P-2 has semiamplitude

The optical emission-line properties of the nova-like cataclysmic variable V795 Her are studied using high-resolution Isaac Newton Telescope [Intermediate Dispersion Spectrograph (IDS) and Faint-Object Spectrograph (FOS)] data secured during 1994 June. The observed Balmer and He emission lines, and He I lambda 4471 absorption, modulate on the 2.6-h orbital period of this system. The detailed nature of these changes is complex, however, with the incidence of separate low- and high-velocity fluctuations. Low-intensity 'S'-wave features are apparent in the blue and red outer wings of the Balmer lines, extending to similar to +/- 1600 km s(-1). These phased changes are seen as two synchronized components with net blueshift and redshift. The Balmer profiles are also affected by absorption which dominates during the first part of the cycle. We propose an empirical interpretation of this behaviour in terms of a single broad emission feature which follows a high-velocity 'S' wave, plus a superimposed, sympathetically phased, absorption component. The associated physical interpretation is that of a gas stream (seen in absorption) that overflows the outer accretion disc and re-impacts on the inner disc regions.The 'double-peaked' inner cores of the Balmer lines have relatively fixed central velocities, and do not reveal an obvious 'S'-wave variation. This inner-core emission likely arises from material located in the outer regions of the accretion disc. An similar to 10 per cent variation is present in the continuum flux of V795 Her, restricted to less than 25 per cent of the system orbit. We find some correspondence between the overall optical emission changes and those found by us in the UV resonance lines of V795 Her in a separate study based on Hubble Space Telescope data.We discuss our observational results in terms of magnetic white dwarf and disc-overflow gas stream scenarios. Constraints are presented that argue against recently proposed models for V795 Her which invoke channelled accretion columns flowing on to a synchronously rotating white dwarf. Disc-overflow model simulations are presented which quantitatively account for several of the observed dynamical properties of V795 Her. There remain some discrepancies, however, which call for a more detailed physical model.

We present a catalogue of homogeneous measures of the linewidth parameter, v(e) sin i, for 373 O-type stars and early B supergiants (including the separate components of 25 binary and three triple systems), produced by cross-correlating high-resolution, short-wavelength IUE spectra against a 'template' spectrum of tau Sco. We also tabulate terminal velocities. There are no O supergiants in our sample with v(e) sin i < 65 km s(-1), and only one supergiant earlier than B5 has v(e) sin i < 50 km s(-1), confirming that an important line broadening mechanism in addition to rotation must be present in these objects. A calibration of the area under the cross-correlation peak against spectral type is used to obtain estimates of continuum intensity ratios of the components in 28 spectroscopically binary or multiple systems. At least seven SB2 systems show evidence for the 'Struve-Sahade effect', a systematic variation in relative line strength as a function of orbital phase. The stellar wind profiles of the most rapid rotator in our sample, the O9 III:n* star HD 191423 (v(e) sin i = 436 km s(-1)), show it to have a 'wind-compressed disc' similar to that of HD 93521; this star and other rapid rotators are good candidates for studies of non-radial pulsation.

We present three years of long-cadence and over one year of short-cadence photometry of the central star of the Planetary Nebula NGC 6826 obtained with the Kepler spacecraft, and temporally coinciding optical spectroscopy. The light curves are dominated by incoherent variability on time scales of several hours, but contain a lower-amplitude periodicity of 1.23799 d. The temporal amplitude and shape changes of this signal are best explicable with a rotational modulation, and are not consistent with a binary interpretation. We argue that we do not observe stellar pulsations within the limitations of our data, and show that a binary central star with an orbital period less than seven days could only have escaped our detection in the case of low orbital inclination. Combining the photometric and spectroscopic evidence, we reason that the hourly variations are due to a variable stellar wind, and are global in nature. The physical cause of the wind variability of NGC 6826 and other ZZ Leporis stars is likely related to the mechanism responsible for wind variations in massive hot stars., Comment: 9 pages, 8 figures, accepted for MNRAS

We review the historical development of observations of mass loss from hot, luminous stars, and sketch the physical principles underlying the theory of radiatively-driven stellar winds. The theory makes predictions which are shown to be in general accord with the data. We summarize recent results, primarily from the IUE satellite, which demonstrate the importance of time-dependent phenomena in hot-star outflows, and which, in particular, point to effects related to rotational modulation.

Cyg OB2 #9 is one of a small set of non-thermal radio emitting massive O-star binaries. The non-thermal radiation is due to synchrotron emission in the colliding-wind region. Cyg OB2 #9 was only recently discovered to be a binary system and a multi-wavelength campaign was organized to study its 2011 periastron passage. We report here on the results of the radio observations obtained in this monitoring campaign. We used the Expanded Very Large Array (EVLA) radio interferometer to obtain 6 and 20 cm continuum fluxes. The observed radio light curve shows a steep drop in flux sometime before periastron. The fluxes drop to a level that is comparable to the expected free-free emission from the stellar winds, suggesting that the non-thermal emitting region is completely hidden at that time. After periastron passage, the fluxes slowly increase. We introduce a simple model to solve the radiative transfer in the stellar winds and the colliding-wind region, and thus determine the expected behaviour of the radio light curve. From the asymmetry of the light curve, we show that the primary has the stronger wind. This is somewhat unexpected if we use the astrophysical parameters based on theoretical calibrations. But it becomes entirely feasible if we take into account that a given spectral type - luminosity class combination covers a range of astrophysical parameters. The colliding-wind region also contributes to the free-free emission, which can help to explain the high values of the spectral index seen after periastron passage. Combining our data with older Very Large Array (VLA) data allows us to derive a period P = 860.0 +- 3.7 days for this system. With this period, we update the orbital parameters that were derived in the first paper of this series., 10 pages, 4 figures, accepted for publication in A&A

The winds from six dwarf novae and four nova-like cataclysmic variables are studied using 31 high-resolution IUE spectra. The data provide details on the time- and phase-averaged nature of disc-driven outflows, which are diagnosed via the presence of P Cygni-like and extended absorption profiles due to the C IV, N V and Si IV resonance line doublets, and He II lambda 1640. The profiles are parametrized using measures of the absorption and emission velocities, widths and strengths. The maximum wind velocity can exceed -4000 km s(-1), although the absorption maximum (minimum flux) typically occurs at similar to 20 per cent of the shortward profile edge. Optical depth and velocity structure is identified in the absorption troughs which may indicate inhomogeneities in the outflows. The relative ion behaviour and the respective contributions to the emission profiles of the inner disc and wind are discussed. Synthesized model profiles are used to estimate the products of mass-loss rate and C3+ ion fractions.

We present HST/STIS time-series spectroscopy of the central star of the "Cat's Eye" planetary nebula NGC 6543. Intensive monitoring of the UV lines over a 5.8 hour period reveals well defined details of large-scale structure in the fast wind, which are exploited to provide new constraints on the rotation rate of the central star. We derive characteristics of the line profile variability that support a physical origin due to co-rotating interaction regions (CIRs) that are rooted at the stellar surface. The recurrence time of the observed spectral signatures of the CIRs is used to estimate the rotation period of the central star and, adopting a radius between 0.3 and 0.6 \Rsun constrains the rotational velocity to the range 54 \leq v_{rot} \leq 108 \kms. The implications of these results for single star evolution are discussed based on models calculated here for low-mass stars. Our models predict a sub-surface convective layer in NGC 6543 which we argue to be causally connected to the occurrence of structure in the fast wind., Accepted for publication in ApJ Letters

We report on the presence of substantial, low-velocity stellar wind structure in the extreme O supergiant HD 152408, based on optical spectroscopic time-series observations. Systematic variations in the form of migrating optical depth enhancements occur in the absorption trough of the He I λ5876 P Cygni profile. These variations start deep in the stellar wind, slowly accelerate bluewards to ≥0.5v∞ over ∼ 1–2 days, and recur at intervals of about 1 day. Sympathetic variations are apparent in the Balmer emission lines. The observations provide constraints on the stability of the low-velocity stellar wind regime, and indicate the presence of large-amplitude perturbations at great depths in the outflow.

Spectroscopic observations are discussed which indicate that the winds of luminous OB stars are highly structured in space and variable in time. Blueward migrating discrete optical depth enhancements in the absorption troughs of P Cygni profiles are the characteristic signatures of the evolving structure. Constraints on physical mechanisms are discussed, provided by the observed accelerations of the migrating features, the evidence for rotationally modulated variability, and the behaviour of the winds at very low velocities.

Low-resolution IUE spectroscopy of V795 Her secured in 1992 August is used to authenticate the presence of a approximately 4.86-h periodic variation in the mainly wind-formed Si IV lambda 1400 and C IV lambda 1 549 resonance lines. The modulation is demonstrated to be coherent across a 3-yr time-span, and is discordant with the mooted orbital (optical spectroscopic) period of approximately 2.60 h. Constraints are discussed for some possible configurations of the system that introduce asymmetries and can potentially yield modulated profile variability. The first ROSAT X-ray detection of V795 Her is also described.

There are currently two optical interferometry recombiners that can provide spectral resolutions better than 10000, AMBER/VLTI operating in the H-K bands, and VEGA/CHARA, recently commissioned, operating in the visible. These instruments are well suited to study the wind activity of the brightest AB supergiants in our vicinity, in lines such as H$\alpha$ or BrGamma. We present here the first observations of this kind, performed on Rigel (B8Ia) and Deneb (A2Ia). Rigel was monitored by AMBER in two campaigns, in 2006-2007 and 2009-2010, and observed in 2009 by VEGA; whereas Deneb was monitored in 2008-2009 by VEGA. The extension of the Halpha and BrGamma line forming regions were accurately measured and compared with CMFGEN models of both stars. Moreover, clear signs of activity were observed in the differential visibility and phases. These pioneer observations are still limited, but show the path for a better understanding of the spatial structure and temporal evolution of localized ejections using optical interferometry., Comment: Proceedings of conf. IAUS272 - Active OB stars - Paris, July 19-23, 2010

The science of extra-solar planets is one of the most rapidly changing areas of astrophysics and since 1995 the number of planets known has increased by almost two orders of magnitude. A combination of ground-based surveys and dedicated space missions has resulted in 560-plus planets being detected, and over 1200 that await confirmation. NASA's Kepler mission has opened up the possibility of discovering Earth-like planets in the habitable zone around some of the 100,000 stars it is surveying during its 3 to 4-year lifetime. The new ESA's Gaia mission is expected to discover thousands of new planets around stars within 200 parsecs of the Sun. The key challenge now is moving on from discovery, important though that remains, to characterisation: what are these planets actually like, and why are they as they are?In the past ten years, we have learned how to obtain the first spectra of exoplanets using transit transmission and emission spectroscopy. With the high stability of Spitzer, Hubble, and large ground-based telescopes the spectra of bright close-in massive planets can be obtained and species like water vapour, methane, carbon monoxide and dioxide have been detected. With transit science came the first tangible remote sensing of these planetary bodies and so one can start to extrapolate from what has been learnt from Solar System probes to what one might plan to learn about their faraway siblings. As we learn more about the atmospheres, surfaces and near-surfaces of these remote bodies, we will begin to build up a clearer picture of their construction, history and suitability for life.The Exoplanet Characterisation Observatory, EChO, will be the first dedicated mission to investigate the physics and chemistry of Exoplanetary Atmospheres. By characterising spectroscopically more bodies in different environments we will take detailed planetology out of the Solar System and into the Galaxy as a whole.EChO has now been selected by the European Space Agency to be assessed as one of four M3 mission candidates.

Results are presented from a study of variability in the UV resonance lines from the cataclysmic variable V795 Her, based on a total of 28 IUE SWP low-resolution spectra. Significant line profile fluctuations are evident in the C IV-lambda-1549 and Si IV-lambda-1400 doublets on time-scales down to less than or similar to 30 min. There is little or no evidence for changes in N V-lambda-1240. Only C IV-lambda-1549 is (occasionally) seen in emission; the morphology of this profile changes from an absorption-dominated line to an emission-dominated one in approximately a few hours. The observed C IV and Si IV absorption strengths vary in concert. Although no correlations are evident between changes in the Si IV and C IV line strengths and the mooted orbital period of V795 Her (approximately 2.6 hr), our time-series analyses of the UV data suggest a approximately 4.8-hr periodic modulation in the line profile variability.Constraints on the origin and geometry of the line formation are discussed, based on these UV data. We consider in particular whether: (i) a continuum-emitting hotspot on the disc, or (ii) wind outflow asymmetry could account for the regular line profile variability. There is freedom in specifying both types of model to ensure that both can reproduce the extent of the observed profile changes, but neither yields the appropriate phase dependence. Alternative specifications for departures from axial symmetry are suggested.

This review deals with some of the key areas where FUSE spectroscopy has advanced our understanding of hot star winds. The power of the far‐UV spectral line diagnostics observed by FUSE is discussed in the context of both time‐averaged and temporally varying winds. The results are collated from three diverse, but related settings: (i) the current serious discordance of different mass‐loss estimates for O‐type stars with clumped winds, (ii) the detection of time‐variable structure and clumping in the fast winds of PN central stars, and (iii) globally (sometimes strictly periodic) modulation of collimated outflows from the inner accretion disks of cataclysmic variable binary stars.

Low-resolution IUE ultraviolet observations of the cataclysmic variable, PG 1711+336, are presented. The spectra reveal extensive variability in the wind-formed C IV lambda-1550 resonance line P Cygni profiles, on time-scales as short as approximately hours. We demonstrate that the high-resolution IUE spectrum of the nova-like system V3885 Sgr, convolved with the IUE low-resolution instrumental profile, provides a good match to the low-resolution wind lines of PG 1711+336 at some epochs. Hot-star wind theory and spherical symmetry are assumed in order to model the high-resolution data. The results yield a crude time-independent (lower-limit) estimate for the product of mass-loss rate and ion fraction. Moments of the observed P Cygni profiles in PG 1711+336 are measured to quantify the wind variability, and suggest that the C IV wind column densities may vary by a factor of approximately 2 in approximately 1 hour. We estimate changes of a factor of approximately 2 in the edge velocities of the shortward-shifted resonance lines, with maximum values of approximately 4500 kms-1.The stellar-wind variability is not accompanied by any significant changes in the continuum flux level or distribution over approximately 1150-3200 angstrom. The mean UV continuum may be fitted by a power law of the form f-lambda-proportional-lambda approximately (-2.0+/-0.1). These limited data do not suggest a simple correlation between the wind variability and the orbital phase of PG 1711+336.

We provide a quantitative analysis of time-variable phenomena in the photospheric, near-star, and outflow regions of the late-B supergiant (SG) HD 199478. The analysis is based primarily on optical spectroscopic datasets secured between 1999 and 2000 from the Bulgarian NAO, Tartu, and Ritter Observatories. The temporal behaviour of HD 199478 is characterised by three key empirical properties: (i) systematic central velocity shifts in the photospheric absorption lines, including C II and He I, over a characteristic time-scale of abou 20 days; (ii) extremely strong, variable H alpha emission with no clear modulation signal, and (iii) the occurrence in 2000 of a (rare) high-velocity absorption (HVA) event in H alpha, which evolved over about 60 days, showing the clear signature of mass infall and outflows. In these properties HD 199478 resembles few other late-B SGs with peculiar emission and HVAs in H alpha (HD 91619, HD 34085, HD 96919). Non-LTE line synthesis modelling is conducted using FASTWIND for these late-B SGs to constrain and compare their fundamental parameters within the context of extreme behaviour in the H alpha lines. Our analysis indicate that at the cooler temperature edge of B SGs, there are objects whose wind properties, as traced by H alpha, are inconsistent with the predictions of the smooth, spherically symmetric wind approximation. This discordance is still not fully understood and may highlight the role of a non-spherical, disk-like, geometry, which may result from magnetically-driven equatorial compression of the gas. Ordered dipole magnetic fields may also lead to confined plasma held above the stellar surface, which ultimately gives rise to transient HVA events., 12 pages. To be published in Astronomy and AStrophysics

We discuss why B supergiant winds are particularly well suited for wind studies, and present or refer to dynamic spectra which suggest the presence of disks, bifurcated winds, shock formation, rotationally modulated winds and the spontaneous generation of wind enhancements. They underscore the strength and richness of wind variability in B supergiants and the challenges these phenomena present to theoretical studies of stellar winds.

We report on the results of an extended optical spectroscopic monitoring campaign on the early-type B supergiant HD64760 (B0.5Ib) designed to probe the deep-seated origin of spatial wind structure. This new study is based on high-resolution echelle spectra obtained with the FEROS instrument at ESO La Silla. 279 spectra were collected over 10 consecutive nights in 2003. From the period analysis of the line-profile variability of the photospheric lines we identify three closely spaced periods around 4.810 hrs and a splitting of +/-3%. The velocity - phase diagrams of the line-profile variations for the distinct periods reveal characteristic prograde non-radial pulsation patterns of high order corresponding to pulsation modes with l and m in the range 6-10. The three pulsation modes have periods clearly shorter than the characteristic pulsation time scale and show small horizontal velocity fields and hence are identified as p-modes. The beating of the three pulsation modes leads to a retrograde beat pattern with two regions of constructive interference diametrically opposite on the stellar surface and a beat period of 162.8hrs (6.8days). This beat pattern is directly observed in the spectroscopic time series of the photospheric lines. The wind-sensitive lines display features of enhanced emission, which appear to follow the maxima of the photospheric beat pattern., 18 pages, 21 figures (reduced resolution)