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[Aims] The final aim of this paper is to expand the sparse group of X-ray binaries with gamma-ray counterparts as laboratories to study high-energy processes under physical conditions that periodically repeat. [Methods] A follow-up of a candidate system has been carried out. We applied both photometric and spectroscopic techniques in the optical domain together with a period analysis using the phase dispersion minimisation and CLEAN methods. A tentative period search was also conducted in the gamma-ray domain. [Results] Our main result is having established the binary nature of the optical star and X-ray emitter HD 3191 towards the Fermi gamma-ray source 4FGL J0035.8+6131, the last one proposed to be associated with a blazar of an unknown type. An orbital period close to 16 d is reported for HD 3191 together with a likely rotation, or pulsation, period of about 0.6 d. Although no convincing evidence for the orbital cycle has been found in the Fermi light curve up to now, the confirmed presence of a high-mass X-ray binary towards 4FGL J0035.8+6131 now strengthens the need for caution about its true nature.

We present the latest results of a long-term observational project aimed at observing, collecting from the literature, and homogenising the light, colour, and spectral variations of the well-known emission-line Be star V923 Aql. Our analysis of these parameters confirms that all of the observables exhibit cyclic changes with variable cycle length between about 1800 and 3000 days, so far documented for seven consecutive cycles. We show that these variations can be qualitatively understood within the framework of the model of one-armed oscillation of the circumstellar disk, with a wave of increased density and prograde revolution in space. We confirm the binary nature of the object with a 214.716 day period and estimate the probable system properties. We also confirm the presence of rapid light, and likely also spectral changes. However, we cannot provide any firm conclusions regarding their nature. A quantitative modelling study of long-term changes is planned as a follow-up to this work., Comment: 21 pages, 13 Figures, Astronomy and Astrophysics (in press)

beta Lyr A is a complex binary system with an extensive observational dataset: light curves (from FUV to FIR), interferometric squared visibility, closure phase, triple product measurements, spectral-energy distribution (SED), high-resolution spectroscopy, differential visibility amplitude, and also differential phase. In particular, we use spectra from Ondrejov 2m telescope from 2013 to 2015, to measure the emission in Halpha, HeI, SiII, NeI, or CII lines, and differential interferometry by CHARA/VEGA from the 2013 campaign to measure wavelength-dependent sizes across Halpha and HeI 6678. This allows us to constrain not only optically thick objects (primary, secondary, accretion disk), but also optically thin objects (disk atmosphere, jets, shell). We extended our modelling tool Pyshellspec (based on Shellspec; a 1D LTE radiative transfer code) to include all new observables, to compute differential visibilities/phases, to perform a Doppler tomography, and to determine a joint chi^2 metric. After an optimisation of 38 free parameters, we derive a robust model of the beta Lyr A system. According to the model, the emission is formed in an extended atmosphere of the disk, two perpendicular jets expanding at ~700 km s^-1, and a symmetric shell with the radius ~70 R_S. The spectroscopy indicates a low abundance of carbon, 10^-2 of the solar value. We also quantify systematic differences between datasets and discuss alternative models, with higher resolution, additional asymmetries, or He-rich abundance., Comment: 19 pages, 31 figures

Context. Be stars are physically complex systems that continue to challenge theory to understand their rapid rotation, complex variability and decretion disks. $\gamma$ Cassiopeiae ($\gamma$ Cas) is one such star but is even more curious because of its unexplained hard thermal X-ray emission. Aims. We aim to examine the optical variability of $\gamma$ Cas and thereby to shed more light on its puzzling behaviour. Methods. Three hundred twenty-one archival H$\alpha$ spectra from 2006 to 2017 are analysed to search for frequencies corresponding to the 203.5 day orbit of the companion. Space photometry from the SMEI satellite from 2003 to 2011 and the BRITE-Constellation of nano-satellites between 2015 and 2019 is investigated in the period range from a couple of hours to a few days. Results. The orbital period of the companion of 203.5 days is confirmed with independent measurements from the structure of the H$\alpha$ line emission. A strong blue/red asymmetry in the amplitude distribution across the H$\alpha$ emission line could hint at a spiral structure in the decretion disk. With the space photometry, the known frequency of 0.82 d$^{-1}$ is confirmed in data from the early 2000s. A higher frequency of 2.48 d$^{-1}$ is present in the data from 2015 to 2019 and possibly also in the early 2000s. A third frequency at 1.25 d$^{-1}$ is proposed to exist in both SMEI and BRITE data. The only explanation covering all three rapid variations seems to be nonradial pulsation. The two higher frequencies are incompatible with rotation., Comment: 13 pages, 12 figures. Accepted for publication in A&A

Mass exchange and mass loss in close binaries can significantly affect their evolution, but a complete self-consistent theory of these processes is still to be developed. Processes such as radiative shielding due to a hot-spot region, or a hydrodynamical interaction of different parts of the gas stream have been studied previously. In order to test the respective predictions, it is necessary to carry out detailed observations of binaries undergoing the largescale mass exchange, especially for those that are in the rapid transfer phase.βLyr A is an archetype of such a system, having a long and rich observational history. Our goal for this first study is to quantitatively estimate the geometry and physical properties of the optically thick components, namely the Roche-lobe filling mass-losing star, and the accretion disk surrounding the mass-gaining star ofβLyr A. A series of continuum visible and NIR spectro-interferometric observations by the NPOI, CHARA/MIRC and VEGA instruments covering the whole orbit ofβLyr A acquired during a two-week campaign in 2013 were complemented withUBVRphotometric observations acquired during a three-year monitoring of the system. We included NUV and FUV observations from OAO A-2, IUE, and Voyager satellites. All these observations were compared to a complex model of the system. It is based on the simple LTE radiative transfer codeSHELLSPEC, which was substantially extended to compute all interferometric observables and to perform both global and local optimization of system parameters. Several shapes of the accretion disk were successfully tested – slab, wedge, and a disk with an exponential vertical profile – and the following properties were consistently found: the radius of the outer rim is 30.0±1.0R⊙, the semithickness of the disk 6.5±1.0R⊙, and the binary orbital inclinationi=93.5±1.0deg. The temperature profile is a power-law or a steady-disk in case of the wedge geometry. The properties of the accretion disk indicate that it cannot be in a vertical hydrostatic equilibrium, which is in accord with the ongoing mass transfer. The hot spot was also detected in the continuum but is interpreted as a hotter part of the accretion disk illuminated by the donor. As a by-product, accurate kinematic and radiative properties ofβLyr B were determined.

We study the temporal and spectral characteristics of SMC X-3 during its 2016 outburst. To probe accretion onto highly magnetized neutron stars (NSs), at the Eddington limit. We obtained XMM-Newton observations of SMC X-3 and combined them with long-term observations by Swift. We studied the temporal and spectral behavior of the source, and its short- and long-term evolution. We constructed a simple toy-model to gain insight into the complex emission pattern of SMC X-3. We confirm the pulse period of the system, derived by previous works and note that the pulse has a complex, three peaked shape. We find that the pulsed emission is dominated by hard photons, while at energies below ~1 keV, the emission is virtually non-pulsating. We further find that the shape of the pulse profile and the short and long-term evolution of the source light-curve can be explained by invoking a combination of a "fan" and a "polar" beam. Our spectroscopic analysis, reveals a two-component emission: a hard power law and a soft thermal component. We find that the latter produces the bulk of the non-pulsating emission and is most likely the result of reprocessing of the primary hard emission, by optically thick material that partially obscures the central source. We also detect strong emission lines from highly ionized metals. The strength of the emission lines are strongly phase-depended. The energy and temporal evolution and the shape of the pulse profile and the long-term spectra evolution of the source are consistent with the expected emission pattern of the accretion column in the super-critical regime, while the presence of a large reprocessing region is consistent with the analysis of previously studied X-ray pulsars observed at high accretion rates. The presence of this region is consistent with recently proposed works that suggest that high-B NSs occupy a considerable fraction of ULXs., Comment: 16 pages, 16 figures, Accepted for publication in A&A. Added final, minor proof corrections

10 pages, 5 figures, accepté par A&A; International audience; Be stars show evidence of mass loss and circumstellar envelopes (CSE), from UV resonance lines, near-IR excesses and the presence of episodic hydrogen emission lines. The geometry of these envelopes is still uncertain, though it is often assumed that they are formed by a disk around the stellar equator and a hot polar wind. We probe the close environment of the fast rotating Be star Achernar at angular scales of a few mas in the infrared, in order to constrain the geometry of a possible polar CSE. We obtained long-baseline interferometric observations of Achernar with the VINCI/VLTI beam combiner in the $H$ and $K$ bands, using various telescope configurations and baseline lengths with a large azimuthal coverage. The observed visibility measurements along the polar direction are significantly lower than the visibility function of the photosphere of the star alone, in particular at low spatial frequencies. This points at the presence of an asymmetric diffuse CSE elongated along the polar direction of the star. We fit to our data a simple model consisting of two components: a 2D elliptical Gaussian superimposed on a uniform ellipse representing the distorted photosphere of the fast rotating star. We clearly detect a CSE elongated along the polar axis of the star, as well as the rotational flattening of the stellar photosphere. The relative near-IR flux measured for the CSE compared to the stellar photosphere is 5\%. Its angular dimensions are loosely constrained by the available data$2.7 \pm 1.3$ mas and $17.6 \pm 4.9$ mas. This CSE could be linked to free-free emission from the radiative pressure driven wind originating from the hot polar caps of the star.

We present an INTEGRAL data analysis of the X-ray transient \object{SAX J2103.5+4545} during two outbursts detected in December 2002. The INTEGRAL coordinates and error circle agree with the position of the recently proposed optical counterpart. A power-law plus cut-off model provided a good fit to the 4-150 keV spectrum yielding a photon index of 1.0+-0.1, a cut-off energy E_cut=7.6+-2.0 keV and a folding energy E_fold=30.9+-2.5 keV. The X-ray luminosity in the 4-150 keV energy range was found to be 6.0x10^36 erg/s, assuming a distance of 6.5 kpc. This luminosity, together with the derived photon index, indicate that the source is in a bright state. A 354.9$+-0.5 second pulse period is measured. This value is significantly smaller than previous measurements, indicating a long-term spin-up episode., 6 pages, 8 figures

Multiwavelength monitoring of Be/X-ray binaries is crucial to understand the mechanisms producing their outbursts. H 1145-619 is one of these systems, which has recently displayed X-ray activity. We investigate the correlation between the optical emission and the X-ray activity to predict the occurrence of new X-ray outbursts from the inferred state of the circumstellar disc. We have performed a multiwavelength study of H 1145-619 from 1973 to 2017 and present here a global analysis of its variability over the last 40 years. We have used optical spectra from the SAAO, SMARTS and SALT telescopes and optical photometry from INTEGRAL/OMC and ASAS. We also used X-ray observations from INTEGRAL/JEM-X, and IBIS to generate the light curves and combined them with Swift/XRT to extract the X-ray spectra. In addition, we have compiled archival observations and measurements from the literature to complement these data. Comparing the evolution of the optical continuum emission with the Halpha line variability, we have identified three different patterns of optical variability: Global increases and decreases of the optical brightness (observed from 1982 to 1994 and from 2009 to 2017) that can be explained by the dissipation and replenishment of the circumstellar disc, superorbital variations with a period of Psuperorb~590 days (observed in 2002-2009) which seems to be related with the circumstellar disc, and optical outbursts (observed in 1998-1999 and 2002-2005) that we interpret as mass ejections. We have discovered the presence of a retrograde one-armed density wave, which appeared in 2016 and is still present in the circumstellar disc. We have carried out the most complete long-term optical study of the Be/X-ray binary H 1145-619 in correlation with its X-ray activity. We found for the fist time the presence of a retrograde density perturbation in the circumstellar disc of a Be/X-ray binary., Comment: Accepted on 2 September 2017, 13 pages, 12 figures

International audience; Context. Medium-resolution échelle spectra of the Red Square Nebula surrounding the star MWC 922 are presented. The spectra have been obtained in 2010 and 2012 using the X-shooter spectrograph mounted on the Very Large Telescope (VLT) in Paranal, Chile. The spectrum covers a wavelength range between 300 nm-2.5 μm and shows that the nebula is rich in emission lines. Aims: We aim to identify the emission lines and use them as a tool to determine the physical and chemical characteristics of the nebula. The emission lines are also used to put constraints on the structure of the nebula and on the nature of the central stars. Methods: We analyzed and identified emission lines that indicated that the Red Square Nebula consists of a low density bipolar outflow, eminent in the broad emission component seen in [Fe II], as well as in P Cygni line profiles indicative of fast outflowing material. The narrow component in the [Fe II] lines is most likely formed in the photosphere of a surrounding disk. Some of the emission lines show a pronounced double peaked profile, such as Ca II, indicating an accretion disk in Keplerian rotation around the central star. [O I] emission lines are formed in the neutral atomic zone separating the ionized disk photosphere from the molecular gas in the interior of the disk, which is prominent in molecular CO emission in the near-IR. [N II] and [S II] emission clearly originates in a low density but fairly hot (7 000-10 000 K) nebular environment. H I recombination lines trace the extended nebula as well as the photosphere of the disk. Results: These findings put constraints on the evolution of the central objects in MWC 922. The Red Square shows strong similarities to the Red Rectangle Nebula, both in morphology and in its mid-IR spectroscopic characteristics. As for the Red Rectangle, the observed morphology of the nebula reflects mass-loss in a binary system. Specifically, we attribute the biconical morphology and the associated rung-like structure to the action of intermittent jets blown by the accreting companion in a dense shell, which has been created by the primary. We stress, though, that despite the morphological similarities, these two objects represent very different classes of stellar objects. The data-reduced spectra are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/601/A69

The ISO and IUE spectra of the bipolar planetary nebulae NGC 6537 and He2-111 are presented. These spectra are combined with the spectrum in the visual wavelength region from the nebulae to obtain a complete spectrum that is corrected for extinction. The chemical abundance of the nebulae is then determined and compared to previous determinations, The abundance of the two nebulae is quite similar. A comparison is then made with the abundance of two other bipolar planetary nebulae whose abundance is also determined with the help of ISO observations. It is shown that not all bipolar nebulae have similar abundance. NGC 6445 has a much lower nitrogen to oxygen ratio, similar to NGC 7027, but still not as low as the Orion nebula.

The ISO and IUE spectra of the bipolar planetary nebulae NGC 6537 and He2-111 are presented. These spectra are combined with the spectrum in the visual wavelength region from the nebulae to obtain a complete spectrum that is corrected for extinction. The chemical abundance of the nebulae is then determined and compared to previous determinations, The abundance of the two nebulae is quite similar. A comparison is then made with the abundance of two other bipolar planetary nebulae whose abundance is also determined with the help of ISO observations. It is shown that not all bipolar nebulae have similar abundance. NGC 6445 has a much lower nitrogen to oxygen ratio, similar to NGC 7027, but still not as low as the Orion nebula.

The UV spectrum of PC 11 is found to show variations in the strength of the O III] 1666 Angstrom, N III] 1750 Angstrom and C III] 1909 Angstrom emission lines. The detection of continuum emission in the wavelength interval 2650 Angstrom to 3200 Angstrom indicates that the central star of PC 11 has an early F-type dwarf companion. The very low level of UV continuum in the wavelength interval 1150 Angstrom to 1900 Angstrom and the non-detection of the central star in the UV images recently taken with I-IST suggest that the hot whitedwarf or sub-dwarf like central star may be obscured by a dusty disk. The variations in the UV emission lines observed during the period 1987 to 1994 may be the consequence of variable emission coming from high-velocity jet-like emission visible in optical images also taken with HST in the light of [O III]. Based on our UV observations, we confirm our identification of PC 11 as a planetary nebula with a close binary central star. Adopting the absolute magnitude of a F0V companion yields a distance of 485 pc to PC 11. If we assume a typical expansion velocity of 12.5 km s(-1) and considering the observed angular diameter of the nebula (4.1 "), we find the age of PC 11 to be 376 years. The AGE phase of evolution of the central star seems to have been terminated only recently.

The UV spectrum of PC 11 is found to show variations in the strength of the O III] 1666 Angstrom, N III] 1750 Angstrom and C III] 1909 Angstrom emission lines. The detection of continuum emission in the wavelength interval 2650 Angstrom to 3200 Angstrom indicates that the central star of PC 11 has an early F-type dwarf companion. The very low level of UV continuum in the wavelength interval 1150 Angstrom to 1900 Angstrom and the non-detection of the central star in the UV images recently taken with I-IST suggest that the hot whitedwarf or sub-dwarf like central star may be obscured by a dusty disk. The variations in the UV emission lines observed during the period 1987 to 1994 may be the consequence of variable emission coming from high-velocity jet-like emission visible in optical images also taken with HST in the light of [O III]. Based on our UV observations, we confirm our identification of PC 11 as a planetary nebula with a close binary central star. Adopting the absolute magnitude of a F0V companion yields a distance of 485 pc to PC 11. If we assume a typical expansion velocity of 12.5 km s(-1) and considering the observed angular diameter of the nebula (4.1 "), we find the age of PC 11 to be 376 years. The AGE phase of evolution of the central star seems to have been terminated only recently.

We report the serendipitous discovery of seven luminous irregular variables in the LMC by the EROS project. The stars have V similar or equal to 15(m) to 17(m), (B(E) - R(E)) similar or equal to 0(m), and vary by about 0.4(m) on timescales of 10 to 40 days. The variations in B(E) and R(E) are about equal but the stars are slightly bluer when they an fainter. Medium resolution optical spectra show strong H alpha emission, weak H beta emission and absorption lines of the higher Balmer lines. Absorption lines of He I, C III, O II and Si IV are present in the spectra of some of the stars. The spectral types derived from the presence or absence of the lines are between late-O and late-B. Effective temperatures and luminosities were derived from the energy distributions and independently from the EROS photometry combined with the approximate spectral types. The luminosity, derived from V, E(B - V), and the distance of the LMC, are in the range of 10(3) to 10(4) L.. The strong Hey emission, the spectral types, the luminosities and the irregular variations are similar (but not the same) to those of the Galactic pre-main sequence HAeBe stars (i.e. the Herbig Ae/Be stars). However the stars are about a factor 10 more luminous than the luminosity upper limit for Galactic HAeBe stars. This might be due to a shorter accretion timescale (tau(accr) = M(*) /(M) over dot), or to the smaller dust-to-gas ratio in the LMC.

We report the serendipitous discovery of seven luminous irregular variables in the LMC by the EROS project. The stars have V similar or equal to 15(m) to 17(m), (B(E) - R(E)) similar or equal to 0(m), and vary by about 0.4(m) on timescales of 10 to 40 days. The variations in B(E) and R(E) are about equal but the stars are slightly bluer when they an fainter. Medium resolution optical spectra show strong H alpha emission, weak H beta emission and absorption lines of the higher Balmer lines. Absorption lines of He I, C III, O II and Si IV are present in the spectra of some of the stars. The spectral types derived from the presence or absence of the lines are between late-O and late-B. Effective temperatures and luminosities were derived from the energy distributions and independently from the EROS photometry combined with the approximate spectral types. The luminosity, derived from V, E(B - V), and the distance of the LMC, are in the range of 10(3) to 10(4) L.. The strong Hey emission, the spectral types, the luminosities and the irregular variations are similar (but not the same) to those of the Galactic pre-main sequence HAeBe stars (i.e. the Herbig Ae/Be stars). However the stars are about a factor 10 more luminous than the luminosity upper limit for Galactic HAeBe stars. This might be due to a shorter accretion timescale (tau(accr) = M(*) /(M) over dot), or to the smaller dust-to-gas ratio in the LMC.

We present theoretical H alpha and HI infrared recombination line calculations for low-density discs around B stars. Such a disc shows no visible emission in H alpha, while the HI IR recombination lines are in emission. This phenomenon has been found in the spectrum of the B0.2V star, tau Sco and could be simulated with a simple disc model. As an extension of that particular case we calculate the entire IR HI line spectrum of a normal B star surrounded by a low-density disc with a theoretical curve of growth for HI IR line fluxes, which we introduce as a tool for studying low-density discs. We find that IR emission lines may be detectable for densities up to about 10(-14) gcm(-3) which is a factor 10(2) - 10(3) lower than typically found in Be stars. For different spectral types, B0, B2, B5 and B8 we determined the density range for which emission is prominent in the IR recombination lines but not in Ha alpha.

We present theoretical H alpha and HI infrared recombination line calculations for low-density discs around B stars. Such a disc shows no visible emission in H alpha, while the HI IR recombination lines are in emission. This phenomenon has been found in the spectrum of the B0.2V star, tau Sco and could be simulated with a simple disc model. As an extension of that particular case we calculate the entire IR HI line spectrum of a normal B star surrounded by a low-density disc with a theoretical curve of growth for HI IR line fluxes, which we introduce as a tool for studying low-density discs. We find that IR emission lines may be detectable for densities up to about 10(-14) gcm(-3) which is a factor 10(2) - 10(3) lower than typically found in Be stars. For different spectral types, B0, B2, B5 and B8 we determined the density range for which emission is prominent in the IR recombination lines but not in Ha alpha.

International audience; Context. Be stars are probably the most rapid rotators among stars in the main sequence (MS) and, as such, are excellent candidates to study the incidence of the rotation on the characteristics of their non-radial pulsations, as well as on their internal structure. Pulsations are also thought to be possible mechanisms that help the mass ejection needed to build up the circumstellar disks of Be stars.Aims. The purpose of this paper is to identify a number of faint Be stars observed with the CoRoT satellite and to determine their fundamental parameters, which will enable us to study their pulsation properties as a function of the location in the HR diagram and to search for correlations with the light outbursts, which are possibly produced by discrete mass ejections.Methods. We identified those objects in the exofields of CoRoT presenting the Be phenomenon using Hα surveys, as well as automated methods based on pulsation properties that we finally confirmed with FLAMES/GIRAFFE and X-shooter spectroscopic observations at VLT/ESO, and with near-IR photometry. The spectra were 1) corrected for the veiling effect, 2) treated with the GIRFIT code to determine apparent fundamental parameters, and 3) corrected with the FASTROT code for effects induced by the rapid rotation.Results. A list of 41 Be star candidates were found from photometric and spectroscopic criteria. The spectral coverage useful for determining the fundamental parameters was obtained for only about half of them. We then spectroscopically identified 21 Be stars, two probable Be stars, and two B stars contaminated by the Sh 2-284 nebulosity. A short description of the spectral characteristics of each star is given. The fundamental parameters and, in particular, the rotation frequency νr (cycles per day) were all corrected for rotational effects at rotation rates ranging from Ω/Ωc = 0.8 to 1.0. We have determined the positions of Be stars in the HR diagram and find two of them located beyond the MS phase.Conclusions. The well-determined fundamental parameters presented in this paper for a statistically reliable sample of Be stars will enable us in forthcoming papers to compare the properties of stars as pulsators either according to their location in different regions of the HR diagram or with those predicted from theory.

The intriguing binary LS V +22 25 (LB-1) has drawn much attention following claims of it being a single-lined spectroscopic binary with a 79-day orbit comprising a B-type star and a ~70 Msun black hole. Recent analyses have implied that the visible primary star is a stripped He-rich star. However, the nature of the secondary, which was proposed to be a black hole, a neutron star, or a main sequence star, remains unknown. Based on 26 newly acquired spectroscopic observations, we perform an orbital analysis and spectral disentangling of LB-1 to elucidate the nature of the system. Our analysis reveals that LB-1 contains two components of comparable brightness in the optical. The narrow-lined primary, which we estimate to contribute ~55% in the optical, has spectral properties that suggest that it is a stripped star: it has a small spectroscopic mass (~1 Msun) for a B-type star and it is He- and N-rich. The "hidden" secondary, which contributes about 45% of the optical flux, is a rapidly rotating (vsini ~ 300 km/s) B3 V star with a decretion disk -- a Be star. Hence, LB-1 does not contain a compact object. Instead, it is a rare Be binary system consisting of a stripped star (the former mass donor) and a Be star rotating at near its critical velocity (the former mass accretor). This system is a clear example that binary interactions play a decisive role in the production of rapid stellar rotators and Be stars., Comment: Accepted to A&A. 4 pages (1 figure, 1 table); 3 pages of supporting material (7 figures and 1 table)

HD49330 is a Be star that underwent an outburst during its five-month observation with the CoRoT satellite. An analysis of its light curve revealed several independent p and g pulsation modes, in addition to showing that the amplitude of the modes is directly correlated with the outburst. We modelled the results obtained with CoRoT. We modelled the flattening of the structure of the star due to rapid rotation in two ways: Chandrasekhar-Milne's expansion and 2D structure computed with ROTORC. We then modelled kappa-driven pulsations. We also adapted the formalism of the excitation and amplitude of stochastically excited gravito-inertial modes to rapidly rotating stars, and we modelled those pulsations as well. We find that while pulsation p modes are excited by the kappa mechanism, the observed g modes are a result of stochastic excitation. In contrast, g and r waves are stochastically excited in the convective core and transport angular momentum to the surface, increasing its rotation rate. This destabilises the external layers of the star, which then emits transient stochastically excited g waves. These transient waves produce most of the low-frequency signal detected in the CoRoT data and ignite the outburst. During this unstable phase, p modes disappear at the surface because their cavity is broken. Following the outburst and ejection of the surface layer, relaxation occurs, making the transient g waves disappear and p modes reappear. This work includes the first coherent model of stochastically excited gravito-inertial pulsation modes in a rapidly rotating Be star. It provides an explanation for the correlation between the variation in the amplitude of frequencies detected in the CoRoT data and the occurrence of an outburst. This scenario could apply to other pulsating Be stars, providing an explanation to the long-standing questions surrounding Be outbursts and disks., Comment: Accepted in A&A, 15 pages, abstract shown here has been abridged to fit Arxiv's character limit

About 20% of all B-type stars are classical Be stars. The Be phenomenon is strongly correlated with rapid rotation, the origin of which remains unclear. It may be rooted in single- or binary-star evolution. In the framework of the binary channel, the initially more massive star transfers mass and angular momentum to the original secondary, which becomes a Be star. The system then evolves into a Be binary with a post-main-sequence companion, which may later be disrupted in a supernova event. Hence, if the binary channel dominates the formation of Be stars, one may expect a strong lack of close Be binaries with main sequence (MS) companions. Through an extensive, star-by-star review of the literature of a magnitude-limited sample of Galactic early-type Be stars, we investigate whether Be binaries with MS companions are known to exist. Our sample is constructed from the BeSS database and cross-matched with all available literature on the individual stars. Out of an initial list of 505 Be stars, we compile a final sample of 287 Galactic Be stars earlier than B1.5 with V, 15 pages (incl. appendix), 6 figures, 3 tables, accepted for publication in A&A