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This paper investigates the gravitational trapping of H  ii regions predicted by steady-state analysis using radiation hydrodynamical simulations. We present idealized spherically symmetric radiation hydrodynamical simulations of the early evolution of H  ii regions including the gravity of the central source. As with analytic steady-state solutions of spherically symmetric ionized Bondi accretion flows, we find gravitationally trapped H  ii regions with accretion through the ionization front on to the source. We found that, for a constant ionizing luminosity, fluctuations in the ionization front are unstable. This instability only occurs in this spherically symmetric accretion geometry. In the context of massive star formation, the ionizing luminosity increases with time as the source accretes mass. The maximum radius of the recurring H  ii region increases on the accretion time-scale until it reaches the sonic radius, where the infall velocity equals the sound speed of the ionized gas, after which it enters a pressure-driven expansion phase. This expansion prevents accretion of gas through the ionization front, the accretion rate on to the star decreases to zero, and it stops growing from accretion. Because of the time required for any significant change in stellar mass and luminosity through accretion our simulations keep both mass and luminosity constant and follow the evolution from trapped to expanding in a piecewise manner. Implications of this evolution of H  ii regions include a continuation of accretion of material on to forming stars for a period after the star starts to emit ionizing radiation, and an extension of the lifetime of ultracompact H  ii regions. [ABSTRACT FROM AUTHOR]

Statistical analysis of Faraday rotation measure (RM) maps of the intracluster medium (ICM) of galaxy clusters provides a unique tool to evaluate some spatial features of the magnetic fields there. Its combination with numerical simulations of magnetohydrodynamic (MHD) turbulence allows the diagnosis of the ICM turbulence. Being the ICM plasma weakly collisional, the thermal velocity distribution of the particles naturally develops anisotropies as a consequence of the large-scale motions and the conservation of the magnetic moment of the charged particles. A previous study (Paper I) analysed the impact of large-scale thermal anisotropy on the statistics of RM maps synthesized from simulations of turbulence; these simulations employed a collisionless MHD model that considered a tensor pressure with uniform anisotropy. In this work, we extend that analysis to a collisionless MHD model in which the thermal anisotropy develops according to the conservation of the magnetic moment of the thermal particles. We also consider the effect of anisotropy relaxation caused by the microscale mirror and firehose instabilities. We show that if the relaxation rate is fast enough to keep the anisotropy limited by the threshold values of the instabilities, the dispersion and power spectrum of the RM maps are indistinguishable from those obtained from collisional MHD. Otherwise, there is a reduction in the dispersion and steepening of the power spectrum of the RM maps (compared to the collisional case). Considering the first scenario, the use of collisional MHD simulations for modelling the RM statistics in the ICM becomes better justified. [ABSTRACT FROM AUTHOR]

Strong downstream magnetic fields of the order of ∼1 G, with large correlation lengths, are believed to cause the large synchrotron emission at the afterglow phase of gamma-ray bursts (GRBs). Despite the recent theoretical efforts, models have failed to fully explain the amplification of the magnetic field, particularly in a matter-dominated scenario. We revisit the problem by considering the synchrotron emission to occur at the expanding shock front of a weakly magnetized relativistic jet over a magnetized surrounding medium. Analytical estimates and a number of high-resolution 2D relativistic magnetohydrodynamical (RMHD) simulations are provided. Jet opening angles of θ = 0°–20°, and ambient to jet density ratios of 10−4–102 were considered. We found that most of the amplification is due to compression of the ambient magnetic field at the contact discontinuity between the reverse and forward shocks at the jet head, with substantial pile-up of the magnetic field lines as the jet propagates sweeping the ambient field lines. The pile-up is maximum for θ → 0, decreasing with θ, but larger than in the spherical blast problem. Values obtained for certain models are able to explain the observed intensities. The maximum correlation lengths found for such strong fields is of lcorr ≤ 1014 cm, 2–6 orders of magnitude larger than the found in previous works. [ABSTRACT FROM AUTHOR]

Turbulence is ubiquitous in the interstellar medium (ISM) of the Milky Way and other spiral galaxies. The energy source for this turbulence has been much debated with many possible origins proposed. The universality of turbulence, its reported large-scale driving, and that it occurs also in starless molecular clouds, challenges models invoking any stellar source. A more general process is needed to explain the observations. In this work, we study the role of galactic spiral arms. This is accomplished by means of three-dimensional hydrodynamical simulations which follow the dynamical evolution of interstellar diffuse clouds (∼100 cm−3) interacting with the gravitational potential field of the spiral pattern. We find that the tidal effects of the arm's potential on the cloud result in internal vorticity, fragmentation and hydrodynamical instabilities. The triggered turbulence results in large-scale driving, on sizes of the ISM inhomogeneities, i.e. as large as ∼100 pc, and efficiencies in converting potential energy into turbulence in the range ∼10–25 per cent per arm crossing. This efficiency is much higher than those found in previous models. The statistics of the turbulence in our simulations are strikingly similar to the observed power spectrum and Larson scaling relations of molecular clouds and the general ISM. The dependence found from different models indicate that the ISM turbulence is mainly related to local spiral arm properties, such as its mass density and width. This correlation seems in agreement with recent high angular resolution observations of spiral galaxies, e.g. M51 and M33. [ABSTRACT FROM AUTHOR]

In this work, we present a semi-analytical model of galactic wind for dwarf galaxies where thermal and turbulent/momentum driving mechanisms are studied. The model takes into account wave and internal adiabatic heating mechanisms, as well as radiative and adiabatic cooling. The importance of external sources of energy is discussed. We also studied the role of the spatial distribution of dark matter in the acceleration of the wind and in the mass-loss rates. The basic model parameters that regulate the wind mass-loss rate and terminal velocity are the gravitational potential profile, the equilibrium temperature of the gas and the amplitude of the turbulent motions of the gas. We found that dwarf galaxies are likely to present quasi-stationary winds with mass-loss rates larger than 10−3 M⊙ yr−1 even in the absence of turbulent motions (which is possibly related to the supernovae feedback), if the interstellar gas is heated to T > 104–105 K. We also found that the wind mass-loss rate is enhanced for cusped dark matter distributions, such as the Navarro–Frenk–White profile, due to the increased pressure gradients at the centre of the galaxy. The solutions presented here may serve as benchmarks for numerical simulations, and as inputs for single-zone chemical evolution models of dwarf galaxies. [ABSTRACT FROM AUTHOR]

Theoretical Λcold dark matter (ΛCDM) cosmological models predict a much larger number of low-mass dark matter haloes than has been observed in the Local Group of galaxies. One possible explanation is the increased difficulty of detecting these haloes if most of the visible matter is lost at early evolutionary phases through galactic winds. In this work we study the current models of triggering galactic winds in dwarf spheroidal galaxies (dSph) from supernovae, and study, based on 3D hydrodynamic numerical simulations, the correlation of the mass-loss rates and important physical parameters as the dark matter halo mass and its radial profile, and the star formation rate. We find that the existence of winds is ubiquitous, independent of the gravitational potential. Our simulations revealed that the Rayleigh–Taylor Instability (RTI) may play a major role on pushing matter out of these systems, even for very massive haloes. The instability is responsible for 5–40 per cent of the mass loss during the early evolution of the galaxy, being less relevant at t > 200 Myr. There is no significant difference in the mass-loss rates obtained for the different dark matter profiles studied (NFW and logarithmic). We have also found a correlation between the mass-loss rate and both the halo mass and the rate of supernovae, as already reported in previous works. Besides, the epoch in which most of the baryon galactic matter is removed from the galaxy varies depending on the SN rate and gravitational potential. The later, combined to the importance of the RTI in each model, may change our understanding about the chemical evolution of dwarf galaxies, as well as in the heavy element contamination of the intergalactic medium at high redshifts. [ABSTRACT FROM AUTHOR]

ABSTRACT We report a study of the stellar content of the near-infrared (NIR) cluster [DBS2003] 157 embedded in the extended H ii region GAL 331.31−00.34, which is associated with the IRAS source 16085−5138. JHK photometry was carried out in order to identify potential ionizing candidates, and the follow-up NIR spectroscopy allowed the spectral classification of some sources, including two O-type stars. A combination of NIR photometry and spectroscopy data was used to obtain the distance of these two stars, with the method of spectroscopic parallax: IRS 298 (O6 V, 3.35 ± 0.61 kpc) and IRS 339 (O9 V, 3.24 ± 0.56 kpc). Adopting the average distance of 3.29 ± 0.58 kpc and comparing the Lyman continuum luminosity of these stars with that required to account for the radio continuum flux of the H ii region, we conclude that these two stars are the ionizing sources of GAL 331.31−00.34. Young stellar objects (YSOs) were searched by using our NIR photometry and mid-infrared (MIR) data from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) survey. The analysis of NIR and MIR colour-colour diagrams resulted in 47 YSO candidates. The GLIMPSE counterpart of IRAS 16085−5138, which presents IRAS colour indices compatible with an ultracompact H ii region, has been identified. The analysis of its spectral energy distribution between 2 and m revealed that this source shows a spectral index α= 3.6 between 2 and m, which is typical of a YSO immersed in a protostellar envelope. Lower limits to the bolometric luminosity and the mass of the embedded protostar have been estimated as L= 7.7 × 103 L⊙ and M= 10 M⊙, respectively, which correspond to a B0-B1 V zero-age main sequence star. [ABSTRACT FROM AUTHOR]

We report a study of the stellar content of the near-infrared (NIR) cluster [DBS2003] 157 embedded in the extended H ii region GAL 331.31−00.34, which is associated with the IRAS source 16085−5138. JHK photometry was carried out in order to identify potential ionizing candidates, and the follow-up NIR spectroscopy allowed the spectral classification of some sources, including two O-type stars. A combination of NIR photometry and spectroscopy data was used to obtain the distance of these two stars, with the method of spectroscopic parallax: IRS 298 (O6 V, 3.35 ± 0.61 kpc) and IRS 339 (O9 V, 3.24 ± 0.56 kpc). Adopting the average distance of 3.29 ± 0.58 kpc and comparing the Lyman continuum luminosity of these stars with that required to account for the radio continuum flux of the H ii region, we conclude that these two stars are the ionizing sources of GAL 331.31−00.34. Young stellar objects (YSOs) were searched by using our NIR photometry and mid-infrared (MIR) data from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) survey. The analysis of NIR and MIR colour–colour diagrams resulted in 47 YSO candidates.The GLIMPSE counterpart of IRAS 16085−5138, which presents IRAS colour indices compatible with an ultracompact H ii region, has been identified. The analysis of its spectral energy distribution between 2 and m revealed that this source shows a spectral index α= 3.6 between 2 and m, which is typical of a YSO immersed in a protostellar envelope. Lower limits to the bolometric luminosity and the mass of the embedded protostar have been estimated as L= 7.7 × 103 L⊙ and M= 10 M⊙, respectively, which correspond to a B0–B1 V zero-age main sequence star. [ABSTRACT FROM AUTHOR]

ABSTRACT In the past few decades detailed observations of radio and X-ray emission from massive binary systems revealed a whole new physics present in such systems. Both thermal and non-thermal components of this emission indicate that most of the radiation at these bands originates in shocks. O and B-type stars and Wolf-Rayet (WR) stars present supersonic and massive winds that, when colliding, emit largely due to the free-free radiation. The non-thermal radio and X-ray emissions are due to synchrotron and inverse Compton processes, respectively. In this case, magnetic fields are expected to play an important role in the emission distribution. In the past few years the modelling of the free-free and synchrotron emissions from massive binary systems have been based on purely hydrodynamical simulations, and ad hoc assumptions regarding the distribution of magnetic energy and the field geometry. In this work we provide the first full magnetohydrodynamic numerical simulations of wind-wind collision in massive binary systems. We study the free-free emission characterizing its dependence on the stellar and orbital parameters. We also study self-consistently the evolution of the magnetic field at the shock region, obtaining also the synchrotron energy distribution integrated along different lines of sight. We show that the magnetic field in the shocks is larger than that obtained when the proportionality between B and the plasma density is assumed. Also, we show that the role of the synchrotron emission relative to the total radio emission has been underestimated. [ABSTRACT FROM AUTHOR]

It is believed that η Carinae is actually a massive binary system, with the wind–wind interaction responsible for the strong X-ray emission. Although the overall shape of the X-ray light curve can be explained by the high eccentricity of the binary orbit, other features like the asymmetry near periastron passage and the short quasi-periodic oscillations seen at those epochs have not yet been accounted for. In this paper we explain these features assuming that the rotation axis of η Carinae is not perpendicular to the orbital plane of the binary system. As a consequence, the companion star will face η Carinae on the orbital plane at different latitudes for different orbital phases and, since both the mass-loss rate and the wind velocity are latitude dependent, they would produce the observed asymmetries in the X-ray flux. We were able to reproduce the main features of the X-ray light curve assuming that the rotation axis of η Carinae forms an angle of with the axis of the binary orbit. We also explained the short quasi-periodic oscillations by assuming nutation of the rotation axis, with an amplitude of about and a period of about 22 days. The nutation parameters, as well as the precession of the apsis, with a period of about 274 years, are consistent with what is expected from the torques induced by the companion star. [ABSTRACT FROM AUTHOR]

During the past decade, several observational and theoretical works have provided evidence of the binary nature of η Carinae. Nevertheless, there is still no direct determination of the orbital parameters, and the different current models give contradictory results. The orbit is, in general, assumed to coincide with the Homunculus equator although the observations are not conclusive. Among all systems, η Car has the advantage that it is possible to observe both the direct emission of line transitions in the central source and its reflection by the Homunculus, which is dependent on the orbital inclination. In this work, we studied the orbital phase-dependent hydrogen Paschen spectra reflected by the south-east lobe of the Homunculus to constrain the orbital parameters of η Car and determine its inclination with respect to the Homunculus axis. Assuming that the emission excess originates in the wind–wind shock region, we were able to model the latitude dependence of the spectral line profiles. For the first time, we were able to estimate the orbital inclination of η Car with respect to the observer and to the Homunculus axis. The best fit occurs for an orbital inclination to the line of sight of , and with respect to the Homunculus axis, indicating that the angular momenta of the central object and the orbit are not aligned. We were also able to fix the phase angle of conjunction as , showing that periastron passage occurs shortly after conjunction. [ABSTRACT FROM AUTHOR]

In this work, considering the impact of a supernova remnant (SNR) with a neutral magnetized cloud we derived analytically a set of conditions that are favourable for driving gravitational instability in the cloud and thus star formation. Using these conditions, we have built diagrams of the SNR radius, RSNR, versus the initial cloud density, nc, that constrain a domain in the parameter space where star formation is allowed. This work is an extension to previous study performed without considering magnetic fields ( Melioli et al. 2006 , hereafter Paper I). The diagrams are also tested with fully three-dimensional MHD radiative cooling simulations involving a SNR and a self-gravitating cloud and we find that the numerical analysis is consistent with the results predicted by the diagrams. While the inclusion of a homogeneous magnetic field approximately perpendicular to the impact velocity of the SNR with an intensity within the cloud results only a small shrinking of the star formation zone in the diagram relative to that without magnetic field, a larger magnetic field causes a significant shrinking, as expected. Though derived from simple analytical considerations these diagrams provide a useful tool for identifying sites where star formation could be triggered by the impact of a supernova blast wave. Applications of them to a few regions of our own Galaxy (e.g. the large CO shell in the direction of Cassiopeia, and the Edge Cloud 2 in the direction of the Scorpious constellation) have revealed that star formation in those sites could have been triggered by shock waves from SNRs for specific values of the initial neutral cloud density and the SNR radius. Finally, we have evaluated the effective star formation efficiency for this sort of interaction and found that it is generally smaller than the observed values in our own Galaxy (SFE ∼ 0.01–0.3). This result is consistent with previous work in the literature and also suggests that the mechanism presently investigated, though very powerful to drive structure formation, supersonic turbulence and eventually, local star formation, does not seem to be sufficient to drive global star formation in normal star-forming galaxies, not even when the magnetic field in the neutral clouds is neglected. [ABSTRACT FROM AUTHOR]

The study of Wolf–Rayet stars plays an important role in evolutionary theories of massive stars. Among these objects, ∼20 per cent are known to be in binary systems and can therefore be used for the mass determination of these stars. Most of these systems are not spatially resolved and spectral lines can be used to constrain the orbital parameters. However, part of the emission may originate in the interaction zone between the stellar winds, modifying the line profiles and thus challenging us to use different models to interpret them. In this work, we analysed the He iiλ4686 Å+ C ivλ4658 Å blended lines of WR 30a (WO4+O5) assuming that part of the emission originate in the wind–wind interaction zone. In fact, this line presents a quiescent base profile, attributed to the WO wind, and a superposed excess, which varies with the orbital phase along the 4.6-d period. Under these assumptions, we were able to fit the excess spectral line profile and central velocity for all phases, except for the longest wavelengths, where a spectral line with constant velocity seems to be present. The fit parameters provide the eccentricity and inclination of the binary orbit, from which it is possible to constrain the stellar masses. [ABSTRACT FROM AUTHOR]

We modelled the He iiλ4686 line profiles observed in the η Carinae binary system close to the 2003.5 spectroscopic event, assuming that they were formed in the shocked gas that flows at both sides of the contact surface formed by wind–wind collision. We used a constant flow velocity and added turbulence in the form of a Gaussian velocity distribution. We allowed emission from both the primary and secondary shocks but introduced infinite opacity at the contact surface, implying that only the side of the contact cone visible to the observer contributed to the line profile. Using the orbital parameters of the binary system derived from the 7-mm light curve during the last spectroscopic event (Paper II) we were able to reproduce the line profiles obtained with the Hubble Space Telescope at different epochs, as well as the line mean velocities obtained with ground-based telescopes. A very important feature of our model is that the line profile depends on the inclination of the orbital plane; we found that to explain the latitude-dependent mean velocity of the line, scattered into the line of sight by the Homunculus, the orbit cannot lie in the Homunculus equatorial plane, as usually assumed. This result, together with the relative position of the stars during the spectroscopic events, allowed us to explain most of the observational features, like the variation of the ‘Purple Haze’ with the orbital phase, and to conciliate the X-ray absorption with the postulated shell effect used to explain the optical and ultraviolet light curves. [ABSTRACT FROM AUTHOR]

One of the most intriguing spectral features of Wolf–Rayet (WR) binary stars is the presence of time-dependent line profiles. Long-term observations of several systems revealed the periodicity of this variability, synchronized with the orbital movement. Several partially successful models have been proposed to reproduce the observed data. The most promising model assumes that the origin of the emission is the wind–wind interaction zone. In this scenario, two high velocity and dense winds produce a strong shock layer, responsible for most of the X-rays observed from these systems. As the gas cools down, flowing along the interaction surface, it reaches recombination temperatures and generates the emission lines. Luhrs noted that, as the secondary star moves along its orbital path, the shock region, of conical shape, changes its position with relation to the line of sight. As a consequence, the stream-measured Doppler shift presents time variations resulting in position changes of the spectral line. However, his model requires a very thick contact layer and also fails to reproduce recently observed line profiles of several other WR binary systems. In our work, we present an alternative model, introducing turbulence in the shock layer to account for the line broadening and opacity effects for the asymetry in the line profiles. We showed that the gas turbulence avoids the need of an unnaturally large contact layer thickness to reproduce line broadening. Also, we demonstrated that if the post-shock gas is optically thick at the observed line frequency, the emission from the opposing cone surface is absorbed, resulting in a single-peaked profile. This result fully satisfies the recent data obtained from massive binary systems, and can help in the determination of both the winds and the orbital parameters. We successfully applied this model to the Br22 system and determined its orbital parameters. [ABSTRACT FROM AUTHOR]

Cool stars at giant and supergiant evolutionary phases present low-velocity and high-density winds, responsible for the observed high mass-loss rates. Although presenting high luminosities, radiation pressure on dust particles is not sufficient to explain the wind acceleration process. Among the possible solutions to this still unsolved problem, Alfvén waves are, probably, the most interesting for their high efficiency in transfering energy and momentum to the wind. Typically, models of Alfvén wave driven winds result in high-velocity winds if they are not highly damped. In this work, we determine self-consistently the magnetic field geometry and solve the momentum, energy and mass conservation equations, to demonstrate that even a low-damped Alfvén wave flux is able to reproduce the low-velocity wind. We show that the magnetic flux tubes expand with a super-radial factor of S > 30 near the stellar surface, larger than that used in previous semi-empirical models. The rapid expansion results in a strong spatial dilution of the wave flux. We obtained the wind parameter profiles for a typical supergiant star of . The wind is accelerated in a narrow region, coincident with the region of high divergence of the magnetic field lines, up to 100 km s−1. For the temperature, we obtained a slight decrease near the surface for low-damped waves, because the wave heating mechanism is less effective than the radiative losses. The peak temperature occurs at reaching 6000 K. Propagating outwards, the wind cools down mainly due to adiabatic expansion. [ABSTRACT FROM AUTHOR]

In this paper we use the 7- and 1.3-mm light curves obtained during the 2003.5 low-excitation phase of the η Carinae system to constrain the possible parameters of the binary orbit. To do that we assumed that the millimetre-wave emission is produced in a dense disc surrounding the binary system; during the low-excitation phase, which occurs close to periastron, the number of ionizing photons decreases, producing the dip in the radio emission. On the other hand, due to the large eccentricity, the density of the shock region at periastron is very high and the plasma is optically thick for free–free radiation at 7 mm, explaining the sharp peak that was observed at this frequency and lasted for about 10 d. From the shape and duration of the peak we were able to determine the orbital parameters of the binary system, independently of the stellar parameters, such as mass-loss rates, wind velocities or temperature at the post-shock region. [ABSTRACT FROM AUTHOR]

The exact nature ofη Carinae is still an open issue. Strict periodicity in the light curves at several wavelengths seem to point to a binary system, but the observed radial velocities, measured from space with high spatial resolution, are in conflict with the ground-based observations used to calculate the binary orbit. Also, the observed 2–10 keV X-ray flux is much larger that what is expected from a single star, and favours the wind–wind collision hypothesis, characteristic of high-mass binary systems. However, to explain the duration of the dip in the light curve by wind collisions, it is necessary to postulate a very large increase in theη Carinae mass loss rate. Finally, the optical and ultraviolet light curves are better explained by periodic shell-ejection events. In this paper we conciliate the two hypotheses. We still assume a binary system to explain the strong X-ray emission, but we also take into account that, near periastron and because of the highly eccentric orbit, the wind emerging fromη Carinae accumulates behind the shock and can mimic a shell-like ejection event. For this process to be effective, at periastron the secondary star should be located betweenη Carinae and the observer, solving also the discrepancy between the orbital parameters derived from ground- and space-based observations. We show that, as the secondary moves in its orbit, the shell cools down and the number of available stellar ionizing photons is not enough to maintain the shell temperature at its equilibrium value of about 7500 K. The central part of the shell remains cold and under these conditions grain formation and growth can take place in time-scales of hours. We also calculated the neutral gas column density intercepting the line of sight at each point of the orbit near periastron, and were able to reproduce the form and duration of the X-ray light curve without any change in theη Carinae mass loss rate. This same column density can explain the observed Hα light curve observed during the 2003 event. [ABSTRACT FROM AUTHOR]

ABSTRACT We report a study of the stellar content of the near-infrared (NIR) cluster [DBS2003] 157 embedded in the extended H ii region GAL 331.31−00.34, which is associated with the IRAS source 16085−5138. JHK photometry was carried out in order to identify potential ionizing candidates, and the follow-up NIR spectroscopy allowed the spectral classification of some sources, including two O-type stars. A combination of NIR photometry and spectroscopy data was used to obtain the distance of these two stars, with the method of spectroscopic parallax: IRS 298 (O6 V, 3.35 ± 0.61 kpc) and IRS 339 (O9 V, 3.24 ± 0.56 kpc). Adopting the average distance of 3.29 ± 0.58 kpc and comparing the Lyman continuum luminosity of these stars with that required to account for the radio continuum flux of the H ii region, we conclude that these two stars are the ionizing sources of GAL 331.31−00.34. Young stellar objects (YSOs) were searched by using our NIR photometry and mid-infrared (MIR) data from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) survey. The analysis of NIR and MIR colour-colour diagrams resulted in 47 YSO candidates. The GLIMPSE counterpart of IRAS 16085−5138, which presents IRAS colour indices compatible with an ultracompact H ii region, has been identified. The analysis of its spectral energy distribution between 2 and m revealed that this source shows a spectral index α= 3.6 between 2 and m, which is typical of a YSO immersed in a protostellar envelope. Lower limits to the bolometric luminosity and the mass of the embedded protostar have been estimated as L= 7.7 × 103 L⊙ and M= 10 M⊙, respectively, which correspond to a B0-B1 V zero-age main sequence star. [ABSTRACT FROM AUTHOR]