Spectropolarimetic campaigns have established that large-scale magnetic fields are present at the surfaces of approximately 10% of massive dwarf stars. However, there is a dearth of magnetic field measurements for their deep interiors. Asteroseismology of gravity-mode pulsations combined with rotating magneto-hydrodynamical calculations of the early-B main-sequence star HD 43317 constrain its magnetic field strength to be approximately 5 × 105 G just outside its convective core. This proof-of-concept study for magneto-asteroseismology opens a new window into the observational characterisation of magnetic fields inside massive stars.

We present the results of high-resolution continuum and molecular line observations towards the Galactic HII region, G10.32-0.26. The continuum map with ALMA reveals the five cores with masses ranging from 2.5–9.2 Me. The results show that the brightest peak, Peak 1, is an HCHII region with an excitation temperature of : 12000 K, an electron density of 3.4×107 cm3, and a radius of 14 au. The central object is estimated to be a B0.5 star. The class II 6.7 GHz CH3OH maser coincides with Peak 1, implying class II CH3OH maser is associated with a later evolutionary stage of star formation. Using KaVA and KVN observation, we detect the class I 44 and 95 GHz CH3OH masers near the weakest peak, Peak 5. We successfully imaged class I 95 GHz CH3OH masers with VLBI for the first time. In Peak 5, the high-velocity SiO emission also exists. The continuum emission can be modelled with grey-body dust emission with Td∼30 K, and the molecular species are poor near Peak 5, suggesting Peak 5 is in an early stage of star formation.

While we have growing numbers of massive star observations, it remains unclear how efficient the key physical processes such as mass loss, convection and rotation are, or indeed how they impact each other. We reconcile this with detailed stellar evolution models, yet these models have their own drawbacks with necessary assumptions for 3-dimensional processes like rotation which need to be adapted into 1-dimensional models. The implementation of empirical mass-loss prescriptions in stellar evolution codes can lead to the extrapolation of base rates to unconstrained evolutionary stages leading to a range of uncertain fates. In short, there remain many free parameters and physical processes which need to be calibrated in order to align our theory better with upcoming observations. We have tested various processes such as mass loss and internal mixing, including rotational mixing and convective overshooting, against multiple observational constraints such as using eclipsing binaries, the Humphreys-Davidson limit, and the final masses of Wolf-Rayet stars, across a range of metallicities. In fact, we developed a method of disentangling the effects of mixing and mass loss in the ‘Mass-Luminosity Plane’ allowing direct calibration of these processes. In all cases, it is important to note that a combined appreciation for both stellar winds and internal mixing are important to reproduce observations.

Recent ALMA observations detected protostellar outflows in 70-μm dark infrared dark clouds (IRDCs). These sources are candidates for the initial stages of high-mass star formation. We launched a new survey for free-free emission from outflow shocks using the Yamaguchi Interferometer (YI) at 8 GHz. We aim to catalog “proto-high-mass protostar” candidates that are still in the low to intermediate-mass phase. We selected starless-like clumps without any 70-μm point source from Traficante et al. (2015). We currently detected 82 sources from 167 clumps. 37 of them are fainter than 20 mJy (down to a few mJy). They tend to associate with colder and denser clumps that are suitable for star formation. This fact suggests that, at least, some of them trace star-formation activities. The highest-density clumps are, in fact, associated with several masers and molecular outflows. Furthermore, some of them have already shown a signature of ongoing cluster formation.

When a star is rapidly rotating, it deviates from spherical symmetry causing non-uniform distributions of the surface gravity and temperature across the surface. These three-dimensional effects lead to an inclination dependence of many observable spectroscopic parameters, however this is often neglected when analyzing rapidly rotating systems. Using spamms, we generate synthetic spectra that account for the 3D geometry of the system and fit them with 1D models to investigate how much the 3D effects can change the derived stellar parameters. We show that these 3D effects can lead to observed temperature differences of thousands of kelvin for the same star viewed at different inclinations, and a systematic underestimation of the helium abundance.

We report recent ESPaDOnS and HARPSpol spectropolarimetric observations from our ongoing magnetic survey of the brightest twenty-five classical Cepheids. Stokes V magnetic signatures are detected in eight of fifteen targets observed to date. The Stokes V profiles show a diversity of morphologies with weak associated longitudinal field measurements of order 1 G. Many of the Stokes V profiles are difficult to interpret in the context of the normal Zeeman effect. They consist of approximately unipolar single or double lobe(s) of positive or negative circular polarization. We hypothesize that these unusual signatures are due to the Zeeman effect modified by atmospheric velocity or magnetic field gradients. In contrast, the Stokes V profiles of Polaris and MY Pup appear qualitatively similar to the complex magnetic signatures of non-pulsating cool supergiants, possibly due to the low pulsation amplitudes of these two stars.

In this study, the correlation between 22 GHz water masers and other maser species with far infrared/submillimeter (FIR/sub-mm) sources is investigated. Comparing luminosity to mass ratio (L/M) of FIR/sub-mm clumps linked to different maser species, 22 GHz water masers have significantly lower L/M values than 6.7 GHz methanol and 1665 MHz OH masers. This suggests 22 GHz water masers may precede them in the evolution timeline of SFRs. The close association between water masers and FIR/sub-mm sources provides insight into maser pumping conditions and evolutionary stages.

A key ingredient in the earliest evolutionary phase of high-mass (M>8 M⊙) star formation (HMSF) is the presence of a jet/outflow system. To study its role in HMSF, we have carried out high resolution (0.1″) VLA K-band (18-26.5 GHz) observations toward IRAS 19035+0641 A, identified as a high-mass protostellar jet candidate based on previous cm continuum data. Our observations resolve the continuum emission into an elongated structure in the NE-SW direction, confirming that the K-band continuum arises from an ionized jet. Furthermore, we detected several 22.2 GHz H2O maser spots aligned in a direction consistent with the jet axis. Zeeman splitting was detected in the strongest maser spot. In this paper, we present our results and discuss the implications of our findings.

Rotation is one of the important parameters affecting the evolution and final fate of massive stars but the origin of fast rotators remains unclear (imprint of the star formation process, result of binary interactions). In this work, we aim at investigating the binary status, photometric variability, and runaway status of a statistically meaningful sample of Galactic fast-rotating O stars. We perform a comprehensive multi-epoch analysis of new high-quality spectroscopic observations gathered by the IACOB and OWN surveys. Notably, we find that the total percentage of spectroscopic binaries in the investigated sample range between 25 and 40%, in agreement with previous finding for the case of O-type stars with lower projected rotational velocities. On the contrary, the fraction of runaway stars among fast rotators (∼35–50%) is significantly higher than in the case of slow rotators (∼20–30%). By combining all these observational results we will evaluate each scenario about the origin of fast rotators.

This is a multi-wavelength study to examine the G45.804-0.355 massive star-forming region (SFR) and its environs. Using MeerKAT with angular resolution (θ) of 8″ at 1.28 GHz, we identify for the first time, a faint radio continuum emission core in G45.804-0.355. At 1.3 mm, ALMA observations (θ∼0″ 7) resolved the core into multiple dust continuum condensations including MM1 which was found to be the primary massive dust dense core in the region (mass Mc∼ 54.3M⊙). The dust continuum shows an arm-like extended emission within which other dense cores are situated. The velocity gradient of the MM1 core indicates that the source is associated with a rotation gas motion. The red- and blue-shifted lobes overlap at the position of MM1. The compact morphology of the 4.5 μm IR emission, the presence of spiral arms and overlapping of the red- and blue-shifted lobes suggest a face-on geometry of G45.80-40.355.

The current angular momentum (AM) transport models fail to reproduce asterosieimic observations. One of the best candidates to explain this discrepancy is the magnetic field in radiative zones with its various possible topologies, for instance axisymmetric toroidal magnetic field. If such azimuthal field is strong enough, the Tayler’s instability could occur which induces a magnetic torque that allows a very efficient transport of AM and could trigger dynamo action in radiative layers. If such important field does not emerge at the surface, spectropolarimetry is blind. In this case, the only way to detect and characterise the field is by using magneto-asteroseismology. It consists in searching for the characteristic signatures of magnetic field in the observed frequency spectra of stellar oscillations.

We used the unprecedented resolution of ∼25 μas of the VLBI array formed with the RadioAstron satellite to study the structures of H2O maser spots in the star forming region W49N. We found that anisotropic diffractive scattering of the ISM dominates the images of the maser spot, but does not completely blur them. The refractive scattering floor is about 0.001 in visibility at a baseline of 8 Gλ.

The young open cluster NGC 6231 hosts a rich population of O-type binary stars. We study several of these eccentric short-period massive eclipsing binaries and assess their fundamental parameters. The properties of these systems make them interesting targets to study tidally induced apsidal motion. The analysis of apsidal motion offers a powerful means to obtain information about the internal structure of the stars. Indeed, since the rate of apsidal motion in a binary system is proportional to the internal structure constants of the stars composing it, its value gives direct insight into the internal structure and evolutionary state of these stars. Stellar evolution models are constructed based on the observationally-determined fundamental parameters and a theoretical rate of apsidal motion is inferred. The results are striking: Adopting standard stellar evolution models yields a theoretical rate of apsidal motion much larger than the observational value. This discrepancy results from the standard models predicting too low an efficiency of internal mixing and thus too homogenous stars in terms of density. By enforcing the theoretical rates of apsidal motion to match the observational values, enhanced mixing is required, through a large overshooting parameter and/or additional turbulent/rotational mixing. Our analysis leads to the conclusion that the chemically mixed cores in those massive stars must be more extended than anticipated from standard models.

We study the apsidal motion in close eccentric massive binaries. Measuring the rate of apsidal motion in such a system gives insight into the internal structure and evolutionary state of the stars. We focus on CPD-41° 7742, for which independent studies in the past showed large discrepancies in the longitude of periastron of the orbit, hinting at the presence of apsidal motion. We perform a consistent analysis of all observational data to solve this apparent discrepancy and report the first determination of apsidal motion in this system. This study confirms the need for enhanced mixing in the stellar evolution models of the primary star to reproduce the observational properties. This points towards larger convective cores than usually considered.

In order to search for new 6.035 GHz excited OH masers 272 star-forming regions visible from the northern hemisphere with known active methanol masers were observed with the 32 m and 16 m radio telescopes of the Ventspils International Radio Astronomy Center (VIRAC). Three possibly new excited OH maser sources at 6.035 GHz were seen.

During the evolution of massive stars, their properties change significantly. But stellar parameters of massive stars have the biggest uncertainties in stellar astrophysics, specifically in the post-main sequence stages where blue supergiant stars are located. These stars experience mass loss events during their evolution which are supposed to be related to strange-modes instabilities. In this work, we explore the stability of oscillation modes in massive stars for different masses, and a range of mass-loss rates, with the aim to provide clues about the connection between strange modes instabilities and mass-loss events.

We are carrying out the intensity monitoring of the water maser emission associated with massive young stellar objects (YSOs) using the VLBI Exploration of Radio Astrometry (VERA) antennas. We are currently monitoring 108 sources. During our long monitoring period, we could find flares on several YSOs. As an example, we show the results from IRAS 16293–2422 and NGC2071 IRS1 here. We also show the results of monitoring of the water maser emission from G36.115+0.552, which the methanol maser flare was reported. We observed it as often as possible, usually once a day.

The galactic binary star LB-1 contains a recently stripped B-type star. Comparing its properties to detailed binary star models shows that tidal braking and magnetic torques lead to low surface rotational velocities in the stripped donors after Roche-lobe overffiow. Models without magnetic torques cannot reproduce the observed low surface rotation.

The FU Orionis (FUor) and EX Lupi (EXor) type objects are rare pre-main sequence low-mass stars undergoing accretion outbursts. Maser emission is widespread and is a powerful probe of mass accretion and ejection on small scales in star forming region. However, very little is known about the overall prevalence of water masers towards FUors/Exors. We present results from our survey using the Effelsberg 100-m telescope to observe the largest sample of FUors and EXors, plus additional Gaia alerted sources (with the potential nature of being eruptive stars), a total of 51 targets, observing the 22.2 GHz H2O maser, while simultaneously covering the NH3 23 GHz.

Since 2017, and the formation of the maser monitoring organisation (M2O), we have observed several intriguing events. These events have included possible accretion bursts, strong jets, periodicity after a flare, a heat-wave of radiation travelling outward at a fraction of the speed of light, to name a few. In September 2019 the M2O was notified of another source showing flaring behavior, and here we present the possibility of the first discovery of long-term maser periodicity from the high-mass star formation region (HMSFR) G024.33+0.14, with a period of about 3000 days.