Context: GR290 (M33 V0532=Romano's star) is a luminous M33 object undergoing photometric variability typical for luminous blue variable (LBV) stars. It lies inside Wolf-Rayet region in the Hertzsprung-Russell diagram and possesses a WN8 type spectrum at the light minima. Analysis of Gran Telescopio Canarias (GTC) spectra obtained in 2016 led to the conclusion that it is surrounded by an unresolved HII region formed mostly of ejected material from the central star, and disclosed the presence of a second, more extended asymmetrical emission region. Aims: The aim of this paper is to further explore the structure of the nearby environment of GR290. Methods: Long-slit spectra of GR290 were obtained with three slit orientations in the visual and red spectral regions. The emission-line distribution for each slit was analyzed. Results: We confirm the presence of an asymmetric HII region that extends ~50 pc to the south; ~30pc to the north and southeast; ~20 pc to the east and northwest and ~10pc to the west. We also present the first spectrum to be acquired of a star belonging to the neighboring OB88 association, J013501.87+304157.3, which we classify as a B-type supergiant with a possible binary companion.
The nebulae associated to four Luminous Blue Variables (LBVs) in the Large Magellanic Cloud (LMC) have been observed at 5.5 and 9 GHz using the Australia Telescope Compact Array, and radio emission has been detected for first time in these sources, R127, R143, S61 and S119. The radio maps of the nebulae have an angular resolution of \sim 1.5" and a sensitivity of 1.5-3.0\times10-2 mJy beam-1, and show a very similar morphology to that observed in Hα. This similarity permit us to assume that the Hα emission is not affected by strong intrinsic extinction due to dust within the nebulae. We estima…
We present new observations of the nebula around the Magellanic candidate Luminous Blue Variable S61. These comprise high-resolution data acquired with the Australia Telescope Compact Array (ATCA), the Atacama Large Millimetre/Submillimetre Array (ALMA), and VISIR at the Very Large Telescope (VLT). The nebula was detected only in the radio, up to 17 GHz. The 17 GHz ATCA map, with 0.8 arcsec resolution, allowed a morphological comparison with the H$α$ Hubble Space Telescope image. The radio nebula resembles a spherical shell, as in the optical. The spectral index map indicates that the radio em…
The luminous blue variable (LBV) RMC143 is located in the outskirts of the 30~Doradus complex, a region rich with interstellar material and hot luminous stars. We report the $3σ$ sub-millimetre detection of its circumstellar nebula with ALMA. The observed morphology in the sub-millimetre is different than previously observed with HST and ATCA in the optical and centimetre wavelength regimes. The spectral energy distribution (SED) of RMC143 suggests that two emission mechanisms contribute to the sub-mm emission: optically thin bremsstrahlung and dust. Both the extinction map and the SED are con…
We report the discovery of a new Galactic candidate Luminous Blue Variable (cLBV) via detection of an infrared circular nebula and follow-up spectroscopy of its central star. The nebula, MN112, is one of many dozens of circular nebulae detected at $24 μ$m in the {\it Spitzer Space Telescope} archival data, whose morphology is similar to that of nebulae associated with known (c)LBVs and related evolved massive stars. Specifically, the core-halo morphology of MN112 bears a striking resemblance to the circumstellar nebula associated with the Galactic cLBV GAL 079.29+00.46, which suggests that bot…
Luminous blue variable stars (LBVs) are of great interest in massive-star evolution as they experience very high mass-loss episodes within short periods of time. HR Car is a famous member of this class in the Galaxy. It has a large circumstellar nebula and has also been confirmed as being in a binary system. One means of gaining information about the evolutionary status and physical nature of LBVs is studying their environments. We investigated the stellar content within ~100 pc of HR Car and also its circumstellar nebula. Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (MUSE) obs…
(Shortened) Luminous blue variable stars (LBVs) form dust as a result of episodic, violent mass loss. To investigate their contribution as dust producers in the Magellanic Clouds, we analyse 31 LBVs from a recent census. We built a maximally complete multi-wavelength dataset of these sources from archival data from near-IR to millimetre wavelengths. We review the LBV classification on the basis of the IR SED. To derive characteristic dust parameters, we fitted the photometry resulting from a stacking analysis. For comparison we also stacked the images of low- and intermediate-mass evolved star…
Far-infrared Herschel PACS imaging and spectroscopic observations of the nebula around the luminous blue variable (LBV) star AG Car have been obtained along with optical imaging in the Halpha+[NII] filter. In the infrared light, the nebula appears as a clumpy ring shell that extends up to 1.2 pc with an inner radius of 0.4 pc. It coincides with the Halpha nebula, but extends further out. Dust modeling of the nebula was performed and indicates the presence of large grains. The dust mass is estimated to be ~ 0.2 Msun. The infrared spectrum of the nebula consists of forbidden emission lines over …
We study the kinematics of luminous blue variables (LBVs) in the Large Magellanic Cloud (LMC). Using high-resolution spectra, we measure the systemic radial velocities for a sample of 16 LBVs and LBV candidates. In order to measure the net motion of LBVs compared to their local environments, we subtract the projected line-of-sight velocity at the same location derived from the rotation curve model of the LMC. Using nebular and wind emission lines, we infer a velocity dispersion for LBVs of $40.0^{+9.9}_{-6.6}$ km s$^{-1}$. To put LBVs in context with other evolved massive stars, we compare thi…
(shortened) We investigate the properties of Galactic WR stars and their environment to identify evolutionary channels that may lead to the formation of LGRBs. To this purpose we compile available information on the spectropolarimetric properties, the presence of CS ejecta, and the CS velocities in the environment of Galactic WR stars. We use linear line-depolarization as an indicator of rotation, nebular morphology as an indicator of stellar ejecta, and velocity patterns in UV absorption features as an indicator of increased velocities in the CS environment. We find that the ~23% WR stars wit…
Context: GR290 (M33/V532=Romano's Star) is a suspected post-LBV star located in M33 galaxy that shows a rare Wolf-Rayet spectrum during its minimum light phase. In spite of many studies, its atmospheric structure, its circumstellar environment and its place in the general context of massive stars evolution is poorly known. Aims: Detailed study of its wind and mass loss, and study of the circumstellar environment associated to the star. Methods: Long-slit spectra of GR290 were obtained during its present minimum luminosity phase with the GTC together with contemporaneous BVRI photometry. The da…
Aims. We obtained Herschel/PACS imaging and spectroscopic observations of the nebula surrounding the candidate LBV HD168625. By combining these data with optical spectra of the star, we want to constrain the abundances in the nebula and in the star and compare them to trace back its evolution. Methods. We use CMFGEN to determine the fundamental parameters and the CNO abundances of the central star whilst the abundances of the nebula are derived from the emission lines present in the Herschel/PACS spectrum. Result. The FIR images show a nebula composed of an elliptical ring/torus of ejecta with…
We have found three new LBV candidates in the star-forming galaxy NGC 4736. They show typical well-known LBV spectra, broad and strong hydrogen lines, He I lines, many Fe II lines, and forbidden [Fe II] and [Fe III]. Using archival Hubble Space Telescope and ground-based telescope data, we have estimated the bolometric magnitudes of these objects from -8.4 to -11.5, temperatures, and reddening. Source NGC 4736_1 (Mv = -10.2 +/- 0.1 mag) demonstrated variability between 2005 and 2018 as Delta V = 1.1 mag and Delta B = 0.82 mag, the object belongs to LBV stars. NGC 4736_2 (Mv < -8.6 mag) shows P…
We identify IRAS 16115-5044, which was previously classified as a protoplanetary nebula (PPN), as a candidate luminous blue variable (LBV). The star has high luminosity (>10$^{5.75}$ L_Sun), ensuring supergiant status, has a temperature similar to LBVs, is photometrically and spectroscopically variable, and is surrounded by warm dust. Its near-infrared spectrum shows the presence of several lines of HI, He I, Fe II, Fe [II], MgII, and Na I with shapes ranging from pure absorption and P Cygni profiles to full emission. These characteristics are often observed together in the relatively rare LBV…
We have undertaken a near-infrared spectral survey of stars associated with compact mid-IR shells recently revealed by the MIPSGAL (24 micron) and GLIMPSE (8 micron) Spitzer surveys, whose morphologies are typical of circumstellar shells produced by massive evolved stars. Through spectral similarity with known Luminous Blue Variable (LBV) and Wolf-Rayet (WR) stars, a large population of candidate LBVs (cLBVs) and a smaller number of new WR stars are being discovered. This significantly increases the Galactic cLBV population and confirms that nebulae are inherent to most (if not all) objects of…
We have obtained far-infrared Herschel PACS imaging and spectroscopic observations of the nebular environment of the luminous blue variable WRAY 15-751. These images clearly show that the main, dusty nebula is a shell of radius 0.5 pc and width 0.35 pc extending outside the H-alpha nebula. They also reveal a second, bigger and fainter dust nebula, observed for the first time. Both nebulae lie in an empty cavity, likely the remnant of the O-star wind bubble formed when the star was on the main sequence. The kinematic ages of the nebulae are about 20000 and 80000 years and each nebula contains a…
Extremely broad emission wings at H$β$ and H$α$ have been found in VFTS data for five very luminous BA supergiants in or near 30 Doradus in the Large Magellanic Cloud. The profiles of both lines are extremely asymmetrical, which we have found to be caused by very broad diffuse interstellar bands (DIBs) in the longward wing of H$β$ and the shortward wing of H$α$. These DIBs are well known to interstellar but not to many stellar specialists, so that the asymmetries may be mistaken for intrinsic features. The broad emission wings are generally ascribed to electron scattering, although we note dif…
The strong mass loss of Luminous Blue Variables (LBVs) is thought to play a critical role in massive-star evolution, but their place in the evolutionary sequence remains debated. A key to understanding their peculiar instability is their high observed luminosities, which often depends on uncertain distances. Here we report direct distances and space motions of four canonical Milky Way LBVs---AG~Car, HR~Car, HD~168607, and (candidate) Hen~3-519---from the Gaia first data release. Whereas the distances of HR~Car and HD~168607 are consistent with previous literature estimates within the considera…
MWC 930 is a star just ~2° above the Galactic plane whose nature is not clear and that has not been studied in detail so far. While a post-Asymptotic Giant Branch (AGB) classification was proposed in the past, studies of its optical spectrum and photometry pointed toward strong variability, therefore the object was reclassified as a Luminous Blue Variable (LBV) candidate. LBVs typically undergo phases of strong mass loss in the form of eruptions that can create shells of ejecta around the star. Our goal is to search for the presence of such a circumstellar nebula in MWC 930 and investigate its…
In this paper, we report the results of spectroscopic and photometric observations of the candidate evolved massive star MN48 disclosed via detection of a mid-infrared circular shell around it with the Spitzer Space Telescope. Follow-up optical spectroscopy of MN48 with the Southern African Large Telescope (SALT) carried out in 2011--2015 revealed significant changes in the spectrum of this star, which are typical of luminous blue variables (LBVs). The LBV status of MN48 was further supported by photometric monitoring which shows that in 2009--2011 this star has brightened by approx 0.9 and 1 …
We combine archival spectral observations of the LBV star V532 (Romano's star) together with the existing photometric data in the B band. Spectroscopic data cover 15 years of observations (from 1992 to 2007). We show that the object in maximum of brightness behaves as an emission line supergiant while in minimum V532 moves along the sequence of late WN stars. In this sense, the object behaves similarly to the well-known Luminous Blue Variable (LBV) stars AG Car and R127, but is somewhat hotter in the minima. We identify about 100 spectral lines in the 3700..7300 Angstrom wavelength range. For …
Context. Luminous blue variables (LBVs) are rare massive stars with very high luminosity. They are characterized by strong photo-metric and spectroscopic variability related to transient eruptions. The mechanisms at the origin of these eruptions is not well known. In addition, their formation is still problematic and the presence of a companion could help to explain how they form. Aims. This article presents a study of seven LBVs (about 20% of the known Galactic population), some Wolf-Rayet stars, and massive binaries. We probe the environments that surround these massive stars with near-, mid…
$η$~Car is one of the most massive stars in the Galaxy. It underwent a massive eruption in the 19th century, which produced the impressive bipolar Homunculus nebula now surrounding it. The central star is an eccentric binary with a period of 5.54\,years. Although the companion has not been detected directly, it causes time-variable ionization and colliding-wind X-ray emission. By characterizing the complex structure and kinematics of the ejecta close to the star, we aim to constrain past and present mass loss of $η$~Car. $η$~Car is observed with the extreme adaptive optics instrument SPHERE at…
Binary mass transfer via Roche-lobe overflow (RLOF) is a key channel for producing stripped-envelope Wolf-Rayet (WR) stars and may be critical to account for SN Ib/c progenitors. RY Scuti is an extremely rare example of a massive binary star caught in this brief but important phase. Its toroidal nebula indicates equatorial mass loss during RLOF, while the mass-gaining star is apparently embedded in an opaque accretion disk. RY Scuti's toroidal nebula has two components: an inner ionised double-ring system, and an outer dust torus that is twice the size of the ionised rings. We present two epoc…
We present a spectroscopic analysis of MWC 314, a luminous blue variable (LBV) candidate with an extended bipolar nebula. The detailed spectroscopic variability is investigated to determine if MWC 314 is a massive binary system with a supersonically accelerating wind or a low-mass B[e] star. We compare the spectrum and spectral energy distribution to other LBVs (such as P Cyg) and find very similar physical wind properties, indicating strong kinship. We combined long-term high-resolution optical spectroscopic monitoring and V-band photometric observations to determine the orbital elements and …
We study and analyse low-resolution spectra of the unordinary late WN star FSZ35 in M33. We classify the object as a hydrogen-rich WN8 star. Using the radiative transfer code CMFGEN, we determine the physical parameters of this object and compare them to the parameters of other WN8 stars including the LBV star Romano's star during the minimum of brightness. Unlike Romano's star, the object is fairly stable both spectrally and photometrically, that may be attributed to its more advanced evolutionary stage or lower luminosity. FSZ35 is shown to possess a compact nebula producing faint but detect…
We present medium-resolution spectroscopy and multicolor photometry for the optical transient PSN J09093496+3307204 (SN 2015bh) in the galaxy NGC 2770, which has transferred into the supernova phase. The observations were carried out between February 2015 to May 2016. Both at the phase of the SN impostor (2015a) and at the supernova phase (2015b), besides Balmer emissions, the strong Fe II emissions are seen in the spectrum; so, these spectra resemble those of Williams Fe II type classical novae. The star is located near the edge of a dark nebula and notably absorbed (Av = 1.14 +/-0.15 mag). T…
We present SOFIA/FORCAST imaging of the circumstellar dust shells surrounding the luminous blue variable (LBV) candidates MN 90 and HD 168625 to quantify the mineral abundances of the dust and to constrain the evolutionary state of these objects. Our image at 37.1 micron of MN 90 shows a limb-brightened, spherical dust shell. A least-squares fit to the spectral energy distribution of MN 90 yields a dust temperature of 59 \pm 10 K, with the peak of the emission at 42.7 micron. Using 2-Dust radiative transfer code, we estimate for MN 90 that mass-loss occurred at a rate of (7.3 \pm 0.4)x10^-7 M_…
