A massive nebula around the luminous blue variable star RMC 143 revealed by ALMA

view Abstract Citations (37) References (27) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Luminous variable stars in M31 and M33. Humphreys, R. M. Abstract Spectra and UBVRI photometry of four luminous blue variables in M31 and four luminous blue variables in M33 are presented along with a spectrum of a red supergiant variable in M31 and a 2-micron measurement of one of the blue variables in M31. The spectra were obtained over the wavelength range from about 3000 to 5500 A at a dispersion of 79 A/mm with a resolution of approximately 4 A. The spectra of two blue variables in M31 and one in M33 are found to be characterized by Fe II and forbidden Fe II emission lines, hydrogen and helium emission, a very strong UV continuum, and no evident Balmer discontinuity. Changes in the spectra of two other blue variables in M33 are briefly described, and the spectra of all eight blue variables are shown to be very similar. It is concluded that the eight blue variables in M31 and M33, together with Eta Car in the Milky Way, S Dor in the Large Magellanic Cloud, and related objects in the latter two galaxies, form a recognizable group of very luminous hot stars with very low surface gravities. Publication: The Astrophysical Journal Pub Date: January 1978 DOI: 10.1086/155797 Bibcode: 1978ApJ...219..445H Keywords: Andromeda Galaxy; Stellar Luminosity; Stellar Spectrophotometry; Supergiant Stars; Ubv Spectra; Variable Stars; Absorption Spectra; Emission Spectra; Hot Stars; Infrared Spectra; Stellar Magnitude; Astrophysics; Andromeda Nebula:Blue Variables; Blue Variables:Galaxies; Galaxies:Supergiants full text sources ADS | data products SIMBAD (20) NED (3) GCPD (1)

The winds of hot stars are generally understood to be driven by the absorption of momentum from the intense stellar radiation field by line transitions in the ultraviolet and farultraviolet regions of the spectrum. Observational diagnostics of these dense winds can be reproduced quite well for most early-type stars within the context of a “standard model,” in which the outflow is spherically symmetric, smooth, and steady. This model serves as a useful starting point for estimating global properties such as mass-loss rates and for investigating the various ways that winds interact with their local interstellar environments. However, there is abundant evidence that essentially all hot-star winds contain time-dependent structure on a variety of spatial scales. Observations of anisotropy, clumpiness, and variability contradict the assumptions of the standard model and imply that our understanding of mass loss via stellar winds is still incomplete. IAU Colloquium 169 was convened to review the observational evidence for variability and asphericity in hotstar winds; to discuss the physical processes that might cause such behavior; and to look for evolutionary consequences. The meeting was hosted by the Landessternwarte HeidelbergKonigstuhl, a venue that was fitting not only because 1998 marked the centennial of its founding, but also because of its enviable history as a center for hot-star research. The meeting attracted nearly 150 researchers from 26 countries. Over the course of four and one-half days, 62 oral review and contributed papers and approximately 70 poster papers were presented. The topics of these papers included both garden-variety OBA stars and their more exotic cousins: Be stars, Wolf-Rayet stars, and the rare B[e] stars and luminous blue variables (LBVs). The role played by rotation in shaping the emergence of the stellar wind was a recurrent theme in these presentations and also provides a framework for this brief report on the meeting. The proceedings contain comprehensive discussions of these and other highlights, which included reports of impressive progress in modeling disk winds; analysis and simulations of the nebulae ejected by hot stars in episodic mass-loss events; and distance determination from quantitative spectral analysis of the photospheres and winds of hot stars. Rotation is the most obvious, universal process that can induce large-scale asphericity in the stellar winds of single stars, and it is therefore not surprising that it was a focus for this

MCA-1B (also called UIT003) is a luminous hot star in the western outskirts of M33, classified over 20 yr ago with a spectral type of Ofpe/WN9 and identified then as a candidate luminous blue variable (LBV). Palomar Transient Factory data reveal that this star brightened in 2010, with a light curve resembling that of the classic LBV star AF And in M31. Other Ofpe/WN9 stars have erupted as LBVs, but MCA-1B was unusual because it remained hot. It showed a WN-type spectrum throughout its eruption, whereas LBVs usually get much cooler. MCA-1B showed an almost four-fold increase in bolometric luminosity and a doubling of its radius, but its temperature stayed ≳29 kK. As it faded, it shifted to even hotter temperatures, exhibiting a WN7/WN8-type spectrum, and doubling its wind speed. MCA-1B is reminiscent of some supernova impostors, and its location resembles the isolated environment of SN 2009ip. It is most similar to HD 5980 (in the Small Magellanic Cloud) and GR 290 (also in M33). Whereas these two LBVs exhibited B-type spectra in eruption, MCA-1B is the first clear case where a Wolf–Rayet (WR) spectrum persisted at all times. Together, MCA-1B, HD 5980, and GR 290 constitute a class of WN-type LBVs, distinct from S Doradus LBVs. They are most interesting in the context of LBVs at low metallicity, a possible post-LBV/WR transition in binaries, and as likely Type Ibn supernova progenitors.

The appearance of Fe II in the spectra of hot luminous stars of the Magellanic Clouds (Luminous Blue Variables and B [e] -Supergiants) is discussed.KeywordsStellar WindCircumstellar DiskBright PhaseBolometric LuminosityLuminous StarThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

We have carried out a high-dispersion (R ∼ 30,000) echelle spectroscopic survey of 16 Type II supernovae (SNe) to search for narrow emission lines from circumstellar nebulae ejected by their massive progenitors. Circumstellar nebulae, if detected, provide invaluable opportunities to probe SN progenitors. Of the 16 SNe observed, SN ejecta are clearly detected in four SNe and possibly in another two SNe, interstellar gas is detected in 12 SNe, and circumstellar material is detected only in SN 1978K and SN 1998S. In the case of SN 1978K, we are able to place an upper limit of ∼2.2 pc for the size of the circumstellar ejecta nebula and note that this is more consistent with the typical sizes observed for ejecta nebulae around luminous blue variables, rather than Wolf-Rayet stars. In the case of SN 1998S, our observations of the narrow lines ∼1 yr after the SN explosion show variations compared to early epochs. The nebular lines we observe from SN 1998S either originate from the low-density outer region of a circumstellar nebula or have become dominated by an interstellar component.

Context. Previous studies have concluded that low- and intermediate-mass stars cannot account for the interstellar dust yield in the Magellanic Clouds inferred from far-infrared and sub-millimetre observations. Aims. 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 confirmed and candidate LBVs from a recent census. Methods. We built a maximally complete multi-wavelength dataset of these sources from archival space telescope images and catalogues from near-infrared to millimetre wavelengths. We also present new Very Large Telescope VISIR observations of three sources in the Large Magellanic Cloud (LMC). We review the LBV classification on the basis of the infrared spectral energy distribution. To derive characteristic dust parameters, we fitted the photometry resulting from a stacking analysis, which consists of co-adding images of the same wavelength band of several targets to improve the signal-to-noise. For comparison we also stacked the images of low- and intermediate-mass evolved stars in the LMC. Results. We find four classes of sources: (1) LBVs showing mid-infrared dust emission plus near-infrared free-free emission from an ionised stellar wind (Class 1a) or only mid-infrared dust emission (Class 1b); (2) LBVs with a near-infrared excess due to free-free emission only (Class 2); (3) objects with an sgB[e] classification in the literature, displaying a distinctive hot dust component; and (4) objects with no detected stellar winds and no circumstellar matter in their SEDs. From the stacking analysis of the 18 Class 1 and 2 objects in the LMC, we derived an integrated dust mass of 0.11−0.03+0.06 M⊙. This is two orders of magnitude larger than the value inferred from stacking 1342 extreme-asymptotic giant branch stars. The dust mass of individual LBVs does not correlate with the stellar parameters, possibly suggesting that the dust production mechanism is independent of the initial stellar mass or that the stars have different evolutionary histories. The total dust yield from LBVs over the age of the LMC is ∼104 − 105 M⊙. The one order of magnitude uncertainty is mainly due to uncertainties of the LBV population, star formation history, and initial mass function. Conclusions. LBVs are potentially the second most important source of dust in normal galaxies. The role of dust destruction in LBV nebulae by a possible subsequent supernova (SN) blast wave has yet to be determined. Recent theoretical developments in the field of dust processing by SN shocks highlight the potential survival of dust grains from the pre-existing circumstellar nebula.

An ongoing SAO RAS program for the 6-m telescope to search for and study luminous blue variable (LBV) candidates in the M31 and M33 galaxies was started in 1997. This paper summarizes the results of our observations over the last 20 years. Over this time, we have a general lists of candidates and obtained photometry and spectroscopy for approximately one hundred stars from the list. A detailed study and classification of LBV candidates were carried out.We alsomonitored spectrally and photometrically the confirmed LBV stars in these galaxies. Based on these results, the spectral energy distributions (SEDs) of LBVs and LBV candidates were computed, and the interstellar extinction values, temperature, and luminosity were derived. We propose a new method of confirming the nature of LBV stars. It is based on a special property exhibited only by LBV stars—the constancy of the bolometric luminosity, with except of a rare phase of giant eruption, registered for two historical LBVs in our galaxy and about few dozen extragalactic LBVs. Using this method, we determine the fundamental parameters of these stars: temperature, radius, luminosity, and interstellar extinction. We discuss the nature of several individual LBV stars discovered by us in M33 and the classification of the LBV candidates in M31. Thus, for 20 years of observations we have found four LBV stars in M33; in the M31 galaxy with different methods, we have confirmed seven objects as a LBV class.

Massive evolved stars lose a large fraction of their mass via copious stellar wind or instant outbursts. During certain evolutionary phases, they can be identified by the presence of their circumstellar nebulae. In this paper, we present the results of a search for compact nebulae (reminiscent of circumstellar nebulae around evolved massive stars) using archival 24-μm data obtained with the Multiband Imaging Photometer for Spitzer. We have discovered 115 nebulae, most of which bear a striking resemblance to the circumstellar nebulae associated with luminous blue variables (LBVs) and late WN-type (WNL) Wolf–Rayet (WR) stars in the Milky Way and the Large Magellanic Cloud (LMC). We interpret this similarity as an indication that the central stars of detected nebulae are either LBVs or related evolved massive stars. Our interpretation is supported by follow-up spectroscopy of two dozen of these central stars, most of which turn out to be either candidate LBVs (cLBVs), blue supergiants or WNL stars. We expect that the forthcoming spectroscopy of the remaining objects from our list, accompanied by the spectrophotometric monitoring of the already discovered cLBVs, will further increase the known population of Galactic LBVs. This, in turn, will have profound consequences for better understanding the LBV phenomenon and its role in the transition between hydrogen-burning O stars and helium-burning WR stars. We also report on the detection of an arc-like structure attached to the cLBV HD 326823 and an arc associated with the LBV R99 (HD 269445) in the LMC.

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 Multi Unit Spectroscopic Explorer (MUSE) observations of a 2′×2′ region around the star highlight the incompleteness of stellar classification for stars with magnitudes of V > 13 mag. Eight B0 to B9 stars have been identified which may lie in close spatial vicinity to HR Car. For a region with a radius of r = 1.2° (∼100 pc at a distance of 4.8 kpc) around HR Car, existing catalogs list several late O-type and early B-type stars, but only one early O-type star. Given the relatively low stellar and nebular masses in the HR Car system, no early O-type stars and only a few late O-type stars would be expected in association with HR Car. Instead, HR Car’s location in a point vector diagram suggests that HR Car is not isolated, but is part of a moving group with a population of B-type stars in a spiral arm, and it has not received a strong kick from a supernova explosion of a companion star or a merger event. Potential binary evolution pathways for the HR Car system cannot be fully explored because of the unknown nature of the companion star. Furthermore, the MUSE observations reveal the presence of a fast outflow and “bullets” that have been ejected at intervals of about 400 years. These features may have been caused by recurrent mass transfer in the system.

In a recent paper, Smith & Tombleson state that the luminous blue variables (LBVs) in the Milky Way and the Magellanic Clouds are isolated; they are not spatially associated with young O-type stars. They propose a novel explanation that would overturn the standard view of LBVs. In this paper we test their hypothesis for the LBVs in M31 and M33, as well as the LMC and SMC. We show that in M31 and M33 the LBVs are associated with luminous young stars and supergiants that are appropriate to their luminosities and positions on the H-R diagram. Moreover, in the Smith and Tombleson scenario most of the LBVs should be runaway stars, but the stars’ velocities are consistent with their positions in the respective galaxies. In the Magellanic Clouds, those authors’ sample was a mixed population. We reassess their analysis, removing seven stars that have no clear relation to LBVs. When we separate the more massive classical and the less luminous LBVs, the classical LBVs have a distribution similar to the late O-type stars, while the less luminous LBVs have a distribution like the red supergiants. None of the confirmed LBVs have high velocities or are candidate runaway stars. These results support the accepted description of LBVs as evolved massive stars that have shed a lot of mass and are now close to their Eddington limit.

Only ten years ago a symposium on the special class of stars we now call Luminous Blue Variables (LBV’s) would not have been possible. At that time we were only just beginning to recognize the similarities among the stars we call S Doradus variables, P Cygni stars, and Hubble-Sandage variables, and their importance in the evolution of the most massive stars. About a decade ago it became clear that the observed H-R diagram has an upper luminosity limit and that η Car, P Cyg, and S Dor are all near the temperature-dependent boundary for hot stars. With hindsight the luminosity boundary can be seen in an H-R diagram for hot stars published by Hutchings (1976), but the full temperature range is necessary to show that it really exists. When more data became available in 1977—1978, including the evolved and cool supergiants, the upper luminosity limit became obvious; and we proposed that an instability causing rapid and unsteady mass loss (i.e., LBV’s) is the basic reason for this boundary (Humphreys and Davidson 1979). We emphasized the temperature-dependence of the boundary for the most luminous hot stars, the lack of cooler counterparts at similar luminosities, the nearly temperature-independent limit to the luminosities of cool hypergiants, and the critical role that objects like η Car, P Cyg, and S Dor may play in the evolution of the most massive stars.

Luminous blue variables (LBVs) represent a brief transitional phase in the evolution of massive stars. Multi-wavelength studies of their circumstellar environments are essential to quantify their feedback at Galactic scales. Dominant emission mechanisms at millimetre wavelengths are, however, still poorly understood. Stellar winds, circumstellar dust, and ionised gas have not been explored together in the case of LBVs. We aim to study the millimetre continuum emission of Galactic LBVs to disclose the presence of these components, to describe their morphology, and to measure their relevance in the mass and energy injection to the interstellar medium. We used the NIKA2 continuum camera at the IRAM 30 m radio telescope to observe and analyse 1.15 and 2 mm continuum from the LBVs HD168607 HD168625 GKF2010 MN87 GKF2010 MN101 and G79.29+0.46 . We used the Virtual Observatory to complement our observations with archival data from optical, infrared, millimetre, and centimetre wavelengths. With this information, we built complete spectral energy distributions (SEDs) for the five sources that cover six decades of the electromagnetic spectrum. All targets except MN87 were detected at both wavelengths, with features including compact sources, extended nebular emission, shells, and unrelated background structures. The spectral indices of compact sources are consistent with thermal emission from stellar winds. We modelled the SEDs and successfully reproduced the emission from stellar photospheres, circumstellar dust, thermal stellar winds, and enshrouding Hii regions. Our models, in agreement with previous literature results, reveal unresolved hot dust very close to the stars and provide the first estimates for the fundamental parameters of MN101. This pilot study highlights the great potential of millimetre continuum studies of LBVs and possibly other evolved massive stars. The millimetre spectral window bridges the far-IR and radio regimes and can disclose the relative contribution of dust and free-free emission in this type of source.

We study Luminous Blue Variable (LBV) candidate J004341.84+411112.0 in the Andromeda galaxy. We present optical spectra of the object obtained with the 6 m telescope of BTA SAO RAS. The candidate shows typical LBV features in its spectra: broad and strong hydrogen lines and the He i lines with P Cygni profiles. Its remarkable spectral resemblance to the well known LBV P Cygni suggests a common nature of the objects and supports LBV classification of J004341.84+411112.0. We estimate the temperature, reddening, radius and luminosity of the star using its spectral energy distribution. Obtained bolometric luminosity of the candidate (M bol = −10.41 ± 0.12 mag) is quite similar to those of known LBV stars in the Andromeda galaxy. We analyzed a ten year light curve of the object in R filter. The candidate demonstrates photometric variations of the order of 0.4 mag, with an overall brightness increasing trend ΔR > 0.1 mag. Therewith, the corresponding color variations of the object are fully consistent with LBV behavior when a star become cooler and brighter in the optical spectral range with a nearly constant bolometric luminosity. LBV-type variability of the object, similarity of its spectrum and estimated luminosity to those of known LBVs allow us to classify J004341.84+411112.0 as an LBV.

view Abstract Citations (159) References (116) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Infrared Spectra of Massive Stars in Transition: WNL, Of, Of/WN, Be, B[e], and Luminous Blue Variable Stars Morris, Patrick W. ; Eenens, P. R. J. ; Hanson, Margaret M. ; Conti, Peter S. ; Blum, R. D. Abstract We present an overview of the spectroscopic properties of several luminous stars belonging to Of supergiant, Ofpe/WN9, late-type nitrogen sequence Wolf-Rayet (WNL), B[e], Be supergiant, and luminous blue variable (LBV) classes at 2 μm and 1.6 μm, using recently published and new spectra of moderate to high resolution (500-1600). These objects are "transitional" in their optical classification and may be related in their evolution. The 2 μm spectrum of the LBV AG Car has changed from its 1984-1985 appearance as an Of/WN star, now appearing as a Be or B[e] star by comparison to new spectra of HD 72754 (B2Iape) and GG Car (B[e], whose spectrum has varied since 1984-1985). Further support for a link between B[e] stars and LBVs is seen in the case of the SMC B[e] star S18, which has changed its 1987-1989 spectrum from one of Brγ emission only to one in which emission lines of Fe II, Mg II, Na I, 12CO overtone, He I 2.112-3 μm, and He I 2.058 μm (strong) are present. As the earlier observations were not of a high signal-to-noise ratio, we confirm only the He I and 12CO as new emission, where the latter was previously expected on the basis of TiO emission but was undetected. The overall morphology of the atomic spectrum of S18, including the He I 2.112-3 μm emission, are shared by only one other B star, namely, the quiescent LBV P Cyg (B1 Ia+), but is shared also by the LBV and Ofpe/WN9 star HDE 269582. Only AG Car is observed to have also varied in the 2.112-3 μm line. We thus consider S18 a strong candidate LBV. Our new high-resolution 2 μm spectra also include HD 5980, a WN binary recently observed to undergo an LBV-like outburst in short-term brightness and spectroscopic variations. We provide a detailed K-band line identification of the probable LBV He 3-591 (WRA 751), which is rich in lines of permitted and forbidden iron (mainly Fe II) and includes new identification of [Ni II] at 2.308 μm and 2.369 μm. A significant degree of overlap in spectral morphology exists between the groups, where at least one example from each group may be classified as a member of another from its 2 μm spectrum. This has serious consequences for observations of hot, luminous objects in visually obscured regions. The overlapping infrared spectral morphology reinforces the notion that the objects in this study are interrelated in their evolution. We propose that "transitional" massive stars with hydrogen present at their surfaces (including the least extreme WN types) may not yet be in the stage of core-helium burning but rather are in a previous phase in which the stellar atmosphere/wind is sometimes dynamically unstable. Publication: The Astrophysical Journal Pub Date: October 1996 DOI: 10.1086/177892 Bibcode: 1996ApJ...470..597M Keywords: INFRARED: STARS; STARS: EARLY-TYPE; STARS: EMISSION-LINE; BE; STARS: WOLF-RAYET; STARS: SUPERGIANTS full text sources ADS | data products SIMBAD (43)

NIR properties of Be stars in star clusters in the Magellanic Clouds