A slowly expanding torus associated with the candidate LBV MGE 042.0787+00.5084

Bordiu, Cristobal; Rizzo, J. R.; Ritacco, A.

doi:10.1093/mnras/sty2726

Cited by 4 publications

(4 citation statements)

References 32 publications

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“…Recently, ALMA observations with a resolution of about 1 arcsec (Smith et al 2018) revealed an expanding torus of CO in the waist of the Homunculus. A similar structure has been already discovered around the LBV object MN101 (MGE042.0787+00.5084), possibly in a more advanced stage (Bordiu et al 2019).…”

Section: Introductionsupporting

confidence: 76%

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The peculiar chemistry of the inner ejecta of Eta Carina

Bordiu

Rizzo

2019

Monthly Notices of the Royal Astronomical Society

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We investigated continuum and molecular line emission of four species (CO, HCN, H 13 CN, and HCO + ) at 0.8 mm in the inner region around η Car, using ALMA archival observations at a resolution better than 0.2 arcsec. We report the discovery of an asymmetric extended structure northwest of the star, independent from the continuum point source. The structure is only traced by continuum and HCO + , and not detected in the other lines. Kinematics of this structure reveal that the HCO + gas likely arises from ejecta expelled in the 1890s eruption. The ejecta is propagating outward within the cavity produced by the current wind-wind interaction of η Car A and its companion. Chemical analysis of the ejecta reveals an apparent lack of CO and nitrogen-bearing species. We explore possible explanations for this peculiar chemistry, that differentiates this structure from the ejecta of the Great Eruption, rich in HCN and H 13 CN. We also report an absorption component near the continuum point source, only traced by HCN and H 13 CN in their vibrational-ground and vibrationally-excited states. This absorbing gas is attributed to a hot bullet of N-enriched material expelled at a projected velocity of 40 km s −1 .

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Section: Introductionsupporting

confidence: 76%

“…It indicates an extremely low [ 12 C]/[ 13 C] isotopic ratio, even for a massive star (typically in the range 3 − 10, e.g. Lambert et al 1984, Bordiu et al 2019.…”

Section: Abundances In the Torusmentioning

confidence: 99%

The peculiar chemistry of the inner ejecta of Eta Carina

Bordiu

Rizzo

2019

Monthly Notices of the Royal Astronomical Society

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“…The best studied object is probably G79.29+0.46, where we discovered a number of concentric, shocked shells associated with mass-loss events developed in the last 10 3 − 10 4 yr [7][8][9][10]. In MGE042.0787+00.5084 (hereafter MGE042), we also found a molecular torus in slow expansion, with similar dynamical ages [11]. Recently, η Carina was also the subject of molecular studies, where molecular material connected to the Homunculus and a more recent outburst were discovered [12][13][14][15][16].…”

supporting

confidence: 54%

“…It is noteworthy that the star is relatively more intense at 2mm, while the compact cloud looks the opposite. The compact cloud is spatially almost coincident to the densest part of the expanding CO torus [11].…”

Section: Resultsmentioning

confidence: 96%

NIKA2 observations around LBV stars Emission from stars and circumstellar material

2020

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Luminous Blue Variable (LBV) stars are evolved massive objects, previous to core-collapse supernova. LBVs are characterized by photometric and spectroscopic variability, produced by strong and dense winds, mass-loss events and very intense UV radiation. LBVs strongly disturb their surroundings by heating and shocking, and produce important amounts of dust. The study of the circumstellar material is therefore crucial to understand how these massive stars evolve, and also to characterize their effects onto the interstellar medium. The versatility of NIKA2 is a key in providing simultaneous observations of both the stellar continuum and the extended, circumstellar contribution. The NIKA2 frequencies (150 and 260 GHz) are in the range where thermal dust and free-free emission compete, and hence NIKA2 has the capacity to provide key information about the spatial distribution of circumstellar ionized gas, warm dust and nearby dark clouds; non-thermal emission is also possible even at these high frequencies. We show the results of the first NIKA2 survey towards five LBVs. We detected emission from four stars, three of them immersed in tenuous circumstellar material. The spectral indices show a complex distribution and allowed us to separate and characterize different components. We also found nearby dark clouds, with spectral indices typical of thermal emission from dust. Spectral indices of the detected stars are negative and hard to be explained only by free-free processes. In one of the sources, G79.29+0.46, we also found a strong correlation of the 1mm and 2mm continuum emission with respect to nested molecular shells at ≈1 pc from the LBV. The spectral index in this region clearly separates four components: the LBV star, a bubble characterized by free-free emission, and a shell interacting with a nearby infrared dark cloud.

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The rich molecular environment of the luminous blue variable star AFGL 2298

Rizzo,

Bordiu,

Buemi

et al. 2023

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Context. Luminous blue variable (LBV) stars represent a short-lived stage in the late evolution of the most massive stars. Highly unstable, LBVs exhibit dense stellar winds and episodic eruptions that produce complex circumstellar nebulae, the study of which is crucial for properly constraining the impact of these sources at a Galactic scale from a structural, dynamical, and chemical perspective. Aims. We aim to investigate the molecular environment of AFGL 2298, an obscured Galactic LBV that hosts a highly structured circumstellar environment with hints of multiple mass-loss events in the last few 104 a. Methods. We present spectral line observations of AFGL 2298 at 1 and 3 mm performed with the IRAM 30 m radio telescope. Results. We report the detection of several carbon- and nitrogen-bearing species (CO, 13CO, C18O, C17O, HCO+, HCN, HNC, H13CO+, CN, N2H+, and C2H) in the surroundings of AFGL 2298. We identified three velocity components that clearly stand out from the Galactic background. The morphology, kinematics, masses, and isotopic ratios, together with a comparative study of the fractional abundances, lead us to suggest that two of these components (36 and 70 km s−1) have a stellar origin. The other component (46 km s−1) most likely traces swept-up interstellar material, and probably also harbours a photon-dominated region. Conclusions. We provide the first inventory of the circumstellar molecular gas around AFGL 2298. Our results are compatible with the hypothesis of former mass-loss events produced before the one that created the infrared nebula. The chemistry of this LBV suggests the presence of ejected stellar material, and also swept up gas. These findings will help us to better understand the mass-loss history of this class of evolved massive stars, which is important given that they heavily influence the overall chemical evolution of the Galaxy.

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A slowly expanding torus associated with the candidate LBV MGE 042.0787+00.5084

Cited by 4 publications

References 32 publications

The peculiar chemistry of the inner ejecta of Eta Carina

The peculiar chemistry of the inner ejecta of Eta Carina

NIKA2 observations around LBV stars Emission from stars and circumstellar material

The rich molecular environment of the luminous blue variable star AFGL 2298

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