Resolving the kinematics of the discs around Galactic B[e] supergiants

Maravelias, G.; Kraus, M.; Cidale, L. S.; Fernandes, M. Borges; Arias, María Laura; Curé, M.; Vasilopoulos, Georgios

doi:10.1093/mnras/sty1747

Cited by 36 publications

(58 citation statements)

References 60 publications

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“…The distance to Hen 3-365 is uncertain and contributes to the unknown evolutionary status of the star. The extinction and kinematics indicate that Hen 3-365 is more likely an evolved supergiant at a distance of several kpc than a close young star (Oudmaijer et al 1998), andMaravelias et al (2018) classify Hen 3-365 as a massive supergiant. However the HI column density is far too high for Hen 3-365 to be a supergiant (Oudmaijer et al 1998).…”

Section: Hen 3-365 (Hd 87643)mentioning

confidence: 99%

Irregular Dust Features around Intermediate-mass Young Stars with GPI: Signs of Youth or Misaligned Disks?

Laws

Harries

Setterholm

et al. 2019

ApJ

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We are undertaking a large survey of over thirty disks using the Gemini Planet Imager (GPI) to see whether the observed dust structures match spectral energy distribution (SED) predictions and have any correlation with stellar properties. GPI can observe near-infrared light scattered from dust in circumstellar environments using high-resolution Polarimetric Differential Imaging (PDI) with coronagraphy and adaptive optics. The data have been taken in J and H bands over two years, with inner working angles of 0.08 " and 0.11 " respectively. Ahead of the release of the complete survey results, here we present five objects with extended and irregular dust structures within 2 " of the central star. These objects are: FU Ori; MWC 789; HD 45677; Hen 3-365; and HD 139614. The observed structures are consistent with each object being a pre-main-sequence star with protoplanetary dust. The five objects' circumstellar environments could result from extreme youth and complex initial conditions, from asymmetric scattering patterns due to shadows cast by misaligned disks, or in some cases from interactions with companions. We see complex U φ structures in most objects that could indicate multiple scattering or result from the illumination of companions. Specific key findings include the first high-contrast observation of MWC 789 revealing a newly-discovered companion candidate and arc, and two faint companion candidates around Hen 3-365. These two objects should be observed further to confirm whether the companion candidates are co-moving. Further observations and modeling are required to determine the causes of the structures.

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Section: Hen 3-365 (Hd 87643)mentioning

confidence: 99%

Irregular Dust Features around Intermediate-mass Young Stars with GPI: Signs of Youth or Misaligned Disks?

Laws

Harries

Setterholm

et al. 2019

ApJ

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“…With the identification of the lines of [Ca II] λλ7291,7324 in the spectra of numerous B[e]SGs, a further highly valuable tracer for the disk kinematics has been found. These lines typically display double-peaked profiles as well, with velocities comparable to or even greater than the one traced by the [O I] λ5577 line ( [53,57,58]). This implies that they form in the same region, or at least very close to each other, which is in agreement with their comparably high critical density.…”

Section: Disk Dynamics and Structurementioning

confidence: 99%

“…While, in general, the rotational motion of the material within the circumstellar disks of B[e]SGs seems now to be well established, maybe in connection with a (very) slow outflow component ( [57]), recent investigations of the spatial distribution of the circumstellar gas revealed that it is more likely accumulated in multiple rings, partial rings, and possible spiral arm-like structures rather than in a smooth disk ( [43,44,58]). These rings might result from multiple mass ejection phases caused by (pulsational) instabilities acting in the outer layers of these luminous objects (e.g., [73][74][75]), or from binary interaction in close systems as seems to be the case for some of the Galactic objects ( [58]) in which the rings are circumbinary rather than circumstellar. Other disk-forming mechanisms that have been proposed in the literature over the years include equatorial mass-loss from a critically rotating star ( [76,77]), the rotationally induced bi-stability mechanism ([78]), the slow-wind solution ( [79]), and the combination of the latter two ( [80]).…”

Section: Disk Dynamics and Structurementioning

confidence: 99%

A Census of B[e] Supergiants

Kraus

2019

Galaxies

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Stellar evolution theory is most uncertain for massive stars. For reliable predictions of the evolution of massive stars and their final fate, solid constraints on the physical parameters, and their changes along the evolution and in different environments, are required. Massive stars evolve through a variety of short transition phases, in which they can experience large mass-loss either in the form of dense winds or via sudden eruptions. The B[e] supergiants comprise one such group of massive transition objects. They are characterized by dense, dusty disks of yet unknown origin. In the Milky Way, identification and classification of B[e] supergiants is usually hampered by their uncertain distances hence luminosities, and by the confusion of low-luminosity candidates with massive pre-main sequence objects. The extragalactic objects are often mistaken as quiescent or candidate luminous blue variables, with whom B[e] supergiants share a number of spectroscopic characteristics. In this review, proper criteria are provided, based on which B[e] supergiants can be unambiguously classified and separated from other high luminosity post-main sequence stars and pre-main sequence stars. Using these criteria, the B[e] supergiant samples in diverse galaxies are critically inspected, to achieve a reliable census of the current population.In the HR diagram these objects are all found beyond the main-sequence and with luminosities spreading from about log L/L ∼ 4 to about log L/L ∼ 6 implying that they are all evolved, massive stars. This luminosity range was determined from the sample residing in the Magellanic Clouds (MCs), for which the luminosity determination is unquestionable, due to the low extinction towards the MCs and their well constraint distances. The classification of Galactic objects as supergiants bears much higher uncertainties due to their often poorly constraint distances hence luminosities. We will come back to this issue in Section 4.4.The position of the MC sample in the HR diagram is shown in Figure 1 for the values of luminosity and effective temperature listed in Table 1. The stellar parameters (effective temperature T eff , visual magnitude V, and color excess E(B − V)) of the sample have been taken from the references listed in the last column of Table 1. For the calculations of the luminosities, distance moduli of 18.5 and 18.9 mag for the Large respectively Small Magellanic Clouds have been utilized (see the review paper by Humphreys, this volume) along with bolometric corrections from [29].The presence of dust around an early-type (typically of spectral type B) supergiant, along with the often pure emission-line spectra with numerous forbidden lines predominantly of [Fe II] and [O I] finally resulted in the designation of these objects as B[e] supergiants (B[e]SGs) 1 . 1 Note that these objects have previously been abbreviated sgB[e] ([24]), to separate them from other stars showing the B[e] phenomenon. We prefer the designation B[e]SG, to be in line with the naming and abbreviation of other type o...

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“…Within the discs, the molecules are shielded from the dissociating stellar ultraviolet radiation field. Emission from hot CO gas has been detected in the IR spectra of both accretion discs of pre-main sequence stars (e.g., Geballe & Persson 1987;Carr 1989Carr , 1995Wheelwright et al 2010;Ilee et al 2013Ilee et al , 2018 and discs formed from the outflows and ejecta of evolved massive stars such as the B[e] supergiants (McGregor et al 1988a(McGregor et al ,b, 1989Morris et al 1996;Wheelwright et al 2012;Kraus et al 2016Kraus et al , 2017Torres et al 2018;Maravelias et al 2018;Kourniotis et al 2018). Enrichment in 13 CO has been found, based on measurements of the 12 CO/ 13 CO ratio in high-quality near-IR spectra, solely in the discs of confirmed evolved objects (Liermann et al 2010;Oksala et al 2013;Kraus et al 2013bKraus et al , 2014, reinforcing the power of this isotope-ratio method for the discrimination between young and evolved stars (Muratore et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Evidence of an evolved nature of MWC 349A

Kraus

Arias

Cidale

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The Galactic emission-line object MWC 349A is one of the brightest radio stars in the sky. The central object is embedded in an almost edge-on oriented Keplerian rotating thick disc that seems to drive a rotating bipolar wind. The dense disc is also the site of hot molecular emission such as the CO bands with its prominent band heads in the near-infrared spectral range. Despite numerous studies, the nature of MWC 349A is still controversial with classifications ranging from a pre-main sequence object to an evolved supergiant. We collected new high-resolution near-infrared spectra in the K-and L-bands using the GNIRS spectrograph at Gemini-North to study the molecular disc of MWC 349A, and in particular to search for other molecular species such as SiO and the isotope 13 CO. The amount of 13 CO, obtained from the 12 CO/ 13 CO ratio, is recognized as an excellent tool to discriminate between pre-main sequence and evolved massive stars. We find no signatures of SiO band emission, but detect CO band emission with considerably lower intensity and CO gas temperature compared to previous observations. Moreover, from detailed modelling of the emission spectrum, we derive an isotope ratio of 12 CO/ 13 CO = 4±1. Based on this significant enrichment of the circumstellar environment in 13 CO we conclude that MWC 349A belongs to the group of B[e] supergiants, and we discuss possible reasons for the drop in CO intensity.

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Resolving the kinematics of the discs around Galactic B[e] supergiants

Cited by 36 publications

References 60 publications

Irregular Dust Features around Intermediate-mass Young Stars with GPI: Signs of Youth or Misaligned Disks?

Irregular Dust Features around Intermediate-mass Young Stars with GPI: Signs of Youth or Misaligned Disks?

A Census of B[e] Supergiants

Evidence of an evolved nature of MWC 349A

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