Properties of the circumstellar dust in galactic FS CMa objects

Мирошниченко, А. С.; Gray, R. O.; Bjorkman, K. S.; Rudy, R. J.; Lynch, D. K.; Carciofi, A. C.

doi:10.1017/s1743921311010970

Cited by 3 publications

(2 citation statements)

References 3 publications

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“…This assumption is supported by evolutionary arguments, since carbon is depleted due to the CNO processing cycle in massive stars, therefore ruling out carbon-based grains, such as graphite, for the object in question. Furthermore, IR spectra of nearly 20 FS CMa objects obtained with the Spitzer Space Observatory (IRAS00470+6429 was not observed due to the presence of a bright nearby IR source) show silicate emission features (Miroshnichenko et al 2008).…”

Section: A Parametric Model For the Circumstellar Envelopementioning

confidence: 99%

TOWARD UNDERSTANDING THE B[e] PHENOMENON. IV. MODELING OF IRAS 00470+6429

Carciofi

Мирошниченко

Bjorkman

2010

ApJ

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FS CMa type stars are a recently described group of objects with the B[e] phenomenon that exhibit strong emission-line spectra and strong IR excesses. In this paper we report the first attempt for a detailed modeling of IRAS 00470+6429, for which we have the best set of observations. Our modeling is based on two key assumptions: the star has a main-sequence luminosity for its spectral type (B2) and the circumstellar envelope is bimodal, composed of a slowly outflowing disk-like wind and a fast polar wind. Both outflows are assumed to be purely radial. We adopt a novel approach to describe the dust formation site in the wind that employs timescale arguments for grain condensation and a self-consistent solution for the dust destruction surface. With the above assumptions we were able to reproduce satisfactorily many observational properties of IRAS 00470+6429, including the H I line profiles and the overall shape of the spectral energy distribution. Our adopted recipe for dust formation proved successful in reproducing the correct amount of dust formed in the circumstellar envelope. Possible shortcomings of our model, as well as suggestions for future improvements, are discussed.

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Section: A Parametric Model For the Circumstellar Envelopementioning

confidence: 99%

TOWARD UNDERSTANDING THE B[e] PHENOMENON. IV. MODELING OF IRAS 00470+6429

Carciofi

Мирошниченко

Bjorkman

2010

ApJ

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“…de la Fuente et al (2015) presented an alternative hypothesis, that a stellar merger can also explain the formation of large amounts of circumstellar dust, thus unclassified B[e] stars could be the products of a recent merger. From the observational side, Miroshnichenko et al (2011) studied the mid-IR spectra of 25 unclassified B[e] stars, and they detected silicate emission features in most observed objects, and PAH emission in some.…”

Section: Dust Propertiesmentioning

confidence: 99%

Dust evolution in the circumstellar disc of the unclassified B[e] star HD 50138

Varga

Gerják

Ábrahám

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We studied the disc of the unclassified B[e] star HD 50138, in order to explore its structure, and to find indications for the evolutionary status of this system, whether it is a young Herbig Be or a post-main-sequence star. Using high spatial resolution interferometric measurements from MIDI instrument (N-band) on the Very Large Telescope Interferometer, we analysed the disc size, the time-variability of the disc's thermal emission, and the spectral shape of the 10 µm silicate feature. By fitting simple disc models, we determined the inclination and the mid-infrared size of the disc, confirming earlier results based on a lower number of observations. We searched for mid-infrared temporal variability of different regions of the disc, and concluded that its morphology is not experiencing significant changes over the observed epochs. We characterized the mid-infrared silicate feature by determining the feature amplitude and the 11.3/9.8 µm flux ratio. The latter parameter is a good indicator of the grain size. The shape of the feature suggests the presence of crystalline silicate grains in the disc. The interferometric data revealed a strong radial trend in the mineralogy: while the disc's innermost region seems to be dominated by forsterite grains, at intermediate radii both forsterite and enstatite may be present. The outer disc may predominantly contain amorphous silicate particles. A comparison of the observed spectral shape with that of a sample of intermediate-mass stars (supergiants, Herbig Ae/Be stars, unclassified B[e] stars) implied that the evolutionary state of HD 50138 cannot be unambiguously decided from mid-IR spectroscopy. nandes et al. 2011), however, high spatial resolution observations can provide an efficient classification tool for them (Miroshnichenko 2007). A notable feature of unclassified B[e] stars is their high mass loss rates, compared to normal mainsequence stars, which can not be explained by the windtheory for main-sequence B-type stars (de la Fuente et al. 2015). Originally unclassified B[e] stars were thought to be isolated objects, but recently de la Fuente et al. (2015) reported that these objects can be also found in clusters. They estimated the age of the stars in the range from 3.5 to 6.5 Myr, which is out of the range for both pre-and post-main sequence origin, as the former phase lasts for ∼ 0.1 Myr, and the main-sequence lifetime is 15 − 20 Myr for a 12 M star.

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First detections of FS Canis Majoris stars in clusters

Fuente

Najarro

Trombley

et al. 2015

A&A

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Context. FS CMa stars are low-luminosity objects showing the B[e] phenomenon whose evolutionary state remains a puzzle. These stars are surrounded by compact disks of warm dust of unknown origin. Hitherto, membership of FS CMa stars to coeval populations has never been confirmed. Aims. The discovery of low-luminosity line emitters in the young massive clusters Mercer 20 and Mercer 70 prompts us to investigate the nature of such objects. We intend to confirm membership to coeval populations in order to characterize these emission-line stars through the cluster properties.

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Properties of the circumstellar dust in galactic FS CMa objects

Cited by 3 publications

References 3 publications

TOWARD UNDERSTANDING THE B[e] PHENOMENON. IV. MODELING OF IRAS 00470+6429

TOWARD UNDERSTANDING THE B[e] PHENOMENON. IV. MODELING OF IRAS 00470+6429

Dust evolution in the circumstellar disc of the unclassified B[e] star HD 50138

First detections of FS Canis Majoris stars in clusters

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