The Galactic unclassified B[e] star HD 50138

Abstract

Context. HD 50138 is a southern star that presents the B[e] phenomenon, but its evolutionary stage is still not well known. This object presents spectral variability, which can be explained by outbursts or shell phases. Spectropolarimetric observations have shown the presence of a non-spherically symmetric circumstellar environment that is responsible for the B[e] phenomenon. However, up to now, the structure of the circumstellar medium of this object has not been studied deeply. Aims. Based on recent optical long baseline interferometric observations from the VLTI/MIDI and VLTI/AMBER, and also from the Keck segment-tilting experiment, we study the structure of the circumstellar environment of HD 50138. Methods. The analysis of our data is based on geometrical analytical modeling, also using the recent LITpro software and considering a large space of parameters, which allows us to obtain a good estimate of the geometry of the circumstellar medium of HD 50138, responsible for the emission in the H, K, and N-bands. Results. We resolve the circumstellar environment of HD 50138 and describe its geometry for the first time in detail. Through analysis of multiwavelength data, the presence of a dusty circumstellar disk with an orientation onto the sky-plane of 71 ± 7 • , which is perpendicular to the polarimetric measurements from the literature, was derived. We also derived that HD 50138 is seen under an intermediate angle related to the line of sight, 56 ± 4 • . In addition, the structure of the disk and the flux contributions of the gas and dust components is discussed. Conclusions. Based on analysis of different sets of interferometric data, we describe the circumstellar disk whose geometric parameters were determined, allowing us to understand the geometry of the circumstellar material of this bright star with the B[e] phenomenon.

Intrincate visibility effects from resolved emission of young stellar objects: the case of MWC158 observed with the VLTI

“…They are closed to the images get by reconstruction. The results are also consistent with that found with previous observations 19,27 . The authors found similar P.A.…”

“…They are useful to analyze MWC158 (also known as HD50138). This star is a Be star known to have the B[e] phenomenon and presents a strong variability [14][15][16][17] which complexify the evolutionary stage identification of the source. Its distance is poorly constrain (d = 500pc ± 150pc 18 ).…”

SPARCO : a semi-parametric approach for image reconstruction of chromatic objects

“…5 of Borges Fernandes et al 2011). First believed to be quality (...) clearly lower compared to the K-band data (Borges Fernandes et al 2011), the increase of the visibilities of the H-band data has been observed not only on VLTI/AMBER, but also with A&A 564, A80 (2014) VLTI/PIONIER. This indication caused us to consider an astrophysical interpretation: the change of visibility is generated by the different chromatic behavior between the central star that peaks in the visible and the circumstellar material that radiates out mainly in the NIR (Kluska et al 2012).…”

First detections of FS Canis Majoris stars in clusters

“…Subsequent observations (Miroshnichenko et al , 2009(Miroshnichenko et al , 2011aBorges Fernandes et al 2009Rodríguez et al 2012;Polster et al 2012;Liermann et al 2014) and modeling (Carciofi et al 2010;Borges Fernandes et al 2011) of FS CMa stars have not been capable of unraveling the enigmatic nature of these objects. One of the most puzzling issues refers to the observationally inferred mass-loss rates, which are 2-3 dex higher than predicted by wind theory for B-type main-sequence stars.…”