A K-band spectral mini-survey of Galactic B[e] stars

TL;DR

This study uses near-infrared spectroscopy to analyze Galactic B[e] stars, revealing their evolved nature, binary companions, and circumstellar dust features, with new insights into their spectral characteristics and evolutionary status.

Contribution

First near-infrared spectral survey of Galactic B[e] stars, identifying key features and evolutionary indicators, including binary companions and circumstellar dust evolution.

Findings

Identified spectral features such as Brackett gamma and CO band heads.

Characterized stars as evolved objects, including LBV and supergiant B[e] candidates.

Observed disappearance of CO emission in MWC84 over several years.

Abstract

We present a mini-survey of Galactic B[e] stars mainly undertaken with the Large Binocular Telescope (LBT). B[e] stars show morphological features with hydrogen emission lines and an infrared excess, attributed to warm circumstellar dust. In general, these features are assumed to arise from dense, non-spherical, disk-forming circumstellar material in which molecules and dust can condensate. Due to the lack of reliable luminosities, the class of Galactic B[e] stars contains stars at very different stellar evolutionary phases like Herbig AeBe, supergiants or planetary nebulae. We took near-infrared long-slit K-band spectra for a sample of Galactic B[e] stars with the LBT-Luci I. Prominent spectral features, such as the Brackett gamma line and CO band heads are identified in the spectra. The analysis shows that the stars can be characterized as evolved objects. Among others we find one LBV candidate (MWC314), one supergiant B[e] candidate with 13CO (MWC137) and in two cases (MWC623 and AS 381) indications for the existence of a late-type binary companion, complementary to previous studies. For MWC84, IR spectra were taken at different epochs with LBT-Luci I and the GNIRS spectrograph at the Gemini North telescope. The new data show the disappearance of the circumstellar CO emission around this star, previously detectable over decades. Also no signs of a recent prominent eruption leading to the formation of new CO disk emission are found during 2010 and 2013.