English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

It is already accepted that Be stars are surrounded by circumstellarenvelopes, which are mostly compatible with a disc geometry in Keplerianrotation. We aim to obtain a more complete characterisation of the propertiesof the circumstellar environment of Be stars that helps to constrain thetheoretical models of the Be phenomenon. We present near-infrared,medium-resolution spectra of a sample of galactic Be stars with differentspectral subtypes and luminosity classes. We measure different parameters ofthe hydrogen recombination lines from the Paschen, Brackett, Pfund, andHumphreys series, and use them to diagnose physical conditions in thecircumstellar environment. We analysed the equivalent-width (EW) ratio betweenBr$\alpha$ and Br$\gamma$ lines and different diagrams of flux ratios. We alsoidentify lines from He I, C I, N I, O I, Na I, Mg I, Mg II, Si I, Fe I, and FeII. Analysing the EW measurements of particular He I, Mg II, Fe I, Fe II and OI lines, we find that for some lines they correlate with the spectral type ofthe star. Particularly, the emission of the O I~$\lambda\,1.3168\,\mu$m linedecreases towards the later spectral types. We present an atlas of 22 Be stars,that covers a wide infrared (IR) spectral range with quasi-simultaneousobservations. From a detailed analysis, we define new complementary criteria toMennickent's classification of Be stars according to their disc opacity. Someobjects in our sample present compact thick envelopes, while in others theenvelope is extended and optically thin. The correlation between the fullwidths at half maximum (FWHM) and the peak separation ($\Delta \mathrm{V}$)versus $V\,\sin\,i$ for the Br10, Br$\delta$, and Hu14 lines reveals that thebroadening mechanism is rotational. The Ly$\beta$ fluorescence is a keymechanism to explain the intensity of the emission of Mg II and O I lines.

Simultaneous J-, H-, K- and L-band spectroscopic observations of galactic Be stars. I. IR atlas