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MWC 930 is a star just ~2{\deg} above the Galactic plane whose nature is notclear and that has not been studied in detail so far. While a post-AsymptoticGiant Branch (AGB) classification was proposed in the past, studies of itsoptical spectrum and photometry pointed toward strong variability, thereforethe object was reclassified as a Luminous Blue Variable (LBV) candidate. LBVstypically undergo phases of strong mass loss in the form of eruptions that cancreate shells of ejecta around the star. Our goal is to search for the presenceof such a circumstellar nebula in MWC 930 and investigate its properties. To doso, we make use of space-based infrared data from our Spitzer campaignperformed with the InfraRed Array Camera (IRAC) and the InfraRed Spectrograph(IRS) as well as data from optical and infrared (IR) surveys. In our Spitzerimages, we clearly detect an extended shell around MWC 930 at wavelengthslonger than 5 um. The mid-infrared spectrum is dominated by the central starand mostly shows forbidden lines of [FeII], with an underlying continuum thatdecreases with wavelength up to ~15 um and then inverts its slope, displaying asecond peak around 60 um, evidence for cold dust grains formed in a pasteruption. By modeling the SED, we identify two central components, besides thestar and the outer shell. These extra sources of radiation are interpreted asmaterial close to the central star, maybe due to a recent ejection. Features ofC-bearing molecules or grains are not detected.

Spitzer observations of a circumstellar nebula around the candidate Luminous Blue Variable MWC 930