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We re-examine the nature of NGC2024-IRS2 in light of the recent discovery of the late O-type star, IRS2b, located 5 arcsec from IRS2. Using L-band spectroscopy, we set a lower limit of Av = 27.0 mag on the visual extinction towards IRS2. Arguments based on the nature of the circumstellar material, favor an Av of 31.5 mag. IRS2 is associated with the UCHII region G206.543-16.347 and the infrared source IRAS 05393-0156. We show that much of the mid-infrared emission towards IRS2, as well as the far infrared emission peaking at ~ 100 micron, do not originate in the direct surroundings of IRS2, but instead from an extended molecular cloud. Using new K-, L- and L-band spectroscopy and a comprehensive set of infrared and radio continuum measurements from the literature, we apply diagnostics based on the radio slope, the strength of the infrared hydrogen recombination lines, and the presence of CO band-heads to constrain the nature and spatial distribution of the circumstellar material of IRS2. Using simple gaseous and/or dust models of prescribed geometry, we find strong indications that the infrared flux originating in the circumstellar material of IRS2 is dominated by emission from a dense gaseous disk with a radius of about 0.6 AU. At radio wavelengths the flux density distribution is best described by a stellar wind recombining at a radius of about 100 AU. Although NGC2024/IRS2 shares many similarities with BN-like objects, we do not find evidence for the presence of a dust shell surrounding this object. Therefore, IRS2 is likely more evolved.
We present optical and near-IR spectroscopic observations of the luminous blue variable SN 2009ip during its remarkable photometric evolution of 2012. The spectra sample three key points in the SN 2009ip lightcurve, corresponding to its initial brigh
The HIFI instrument on board of the Herschel Space Observatory (HSO) has been very successful in detecting molecular lines from circumstellar envelopes around evolved stars, like massive red supergiants, Asymptotic Giant Branch (AGB) and post-AGB sta
We analyze 45 spectropolarimetric observations of the eclipsing, interacting binary star V356 Sgr, obtained over a period of 21 years, to characterize the geometry of the systems circumstellar material. After removing interstellar polarization from t
We investigate properties of the interstellar medium (ISM) in galaxies hosting long-duration gamma-ray bursts (GRBs) from an analysis of atomic species (MgI, FeI) and excited fine-structure levels of ions (e.g. SiII). Our analysis is guided primarily
EC53 is an embedded protostar with quasi-periodic emission in the near-IR and sub-mm. We use ALMA high-resolution observations of continuum and molecular line emission to describe the circumstellar environment of EC 53. The continuum image reveals a