1994A&A...290..463N

We present new near infrared spectroscopy, photometry, and narrow band imaging of the young stellar object NGC 2024-IRS2. The data include high and low resolution spectra of Brγ, Brα, and Pfγ, single channel, JHKL' photometry, and images in Brγ and nearby continuum. The source has had a burst in its infrared emission, typically increasing by one magnitude in continuum brightness and by factors of 4-8 in line intensity, since 1989, and apparently reached a maximum in 1991. A large velocity shift has occurred in the peaks of the hydrogen lines, from ~+40km/s LSR in 1984 to ~-25km/s at present. Observation of such dramatic changes is unprecedented in studies of luminous YSO's. The data exclude external phenomena such as variable extinction or binary occultation as the origin of the observed variability, and appear more indicative of changes in the physical conditions of the star and its circumstellar environment.