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Astron. Astrophys. 332, 999-1016 (1998)

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Broad band infrared spectroscopy of massive young stellar objects

John M. Porter 1, Janet E. Drew 2 and Stuart L. Lumsden 3

1 Astrophysics Research Institute, School of Engineering, Liverpool John Moores University, Byrom St., Liverpool L3 3AF, UK
2 Astrophysics Group, Blackett Laboratory, Imperial College, London SW7 2BZ, UK
3 Anglo-Australian Observatory, P.O. Box 296, Epping, NSW 2121, Australia

Received 25 August 1997 / Accepted 24 December 1997

Abstract

We present intermediate resolution 0.9-2.5µm IR spectra of 12 highly reddened stars, including some well known and some unfamiliar sources. A new technique for extracting calibration curves from standard star data is employed, and is found to be very successful.

The reddening to each object is fully discussed and is calculated from both the continua (which was split into short- and long-wavelength regions [FORMULA] µm and [FORMULA] µm) and the HI lines. We find that, typically, there is consistency between the values derived from the HI lines and the short-wavelength continua, but not with the value from the long-wavelength continua. This discrepancy is due to an IR excess at [FORMULA] 1.5µm, which is consistent with emission from hot dust (we derive dust temperatures in the range 750-1500K).

We note that some of our sources have highly discrepant Paschen decrements, and may have a significant amount of scattered light for [FORMULA] µm.

The spectra show a variety of metallic emission lines and some evidence for different distinct emission regions in the same source. The range of line-to-continuum contrast between the sources is high, and where previous observations have been taken, there is evidence of variability of emission line strength in some sources.

Key words: infrared: stars – stars: pre-main-sequence – dust, extinction

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© European Southern Observatory (ESO) 1998

Online publication: March 30, 1998
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