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Far-infrared photometry and mapping of Herbig Ae/Be stars with ISO *
P. Ábrahám 1,2,
Ch. Leinert 1,
A. Burkert 3,
Th. Henning 3 and
D. Lemke 1
Received 23 August 1999 / Accepted 8 December 1999
Seven Herbig Ae/Be stars were observed at mid- and far-infrared wavelengths with ISOPHOT, the photometer on-board the Infrared Space Observatory. At m, where the emission mainly arises from a compact circumstellar region, the observed spectral energy distributions can be described by power-law relationships between wavelength and flux density (). The exponent of the power-law changes considerably among the stars, from for MWC 1080 to in the case of LkH 234, with a typical value of around 1. Interpreting the observed power-law relationships in terms of circumstellar disks, in 5 out of 6 cases relatively shallow radial temperature distributions have to be assumed ( where ). At longer wavelengths the observed emission is spatially extended, and in some cases significant discrepancy with IRAS was found due to beam size effects. The peak of the SEDs (in ) is typically at 60-100µm, corresponding to temperatures of around 50 K. At m the emission observed by ISOPHOT is never dominated by the Herbig Ae/Be stars. The most likely sources of the far-infrared radiation are dust cores of about 1 arcminute in size. The dust cores are probably located in the vicinity of the stars, and may be related to the star forming process.
Key words: stars: formation stars: pre-main sequence ISM: clouds ISM: dust, extinction radio continuum: ISM stars: circumstellar matter
* Based on observations with ISO, an ESA project with instruments funded by ESA member states (especially the P/I countries France, Germany, the Netherlands and the United Kingdom) with participation of ISAS and NASA.
Send offprint requests to: P. Ábrahám, Heidelberg
Online publication: February 25, 2000