Study of the properties and spectral energy distributions of the Herbig AeBe stars HD 34282 and HD 141569

Abstract

We present an study of the stellar parameters, disctance and spectral energy distributions (SEDs) of HD 34282 and HD 141569, two pre-main sequence Herbig AeBe stars. Both objects have been reported to show "anomalous positions" in the HRD diagram in the sense that they appear below the main sequence. A significant result of this work is that both stars are metal-deficient. The Hipparcos distance of HD 34282 is very uncertain and the current stdy places the star at the expected evolutionary position in the HRD diagram, i.e. as a PMS star. The distance for HD 141569 found in this work matches the Hipparcos distance, and the problem of its anomalous position is solved as a result of the low metallicity of the object: using the right metallicity tracks, the star is in the PMS region. The SEDs are constructed using data covering ultraviolett to millimetre wavelengths. Physical, non-parametric models, have been applied in order to extract some properties of the disks surrounding the stars. The disk arount HD 34282 is actreting actively, it is massive and presents large grains in the mid-plane and small grains in the surface. HD 141569 has a very low mass disk, which is in an intermediate state towards a debris-type disk.