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

Abstract

Abstract. We present a study of the stellar parameters, distances 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 HR 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 study places the star at the expected evolutionary position in the HR 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 ultraviolet to millimetre wavelengths. Physical, non-parametric models, have been applied in order to extract some properties of the disks surrounding the stars. The disk around HD 34282 is accreting 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 stage towards a debris-type disk.

Resolved Co Gas Interior to the Dust Rings of the Hd 141569 Disk

“…The disk structure and radiative transfer calculation are carried out using code originally developed in Rosenfeld et al (2012Rosenfeld et al ( , 2013 and Flaherty et al (2015) with modifications for our simplified disk structure. The central star is assumed to lie at a distance of 108 pc (Merín et al 2004) with a position angle of 356° (Weinberger et al 2000). Unless otherwise specified, we also assume a stellar mass of 2 M e (Merín et al 2004).…”

“…The central star is assumed to lie at a distance of 108 pc (Merín et al 2004) with a position angle of 356° (Weinberger et al 2000). Unless otherwise specified, we also assume a stellar mass of 2 M e (Merín et al 2004). The disk emission in the SMA data is offset by [−0 2, −0 2] from the phase center due to the proper motion of the system between the J2000 epoch coordinates and when the data were taken; this offset is included in our model.…”

“…HD 141569, a B9.5, 5 Myr old star located 108 pc away (Merín et al 2004), hosts one of the first debris disks discovered to have a significant gas reservoir (Zuckerman et al 1995). While still fairly young, this system does not exhibit a strong infrared excess; instead its dust emission is more characteristic of an optically thin debris disk with L IR /L * ∼8×10 −3 (Sylvester et al 1996).…”

The Gemini NICI Planet-Finding Campaign: The Frequency of Giant Planets around Young B and A Stars

“…Weinberger et al (2000) note that the two M-dwarf companions to HD 141569 show lithium absorption and X-ray flux consistent with youth, and find an age for the system of 5 Myr. Merín et al (2004) examined high-resolution spectra of HD 141569 and confirm that it is a pre-main sequence star with low metallicity ([Fe/H] = −0.5). As with other very young B and A stars additional information beyond photometry (in this case the ages of the two M-dwarf companions) helps refine the age.…”

“…HD 141569 is a B9 star that hosts a resolved disk (Weinberger et al 1999) containing both gas and dust (Merín et al 2004). Our Bayesian method find a median age of 318 Myr with a 68% confidence interval between 163 and 440 Myr.…”