SpringerLink
Forum Springer Astron. Astrophys.
Forum Whats New Search Orders


Astron. Astrophys. 325, 551-558 (1997)

Previous Section Next Section Title Page Table of Contents

3. Results

Three circumstellar dust models were investigated (each for dust disk masses of [FORMULA] and [FORMULA]):

  1. with bare silicate grains, without gaps in the disk,
  2. with core/mantle grains, without gaps in the disk, and,
  3. with core/mantle grains and gaps in the disk.

We performed the radiative transfer separating the effects of scattered stellar radiation and the thermally emitted (and scattered) dust radiation from the planet radiation. The last one was taken without transfer because of the negligible changes expected in comparison to the effects mentioned before.

Three "observer's positions" between the pole-on and edge-on view and normally to the line connecting the central star with the planets (x -axis in our model) were selected.

Despite the large number of weighted photons started from the star ([FORMULA] for each wavelength), the statistical error is still large because of the very low probability of scattering in case of the debris disks used for the calculations. The error increases (as the number of collected weighted photons decreases) going from the Earth-like to the Jupiter-like planet, from edge-on to pole-on positions, and from large to small beam sizes. For the interpretation we have to take notice of this "noise effect".

The effects of the beam size and the position in respect to the disk are obvious (see Figs. 4, 5, 6). Close to the pole-on view no absorption acts and the curves for scattered stellar light show the distribution of [FORMULA] (see Fig. 1). For higher inclination angles [FORMULA] this light becomes increasingly absorbed. As a consequence the minimum in the [FORMULA] m range is partly filled in and shifted to larger wavelengths. In case of the thermal dust contribution, the curves for the Earth are similiar to the curves for the emission from the whole dust. The course of the Jupiter curves differs especially in the O3 band range.

[FIGURE] Fig. 4a-f. Photon fluxes of scattered stellar radiation and thermal dust radiation at a distance of 5 pc for different models with debris dust masses of [FORMULA]. Beam sizes decrease with decreasing line thickness: 1.7, 1.3, 1.0 AU. Various "observer's positions" between the edge-on and pole-on view normally to the line connecting the central star with the planets are presented by various line styles: dotted lines: [FORMULA], dashed lines: [FORMULA], solid lines: [FORMULA]. To get a better statistics, we averaged the results within the angular ranges indicated.
[FIGURE] Fig. 5a-f. Photon fluxes of scattered stellar radiation and thermal dust radiation at a distance of 5 pc for different models with debris dust masses of [FORMULA].. Beam sizes decrease with decreasing line thickness: 1.7, 1.3, 1.0 AU. Various "observer's positions" between the edge-on and pole-on view normally to the line connecting the central star with the planets are presented by various line styles: dotted lines: [FORMULA], dashed lines: [FORMULA], solid lines: [FORMULA]. To get a better statistics, we averaged the results within the angular ranges indicated.

The resulting scattered and reemitted photon portions are shown in Figs. 4 and 5for a dust disk mass of [FORMULA] and of [FORMULA], respectivly. In Fig. 6 we summed up all photon portions to show the influence of the circumstellar dust radiation on the O3 and CO2 bands at different beam sizes.

[FIGURE] Fig. 6a-c. Sum of all photon flux components, i. e., planet radiation + scattered stellar radiation + thermal dust radiation, in the observer's beam for the pole-on view onto the [FORMULA] dust disk. Beam sizes (diameters) correspond to linear disk dimensions of [FORMULA]  AU for Earth-like and [FORMULA]  AU for Jupiter-like planets (thin lines). The lowest (thick) line represents the planet radiation alone (see also Fig. 3). The graphs for the Earth-like planet show a large statistical noise because of the low number of photons collected (in the Monte Carlo calculation) with very small beam sizes.
Previous Section Next Section Title Page Table of Contents

© European Southern Observatory (ESO) 1997

Online publication: April 28, 1998

helpdesk.link@springer.de