UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

Optical, infrared and millimetre-wave properties of Vega-like systems - III. Models with thermally spiking grains

Sylvester, RJ; Skinner, CJ; Balow, MJ; (1997) Optical, infrared and millimetre-wave properties of Vega-like systems - III. Models with thermally spiking grains. Monthly Notices of the Royal Astronomical Society , 289 (4) pp. 831-846. 10.1093/mnras/289.4.831. Green open access

[thumbnail of Barlow_289-4-831.pdf]
Preview
Text
Barlow_289-4-831.pdf - Published version

Download (1MB) | Preview

Abstract

Vega-like stars are main-sequence stars that exhibit excess IR emission due to circumstellar dust grains which are probably distributed in discs. We have recently published an obser- vational data base for a large sample of candidate Vega-like systems, comprising optical, near- IR and mm/submm-wave photometry, and mid-IR spectra. In a previous paper we presented radiative transfer models of eight sources from our sample that had low fractional excess luminosities. Here we present models of a further eight sources, all with large fractional excess luminosities dominated by excess emission at near-IR wavelengths. It was found that no single distribution of dust grains at thermal equilibrium in a disc could simultaneously match the excess emission at near-IR and longer wavelengths. We attempted to model the near-IR emission as due to thermally spiking small grains, which can temporarily attain the high temperatures required to produce excess near-IR emission. A near-IR spectrum of SAO 186777 shows the 3.3-μm UIR emission band, confirming our earlier detection of UIR emission at longer wavelengths, and suggesting that small carbonaceous particles are responsible for some of the near-IR emission. The thermally spiking models were only partially successful and many of the sources required the presence of grains emitting in thermal equilibrium at ∼ 1000- 1500 K. These grains must either be located very close to the stars (<1 au), or else be powered by accretion luminosity. Calculations of the optical depths of the model discs suggest the discs are optically thick at visual wavelengths; optically thick modelling of these sources is desirable. The discs are optically thin at mm wavelengths, allowing us to confirm the presence of large grains in the discs. The stars presented in this paper may well be younger than the prototype Vega-like stars.

Type: Article
Title: Optical, infrared and millimetre-wave properties of Vega-like systems - III. Models with thermally spiking grains
Open access status: An open access version is available from UCL Discovery
DOI: 10.1093/mnras/289.4.831
Publisher version: https://doi.org/10.1093/mnras/289.4.831
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: circumstellar matter, planetary systems, infrared: stars
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/10102759
Downloads since deposit
16Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item