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Elias 1

Page history last edited by PBworks 12 years, 11 months ago

Elias 1

 

[SIMBAD Data Link]

Elias 1 (V892 Tau, Elias 3-1) is actually a triple system consisting of a close binary pair (Herbig star and 1.5 - 2 M companion) separated by around 5-7 AU) and a low mass (type M2) companion at about 574 AU. The core component is a young pre-main sequence binary of variable spectral type - observed values are generally in the range A0 - B9. It is classed as a Herbig Ae star (determined by Hα emission). It also displays infrared photometric variability, due to being obscured mainly by cold dust (visual extinction (Av is estimated at 6 - 10 magnitude). Observations imply an envelope as well as a circumstellar disk. X-ray and radio frequency emissions have also been observed.

Artists conception of a possible morphology of the Elias 1 triple star system.

Elias 1 is located east of the B7 cloud in the Taurus Dark Cloud complex, and is the source of illumination for the reflection nebula IC 359.

 

Circumstellar Environment

There is ample evidence of a circumstellar dust shell surrounding Elias 1. This shell is embedded in a local dark cloud environment.

Nebula

It has been deduced that an observed E-W elongation is due to scattered light from bipolar (nebular) lobes. This is from an observed asymmetric PAH (3.3µm) emission extending up to 100AU away. This is not commonly observed elsewhere, as the PAH emission is normally significantly less extended than for UIR bands.

J & H data show a well resolved blue structure. Alongside the E-W (WHM ~ 1" observation, a second marginally resolved observation is made at FWHM < 0.2")

Close Binary Companion

Image of a stellar system similar to Elias 1

K & L' data (marginally resolved red structure) are consistent with the presence of a close binary. This companion is oriented at PA 50° with a separation of 0.05" (~5 AU?). Some approximately circular and symmetric extended structure is also observed.

Circumstellar Disk

Diamond and near-IR continuum emission arises from a symmetrical region ~ 48AU in size. A continuum emission of 1.3mm shows a disk mass of 0.013M.Scattered light from the disk region also implies that the disk is fairly evolved.

Ice Band

Though there is no clear evidence of structure, there is a high extinction ice band surrounding Elias 1 (τice~0.51). It's IR spectrum is consistent with grains of unannealed H20-NH3 (at a ratio of 9:1). CO2 has also been observed.

 

Emission Features

There are a number of interesting spectroscopic features. PAH, diamond and continuum emissions are observed.

Range 2.5 - 13.5µm

In this range, absorbtion features have been observed, corresponding to water and CO2 ice, and emission features are observed, corresponding to silicates, PAHs and H-terminated diamonds.

3.29µm

PAH emission feature.

3.43µm, 3.53µm (and others in the region 3.2-3.6µm)

H-terminated diamond feature. (NB: no data on unterminated diamonds)

 

Circumstellar Species

Diamonds

The diamonds detected are estimated to be at least 50nm in size (cf. meteoric nanodiamonds ~ 2-3nm). The diamonds are confined to a region up to 48AU from the central star. These diamonds are postulated to have formed via a process akin to chemical vapour deposition. A specific set of formation conditions is likely.

PAHs

PAH emissions observed are in the (relatively weak) 3.3µm feature.

 

Related stars

A spectroscopicaly related object is the Herbig Be star HD 97048.

Diamonds have also been detected in the stars:

  • BD+40° 4124
  • MWC 297
  • HR 4049 (relatively weak)

 

2MASS image of Elias 1 and a nearby YSO.

Note the blue colour of Elias 1 (spectral type A6e).

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