Using the Star Analyser

Using the Star Analyser

Postby Robin Leadbeater » Sat Nov 17, 2012 3:56 pm

I am discussing with PI Darryl Sergison how best to use the Star Analyser results. His plan is to use it measure the continuum shape, accurately corrected for atmospheric extinction using a reference star in the same field.

From Darryl:-

" I am interested in using it to extract the tail of the UV/blue accretion continuum that T-Tauri stars often exhibit. They can essentially be modelled as a regular late type photosphere with a fraction of early type (approx. spectral type A) continuum superimposed on top corresponding to the accretion hotspots. Often the integrated luminosity from the accretion hotspots will be equivalent to or in some cases exceed that of the entire photosphere.

So my thinking is that even with low resolution spectra, we could flux-fit a photospheric template (which we will be collecting ourselves using the LT) to the red end of the low-res spectrum and then subtract leaving the blue excess. Fitting of a late type template or even a black body will then let us estimate the temperature and area coverage fraction of the accretion.

I assume that the atmospheric UV/Ozone cutoff will be variable from night to night and hence having a standard in the field (or being really careful with other standards) is critical because we are trying to extract some measure of flux right up to the UV limit. "

I am working with him to identify potential reference stars and here are some preliminary fields to try based on my setup of C11 at f6.3, SA100 and ATK16IC-S at 14A/pixel. The yellow lines show where the spectra from 3500-7200 would fall. (The suitability of reference star for DR Tau is to yet to be confirmed)

Potential problems are

Lack of signal relative to the sky background at the blue end
Background removal
Avoiding contamination from other stars and spectra
Flat field correction which will be important with the target and reference being in different parts of the field.

It might not be possible to get a good result but it will be interesting to try

LHIRES III #29 ATIK314 ALPY 600/200 ATIK428 Star Analyser 100/200 C11 EQ6
Robin Leadbeater
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Joined: Mon Sep 26, 2011 4:41 pm

Re: Using the Star Analyser

Postby Andrew Smith » Sat Nov 17, 2012 6:51 pm

Robin - I think this will be quite difficult and test even your skills. It will require you to rotate the SA/CCD between fields and in addition as you point out flat fielding on the edges of the field may prove a challenge. However, I am sure you will be up to it.

Regards Andrew
Andrew Smith
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Joined: Fri Sep 30, 2011 12:23 pm

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