S Dor

[Terry Bohlsen]

I successfully took 9 minutes of spectrum of S Dor last night to coincied with "AAVSO Special Notice #280: HST UV spectroscopy observations of S Dor"
Bernard was not able to any data and I had a very short window of opportunity before the star sets below the trees from my observatory. The airmass was 2.25 so it was very low in the sky.
I took BVRI images and then the spectra using my LISA with the 24um slit.
The Ha line measures at 6569A and the Hb line 4864.8A
Hg 4345.7
I have made 2 versions of the data. One just corrected with a flat field and the other continuum corrected from an A star that I took a spectrum of just after the S Dor data. The A star was higher in the sky though as it was impossible to find a suitable star at the same low altitude.







The fits spectrum files are here.
http://users.northnet.com.au/~bohlsen/N ... 11_445.fit

http://users.northnet.com.au/~bohlsen/N ... 11_445.fit


Terry Bohlsen
Armidale

[Bernard Heathcote]

Terry,
Good work! Even though the resolution is less that the PI (Noel Richardson) was hoping for I'm sure it will still be much appreciated ... especially if CTIO, like me, are clouded out. Based on earlier S Dor spectra I would have expected He lines 5876, 6678 and 5169 FeII to have been more prominent, but I think a higher resolution is probably needed for that to be seen. Ha, based on what Richardson told me, isn't as large as I was expecting ... again, this may be a resolution limitation. The separation between your Ha and Hb is about 5A greater than the stationary value (and Hb-Hg to a lesser degree), which means either your calibration is a bit off or there really is an RV difference between the source of these two lines. I don't know enough about this star to suggest which is the most likely reason.

Is your spectra heliocentric RV corrected? Either way, please let Richardson know.

Any chance you can grab another spectra tonight, the last night (Sat) of the HST UV coverage?

Cheers,
Bernard

[Bernard Heathcote]

Terry,

As I see, from the header, that your spectra is not HC corrected I applied an approx value of 2.32 km/s (I don't have your exact coords) and, using the mirror image method, I find RV=+315 km/s (a shift of 6.9A). This is too high, as the published value is around 230-250 km/s, in line with the LMC's radial velocity. Given that LISA's resolution is around 600-1000 we can't expect any better RV accuracy and applying a heliocentric correction is pointless.

Cheers,
Bernard

[Terry Bohlsen]

Bernard.
Thanks for the info.
The calibration I have used is the automatic one from Isis using both the int neon lines plus the H lines form the A8 star I took straight after the S Dor data.
No chance for follow up tonight as we had thunderstorms and I had a dinner to go to just to make sure no observing could occur.
Cheers

Terry