Wednesday, June 15, 2011

RSS spectra & inaugurating Amanda's new place

Here you go Dave - at long last, a few RSS spectra for you to pore over!  The first 3 were all taken with the PG0900 grating.  Remember that the 2 square "absorption features" in all the spectra are actually due to the gaps between the 3 chips that make up the RSS detector.  

The first spectrum is that of a spectrophotometric standard star known as LTT7987, a DA white dwarf with a V magnitude of 12.2.  The spectrum's completely dominated by the broad Balmer lines of hydrogen.

Next up is another spectrophotometric standard - an A-type dwarf (main sequence star) according to the literature.  It too shows the Balmer series in absorption, but the lines are much sharper due to the vastly lower pressure in the atmosphere of a main sequence star.  In fact, as Darragh pointed out, it actually looks more like an F-type star as the Balmer lines are there, but not very strong.  Hmmm...

Here's a spectrum of an object with emission lines.  This is a Wolf-Rayet star with strong helium & nitrogen features & hence belonging to the WN subtype.  These are massive stars (10-25x the mass of the Sun) which evolve rapidly through this phase (in about half a million years) & so they appear to be rare.  Wolf-Rayets lose enormous amounts of material in the form of a powerful (~2000 km/s) stellar wind & act as indicators for massive star formation in other galaxies.

Finally, another object with huge emission lines - the recurrent nova T Pyx, which ever-so-kindly waited for SALT to be ready before undergoing its long-overdue outburst in April!  This really is the *perfect* object for commissioning our multi-purpose spectrograph :)  The spectrum below was obtained with the PG2300 grating, set so as to observe the H-alpha region where hydrogen traces the material ejected during the nova eruption.
On what turned out to be Ken's last night of on-sky observing before leaving Sutherland (the next night was wiped out by an impressive storm), he obtained some wonderful spectro-polarimetric data of T Pyx.  This mode results in pairs of polarised spectra as the PG0900 grating was used in conjunction with the beamsplitter.  Even cooler than That, is the cunning use of the grating about 3 degrees off-Littrow, in order to boost the UV performance down near the atmospheric limit!  This data is amongst the most exciting stuff obtained with RSS so far & will yield unique & intriguing science :)

As much fun as the subsequent attempt to get the RSS multi-object spectroscopy (MOS) mode to work (in spite of thick cloud) was, good things were happening down at House 13 where Amanda had assembled most of the Tech Ops hooligans & a spirited bunch of wannabes up from Cape Town.

Shatteringly, the mechanical bunch made short work of the Astro Ops & IT representatives - at one point even resorting to rather condescending behaviour...

Apparently all such hubris was forgiven though - as demonstrated here by Vic & Hamish getting comfortable with their special feelings for one other.  It's slightly unfortunate that the Tech Ops jackets make the team look like Trekkie convention delegates - best we give that a bit more thought next time!


  1. Thanx for that Lisa, excellent spectra shots - and explanations - keep it up :-)


  2. I must say, I am pretty miffed that Hamish got a SALT ops jacket and I didn't **pout**

    To whom can I send my address? :-)