Here are some results for review and discussion...
I have a medium res around Hb (showing P Cygni?) and the He and Fe emissions (look at the shape of the peaks - absorption?)
Moved across towards the Na region - again some profile detail...
Finally around the Ha (again some P Cygni?) - the emission is still so strong, I zoomed into show some of the underlying detail....
Processed with BASS Project.
Feedback welcome....
(EDIT: The R value on the charts is incorrect. It should be R=1650)
Here is my spectrum from this morning, and a comparison with yesterday. Little change from yesterday. Actually, I'm quite pleased how the two spectra line up - it shows that the small undulations I'm rather optimistically identifying as lines are real, not noise :-)
Based on my measures of the P Cygni profiles, I get 1796 Km/s at Ha, and 1789 Km/s at Hb. Seems consistant....say 1790 Km/s +/-
Interesting. ATEL #5639 (http://www.astronomerstelegram.org/?read=5639) showed up to ~ -1300 km/s and I get a figure consistent with that from Rogerio and Tasso's spectra, up to the point where their spectra lose the p cyg profile, see attached.
Is an acceleration here an expected part of the evolution?
Malc,
I could be wrong....
the difference at Ha was 39.3A and Hb 29A. When you plug in these numbers I get the 1790 Km/s....
I'm collecting more data as I type (thanks to Teamviewer!!) - let's see what that shows.
I've also made contact with Steve Shore who wants to helps us. Drop me an email for details.
Malc,
I could be wrong....
the difference at Ha was 39.3A and Hb 29A. When you plug in these numbers I get the 1790 Km/s....
I'm collecting more data as I type (thanks to Teamviewer!!) - let's see what that shows.
I've also made contact with Steve Shore who wants to helps us. Drop me an email for details.
Everything I've been reading suggest that it all gets pretty complex around now. Ken's emission lines all show a consistent saddle shape to the peak - look at the FeII lines 490-530 nm in particular. Payne-Gaposchkin talks about these (p.63) as a consequence of the ejects not being a uniform sphere, but instead a ring or jets. So, if the ejecta were concentrated in a disk inclined at an angle of 40 degrees to us, that might account for what we are seeing, if I've read P-G correctly.
Furthermore, the red-ward peak of the emission line saddle is slightly stronger than the violet side. The geometry of all this is I'm sure telling us something significant, and I'd be really interested in what Steve had to say about it.
However, in terms of measuring the Doppler shift of the P Cygni profile - which is what we are debating - the is a simple question. What do you measure - the distance between the centre of the absorption line and the blue-ward or red-ward peak of the saddle, or he barycenter of the entire emission line?
I guess what I'm saying is, from everything I've read, the simple model for understanding Doppler shifted P Cygni lines - a uniform expanding sphere of gas, with emission lines from the radially-expanding component and (blue-shifted) absorption lines from the component coming directly towards us - pretty quickly breaks down in the case of novae, where the ejects are more complex.
I'd be keen to help out with whatever I can as far as Steve is concerned. Particularly once my L200 arrives.
KISS....
I followed the details in "Spectroscopy - key to the stars", Keith Robinson.
Page 121
"...simply from the difference in wavelength between the center of the emission line and that of the absorption line. Simply plug in this wavelength difference into the simple Doppler effect formula to get the wind velocity"
I was using John's BASS Project which calculates the max and min flux value wavelengths......
I should re-run the profiles through Vspec for comparison.
Makes sense. Sorry, Ken, I wasn't trying to be difficult :-). My head is spinning from all the stuff I've been reading about this. Just trying to account for why there might be different measurements of velocity between you and Malc.
I've just been reading Steve Shore's "Spectroscopy of Novae - a users manual". He talks about changes in he ejecta velocity, but also changes in what parts of the ejecta become visible owing to changes in the optical thickness of the ejecta with different phases ... I can't pretend I understand all he's saying!
But I liked the bit where he said to take a look at YouTube videos of slo-motion explosions of Hydrogen bombs to get a general idea :-)
However, in terms of measuring the Doppler shift of the P Cygni profile - which is what we are debating - the is a simple question. What do you measure - the distance between the centre of the absorption line and the blue-ward or red-ward peak of the saddle, or he barycenter of the entire emission line?
I'm not sure whether it is best to measure the fitted centre of the emission line or the text book wavelength. I'd be tempted to use the latter, and that is what I have used, because I don't really understand the cause of the asymmetry of the line profiles.
I believe (could well be wrong) that the end of the blue wing of the absorption gives the maximum velocity, which should represent the material that is heading directly towards us and hence the ejecta velocity.
Due to my general lack of knowledge of the details I'm treating all of my measurements with a high level of uncertainty.
I've just been reading Steve Shore's "Spectroscopy of Novae - a users manual". He talks about changes in he ejecta velocity, but also changes in what parts of the ejecta become visible owing to changes in the optical thickness of the ejecta with different phases ... I can't pretend I understand all he's saying!
You are definitely not alone there Jonathan. I find some of Steve's write ups assume a little more prior knowledge than I currently have at my disposal.
By the way, I see your spectra have made it into the ARAS database, nice work.
Keith Robinson's "Spectroscopy -key to the stars" has a good chapter "Glowing Vortices-Accretion Disks" - p105>
Goes some way to explain the peaks and blue/red wings.......
Clear through until about 3:30am....
Screwed up the camera settings and ended up with 2 x 2 binning! This reduced the resolution to around R=1600.
The P Cygni at Ha and Hb give around 1500-1600 Km/s.
No dramatic changes that I can see......
Clear through until about 3:30am....
Screwed up the camera settings and ended up with 2 x 2 binning! This reduced the resolution to around R=1600.
The P Cygni at Ha and Hb give around 1500-1600 Km/s.
No dramatic changes that I can see......
Very nice job Ken! FWIW, here's my low-res spectrum from last night.
I've had a light-globe moment with my spectra, particularly the relative intensity of Ha & Hb showing in my graphs of V1369 Cen. I shoot only in jpeg and the method I use to create the graphs is to grayscale the bar spectrum and save as FIT files using Registax. The red of Ha, no matter how intense, is never going to be 'less grey' than the cyan of Hb so the graph simply won't display the relative intensity of Ha that shows in the line or bar spectrum.
The answer would be to shoot in RAW and do whatever it takes to transfer the luminosity rather than shade to a bar spectrum and hence to the graph. But unfortunately that's a step I'm unwilling to take. Aside from the fact that my poor old computer has convulsions just dealing with full-size jpegs, I'm quite happy with my level of commitment equipment & time-wise to spectroscopy. I have lots of other keen interests in astronomy (comets, comet search, nova search, RNe etc) - I'm not retired, have a very busy life and there's just no time left!
So you guys might just have to put up with my wonky spectra!
