Spectroscopy of Long Period Variable stars

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James Ley
Posts: 70
Joined: Tue Jan 23, 2018 6:57 pm

Spectroscopy of Long Period Variable stars

Post by James Ley »

Long Period Variable stars are classified as Mira, Semiregular or Irregular types.
https://www.aavso.org/media/jaavso/2840.pdf
Often the arbitrary classes do not reflect physical differences (between RGB or AGB stars, fundamental or overtone pulsators, carbon rich or oxygen rich, for example).
Photometry on thousands of stars! in the LMC has shown that brightness increases with the period length. Mira variables often have the longest periods and greatest luminosities (by definition) but often their position in the period/luminosity plane overlap with other variable types. Mira variables pulsate in the fundamental mode. Other types may pulsate in the fundamental mode and/or first overtone mode.
http://iopscience.iop.org/article/10.10 ... /2/167/pdf
Red Giant Branch stars may also pulsate in the fundamental mode with long periods similar to Mira variables
https://arxiv.org/pdf/1706.09166.pdf

I'm not sure that all the details are worked out, but I think that cool stars with a sufficient hydrogen ionization zone can pulsate in the fundamental mode via the kappa mechanism.
https://en.wikipedia.org/wiki/Kappa_mechanism
One result of this pulsation are shock waves that generate Balmer emission lines that change with the pulsation phase.
Note this survey of Mira variables that suggests that a Balmer increment (H-delta>H-gamma) is found for stars M4 and later.
https://arxiv.org/pdf/1708.04703.pdf

My intent is to observe some of these variable stars with my Alpy 600. Any comments or criticisms are welcome.
I have found the AAVSO to be a great place to find targets
https://www.aavso.org/sites/default/fil ... in2018.pdf

First up is R Leonis (for all but the first spectra I used Eta Leo as the reference)
Mira, period 309.95 days.
It looks like my observation coincided with a relatively brighter maximum
R Leo historical.png
R Leo historical.png (73.85 KiB) Viewed 7165 times
Here is recent AAVSO data
R Leo recent light curve.png
R Leo recent light curve.png (19.03 KiB) Viewed 7172 times
R Leo 03042018.png
R Leo 03042018.png (13.27 KiB) Viewed 7172 times
Last edited by James Ley on Mon Apr 30, 2018 2:50 am, edited 1 time in total.
Shelyak Alpy 600 (spectroscope, guiding module and calibration module) | GSO 8" f/4 | Orion Atlas Pro | ZWO ASI178MM-Cool (mono) | ZWO ASI290 Mini (mono)
"think like a photon" -- Steve Shore
James Ley
Posts: 70
Joined: Tue Jan 23, 2018 6:57 pm

Re: Spectroscopy of Long Period Variable stars

Post by James Ley »

Two weeks later, here is the standard Eta Leo (reference in blue is A0I) 03/17/2018
Eta Leo 03172018.png
Eta Leo 03172018.png (17.98 KiB) Viewed 7172 times
Here is R Leo
R Leo 03172018.png
R Leo 03172018.png (15.85 KiB) Viewed 7172 times
Shelyak Alpy 600 (spectroscope, guiding module and calibration module) | GSO 8" f/4 | Orion Atlas Pro | ZWO ASI178MM-Cool (mono) | ZWO ASI290 Mini (mono)
"think like a photon" -- Steve Shore
James Ley
Posts: 70
Joined: Tue Jan 23, 2018 6:57 pm

Re: Spectroscopy of Long Period Variable stars

Post by James Ley »

A week later 03/24/2018
Eta Leo reference
Eta Leo 03242018.png
Eta Leo 03242018.png (17.88 KiB) Viewed 7171 times
and R Leo
R Leo 03242018.png
R Leo 03242018.png (15.74 KiB) Viewed 7171 times
Shelyak Alpy 600 (spectroscope, guiding module and calibration module) | GSO 8" f/4 | Orion Atlas Pro | ZWO ASI178MM-Cool (mono) | ZWO ASI290 Mini (mono)
"think like a photon" -- Steve Shore
James Ley
Posts: 70
Joined: Tue Jan 23, 2018 6:57 pm

Re: Spectroscopy of Long Period Variable stars

Post by James Ley »

on 03/26/2018
Eta Leo reference
Eta Leo 03262018.png
Eta Leo 03262018.png (17.87 KiB) Viewed 7171 times
and R Leo
R Leo 03262018.png
R Leo 03262018.png (16.69 KiB) Viewed 7171 times
Shelyak Alpy 600 (spectroscope, guiding module and calibration module) | GSO 8" f/4 | Orion Atlas Pro | ZWO ASI178MM-Cool (mono) | ZWO ASI290 Mini (mono)
"think like a photon" -- Steve Shore
James Ley
Posts: 70
Joined: Tue Jan 23, 2018 6:57 pm

Re: Spectroscopy of Long Period Variable stars

Post by James Ley »

On 03/31/2018
Eta Leo reference
Eta Leo 03312018.png
Eta Leo 03312018.png (17.7 KiB) Viewed 7171 times
R Leo
R Leo 03312018.png
R Leo 03312018.png (16.26 KiB) Viewed 7171 times
Shelyak Alpy 600 (spectroscope, guiding module and calibration module) | GSO 8" f/4 | Orion Atlas Pro | ZWO ASI178MM-Cool (mono) | ZWO ASI290 Mini (mono)
"think like a photon" -- Steve Shore
James Ley
Posts: 70
Joined: Tue Jan 23, 2018 6:57 pm

Re: Spectroscopy of Long Period Variable stars

Post by James Ley »

04/07/2018 was a little after maximum, when Balmer emission is likely at maximum, but the results were a little surprising, so any opinions are welcome.
Here is the reference, Eta Leo, 20 images of 12 s, the same as all the others
Eta Leo 04072018.png
Eta Leo 04072018.png (18.12 KiB) Viewed 7170 times
It looks very similar to me. In ISIS the rms for the calibration was often between 0.15 and 0.2.
Here is R Leo
R Leo 04072018.png
R Leo 04072018.png (17.21 KiB) Viewed 7170 times
Not only have the Balmer intensities increased and higher order Balmer lines are visible, the blue continuum seems to have increase.
Here is an overlay with the spectrum of 03/17/2018
R Leo 04072018 overlay.png
R Leo 04072018 overlay.png (19.46 KiB) Viewed 7170 times
and here is a zoom on the Balmer emissions
R Leo 04072018 overlay zoom.png
R Leo 04072018 overlay zoom.png (16.5 KiB) Viewed 7170 times
Notice also the blue shift in the Balmer emissions on 04/07/2018 (black) compared to 03/17/20 (blue).
I could rationalize this as the earlier redshifted Balmer emission as being material falling back towards the star, away from us, that is ionized by the precursor (ahead of the shock front). When the shock passes, the material is then moving towards us and is blueshifted. Does that explanation sound reasonable? Is it possible that I can see that with the Alpy 600?

Is the enhanced blue continuum real or an artifact?

Thanks for any opinions.
Shelyak Alpy 600 (spectroscope, guiding module and calibration module) | GSO 8" f/4 | Orion Atlas Pro | ZWO ASI178MM-Cool (mono) | ZWO ASI290 Mini (mono)
"think like a photon" -- Steve Shore
James Ley
Posts: 70
Joined: Tue Jan 23, 2018 6:57 pm

Re: Spectroscopy of Long Period Variable stars

Post by James Ley »

Two days later...
Eta Leo reference
Eta Leo 04092018.png
Eta Leo 04092018.png (17.79 KiB) Viewed 7166 times
and R Leo
R Leo 04092018.png
R Leo 04092018.png (16.64 KiB) Viewed 7166 times
The increase in the UV part of the continuum seems much less.
R Leo 04092018 overlay zoom.png
R Leo 04092018 overlay zoom.png (15.64 KiB) Viewed 7166 times
Attachments
R Leo 04092018 overlay.png
R Leo 04092018 overlay.png (18.73 KiB) Viewed 7166 times
Shelyak Alpy 600 (spectroscope, guiding module and calibration module) | GSO 8" f/4 | Orion Atlas Pro | ZWO ASI178MM-Cool (mono) | ZWO ASI290 Mini (mono)
"think like a photon" -- Steve Shore
James Ley
Posts: 70
Joined: Tue Jan 23, 2018 6:57 pm

Re: Spectroscopy of Long Period Variable stars

Post by James Ley »

5 days later, slowly decreasing
Eta Leo
Eta Leo 04142018.png
Eta Leo 04142018.png (17.83 KiB) Viewed 7166 times
R Leo
R Leo 04142018.png
R Leo 04142018.png (16.45 KiB) Viewed 7166 times
A week after this.
Eta Leo
Eta Leo 04212018.png
Eta Leo 04212018.png (18.21 KiB) Viewed 7166 times
and R Leo
R Leo 04212018.png
R Leo 04212018.png (16.64 KiB) Viewed 7166 times
Shelyak Alpy 600 (spectroscope, guiding module and calibration module) | GSO 8" f/4 | Orion Atlas Pro | ZWO ASI178MM-Cool (mono) | ZWO ASI290 Mini (mono)
"think like a photon" -- Steve Shore
James Ley
Posts: 70
Joined: Tue Jan 23, 2018 6:57 pm

Re: Spectroscopy of Long Period Variable stars

Post by James Ley »

And finally, last night under a bright moon.
Eta Leo
Eta Leo 04292018.png
Eta Leo 04292018.png (18.21 KiB) Viewed 7166 times
and R Leo, slowly dimishing
R Leo 04292018 overlay zoom.png
R Leo 04292018 overlay zoom.png (16.08 KiB) Viewed 7166 times
R Leo 04292018 overlay.png
R Leo 04292018 overlay.png (17.84 KiB) Viewed 7166 times
Shelyak Alpy 600 (spectroscope, guiding module and calibration module) | GSO 8" f/4 | Orion Atlas Pro | ZWO ASI178MM-Cool (mono) | ZWO ASI290 Mini (mono)
"think like a photon" -- Steve Shore
Francois Teyssier
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Joined: Fri Sep 23, 2011 1:01 pm
Location: Rouen
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Re: Spectroscopy of Long Period Variable stars

Post by Francois Teyssier »

Great!
It will be interesting to see the graph EW = f(JD)
All the best,
François
Last edited by Francois Teyssier on Mon Apr 30, 2018 10:10 am, edited 1 time in total.
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