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red star spectra [AN article]

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#1 nytecam

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Posted 30 September 2012 - 01:08 PM

Despite last night's full moon I managed to recorded [below] some lo-res spectra of red stars renowned for their red appearance in the eyepiece as listed in the September Astronomy Now article. I've added some nearby bright stars like Vega, Deneb and Altair as these show strong hydrogen Balmer lines [marked] and P Cygni with emission lines of H-alpha, H-beta and helium in yellow. Normally colour is a disadvantage for spectra as it tends to mask the absorption lines but it worked ok. The very narrow yellow band, at the transition between red and green, was also helpful in aligning the spectra. I used a 30cm SCT+Rainbow grating before a SX Lodestar-C camera in exposures from ~0.1s - 30s.

Perhaps the most remarkable feature of these spectra is the near-IR radiation recorded to the right via the unfiltered Lodestar-C camera - all this radiation, covering nearly half the whole spectrum, is invisible to the eye and that probably includes H-alpha too.

The red stars themselves are virtually devoid of any 'blue light' and this contributes to their red appearance. As an experiment the 'box' to the exteme left in each spectrum is the averaged 'colour' from H-gamma in blue to H-alpha in red for each star - the warm tones mirror the absence of blue in the spectrum. The reddest star for this series is T Lyrae near Vega. Just one star from the article eg S Cep @ Dec+78 proved too far north for my scope eg the camera colliding with the scope forks. The purity of colour can be beautiful. Hope these spectra are of interest. :grin:

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#2 John59

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Posted 30 September 2012 - 08:09 PM

This is very interesting. I wonder if these were taken over a period of a year if any change would be detected.

#3 nytecam

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Posted 01 October 2012 - 04:33 AM

This is very interesting. I wonder if these were taken over a period of a year if any change would be detected.

'Yes' must be the answer but even for known variable stars the spectral changes can be very subtle - Beta Lyrae is a classic emission-line binary where the line intensity changes with the binary period. This has been known, if not fully understood, for a century but there's little or no pro work on it nowerdays [they like to work at the edge of the universe with the biggest scopes available whilst perfect 1.5m scopes worldwide obscenely gather dust :shocked:] - so many stars, so little time and too few spectroscopists :(

#4 old_frankland

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Posted 01 October 2012 - 10:34 AM

This is very interesting. I wonder if these were taken over a period of a year if any change would be detected.

'Yes' must be the answer but even for known variable stars the spectral changes can be very subtle - Beta Lyrae is a classic emission-line binary where the line intensity changes with the binary period. This has been known, if not fully understood, for a century but there's little or no pro work on it nowerdays [they like to work at the edge of the universe with the biggest scopes available whilst perfect 1.5m scopes worldwide obscenely gather dust :shocked:] - so many stars, so little time and too few spectroscopists :(


The lack of interest in stellar spectroscopy with the 1.5m scopes you refer to probably has more to do with the competition for research funding. The more spectacular, news worthy research tends to get the lion's share of funding and telescope time while those interested in more basic, or, less spectacular research get only scraps in terms of funding. I see it here at Lawrence Livermore National Lab all the time.

#5 jgraham

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Posted 01 October 2012 - 02:13 PM

I think nearly all research labs are feeling the pinch. I've been in contract research for 34 years and I've never seen funding levels this low and so many veteran researchers nervous about their immediate future. The specific case of spectroscopy is unfortunate as the equipment overhead is modest and this has always been such a fertile area.

#6 nerraw

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Posted 01 October 2012 - 02:31 PM

You have captured some beautiful and interesting spectra
Nytecam. Thanks for your efforts.
Warren,an old novice

#7 nytecam

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Posted 02 October 2012 - 09:46 AM

The lack of interest in stellar spectroscopy with the 1.5m scopes you refer to probably has more to do with the competition for research funding. The more spectacular, news worthy research tends to get the lion's share of funding and telescope time while those interested in more basic, or, less spectacular research get only scraps in terms of funding. I see it here at Lawrence Livermore National Lab all the time.

Agreed Jim - I believe some advanced amateurs have tried to use idle 1m-1.5m scopes in La Palma Spain Canaries and Siding Springs Oz observatories but access denied :(

#8 nytecam

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Posted 03 October 2012 - 02:52 AM

Here's spectrum of Arcturus and gamma CrB - latter showing extent of cam sensitivity to <383nm in blue/violet for this hot Sirius-like star and also weak 2nd order spectrum 'attached' to its NIR spectrum to right. Its B9 spectrum is whisker from AO = Vega/Sirius etc. mu Cep added for comparison. :grin:

Intended targets that evening were nearby faint red vars in R,TT and T CrB but cloud ended session abruptly :(

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#9 drollere

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Posted 13 October 2012 - 02:05 AM

Beta Lyrae is a classic emission-line binary where the line intensity changes with the binary period. This has been known, if not fully understood, for a century but there's little or no pro work on it nowerdays.


i think if you go to the SAO/NASA archive web site and query papers with "beta lyrae" you'll be pleasantly surprised. my favorite recent paper reported images of the system, including accretion disk, made with speckle interferometry.

http://adsabs.harvar...onnect?qsearch="beta+lyrae"&version=1

The lack of interest in stellar spectroscopy with the 1.5m scopes you refer to probably has more to do with the competition for research funding. The more spectacular, news worthy research tends to get the lion's share of funding and telescope time while those interested in more basic, or, less spectacular research get only scraps in terms of funding. I see it here at Lawrence Livermore National Lab all the time.


a more prosaic reason may be that spectroscopy is better done in space -- no atmospheric absorption overlay, better infrared and UV coverage -- compounded with the development of methods to digitalize and automate spectral analysis and classification. GAIA will harvest photometric spectral types of roughly a billion stars, and the oldest (lowest "metal" content) population II star was recently discovered in an automated spectral survey.

http://www.hindawi.c...aa/2010/781421/

in addition, quite a lot of spectroscopy has been focused recently on subsolar mass main sequence stars and emerging protostars, where infrared techniques are critical. the stellar physics that produce spectral variety in earlier main sequence stars has been pretty well worked out so it would be hard to get funded for plowing that field. star formation processes and brown dwarf population characteristics are not well understood, yet have great bearing on fundamental topics such as the initial mass function.

#10 nytecam

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Posted 15 October 2012 - 01:54 PM

Hi Bruce - thanks for the interesting info - you're clearly a man-in-the-know and whilst laudable that cutting-edge research is possible via the latest pro telescopes - it's a shame massive telescopes, from an amateur viewpoint and adequate for obtaining initial SN classification spectra for example, just gather dust in observatories around the world :o






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