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Hi,

Is the CH Cyg on the last njght.

Cheers, Joan.

Excel.lent, Joan, as always...

Here is a comparison of two low resolution spectra of CH Cyg. The first one, taken in July 2016; and the last one, only two nights ago. The difference is amazing... Both spectra taken with the DADOS (R=800) and the newton 8".

Also, I upload the photometric curve taken from the AAVSO database. I expected that CH Cyg would be brighter, but not. The only important difference I see is that the star seems brighter in the Johnson-B band, but in Johnson-V band the star has weakened. Maybe the red component has faded and, on the other hand, the hot component and the surrounding nebula are more excited?
Greetings
Fran

A full (almost!) commented spectrum of CH Cygni, with more than 100 identified lines (from various published values)
with PlotSpectra (Tim Lester)

Examples: Range 4800-5000 and 6000-7200
Note [SII] doublet




Other Ranges: http://www.astronomie-amateur.fr/feuill ... html#Lines

François

Here is a belated CH Cyg spectrum I took with my LISA spectroscope with the CDK17 F/6.8 reflector working at F/6.8 on 29Apr17:

Very strong H-Alpha emission is seen (almost 8x the intensity of the continuum from 3800-7400A) and at least two He lines showing at 5875.6 and 6678.2 angstroms respectively.

James

That's good, James!
You can look at [O III] and [O I]

François

To: François,

RE:"You can look at [O III] and [O I]"

I re-plotted the 29Apr17 spectrum for CH Cyg using Tim Lester's PlotSpectra 1.4.1.0:


Its hard to find the OIII and OI line IDs in Bass 1.96, so I use Plotspectra for these.

Are the SII(4068.6A), FeII(5317A), FeII(4416A), HeI(4921.93), HeI(5875.65A), and HeI(6678.15A) lines also good?

I wonder if that "absorption" feature around 4222.65A is real?

James

James,
The latest V1.9.7 release of BASS Project has enhanced labelling and extended element listing.....
A significant absorption at 4226.73A is shown in Walker's atlas as a Ca I feature.......

Hello James,

Ca II 3969 should be replaced by H epsilon 3970
If you have Balmer lines in emission, *all* the lines must appear


[S II] is a possible identification
You can check with Joan's spectra.
If it is [S II], this is a doublet and at higher resolution, the two lines (4068 and 4076)must appear

Ca I 4226 can be strong enough in a ~ K4III constinuum to appear at that resolution

He I lines are correct

About Fe lines, it is difficult at that resolution to be sure. Some features of the TiO band can mimic a line.
I suggest you get a M5III Spectrum and then compare CH Cyg and the reference M5III pseudo-continuum. The *real* emission will clearly appear (or not).



All the best,

François






.

From observations in August, both at low (Woody Sims and James Foster) and high resolution (Joan Guarro, Tim Lester, François Teyssier), strong absorptions in H beta and lower Balmer lines appear clearly with max velocities from -2000 to -3000 km/s (and perhaps more)

H beta profile from echelle spectra François

Spectrum of CH Cygni taken the 12.8/09/2017 at R = 49 000 (VHIRES-MO spectrograph):



Christian