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CH Cyg 2018

PostPosted: Sat Feb 10, 2018 11:40 am
by Francois Teyssier
New season and still surprizing ...

chcyg_20180210_191_FMTeyssier.png


H beta:
Very deep central narrow absorption (under the continuum)
and a broad and deep absorption at -350 km/s (max velocity = -500 km/s)
chcyg_20180210_191_Hb.png
chcyg_20180210_191_Hb.png (16.75 KiB) Viewed 3182 times


Helium lines (He I) have vanished
chcyg_20180210_191_NaID.png
chcyg_20180210_191_NaID.png (14.73 KiB) Viewed 3180 times

(comparison with the last spectrum in the database, obtained by Joan)

chcyg_20180210_191_6300.png
chcyg_20180210_191_6300.png (17.48 KiB) Viewed 3180 times


I recall that several professionnal teams are working on our spectra.
Coverage at the best cadency as possible is requested.

François Teyssier

Re: CH Cyg 2018

PostPosted: Sun May 27, 2018 8:36 pm
by Peter Somogyi
Hello,

Let me report here an experiment I've made.
Last year I've shot 2 x 10 minute exposures for the CaII region (unsent due to low snr and faint blue), that I've repeated yesterday (6 x 10 min, lately found too easy), R~5200 in both cases (35 micron slit, ATIK 428 EXm).
Now using the last year's experiment as a baseline, the emission velocities of that time look as if they were negated:
overall_chcyg_pso_20170527_vs_20180526.png
last year vs yesterday

To compare velocities of more Balmer in overall (borrowing a recent H-beta from Francois):
compare_ha_hzeta_caII_hb.png
compare various Balmer and CaII velocities

I will be curious whether we see this -500 km/sec at H-zeta in the database soon (in 2015 we saw -1500 km/s, last year was mostly silent). At least, the lower Balmer lines are now a matter of suspect consisting of both absorptions + emissions.
For now this was just an experiment, documenting the result.

Peter

Re: CH Cyg 2018

PostPosted: Tue Jul 03, 2018 5:20 pm
by Francois Teyssier
CH Cyg is rapidely fading (see:http://spectro-aras.com/forum/viewtopic.php?f=12&t=2055)
(V = 6.6 to 7.5 in a few days)
CHCyg.PNG
CHCyg.PNG (8.93 KiB) Viewed 2850 times

AAVSO V band
There's now an AAVSO alert upon the request of Margarita Karovska
https://www.aavso.org/aavso-alert-notice-639
We have several spectra in the database during the fading : http://www.astrosurf.com/aras/Aras_DataBase/Symbiotics/CHCyg.htm

High cadency coverage of this event is strongly recommended
Low resolution spectra (R =500) welcome if the atmospheric response is good. There are strong variations of the continuum.

Significant changes of the emission spectrum
For instance [OIII] ranges
chcyg_20180620_143_tlester.png
chcyg_20180620_143_tlester.png (32.17 KiB) Viewed 2846 times




François Teyssier

Re: CH Cyg 2018

PostPosted: Thu Jul 05, 2018 5:09 pm
by Francois Teyssier
Information from Augustin Skopal:

This is an anomalous minimum.
It looks like an eclipse effect, but its time position does not agree
with any ephemeris for eclipse timing in the long-period binary system
or in the short-period triple star system (see e.g. IBVS 4157 (1995)).
Behaviour of colours and spectroscopic observations prior to, throughout
and after the minimum should identify possible nature of the current minimum.


p.s. when the continuum decreases by (to say) a factor of 3, then
also strength of emission lines will decrease with the same factor.
Therefore, comparison of the spectra with different levels of the
continuum, but scaled to the same value, will not show real changes
in line fluxes.

Re: CH Cyg 2018

PostPosted: Thu Jul 05, 2018 7:38 pm
by Robin Leadbeater
Francois Teyssier wrote:Information from Augustin Skopal:

p.s. when the continuum decreases by (to say) a factor of 3, then
also strength of emission lines will decrease with the same factor.
Therefore, comparison of the spectra with different levels of the
continuum, but scaled to the same value, will not show real changes
in line fluxes.[/i]


The wide spectral coverage of the LISA/ALPY spectra could be useful here. These can be combined with the photometric data to produce a flux calibrated continuum level. This can then be applied to the high resolution eg LHIRES spectra covering any specific region to produce high resolution flux calibrated spectra.

Robin

Re: CH Cyg 2018

PostPosted: Sat Jul 07, 2018 11:09 am
by Olivier GARDE
My last spectrum of CH Cyg taken with eShel II

Image

Order #34 (H Alpha)
Image

[OIII] range
Image

And Balmer Lines
Image

Re: CH Cyg 2018

PostPosted: Mon Jul 09, 2018 5:16 pm
by Francois Teyssier
An update during the decline
It looks that the luminosity is stable (with flickering) at about V = 7.5 since the begining of July
CHCyg.PNG
CHCyg.PNG (9.17 KiB) Viewed 2677 times


Evolution a few lines from Echelle spectra obtained by Tim Lester, Joan Guarro and François Teyssier

H Beta
chcyg_2018_Ha.png
chcyg_2018_Ha.png (38.13 KiB) Viewed 2677 times

[OIII] range: incresing [OIII], He I which was in absorption, now in emission
chcyg_2018_oiii.png
chcyg_2018_oiii.png (47.63 KiB) Viewed 2677 times

He I, complex behavior
chcyg_2018_HeI.png
chcyg_2018_HeI.png (38.16 KiB) Viewed 2677 times



As usual, [OI] almost stable (unless its intensity)
chcyg_2018_OI.png
chcyg_2018_OI.png (47.62 KiB) Viewed 2677 times



Of course, we continue the monitoring of the event

François Teyssier

Re: CH Cyg 2018

PostPosted: Sat Jul 14, 2018 3:28 pm
by Peter Somogyi
As per last nights result, CH Cyg is coming back:
chcyg_pso_0526_0713.png
chcyg_pso_0526_0713.png (78.17 KiB) Viewed 2610 times

I've been using the wide slit (2-star method) with HD 191026 for my last 2 observations.
Here is the way I've been extracting absolute flux:
2018-05-26.929: used asdb_20180521_056 (JMO) + aavso around 05-26 (a bit speculative due to the 5 days shift)
2018-06-30.883: used asdb_chcyg_20180630_958 (VMA) + aavso
2018-07-07.865: wide slit + HD 191026 (notice the accidental match with 2018-06-30.883 !!)
2018-07-13.867: wide slit + HD 191026
As I notice, the M-ish features / the tiny emissions (when subtracting M7III they look so) flux remained constant.

Happy observing!
Peter

Re: CH Cyg 2018

PostPosted: Wed Jul 18, 2018 8:31 pm
by Peter Somogyi
Got the possibility to shoot CH Cyg over the whole weekend (all absolute flux), presenting now the outcome:
chcyg_pso_0707_0715.png


I did check several times the flux level of 07.14 (really lower than 07.13 and 07.15), but all the 3 wide slit fluxes show very similar result.
The same continuum level on 07.13 and 07.15 is surprising (whilst 07.14 is really an exception).
Additionally, the H8 profile has changed considerably within 1 day (confirms H9 and maybe H7), compared to a so far very much constant double-peaked absorptions shape observed since 2018.05.26.
I will be curious what has changed in the visual.

- Peter

Re: CH Cyg 2018

PostPosted: Wed Jul 18, 2018 10:12 pm
by Francois Teyssier
Thta's great, Peter

will be curious what has changed in the visual.

As usual, almost nothing :)
H beta
chcyg.png
chcyg.png (37.57 KiB) Viewed 2484 times


CHCyg_V.PNG
CHCyg_V.PNG (6.56 KiB) Viewed 2484 times

The luminosity looked to recover until July, 15th, but declined afterwards
Excellent coverage of the event.
To continue!
François
(Currently on the target)
chcyg_.PNG
chcyg_.PNG (42.09 KiB) Viewed 2484 times