CH Cyg 2018
-
- Posts: 1521
- Joined: Fri Sep 23, 2011 1:01 pm
- Location: Rouen
- Contact:
CH Cyg 2018
New season and still surprizing ...
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) Helium lines (He I) have vanished (comparison with the last spectrum in the database, obtained by Joan)
I recall that several professionnal teams are working on our spectra.
Coverage at the best cadency as possible is requested.
François Teyssier
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) Helium lines (He I) have vanished (comparison with the last spectrum in the database, obtained by Joan)
I recall that several professionnal teams are working on our spectra.
Coverage at the best cadency as possible is requested.
François Teyssier
François Teyssier
http://www.astronomie-amateur.fr
http://www.astronomie-amateur.fr
-
- Posts: 420
- Joined: Sun Jul 13, 2014 8:56 am
Re: CH Cyg 2018
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: To compare velocities of more Balmer in overall (borrowing a recent H-beta from Francois): 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
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: To compare velocities of more Balmer in overall (borrowing a recent H-beta from Francois): 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
-
- Posts: 1521
- Joined: Fri Sep 23, 2011 1:01 pm
- Location: Rouen
- Contact:
Re: CH Cyg 2018
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) 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_Data ... /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
François Teyssier
(V = 6.6 to 7.5 in a few days) 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_Data ... /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
François Teyssier
François Teyssier
http://www.astronomie-amateur.fr
http://www.astronomie-amateur.fr
-
- Posts: 1521
- Joined: Fri Sep 23, 2011 1:01 pm
- Location: Rouen
- Contact:
Re: CH Cyg 2018
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.
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.
François Teyssier
http://www.astronomie-amateur.fr
http://www.astronomie-amateur.fr
-
- Posts: 1933
- Joined: Mon Sep 26, 2011 4:41 pm
- Contact:
Re: CH Cyg 2018
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.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]
Robin
LHIRES III #29 ATIK314 ALPY 600/200 ATIK428 Star Analyser 100/200 C11 EQ6
http://www.threehillsobservatory.co.uk
http://www.threehillsobservatory.co.uk
-
- Posts: 1246
- Joined: Thu Sep 29, 2011 6:35 am
- Location: Rhône Alpes FRANCE
- Contact:
Re: CH Cyg 2018
My last spectrum of CH Cyg taken with eShel II
Order #34 (H Alpha)
[OIII] range
And Balmer Lines
Order #34 (H Alpha)
[OIII] range
And Balmer Lines
LHIRES III #5, LISA, e-Shel, C14, RC400 Astrosib, AP1600
http://o.garde.free.fr/astro/Spectro1/Bienvenue.html
http://o.garde.free.fr/astro/Spectro1/Bienvenue.html
-
- Posts: 1521
- Joined: Fri Sep 23, 2011 1:01 pm
- Location: Rouen
- Contact:
Re: CH Cyg 2018
An update during the decline
It looks that the luminosity is stable (with flickering) at about V = 7.5 since the begining of July Evolution a few lines from Echelle spectra obtained by Tim Lester, Joan Guarro and François Teyssier
H Beta [OIII] range: incresing [OIII], He I which was in absorption, now in emission He I, complex behavior
As usual, [OI] almost stable (unless its intensity)
Of course, we continue the monitoring of the event
François Teyssier
It looks that the luminosity is stable (with flickering) at about V = 7.5 since the begining of July Evolution a few lines from Echelle spectra obtained by Tim Lester, Joan Guarro and François Teyssier
H Beta [OIII] range: incresing [OIII], He I which was in absorption, now in emission He I, complex behavior
As usual, [OI] almost stable (unless its intensity)
Of course, we continue the monitoring of the event
François Teyssier
François Teyssier
http://www.astronomie-amateur.fr
http://www.astronomie-amateur.fr
-
- Posts: 420
- Joined: Sun Jul 13, 2014 8:56 am
Re: CH Cyg 2018
As per last nights result, CH Cyg is coming back:
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
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
-
- Posts: 420
- Joined: Sun Jul 13, 2014 8:56 am
Re: CH Cyg 2018
Got the possibility to shoot CH Cyg over the whole weekend (all absolute flux), presenting now the outcome:
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
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
-
- Posts: 1521
- Joined: Fri Sep 23, 2011 1:01 pm
- Location: Rouen
- Contact:
Re: CH Cyg 2018
Thta's great, Peter
H beta The luminosity looked to recover until July, 15th, but declined afterwards
Excellent coverage of the event.
To continue!
François
(Currently on the target)
As usual, almost nothingwill be curious what has changed in the visual.
H beta The luminosity looked to recover until July, 15th, but declined afterwards
Excellent coverage of the event.
To continue!
François
(Currently on the target)
François Teyssier
http://www.astronomie-amateur.fr
http://www.astronomie-amateur.fr