Transcient in Cygnus

Re: Transcient in Cygnus

Postby David Boyd » Mon Jul 29, 2019 7:49 am

Thanks Robin. It's not often we get a dwarf nova bright enough to play this game with our sort of equipment.
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Re: Transcient in Cygnus

Postby Paolo Berardi » Tue Jul 30, 2019 4:35 pm

Thank you Robin! I agree with David... the dwarf nova in Cygnus is a rare beast!

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Re: Transcient in Cygnus

Postby Vincent Lecocq » Tue Jul 30, 2019 8:11 pm

nice results !

and here is my contribution to TCP J21040470+4631129:

Vincent
Attachments
Figure_1.png
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Re: Transcient in Cygnus

Postby Robin Leadbeater » Mon Aug 05, 2019 12:32 pm

A sudden 1 mag drop in brightness to mag 13
https://www.cloudynights.com/topic/6684 ... ?p=9551215

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Re: Transcient in Cygnus

Postby Robin Leadbeater » Thu Aug 15, 2019 10:54 am

Two bounces in the light curve now
https://www.cloudynights.com/topic/6684 ... try9573481

Does anything change in the spectrum during these dimmings ?

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Re: Transcient in Cygnus

Postby David Boyd » Fri Aug 16, 2019 10:08 pm

Hi Robin,

I can't comment on the dimmings but although superficially similar there are subtle differences in the spectra at similar magnitudes during the main outburst and in the second rebrightening. The spectrum on 15 August near the top of the second rebrightening at V=12.3 is proportionally stronger in the blue than the spectrum on 31 July, close to the end of the main outburst at V=11.7. This is also indicated by a bluer value of (B-V) at the same V magnitude during the rebrightening. The Balmer emission lines are up to 50% wider (FWHM) during the rebrightening than in the main outburst.

David
tcpj21040470+4631129_20190731_906_D.Boyd.png
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Re: Transcient in Cygnus

Postby Robin Leadbeater » Wed Aug 28, 2019 9:07 am

Now undergoing a third rebrightening and showing superhumps again !
-----------------------------------------------------------------------------------------------------------------------------------
-----Original Message-----
From: Taichi Kato
Sent: Wednesday, August 28, 2019 4:54 AM

Subject: [vsnet-alert 23511] TCP J21040470+4631129: further brightening ofthe third rebrightening!

TCP J21040470+4631129: further brightening of the third rebrightening!

> According to observations on 26th by Stephen M. Brincat, Charles
> Galdies and Vihorlat Observatory team, TCPJ21040470+4631129 is now
> ~11.4 mag, brighter than the last 2 rebrightenings which was ~12 mag
> at peak.

And it is now developing superhumps! This is probably
the first case in which a new superoutburst is triggered
during a series of rebrightenings!
Measurement of superhump periods in this state will be
extremely important.
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Re: Transcient in Cygnus

Postby Francois Teyssier » Tue Sep 24, 2019 4:30 pm

New ATel about the very peculier behaviour of this dwarf nova partially based on spectra obtained by David Boyd and Woody Sims during rebrightnings


ATEL #13122 ATEL #13122

Title: The disappearance and reappearance of optical emission lines
and the drop in a Swift/XRT count rate during the recent rebrightening
of TCP J21040470+4631129
Author: V. Neustroev (U. Oulu), D. Boyd, F. Sims (ARAS), K. L. Page
(U. Leicester), T. Tordai (MCSE), S. M. Brincat, C. Galdies, G. Sjoberg
(AAVSO), S. Zharikov (UNAM), J. P. Osborne (U. Leicester), N. P. M.
Kuin (UCL-MSSL), T. R. Marsh, B. T. Gaensicke (U. Warwick), C. Knigge
(U. Southampton)
Queries: vitaly@neustroev.net
Posted: 23 Sep 2019; 17:54 UT
Subjects:Optical, X-ray, Binary, Cataclysmic Variable, Transient,
Variables

We report the results of our continuing optical and X-ray monitoring of
the bright WZ Sge-type dwarf nova TCP J21040470+4631129 (hereafter TCP2104)
discovered on July 12, 2019 (for previous reports, see ATel #12947, #13009).
Our optical photometric observations are mostly performed using 30-cm class
telescopes, while spectroscopic data are obtained with the 2.1-m telescope
at the OAN-SPM, the 2.5-m Isaac Newton Telescope on La Palma, and other
smaller telescopes.

The observations show that the object is exhibiting remarkable, very unusual
behaviour. After the end of the plateau stage on August 3, TCP2104 experienced
2 short rebrightenings on August 8-10 and 14-16, after which the object
underwent the second superoutburst with a relatively short plateau stage
of about 9 days (from August 25 to September 3). After the second plateau
ended, TCP2104 showed another short rebrightening on September 15-17. We
note that the fading after this rebrightening has again decelerated suggesting
that another rebrightening is possible. We also point out that superhump
modulations which were observed from the very beginning of the superoutburst
have never completely disappeared (see also ATel #12947 and #13009), and
they are still present in a light curve after the end of the most recent
rebrightening (their amplitude is about 0.1 mag). Using the observations
obtained between September 18-21, we measured a period of modulations to
be P=77.15+/-0.3 min, which is consistent with the orbital period Porb=77.07+/-0.02
min (ATel #13009).

TCP2104 is currently at the level of V~14.7 mag, that is still about 1.3
mag brighter than just before the discovery (according to ASAS-SN). However,
the Pan-STARRS1 (PS1) catalog lists much lower fluxes; at a mean epoch
of 2014 August 23 the mean V magnitude was measured to be ~18.1 mag (converted
from PS1 magnitudes). We note, however, the PS1 detection tables indicate
that between 2010 and 2014 TCP2104 has gradually brightened by ~0.5 mag.

Our extensive optical spectroscopic monitoring showed a notable difference
between the spectra obtained during the first and the second plateau stages.
During the second plateau, the flux in the emission lines was much reduced,
and especially higher-order Balmer lines were significantly weakened. But
the most dramatic spectral changes were observed during the recent rebrightening.
The spectrum obtained on September 15.84, just before the rebrightening
maximum, shows only Balmer absorption lines, while all the emission lines
completely disappeared. However, another spectrum obtained 9 hours later
(September 16.23) shows very strong emission lines again.

We also continued monitoring TCP2104 with Swift. The observations obtained
between rebrightenings showed a very stable XRT count rate at the level
of 0.11+/-0.02 cts/s. However, during rebrightenings it has dropped by
about 10 times.

We thank the Swift PI, Brad Cenko, for approving the observations, and
the Swift planning and operations teams for their ongoing support.

Light curves and spectra: https://vitaly.neustroev.net/researchfiles/tcp2104/
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